Prefabricating, thermal shrinkage and diameter expansion integrated process method for threaded end part of steel pipe

Abstract

A steel pipe threaded end prefabrication, thermal shrinkage and diameter expansion integrated process method relates to the technical field of steel pipe machining and comprises the following steps: firstly, performing thermal treatment on a to-be-machined part at one end of a steel pipe to reach a certain temperature, then fixing the steel pipe, and pushing an outer mold mounted on a mold towards the steel pipe to perform diameter shrinkage on the to-be-machined part of the steel pipe; and after hole shrinkage is completed, the die is removed, an inner die is installed on the die and pushed towards the steel pipe so that the to-be-machined part of the steel pipe can be expanded, after hole expansion is completed, the die is removed, and the steel pipe is cooled so that machining can be completed. By expanding the diameter of the to-be-machined part at one end of the steel pipe, internal threads can be machined, then the to-be-machined part can be in direct threaded connection with the end, provided with external threads, of the steel pipe, and compared with a traditional steel pipe connected through connecting pieces such as a hoop or a flange plate, the sealing performance, the connecting strength and the mounting efficiency can be improved; and is more suitable for deep wells, oil wells and other occasions.

Description

Technical Field

[0001] The invention relates to the technical field of steel pipe processing, and in particular to an integrated process method for prefabrication of steel pipe thread ends with heat shrinkage and diameter expansion. Background Art

[0002] In the field of oil drilling, steel pipes are the main drilling tools, and their connection methods have an important impact on drilling efficiency and safety. Traditional steel pipe connection technology mainly relies on connectors such as ferrules or flanges to fix two sections of steel pipes together through additional connectors. Although this connection method can meet the connection requirements to a certain extent, it increases the complexity of the connection structure, resulting in cumbersome, time-consuming and labor-intensive installation and disassembly processes. Moreover, this traditional connection method is prone to loosening or breaking at the connection when subjected to high pressure and high torque, affecting the stability and safety of drilling operations. In addition, the sealing performance of the connection is not good, which is prone to oil and gas leakage, which not only affects the operation efficiency, but also may cause safety accidents. In addition, due to the wear and corrosion of the connectors, they need to be replaced regularly, increasing maintenance costs and the risk of operation interruption.

[0003] Chinese patent CN 202391353 U discloses a coupling-free threaded connection for oil pipes and casings, which provides a technical idea for directly connecting two sections of steel pipes by thread, which can improve the sealing performance, connection strength and installation efficiency, and is suitable for deep wells, oil wells and other occasions. This steel pipe direct connection structure seems to be effective, but it is very difficult in the actual processing stage. On the one hand, it is necessary to turn both ends of each section of steel pipe to form a matching step surface structure. On the other hand, due to the strict requirements on steel pipe specifications in the field of oil drilling, the wall thickness usually needs to have a larger size. After turning, the pipe wall becomes thinner, resulting in a significant reduction in the structural strength of the pipe itself. Even if the two sections of the pipe are connected and matched to form the original pipe wall thickness, there is still a problem of low outer pipe wall strength and poor connection reliability at the threaded connection, which poses a great hidden danger for large-scale oil drilling applications. Summary of the invention

[0004] The purpose of the present invention is to provide an integrated process method for prefabricating the threaded end of a steel pipe by heat shrinking and expanding the diameter. By expanding the diameter of one end of the steel pipe for subsequent processing of the internal thread, the steel pipe connected thereto can be directly processed with the external thread for matching, thereby reducing the processing difficulty and avoiding weakening the strength of the steel pipe wall.

[0005] In order to solve the above technical problems, the present invention adopts the following technical scheme: an integrated process method for prefabrication of threaded ends of steel pipes by heat shrinkage and expansion, the steps are as follows: first, the part to be processed at one end of the steel pipe is heat treated to make it reach a certain temperature, and then the steel pipe is fixed, and the outer mold installed on the mold is pushed toward the steel pipe to reduce the diameter of the part to be processed of the steel pipe, and after the reduction is completed, the mold is withdrawn and the outer mold is removed, and an inner mold is installed on the mold and the inner mold is pushed toward the steel pipe to expand the diameter of the part to be processed of the steel pipe, and after the expansion is completed, the mold is withdrawn and the steel pipe is cooled to complete the processing.

[0006] Preferably, when fixing the steel pipe, the steel pipe is clamped by two clamps arranged at intervals to ensure that the axis center line of the steel pipe is aligned with the axis center line of the mold.

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

[0008] More preferably, the heating coil is arranged between two hoops.

[0009] More preferably, in the heat treatment step, the portion 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 forward so that the two clamps clamp the steel pipe at the same time.

[0010] More preferably, the advancement distance of the inner mold in the steel pipe is smaller than the advancement distance of the outer mold 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 die is larger than the inner diameter of the steel pipe, and the diameter of the end of the inner die is reduced to form a step portion.

[0012] More preferably, a combined core mold is installed on the mold to process the other end of the steel pipe. The combined core mold shrinks the diameter of the steel pipe when it is pushed toward the other end of the steel pipe, and expands the diameter of the steel pipe to restore it when it is retracted, so as to straighten the other end of the steel pipe.

[0013] More preferably, the combined core mold includes a center expansion mold and an outer ring shrinking mold which are staggered in the axial direction. During the process of the combined core mold being advanced toward the steel pipe, the center expansion 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 core mold retracts, the center expansion mold expands the reduced diameter portion of the steel pipe.

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

[0015] Compared with the prior art, the present invention expands the diameter of the portion to be processed at one end of the steel pipe so that it can be processed with an internal thread, and then it can be directly threadedly connected to one end of the steel pipe processed with an external thread, thereby reducing the processing difficulty of the direct-connected steel pipe and avoiding weakening the strength of the steel pipe wall.

[0016] In addition, the present invention first performs heat treatment and diameter reduction on the steel pipe before diameter expansion. The effect of this unique process is that the steel pipe material can be plastically deformed in a specific area through heat treatment and diameter reduction, so that it is easier to control the flow of the material in the subsequent diameter expansion step to achieve the desired size and shape, which is more effective for the diameter expansion of steel pipes with thicker walls; reducing the diameter first can help accurately control the size of the steel pipe end and provide a benchmark for the diameter expansion step, which can ensure that the size after diameter expansion is more accurate and meets the requirements of internal thread processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the overall structure of the mold and the steel pipe when they are fixed in the embodiment; Figure 2 This is a schematic diagram of the outer mold reducing the diameter of the steel pipe in the embodiment; Figure 3 This is a schematic diagram of the inner membrane expanding the diameter of the steel pipe in the embodiment; Figure 4 It is a schematic diagram of the process flow of straightening the pipe opening at the other end of the steel pipe in the embodiment.

[0018] In the figure: 1——Steel pipe 2——Mold 3——External mold 4——Inner membrane 5——Holding hoop 6——Center expansion 7——Outer ring shrink mold 8——Heating coil. DETAILED DESCRIPTION

[0019] In order to facilitate the understanding of those skilled in the art, the present invention is further described below in conjunction with embodiments and drawings. The contents mentioned in the implementation modes are not intended to limit the present invention.

[0020] It should be noted in advance that, in the present invention, unless otherwise clearly specified and limited, the terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In addition, in the present invention, unless otherwise clearly specified and limited, the first feature "on" or "under" the second feature may include the first and second features being in direct contact, and may also include the first and second features not being in direct contact but being in contact through another feature between them.

[0021] The process implemented in this embodiment is based on a device that mainly includes a mold 2, two spaced-apart clamps 5, and a medium-frequency heating coil arranged between the two clamps 5. The clamp 5 includes a fixed lower half clamp and an upper half clamp that can move up and down to clamp the steel pipe 1.

[0022] The processing steps are as follows: first, the part of the steel pipe 1 to be processed is 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 forward so that the two clamps 5 clamp the steel pipe 1 at the same time, ensuring that the axis of the steel pipe 1 is aligned with the axis of the mold 2 (such as Figure 1 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 toward the steel pipe 1 to reduce the diameter of the part to be processed of the steel pipe 1 (as shown in FIG. Figure 2 As shown in the figure, after the diameter reduction is completed, the mold is withdrawn and the outer mold 3 is removed, and the inner mold 4 is installed on the mold 2 and pushed toward the steel pipe 1 to expand the diameter of the part to be processed of the steel pipe 1 (as shown in the figure). Figure 3 As shown in the figure, the advancement distance of the inner die 4 in the steel pipe 1 is smaller than the advancement distance of the outer die 3 on the steel pipe 1, so that a step is formed on the inner wall of the steel pipe 1, which is convenient for providing a limit when the threaded portion is formed on this part and connected with another section of steel pipe. After the diameter expansion is completed, the die is withdrawn and the steel pipe 1 is cooled to complete the processing and ensure the shape and size stability of the steel pipe 1.

[0023] Those skilled in the art should know that, during the heat treatment process, the temperature reached by the heating coil 8 to heat the part to be processed of the steel pipe 1 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 a state of thermoplastic deformation, thereby making it easy to form in the subsequent diameter reduction and expansion process, while avoiding overheating and causing a decrease in material properties.

[0024] The above-mentioned heat treatment and diameter reduction can cause the material of the to-be-processed part of the steel pipe 1 to undergo plastic deformation in a specific area, so that it is easier to control the flow of the material in the subsequent diameter expansion step to achieve the desired size and shape, which is more effective for the diameter expansion of steel pipes with thicker walls; and the diameter reduction first can help to accurately control the size of the steel pipe end, providing a benchmark for the diameter expansion step, so as to ensure that the size after diameter expansion is more accurate and meets the requirements of internal thread processing. Compared with the process mentioned in the background technology of turning matching step surface structures at both ends of the steel pipe to affect the structural strength of the steel pipe itself, the process of this embodiment obviously will not weaken the original structural strength of the steel pipe, which is crucial to the reliability of the threaded part of the directly connected steel pipe, and is particularly suitable for applications in the field of large-scale oil drilling.

[0025] In addition, during the production process of steel pipes, the pipe mouth is prone to a certain degree of goose head bend phenomenon. This is because during the hot rolling process, if the local area is water-cooled, it may cause the steel pipe to shrink unevenly during the cooling process, thus causing the phenomenon; in addition, if the straightening machine is improperly adjusted or the straightening roller is severely worn, it may also cause the steel pipe to be subjected to uneven force during the straightening process, thereby causing goose head bend. In the case of directly connecting two sections of steel pipes using connectors such as ferrules or flanges, the impact of this goose head bend phenomenon is not obvious, but if the form of direct connection of steel pipes is adopted, the existence of goose head bend will affect the external thread processing of the outer peripheral surface of the steel pipe mouth, and further affect the thread direct connection effect of the two sections of steel pipes. Therefore, this end of the steel pipe needs to be rounded and straightened, and through the process method of this embodiment, it can be directly performed on the same set of molds (just replace the core mold). Then, since the part to be processed at one end of the steel pipe 1 has been heat treated, reduced in diameter and expanded in diameter, it no longer needs to be straightened. Therefore, after the processing is completed, the other end of the steel pipe 1 can be processed. Specifically, after removing the outer mold 3 and the inner mold 4 of the above process link, install the combined core mold on the mold 2, loosen the clamp 5, and swap the two ends of the steel pipe 1 so that the other end of the steel pipe 1 enters the processing station. Figure 4 As shown, the combined core mold includes a central expansion mold 6 and an outer ring shrinking mold 7 that are staggered in 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 (the central expansion mold 6 does not work at this time), and then the outer ring shrinking mold 7 contacts the steel pipe 1 and shrinks its diameter. After the shrinking is completed, the combined core mold begins to retreat. During the retreat, the outer ring shrinking mold 7 does not work, while the central expansion mold 6 expands the diameter of the reduced diameter portion of the steel pipe 1, thereby achieving the purpose of straightening the pipe mouth. Those skilled in the art should know that in the combined core mold, the central expansion mold 6 itself has a certain floating adjustment ability. This design allows the central expansion mold 6 to have a certain radial activity space (for example, there is about 3mm of activity space upward or downward, which is a common technical means in the prior art to improve the flexibility and adaptability of the core mold), so that it can adaptively adjust its state when encountering an irregular pipe mouth, so that even if a goose-head bend pipe mouth is encountered, it can be smoothly inserted into the steel pipe 1.

[0026] In the above process, when the outer ring shrinking mold 7 is used to reduce the diameter of the steel pipe, it helps to adjust the shape of the pipe mouth and prepare for the expansion. In the subsequent process of demolding, the central expansion mold 6 expands the diameter of the steel pipe 1 to restore the diameter of the pipe mouth, thereby effectively correcting the goose head bend phenomenon. The design of the combined core mold allows the reduction and expansion operations to be performed in stages. The outer ring shrinking mold 7 is responsible for the reduction, and the central expansion mold 6 is responsible for the expansion. This design allows the steel pipe 1 to be straightened and corrected in shape in one processing process, greatly improving the processing efficiency. After correcting the goose head bend phenomenon, the outer peripheral surface of the steel pipe mouth is ensured to be flat, thereby ensuring the quality of the subsequent processing of the external thread and the effect of the direct connection of the two sections of steel pipe.

[0027] In this embodiment, no matter it is processing the internal threaded end pipe mouth or the threaded end pipe mouth, the steel pipe 1 is fixed by two clamps 5 to ensure that the axis line of the steel pipe 1 is aligned with the axis line of the mold 2. The advantage of this processing method is that the clamp fixing the steel pipe can not only provide a stable operating platform, reduce the error caused by the movement or vibration of the steel pipe during the processing, and enhance the stability of the entire processing operation, but also improve the accuracy of the processing process, making the operations of reducing the diameter, expanding the diameter and straightening more accurate, thereby ensuring that the geometric shape and size of the end of the steel pipe after processing meet the design requirements.

[0028] The integrated process method for prefabrication of the threaded end of the steel pipe provided in the above embodiment, through the continuous steps of heat treatment, diameter reduction and diameter expansion, accurately adjusts the size of one end of the steel pipe and forms an inner wall step to facilitate the subsequent processing of the internal thread and improve the reliability of the direct connection of the steel pipe. The process first uses a medium-frequency heating coil to heat treat the part of the steel pipe to be processed, and then reduces and expands the diameter through the sequential action of the outer mold and the inner mold, and finally completes the processing through cooling treatment. This method not only improves the processing accuracy and efficiency, but also enhances the structural strength of the steel pipe end and the sealing performance of the connection.

[0029] The present invention improves the precision and efficiency of steel pipe end processing, reduces material loss, reduces processing costs, enhances the structural strength of steel pipe joints, improves the sealing and safety of connections, and adapts to the processing requirements of steel pipes of different specifications, and has broad industrial application prospects. In addition, the process also simplifies the production process, is easy to automate, and helps to improve the overall automation level of the production line.

[0030] In order to make it easier for ordinary technicians in the field to understand the improvements of the present invention over the prior art, some drawings and descriptions of the present invention have been simplified, and the above-mentioned embodiments are preferred implementation schemes of the present invention. In addition, the present invention can also be implemented in other ways. Any obvious replacement without departing from the concept of the present technical solution is within the protection scope of the present invention.

Claims

1. A steel pipe thread end prefabrication heat shrinkage and diameter expansion integrated process method, characterized by: First, a portion to be processed at one end of the steel pipe (1) is subjected to heat treatment to reach a certain temperature, then the steel pipe (1) is fixed, and an outer die (3) installed on the die (2) is pushed toward the steel pipe (1) to reduce the diameter of the portion to be processed of the steel pipe (1). After the diameter reduction is completed, the die is withdrawn and the outer die (3) is removed. An inner die (4) is installed on the die (2) and the inner die (4) is pushed toward the steel pipe (1) to expand the diameter of the portion to be processed of the steel pipe (1). After the diameter expansion is completed, the die is withdrawn and the steel pipe (1) is cooled to complete the processing.

2. The integrated process for prefabrication of steel pipe threaded end portions by heat shrinkage and diameter expansion according to claim 1 is characterized in that: When the steel pipe (1) is fixed, the steel pipe (1) is clamped by two clamping hoops (5) arranged at intervals to ensure that the axis center line of the steel pipe (1) is aligned with the axis center line of the mold (2).

3. The integrated process for prefabrication of steel pipe threaded end portions by heat shrinkage and diameter expansion according to claim 2, characterized in that: In the heat treatment step, a heating coil (8) is used to heat the portion of the steel pipe (1) to be processed.

4. The integrated process for prefabrication of steel pipe threaded end portions by heat shrinkage and diameter expansion according to claim 3 is characterized in that: The heating coil (8) is arranged between the two clamps (5).

5. The integrated process for prefabrication of steel pipe threaded end portions by heat shrinkage and diameter expansion according to claim 4 is characterized in that: In the heat treatment step, the portion 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 the steel pipe (1) is then pushed forward so that the two clamps (5) clamp the steel pipe (1) at the same time.

6. The integrated process for prefabrication of steel pipe threaded end portions by heat shrinkage and diameter expansion according to claim 1, characterized in that: The advancement distance of the inner mold (4) in the steel pipe (1) is smaller than the advancement distance of the outer mold (3) on the steel pipe (1), so that a step is formed on the inner wall of the steel pipe (1).

7. The integrated process for prefabrication of steel pipe threaded end portions by heat shrinkage and diameter expansion according to claim 6, characterized in that: The outer diameter of the inner die (1) is greater than the inner diameter of the steel pipe (1), and the diameter of the end of the inner die (1) is reduced to form a step portion.

8. The integrated process for prefabrication of steel pipe threaded end portions by heat shrinkage and diameter expansion according to claim 1, characterized in that: 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), the diameter of the steel pipe (1) is reduced, and when it is retracted, the diameter of the steel pipe (1) is expanded to restore it, so as to straighten the other end of the steel pipe (1).

9. The integrated process for prefabrication of steel pipe threaded end portions by heat shrinkage and diameter expansion according to claim 8, characterized in that: The combined core mold comprises a central expansion mold (6) and an outer ring shrinking mold (7) which are staggered in 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 shrinking mold (7) contacts the steel pipe (1) and shrinks its diameter. When the combined core mold is retracted, the central expansion mold (6) expands the reduced diameter portion of the steel pipe (1).

10. The integrated process for prefabrication of steel pipe threaded end portions by heat shrinkage and diameter expansion according to claim 8, characterized in that: When processing the other end of the steel pipe (1), the steel pipe (1) is clamped by two clamping hoops (5) arranged at intervals to ensure that the axis center line of the steel pipe (1) is aligned with the axis center line of the mold (2).

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