Integrated process method for prefabricating threaded end of steel pipe, heat shrinking and expanding diameter

Abstract

The steel pipe threaded end prefabricating, processing, heat shrinking and expanding integrated process method relates to the steel pipe processing technical field, and the method steps are as follows: firstly, the steel pipe one end of the to-be-processed part is heat treated to reach a certain temperature, then the steel pipe is fixed, the outer die installed on the die is pushed towards the steel pipe to shrink the to-be-processed part of the steel pipe, the die is retreated and the outer die is removed after the shrinking is completed, the inner die is installed on the die and pushed towards the steel pipe to expand the to-be-processed part of the steel pipe, the die is retreated after the expanding is completed, and the steel pipe is cooled to complete the processing. The to-be-processed part of the steel pipe one end is expanded, so that the internal thread can be processed, and then the steel pipe one end with the external thread can be directly threaded connected, compared with the traditional steel pipe connected by the sleeve or the flange and other connecting pieces, the sealing performance, the connecting strength and the installation efficiency can be improved, and the method is more suitable for deep well, oil well and other occasions.

Description

Technical Field

[0001] This invention relates to the field of steel pipe processing technology, and in particular to an integrated process for prefabricating and heat-shrinking expansion of the threaded ends of steel pipes. Background Technology

[0002] In the field of oil drilling, steel pipes are the primary drilling tool, and their connection methods have a significant impact on drilling efficiency and safety. Traditional steel pipe connection technology mainly relies on connectors such as clamps or flanges to fix two sections of steel pipe together using additional connectors. While this connection method can meet connection requirements to a certain extent, it increases the complexity of the connection structure, making installation and disassembly cumbersome, time-consuming, and labor-intensive. Moreover, this traditional connection method is prone to loosening or breakage at the connection point under high pressure and high torque, affecting the stability and safety of drilling operations. In addition, the sealing performance of the connection point is poor, which can easily lead to oil and gas leaks, affecting not only operational efficiency but also potentially causing safety accidents. Furthermore, due to wear and corrosion of the connectors, regular replacement is required, increasing maintenance costs and the risk of operational interruptions.

[0003] Chinese patent CN 202391353 U discloses a coupling-free threaded connection for oil tubing and casing, which presents a technical approach of directly connecting two sections of steel pipe with threads. This approach can improve sealing performance, connection strength, and installation efficiency, and is suitable for deep wells, oil wells, and other applications. While this direct connection structure appears effective, it presents significant challenges in actual manufacturing. Firstly, both ends of each steel pipe section need to be machined to create a mating stepped surface structure. Secondly, the oil drilling industry has strict requirements for steel pipe specifications, typically requiring a large wall thickness. After machining, the pipe wall thins, significantly reducing the pipe's structural strength. Even after connecting the two pipe sections to achieve the original wall thickness, the outer wall strength at the threaded connection remains lower, leading to reduced connection reliability. This poses a significant risk for applications in large-scale oil drilling. Summary of the Invention

[0004] The purpose of this invention is to provide an integrated process for prefabricating and expanding the diameter of the threaded end of a steel pipe. By expanding the diameter of one end of the steel pipe to allow for subsequent internal thread processing, the steel pipe connected to it can be directly processed with external threads for mating, thereby reducing processing difficulty and avoiding weakening the strength of the steel pipe wall.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a prefabrication process for heat shrinking and expanding the diameter of a steel pipe threaded end, comprising the following steps: first, heat-treating the part to be processed at one end of the steel pipe to reach a certain temperature; then fixing the steel pipe and pushing the outer mold installed on the mold toward the steel pipe to shrink the diameter of the part to be processed; after shrinking the diameter, removing the mold and dismantling the outer mold; installing the inner mold on the mold and pushing the inner mold toward the steel pipe to expand the diameter of the part to be processed; after expanding the diameter, removing the mold and cooling the steel pipe to complete the processing.

[0006] Preferably, when fixing the steel pipe, the steel pipe is clamped by two spaced clamps to ensure that the centerline of the steel pipe is aligned with the centerline of the mold.

[0007] More preferably, in the heat treatment step, a heating coil is used to heat the part of the steel pipe to be processed.

[0008] More preferably, the heating coil is disposed between the two clamps.

[0009] More preferably, in the heat treatment step, the part of the steel pipe to be processed is first inserted into the heating coil, and then the steel pipe is fixed by the outermost clamp. After the heat treatment is completed, the heating coil is turned off, and then the steel pipe is pushed in so that the two clamps hold the steel pipe at the same time.

[0010] More preferably, the inner mold is pushed a shorter distance inside the steel pipe than the outer mold is pushed a shorter distance on the steel pipe, so that a step is formed on the inner wall of the steel pipe.

[0011] More preferably, the outer diameter of the inner mold is larger than the inner diameter of the steel pipe, and the diameter of the end of the inner mold is reduced to form a stepped portion.

[0012] More preferably, a combined mandrel is installed on the mold to process the other end of the steel pipe. When the combined mandrel is pushed into the other end of the steel pipe, it reduces the diameter of the steel pipe. When it is pulled back, it expands the diameter of the steel pipe to restore its original shape, thereby straightening the other end of the steel pipe.

[0013] More preferably, the combined mandrel includes a central expanding mold and an outer ring shrinking mold offset along the axial direction. During the process of the combined mandrel advancing toward the steel pipe, the central expanding mold first extends into the steel pipe, and then the outer ring shrinking mold contacts the steel pipe and shrinks its diameter. When the combined mandrel retracts, the central expanding mold expands the diameter of the shrinking part of the steel pipe.

[0014] More preferably, when processing the other end of the steel pipe, the steel pipe is clamped by two spaced clamps to ensure that the centerline of the steel pipe is aligned with the centerline of the mold.

[0015] Compared with the prior art, the present invention expands the diameter of the part to be processed at one end of the steel pipe so that it can be processed with internal threads, thereby enabling it to be directly threaded to the end of the steel pipe with external threads. This reduces the processing difficulty of the direct-connection steel pipe and avoids weakening the strength of the steel pipe wall.

[0016] Furthermore, this invention first heat-treats and reduces the diameter of the steel pipe before expanding it. The effect of this unique process is that heat treatment and diameter reduction can cause plastic deformation of the steel pipe material in a specific area, making it easier to control the flow of the material in the subsequent diameter expansion step to achieve the required size and shape. This is more effective for expanding steel pipes with large wall thickness. Pre-diameter reduction can help to accurately control the size of the steel pipe end, providing a benchmark for the diameter expansion step. This ensures that the size after diameter expansion is more accurate and meets the requirements of internal thread processing. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of the mold and steel pipe fixing in the embodiment;

[0018] Figure 2 This is a schematic diagram illustrating the reduction in diameter of the steel pipe by the outer mold in the embodiment.

[0019] Figure 3 This is a schematic diagram illustrating the expansion of the steel pipe diameter by the inner lining in the embodiment.

[0020] Figure 4 This is a schematic diagram of the process for straightening the other end of the steel pipe in the embodiment.

[0021] In the picture:

[0022] 1 - Steel pipe 2 - Mold 3 - Outer mold

[0023] 4—Inner membrane 5—Clamping 6—Central expansion membrane

[0024] 7—Outer ring shrink mold; 8—Heating coil. Detailed Implementation

[0025] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments and accompanying drawings. The content mentioned in the embodiments is not intended to limit the present invention.

[0026] It should be noted in advance that, in this invention, unless otherwise explicitly specified and limited, terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection. Those skilled in the art can understand the specific meaning of these terms in this invention according to the specific circumstances. Furthermore, in this invention, unless otherwise explicitly specified and limited, "on" or "under" a second feature can include direct contact between the first and second features, or contact between the first and second features not in direct contact but through another feature between them.

[0027] The device based on the process implemented in this embodiment mainly includes a mold 2, two spaced clamps 5, and a medium-frequency heating coil disposed between the two clamps 5. The clamps 5 include a fixed lower clamp and an upper clamp that can move up and down to clamp the steel pipe 1.

[0028] The processing steps are as follows: First, insert the part of the steel pipe 1 to be processed into the heating coil 8, then fix the steel pipe 1 with the outermost clamp 5. After the heat treatment is completed, turn off the heating coil 8, and then push the steel pipe 1 forward so that the two clamps 5 clamp the steel pipe 1 simultaneously, ensuring that the axis of the steel pipe 1 is aligned with the axis of the mold 2 (e.g., Figure 1 As shown). At this time, the part to be processed at one end of the steel pipe 1 has a certain temperature, and then the outer mold 3 installed on the mold 2 is pushed towards the steel pipe 1 to reduce the diameter of the part to be processed of the steel pipe 1 (as shown). Figure 2 As shown), after completing the diameter reduction, the mold is removed and the outer mold 3 is taken off. The inner mold 4 is then installed on the mold 2 and pushed towards the steel pipe 1 to expand the diameter of the part of the steel pipe 1 to be processed (as shown). Figure 3 As shown), the inner mold 4 is pushed a distance less than the outer mold 3 is pushed on the steel pipe 1, so that a step is formed on the inner wall of the steel pipe 1. This facilitates the connection of the threaded part with another section of steel pipe, and the mold is removed after the diameter is expanded and the steel pipe 1 is cooled to complete the processing and ensure the shape and size of the steel pipe 1 are stable.

[0029] Those skilled in the art should know that during the heat treatment process, the temperature reached by the heating coil 8 heating the part of the steel pipe 1 to be processed usually depends on the material properties of the steel pipe itself. In this embodiment, the temperature range reached by heating can ensure that the steel pipe material reaches the state of thermoplastic deformation, so that it is easy to form in the subsequent diameter reduction and diameter expansion process, while avoiding overheating that would cause a decline in material properties.

[0030] The heat treatment and diameter reduction described above allow for plastic deformation of the material in a specific area of ​​the steel pipe 1 to be processed. This makes it easier to control the material flow in the subsequent diameter expansion step to achieve the required size and shape, which is more effective for expanding steel pipes with large wall thicknesses. Diameter reduction first helps to precisely control the dimensions of the pipe ends, providing a benchmark for the diameter expansion step. This ensures that the expanded dimensions are more accurate and meet the requirements for internal thread processing. Compared to the process mentioned in the background art, which involves machining mating stepped surfaces at both ends of the steel pipe, thus affecting the structural strength of the pipe itself, the process in this embodiment obviously does not weaken the original structural strength of the steel pipe. This is crucial for the reliability of the threaded portion of the directly connected steel pipe, and is especially suitable for applications in large-scale oil drilling.

[0031] Furthermore, during the production of steel pipes, a certain degree of gooseneck bend is prone to occur at the pipe end. This is because during hot rolling, if a local area is water-cooled, it may cause uneven shrinkage of the steel pipe during cooling, resulting in this phenomenon. In addition, improper adjustment of the straightening machine or severe wear of the straightening rollers may also cause uneven force on the steel pipe during straightening, thus causing a gooseneck bend. In the case of directly connecting two steel pipe sections using fasteners such as clamps or flanges, the impact of this gooseneck bend is not obvious. However, if a direct connection of steel pipes is used, the presence of the gooseneck bend will affect the external thread processing on the outer circumference of the steel pipe end and further affect the thread connection effect of the two steel pipe sections. Therefore, it is necessary to round and straighten this end of the steel pipe. With the process method of this embodiment, this can be done directly on the same set of molds (simply by changing the mandrel). Since the portion of steel pipe 1 to be processed at one end has already undergone heat treatment, diameter reduction, and diameter expansion, and no straightening is required, the other end of steel pipe 1 can be processed after this processing is completed. Specifically, after removing the outer mold 3 and inner mold 4 from the aforementioned process steps, a combined core mold is installed on mold 2, the clamp 5 is loosened, and the two ends of steel pipe 1 are swapped, allowing the other end of steel pipe 1 to enter the processing station. Figure 4As shown, the combined mandrel includes a central expanding mold 6 and an outer ring reducing mold 7, which are offset along the axial direction. During the process of the combined mandrel advancing towards the steel pipe 1, the central expanding mold 6 first extends into the steel pipe 1 (at this time, the central expanding mold 6 is not working). Then, the outer ring reducing mold 7 contacts the steel pipe 1 and reduces its diameter. After the diameter reduction is completed, the combined mandrel begins to retract. During the retraction process, the outer ring reducing mold 7 is not working, while the central expanding mold 6 expands the diameter of the reduced portion of the steel pipe 1, thereby achieving the purpose of straightening the pipe opening. Those skilled in the art should know that in the combined mandrel, the central expanding mold 6 itself has a certain floating adjustment capability. This design allows the central expanding mold 6 to have a certain amount of radial movement space (for example, about 3mm of movement space upwards or downwards, which is a common technique in the prior art to improve the flexibility and adaptability of the mandrel), enabling it to adaptively adjust its state when encountering irregular pipe openings. Therefore, even when encountering a bend in the pipe opening, it can smoothly extend into the steel pipe 1.

[0032] In the above process, when the outer ring reducing mold 7 reduces the diameter of the steel pipe, it helps to adjust the shape of the pipe opening and prepare for the diameter expansion. Subsequently, during the mold removal process, the central expanding mold 6 expands the diameter of the steel pipe 1, restoring the diameter of the pipe opening. This effectively corrects the gooseneck bend phenomenon. The design of the combined mandrel allows for staged diameter reduction and expansion operations. The outer ring reducing mold 7 is responsible for diameter reduction, and the central expanding mold 6 is responsible for diameter expansion. This design allows the steel pipe 1 to complete straightening and shape correction in one processing step, greatly improving processing efficiency. After correcting the gooseneck bend phenomenon, it ensures the smoothness of the outer circumference of the steel pipe opening, thereby guaranteeing the quality of the subsequent external thread processing and the effect of the direct connection between the two sections of the steel pipe.

[0033] In this embodiment, whether processing the internal thread end or the threaded end, the steel pipe 1 is fixed by two clamps 5 to ensure that the axis of the steel pipe 1 is aligned with the axis of the mold 2. The advantage of this method is that fixing the steel pipe with clamps not only provides a stable operating platform and reduces errors caused by the movement or vibration of the steel pipe during processing, thus enhancing the stability of the entire processing operation, but also improves the accuracy of the processing, making operations such as diameter reduction, diameter expansion, and straightening more accurate, thereby ensuring that the geometry and dimensions of the steel pipe end after processing meet the design requirements.

[0034] The integrated heat-shrinking and diameter-expanding process for prefabricating threaded ends of steel pipes provided in the above embodiments achieves precise dimensional adjustment at one end of the steel pipe through continuous steps of heat treatment, diameter reduction, and diameter expansion, forming an inner wall step to facilitate subsequent internal thread processing and improve the reliability of direct connections between the steel pipes. This process first uses a medium-frequency heating coil to heat-treat the portion of the steel pipe to be processed, then achieves diameter reduction and expansion through the sequential action of an outer and inner mold, and finally completes the processing through cooling. This method not only improves processing accuracy and efficiency but also enhances the structural strength of the steel pipe end and the sealing performance of the connection.

[0035] This invention improves the precision and efficiency of steel pipe end processing, reduces material waste, lowers processing costs, enhances the structural strength of steel pipe joints, improves the sealing and safety of connections, and adapts to the processing needs of steel pipes of different specifications, thus having broad industrial application prospects. Furthermore, this process simplifies the production flow, facilitates automation, and helps improve the overall automation level of the production line.

[0036] To facilitate understanding by those skilled in the art of the improvements of this invention over the prior art, some of the accompanying drawings and descriptions have been simplified. The above embodiments are preferred implementations of this invention. In addition, this invention can be implemented in other ways. Any obvious substitutions without departing from the concept of this technical solution are within the protection scope of this invention.

Claims

1. A prefabrication and heat-shrinking expansion integrated process for the threaded ends of steel pipes, characterized in that: First, heat-treat the part to be processed at one end of the steel pipe (1) to reach a certain temperature. Then, fix the steel pipe (1) and push the outer mold (3) installed on the mold (2) toward the steel pipe (1) to reduce the diameter of the part to be processed on the steel pipe (1). After the diameter reduction is completed, remove the mold and dismantle the outer mold (3). Install the inner mold (4) on the mold (2) and push the inner mold (4) toward the steel pipe (1) to expand the diameter of the part to be processed on the steel pipe (1). After the diameter expansion is completed, remove the mold and cool the steel pipe (1) to complete the processing. When fixing the steel pipe (1), clamp the steel pipe (1) with two spaced clamps (5) to ensure that the axis of the steel pipe (1) is aligned with the axis of the mold (2). The pushing distance of the inner mold (4) in the steel pipe (1) is less than the pushing distance of the outer mold (3) on the steel pipe (1) so that the inner mold (4) pushes the outer mold (3) onto the steel pipe (1) to reduce the diameter of the outer mold (3). The inner wall of the steel pipe (1) forms a step. The outer diameter of the inner mold (4) is larger than the inner diameter of the steel pipe (1). The diameter of the end of the inner mold (4) is reduced to form a step. A combined core mold is installed on the mold (2) to process the other end of the steel pipe (1). When the combined core mold is pushed toward the other end of the steel pipe (1), it reduces the diameter of the steel pipe (1). When it is pulled back, it expands the diameter of the steel pipe (1) to restore it, so as to straighten the other end of the steel pipe (1). The combined core mold includes a central expansion mold (6) and an outer ring reduction mold (7) that are staggered along the axial direction. When the combined core mold is pushed toward the steel pipe (1), the central expansion mold (6) first extends into the steel pipe (1), and then the outer ring reduction mold (7) contacts the steel pipe (1) and reduces its diameter. When the combined core mold is pulled back, the central expansion mold (6) expands the diameter of the reduced diameter part of the steel pipe (1).

2. The integrated hot-shrinking and diameter-expanding process for prefabrication of steel pipe thread ends according to claim 1, characterized in that: In the heat treatment step, a heating coil (8) is used to heat the part of the steel pipe (1) to be processed.

3. The integrated hot-shrinking and diameter-expanding process for prefabrication of steel pipe thread ends according to claim 2, characterized in that: The heating coil (8) is positioned between the two clamps (5).

4. The integrated hot-shrinking and diameter-expanding process for prefabrication of steel pipe thread ends according to claim 3, characterized in that: In the heat treatment step, the part of the steel pipe (1) to be processed is first inserted into the heating coil (8), and then the steel pipe (1) is fixed by the outermost clamp (5). After the heat treatment is completed, the heating coil (8) is turned off, and then the steel pipe (1) is pushed in so that the two clamps (5) clamp the steel pipe (1) at the same time.

5. The integrated hot-shrinking and diameter-expanding process for prefabrication of steel pipe thread ends according to claim 4, characterized in that: When processing the other end of the steel pipe (1), the steel pipe (1) is clamped by two spaced clamps (5) to ensure that the center line of the steel pipe (1) is aligned with the center line of the mold (2).

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