Threaded joint for oil casing
By setting the torque bearing part and improved thread shape in the oil casing threaded joint, the stress is dispersed and the processing complexity is reduced, the problems of stress concentration and processing difficulty in the prior art are solved, and the fatigue resistance and processing efficiency are improved .
Patent Information
- Application Number
- CN202421235284.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-31
- Publication Date
- 2024-12-27
- Estimated Expiration
- 2034-05-31
AI Technical Summary
Existing oil casing threaded joints are prone to high stress concentration, resulting in poor fatigue resistance and high processing difficulty.
An oil sleeve threaded joint is designed, by providing a torque bearing portion and an improved threaded tooth shape, including a first bearing surface and a second bearing surface of interference fit, and an inclined first guide surface and a second guide surface, Increase the contact area between the internal threaded teeth and the external threaded teeth, disperse stress, and reduce stress concentration by changing the tooth shape of the threaded part to avoid additional stress relief structures.
The fatigue resistance of the oil casing threaded joint is improved, the processing process complexity and cost is reduced, the stress concentration is significantly reduced, and the contact area and torsion resistance of the threaded part are enhanced.
Smart Images
Figure CN222253869U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of oil pipe threaded connection, in particular to an oil casing threaded joint. Background Art
[0002] In ordinary oil and gas wells, the casing does not bear cyclic loads, so the strength design of ordinary oil casing only involves static strength issues. In recent years, new requirements have been put forward for the fatigue resistance of oil casing, which are mainly reflected in two aspects: 1) Casing drilling. The drill bit is fixed to the end of the casing for drilling. This technology can shorten the drilling time and reduce the drilling cost. In the bending section, the thread is subjected to alternating tensile and compressive loads, and fatigue strength verification needs to be considered. 2) Marine waterproof casing. The pipe body vibrates due to the wind load, the cyclic load of the ocean current and the drift load of the drilling platform. Therefore, the fatigue problem of the waterproof casing connection thread needs to be considered in marine drilling or oil production projects.
[0003] After searching the existing technical documents, it was found that the Chinese patent announcement number is CN2683826Y, the announcement date is March 9, 2005, and the utility model patent name is "Oil well casing that can be used for drilling". The patent discloses an oil well casing that can be used for drilling, which includes multiple pipe bodies connected by couplings, each coupling inner hole has a shoulder in the middle, and empty knife grooves are provided on both sides of the shoulder, and the end face of each pipe body is against the shoulder. Since the end face of each pipe body is against the shoulder in the middle of the inner hole of the coupling, it can withstand a large axial compression force and a large torque during the drilling process. Since the torque acting on the coupling and the pipe body is transmitted to the shoulder, the threads on the coupling and the pipe body can be protected from being damaged by the overload torque. The coupling adds a shoulder in the middle of the coupling on the basis of the API thread, which improves the torsion resistance of the coupling. At the same time, the shoulder bears a high torque, thereby reducing the force on the thread. However, the thread of the coupling is an API trapezoidal shape, and the above-mentioned tooth shape is prone to a high degree of stress concentration, resulting in poor fatigue resistance.
[0004] The Chinese patent announcement number is CN210888836U, and the announcement date is June 30, 2020. The utility model patent named "Threaded joint of anti-fatigue casing" discloses a threaded joint of anti-fatigue casing, which is used for connecting pipes. The threaded joint includes a male end, on which an external threaded joint is provided; and a female end, on which an internal threaded joint is provided. The male end and the female end are connected by threads. Among them, at least one stress release structure is provided on the female end to increase the fatigue strength of the threaded joint. The utility model mainly reduces the stress concentration of the threaded connection by reducing the stiffness of the coupling and optimizing the size of the transition structure at the threaded connection. However, the additional arrangement of the stress release structure will increase the complexity of the processing technology of the threaded joint, resulting in a problem of higher processing difficulty. Utility Model Content
[0005] The main purpose of the utility model is to provide an oil casing threaded joint to solve the problems of high stress concentration in the oil casing threaded joint in the prior art, which leads to poor fatigue resistance and high processing difficulty.
[0006] In order to achieve the above-mentioned purpose, the utility model provides an oil casing threaded joint, the oil casing threaded joint has an axis, the oil casing threaded joint includes a pipe body and a coupling, along the axis of the oil casing threaded joint, a threaded portion and a torque bearing portion are provided between the pipe body and the coupling, the pipe body is connected to the coupling through the threaded portion, and the torque bearing portion is used to bear part of the torque and realize positioning; the threaded portion includes: an external thread, which is arranged on the pipe body, and the external thread teeth of the external thread have a first bearing surface and a first guide surface, along the axis of the oil casing threaded joint, the first bearing surface and the first guide surface are respectively located on both sides of the external thread teeth, and the first bearing surface is relative to the external thread teeth. The axis of the oil casing threaded joint is arranged vertically, and the first guide surface is arranged obliquely relative to the axis of the oil casing threaded joint; the internal thread is arranged on the coupling, and the internal thread teeth of the internal thread have a second bearing surface and a second guide surface. Along the axis of the oil casing threaded joint, the second bearing surface and the second guide surface are respectively located on both sides of the internal thread teeth, the second bearing surface is arranged vertically relative to the axis of the oil casing threaded joint, and the second guide surface is arranged obliquely relative to the axis of the oil casing threaded joint; wherein, the first bearing surface and the second bearing surface are interference fit, and at least part of the first guide surface and at least part of the second guide surface are interference fit.
[0007] Furthermore, from the top of the external thread to the bottom of the external thread, the first guide surface includes a first guide section and a second guide section connected to each other, the angle between the first guide section and the axis of the oil casing threaded joint is greater than or equal to 35° and less than or equal to 55°, and the angle between the second guide section and the axis of the oil casing threaded joint is greater than or equal to 50° and less than or equal to 70°; from the top of the internal thread to the bottom of the internal thread, the second guide surface includes a third guide section and a fourth guide section connected to each other, the angle between the third guide section and the axis of the oil casing threaded joint is greater than or equal to 35° and less than or equal to 55°, and the angle between the fourth guide section and the axis of the oil casing threaded joint is greater than or equal to 50° and less than or equal to 70°; part of the first guide section and part of the third guide section are interference fit.
[0008] Furthermore, the sum of the interference between the first bearing surface and the second bearing surface and the interference between the first guide surface and the second guide surface is greater than or equal to 0.15 mm and less than or equal to 0.25 mm.
[0009] Furthermore, the tooth top of the external thread tooth and the tooth bottom of the internal thread tooth have a clearance match; the tooth bottom of the external thread tooth and the tooth top of the internal thread tooth have a clearance match.
[0010] Furthermore, along the radial direction of the oil casing threaded joint, the gap between the crest of the external thread and the bottom of the internal thread is greater than or equal to 0.3 mm and less than or equal to 0.5 mm.
[0011] Furthermore, along the radial direction of the oil casing threaded joint, the gap between the tooth bottom of the external thread and the tooth top of the internal thread is greater than or equal to 0.2 mm and less than or equal to 0.3 mm.
[0012] Furthermore, the top of the external thread has a first plane, the bottom of the internal thread has a second plane, and the first plane and the second plane are both parallel to the thread generatrix; and / or, the bottom of the external thread has a first arcuate surface, the top of the internal thread has a second arcuate surface, and the first arcuate surface and the second arcuate surface are clearance-matched.
[0013] Furthermore, the torque bearing portion includes a first shoulder and a second shoulder sequentially arranged along the axis of the oil casing threaded joint, the first shoulder is arranged on the pipe body, the second shoulder is arranged on the coupling, and the first shoulder is in contact with the second shoulder.
[0014] Further, along the axis of the oil casing threaded joint, the first shoulder and the second shoulder are interference fit, and the interference between the first shoulder and the second shoulder is greater than or equal to 0.1 mm and less than or equal to 0.2 mm.
[0015] Furthermore, the oil casing threaded joint includes two pipe bodies. Along the axis of the oil casing threaded joint, both ends of the coupling are provided with threaded parts and torque bearing parts. The two torque bearing parts are located between the two threaded parts. The two pipe bodies are respectively connected to the two ends of the coupling through the two threaded parts.
[0016] By applying the technical solution of the utility model, on the one hand, compared with the prior art in which only a shaft shoulder is provided to reduce the torque borne by the threaded portion, in the utility model, not only a torque bearing portion is provided to bear part of the torque of the oil casing threaded joint to reduce the torque borne by the threaded portion, but also the tooth profiles of the internal and external threads are improved, and the first bearing surface and the second bearing surface of the interference fit, as well as the first guide surface and the second guide surface of the interference fit are provided, so that the interference position between the internal thread teeth and the external thread teeth is located on both sides of the tooth top, thereby avoiding stress concentration at the positions of the tooth top and the tooth bottom, and the first guide surface and the second guide surface They are all inclined relative to the axis of the oil casing threaded joint, so that the contact area between the internal thread teeth and the external thread teeth can be increased, thereby dispersing the stress to reduce stress concentration, thereby increasing the fatigue resistance of the oil casing threaded joint; on the other hand, compared with the prior art in which the complexity of the processing technology of the threaded joint is increased due to the additional arrangement of a stress release structure, in the utility model, the effect of reducing stress concentration is achieved by changing the tooth shape of the threaded portion, which can avoid the additional arrangement of a structure for reducing stress concentration, thereby reducing the complexity of the processing technology of the threaded joint, reducing the difficulty of processing the oil casing threaded joint, and reducing the processing cost. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The drawings constituting part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings:
[0018] Figure 1 The structure diagram of the oil casing threaded joint in the prior art is shown;
[0019] Figure 2 Shows Figure 1 A partial enlarged view of the A part of the oil casing threaded joint;
[0020] Figure 3 A structural schematic diagram of an embodiment of an oil casing threaded joint of the utility model is shown;
[0021] Figure 4 Shows Figure 3 A partial enlarged view of the B part of the oil casing threaded joint;
[0022] The above drawings include the following reference numerals:
[0023] 1. Pipe body; 2. External thread; 3. First shoulder; 4. Coupling; 5. Internal thread; 6. Second shoulder; 7. First load-bearing surface; 8. First plane; 9. First guide section; 10. Second guide section; 11. First arcuate surface; 13. Second load-bearing surface; 14. Second plane; 16. Fourth guide section; 17. Third guide section; 18. Second arcuate surface; 19. Thread generatrix; 20. Axis; 21. First guide surface; 22. Second guide surface. DETAILED DESCRIPTION
[0024] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present utility model will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.
[0025] like Figure 3 and Figure 4 As shown, an embodiment of the utility model provides an oil casing threaded joint, the oil casing threaded joint has an axis 20, the oil casing threaded joint includes a pipe body 1 and a coupling 4, along the axis 20 of the oil casing threaded joint, a threaded portion and a torque bearing portion are provided between the pipe body 1 and the coupling 4, the pipe body 1 is connected to the coupling 4 through the threaded portion, and the torque bearing portion is used to bear part of the torque and achieve positioning; the threaded portion includes: an external thread 2, which is arranged on the pipe body 1, and the external thread teeth of the external thread 2 have a first bearing surface 7 and a first guide surface 21, along the axis 20 of the oil casing threaded joint, the first bearing surface 7 and the first guide surface 21 are respectively located on both sides of the external thread teeth, and the first bearing surface 7 is relative to the oil casing thread The axis 20 of the joint is vertically arranged, and the first guide surface 21 is inclined relative to the axis 20 of the oil casing threaded joint; the internal thread 5 is arranged on the coupling 4, and the internal thread teeth of the internal thread 5 have a second bearing surface 13 and a second guide surface 22. Along the axis 20 of the oil casing threaded joint, the second bearing surface 13 and the second guide surface 22 are respectively located on both sides of the internal thread teeth, the second bearing surface 13 is vertically arranged relative to the axis 20 of the oil casing threaded joint, and the second guide surface 22 is inclined relative to the axis 20 of the oil casing threaded joint; wherein, the first bearing surface 7 is interference fit with the second bearing surface 13, and at least part of the first guide surface 21 is interference fit with at least part of the second guide surface 22.
[0026] In the above technical solution, on the one hand, compared with the prior art in which only a shaft shoulder is provided to reduce the torque borne by the threaded portion, in the utility model, not only a torque bearing portion is provided to bear part of the torque of the oil casing threaded joint to reduce the torque borne by the threaded portion, but also the tooth profiles of the internal thread 5 and the external thread 2 are improved, and the interference fit first bearing surface 7 and the second bearing surface 13, as well as the interference fit first guide surface 21 and the second guide surface 22 are provided, so that the interference position between the internal thread tooth and the external thread tooth is located on both sides of the tooth top, thereby avoiding stress concentration at the tooth top and the tooth bottom, and the first guide surface 21 and the second guide surface 22 are provided. The surfaces 22 are all inclined relative to the axis 20 of the oil casing threaded joint, so that the contact area between the internal thread teeth and the external thread teeth can be increased, thereby dispersing the stress to reduce stress concentration, thereby increasing the fatigue resistance of the oil casing threaded joint; on the other hand, compared with the prior art in which the complexity of the processing technology of the threaded joint is increased due to the additional arrangement of a stress release structure, in the utility model, the stress concentration is reduced by changing the tooth shape of the threaded portion, and the additional arrangement of a structure for reducing stress concentration can be avoided, thereby reducing the complexity of the processing technology of the threaded joint, reducing the difficulty of processing the oil casing threaded joint, and reducing the processing cost.
[0027] It should be noted that, in the embodiment of the present invention, the first bearing surface 7 is vertically arranged relative to the axis 20 of the oil casing threaded joint, which means that the angle between the first bearing surface 7 and the axis 20 of the oil casing threaded joint is 90°; the second bearing surface 13 is vertically arranged relative to the axis 20 of the oil casing threaded joint, which means that the angle between the second bearing surface 13 and the axis 20 of the oil casing threaded joint is 90°.
[0028] like Figure 4 As shown, in the embodiment of the utility model, from the top of the external thread to the bottom of the external thread, the first guide surface 21 includes a first guide segment 9 and a second guide segment 10 connected to each other, and the angle between the first guide segment 9 and the axis 20 of the oil casing threaded joint is greater than or equal to 35° and less than or equal to 55°, and the angle between the second guide segment 10 and the axis 20 of the oil casing threaded joint is greater than or equal to 50° and less than or equal to 70°; from the top of the internal thread to the bottom of the internal thread, the second guide surface 22 includes a third guide segment 17 and a fourth guide segment 16 connected to each other, and the angle between the third guide segment 17 and the axis 20 of the oil casing threaded joint is greater than or equal to 35° and less than or equal to 55°, and the angle between the fourth guide segment 16 and the axis 20 of the oil casing threaded joint is greater than or equal to 50° and less than or equal to 70°; part of the first guide segment 9 and part of the third guide segment 17 are interference fit.
[0029] Through the above-mentioned arrangement, on the one hand, the first guide section 9 is inclined and the third guide section 17 is inclined, which can increase the contact area between the internal thread and the external thread, thereby dispersing the stress to reduce stress concentration; on the other hand, by setting the inclination angle of the second guide section 10, the second guide section 10 can play a role in transitionally connecting the tooth bottom of the external thread and the first guide section 9, and can avoid the first guide section 9 directly extending to the tooth bottom of the external thread, thereby increasing the area of the first arc surface 11 at the tooth bottom of the external thread, so as to better reduce the stress concentration at the tooth bottom of the external thread; on the other hand, the fourth guide section 16 can play a role in transitionally connecting the third guide section 17 and the tooth bottom of the internal thread.
[0030] Preferably, in an embodiment of the present invention, the angle between the first guide section 9 and the axis 20 of the oil casing threaded joint is 45°, the angle between the second guide section 10 and the axis 20 of the oil casing threaded joint is 60°; the angle between the third guide section 17 and the axis 20 of the oil casing threaded joint is 45°, and the angle between the fourth guide section 16 and the axis 20 of the oil casing threaded joint is 60°.
[0031] Specifically, in the embodiment of the present invention, the sum of the interference between the first bearing surface 7 and the second bearing surface 13 and the interference between the first guide surface 21 and the second guide surface 22 is greater than or equal to 0.15 mm and less than or equal to 0.25 mm.
[0032] In the above technical solution, by setting the sum of the interference between the first bearing surface 7 and the second bearing surface 13 and the interference between the first guide surface 21 and the second guide surface 22, after the pipe body 1 and the coupling 4 are tightened, on the one hand, it can be avoided that the interference fit of the traditional oil casing threaded joint occurs between the tooth top and the tooth bottom, thereby causing the problem of stress concentration in the dangerous part of the pipe body; on the other hand, the increase of the interference contact area can avoid the problem of stress concentration caused by excessive interference.
[0033] It should be noted that, in the embodiment of the utility model, the external thread 2 of the pipe body 1 and the internal thread 5 of the coupling 4 have a radial interference fit, which can bear 20%-40% of the make-up torque of the oil casing threaded joint.
[0034] Generally, after the pipe body 1 and the coupling 4 are tightened, when radial interference occurs between the internal thread and the external thread, stress concentration often occurs between the top and the bottom of the tooth. If the top and the bottom of the tooth are set to an interference fit, the degree of stress concentration between the top and the bottom of the tooth will be magnified. Figure 4As shown, in the embodiment of the utility model, the tooth top of the external thread tooth and the tooth bottom of the internal thread tooth are matched with each other; the tooth bottom of the external thread tooth and the tooth top of the internal thread tooth are matched with each other. In this way, direct contact between the tooth top of the external thread tooth and the tooth bottom of the internal thread tooth can be avoided, and direct contact between the tooth bottom of the external thread tooth and the tooth top of the internal thread tooth can be avoided, thereby alleviating the problem of stress concentration.
[0035] Specifically, in the embodiment of the utility model, along the radial direction of the oil casing threaded joint, the gap between the crest of the external thread and the root of the internal thread is greater than or equal to 0.3 mm, and less than or equal to 0.5 mm. In this way, on the one hand, the problem of loose connection between the pipe body 1 and the coupling 4 caused by the gap between the crest of the external thread and the root of the internal thread is too large can be avoided; on the other hand, the problem of unclear stress concentration caused by the gap between the crest of the external thread and the root of the internal thread is avoided.
[0036] Specifically, in the embodiment of the utility model, along the radial direction of the oil casing threaded joint, the gap between the root of the external thread and the crest of the internal thread is greater than or equal to 0.2 mm, and less than or equal to 0.3 mm. In this way, on the one hand, the problem of loose connection between the pipe body 1 and the coupling 4 caused by the gap between the root of the external thread and the crest of the internal thread is too large can be avoided; on the other hand, the problem of unclear stress concentration caused by the gap between the root of the external thread and the crest of the internal thread is avoided.
[0037] like Figure 4 As shown, in the embodiment of the utility model, the top of the external thread tooth has a first plane 8, and the bottom of the internal thread tooth has a second plane 14. The first plane 8 and the second plane 14 are both parallel to the thread generatrix 19, and there is a gap between the first plane 8 and the second plane 14.
[0038] like Figure 4 As shown, in the embodiment of the present invention, the tooth bottom of the external thread has a first arc surface 11, and the tooth top of the internal thread has a second arc surface 18, and the first arc surface 11 and the second arc surface 18 are clearance-matched.
[0039] In the above technical solution, by setting the tooth bottom of the external thread and the tooth top of the internal thread as an arc structure, the stress concentration at the tooth bottom of the external thread and the tooth top of the internal thread can be alleviated, thereby improving the fatigue resistance of the oil casing threaded joint.
[0040] Preferably, in the embodiment of the present utility model, the first arcuate surface 11 and / or the second arcuate surface 18 is a circular arc surface.
[0041] like Figure 3As shown, in the embodiment of the utility model, the torque bearing portion includes a first shoulder 3 and a second shoulder 6 sequentially arranged along the axis 20 of the oil casing threaded joint, the first shoulder 3 is arranged on the pipe body 1, the second shoulder 6 is arranged on the coupling 4, and the first shoulder 3 is in contact with the second shoulder 6.
[0042] Through the above arrangement, after the pipe body 1 and the coupling 4 are tightened, the first shoulder 3 and the second shoulder 6 are in close contact, which can play the role of buckle positioning. At the same time, the first shoulder 3 and the second shoulder 6 can bear part of the torque of the oil casing threaded joint to reduce the torque borne by the threaded part, so as to reduce the stress level of the threaded part, thereby alleviating the problem of stress concentration in the threaded part and significantly improving the fatigue resistance of the threaded part.
[0043] Preferably, in the embodiment of the utility model, along the axis 20 of the oil casing threaded joint, the first shoulder 3 and the second shoulder 6 are interference fit, and the interference between the first shoulder 3 and the second shoulder 6 is greater than or equal to 0.1 mm, and less than or equal to 0.2 mm. In this way, on the one hand, the problem of low fatigue resistance between the first shoulder 3 and the second shoulder 6 due to excessive interference between the first shoulder 3 and the second shoulder 6 can be avoided; on the other hand, the problem of small torque due to too small interference between the first shoulder 3 and the second shoulder 6 can be avoided, thereby avoiding the problem of poor stress concentration relief effect on the threaded part.
[0044] It should be noted that in the embodiment of the utility model, the torque bearing portion can share 60%-80% of the torque of the oil casing threaded joint, so that the torque borne by the threaded portion only accounts for 20%-40% of the torque of the oil casing threaded joint.
[0045] like Figure 3 As shown, in the embodiment of the utility model, the oil casing threaded joint includes two pipe bodies 1, along the axis 20 of the oil casing threaded joint, both ends of the coupling 4 are provided with threaded parts and torque bearing parts, the two torque bearing parts are located between the two threaded parts, and the two pipe bodies 1 are connected to the two ends of the coupling 4 through the two threaded parts. In this way, the two pipe bodies 1 can be connected through the coupling 4.
[0046] like Figure 1 and Figure 2 As shown in the figure, the inventor knows a kind of oil casing threaded joint (i.e., API type threaded joint), the structure of the joint is also composed of two parts: a pipe 1a and a coupling 4a. The end of the pipe 1a is processed with an external thread 2a and a right-angle end face 3a, and the two ends of the coupling 4a are respectively processed with an internal thread 5a and a torsion-resistant shoulder 6a. Figure 2As shown, the external thread 2a is composed of a bearing surface 7a, a tooth top 8a, a guide surface 9a and a tooth bottom 11a; correspondingly, the internal thread 5a is composed of a bearing surface 12a, a tooth bottom 13a, a guide surface 15a and a tooth top 16a. After the pipe 1a and the coupling 4a are tightened, there is a gap 14a of about 0.2 mm between the tooth top 8a of the external thread and the tooth bottom 13a of the internal thread. At the same time, there is also a gap 10a of about 0.2 mm between the guide surface 9a of the external thread and the guide surface 15a of the internal thread. The setting of this gap is to store thread grease so that the joint can be well lubricated during the process of making and breaking the joint. After the pipe 1a and the coupling 4a are tightened, the external thread 2a and the internal thread 5a are interference fit. Although the bearing surfaces 7a and 12a are in contact, since the bearing surface angle is a right angle, no large contact force will be generated in the case of making and breaking the joint. The contact part mainly occurs between the tooth bottom 11a of the external thread and the tooth top 16a of the internal thread. Since the interference fit between the tooth bottom 11a and the tooth top 16a will amplify the stress concentration between the tooth bottom 11a and the tooth top 16a, and the contact area between the tooth bottom 11a and the tooth top 16a is limited, a large stress concentration will occur between the tooth bottom 11a and the tooth top 16a.
[0047] Therefore, the oil casing threaded joint of the embodiment of the utility model reduces the stress concentration factor of the threaded portion by changing the thread shape, that is, after the pipe body 1 and the coupling 4 are tightened, the first guide surface 21 and the second guide surface 22 of the external thread are in contact, and the first bearing surface 7 and the second bearing surface 13 are in contact. In this way, not only the contact area is increased, but also the direct contact between the top and the bottom of the threaded portion can be avoided, thereby reducing the stress concentration degree under the same force.
[0048] It should be noted that in the embodiment of the utility model, a torque-bearing portion is added to bear part of the torque of the oil casing threaded joint to reduce the torque borne by the threaded portion, and then the stress concentration factor of the threaded portion is reduced by optimizing the thread shape (that is, the first guide surface 21 and the second guide surface 22 are in uniform contact, the first bearing surface 7 and the second bearing surface 13 are in uniform contact, and a certain gap is left between the top and the bottom of the threaded portion, and the first guide surface 21 and the second guide surface 22 are inclined to increase the meshing area between the internal thread and the external thread). Finally, the stress concentration factor of the threaded portion can be controlled below 2.2, so that the oil casing threaded joint has better fatigue resistance.
[0049] From the above description, it can be seen that the above embodiments of the utility model achieve the following technical effects: on the one hand, compared with the prior art in which only a shaft shoulder is provided to reduce the torque borne by the threaded portion, in the utility model, not only a torque-bearing portion is provided to bear part of the torque of the oil casing threaded joint to reduce the torque borne by the threaded portion, but also the tooth profiles of the internal and external threads are improved, and the first bearing surface and the second bearing surface of the interference fit, as well as the first guide surface and the second guide surface of the interference fit are provided, so that the interference position between the internal thread teeth and the external thread teeth is located on both sides of the tooth top, thereby avoiding stress concentration at the positions of the tooth top and the tooth bottom, and the first The first guide surface and the second guide surface are both inclined relative to the axis of the oil casing threaded joint, so that the contact area between the internal thread teeth and the external thread teeth can be increased, thereby dispersing the stress to reduce stress concentration, thereby increasing the fatigue resistance of the oil casing threaded joint; on the other hand, compared with the prior art in which the processing complexity of the threaded joint is increased due to the additional arrangement of a stress release structure, in the utility model, the effect of reducing stress concentration is achieved by changing the tooth shape of the threaded portion, which can avoid the additional arrangement of a structure for reducing stress concentration, thereby reducing the processing complexity of the threaded joint, reducing the processing difficulty of the oil casing threaded joint, and reducing the processing cost.
[0050] The above description is only the preferred embodiment of the utility model, and is not intended to limit the utility model. For those skilled in the art, the utility model can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the utility model shall be included in the protection scope of the utility model.
Claims
1. A threaded joint for oil casing, characterized in that: An oil casing threaded joint has an axis (20), the oil casing threaded joint comprises a pipe body (1) and a coupling (4), a threaded portion and a torque bearing portion are provided between the pipe body (1) and the coupling (4) along the axis (20) of the oil casing threaded joint, the pipe body (1) is connected to the coupling (4) via the threaded portion, and the torque bearing portion is used to bear part of the torque and achieve positioning; The threaded portion comprises: An external thread (2) is arranged on the pipe body (1), the external thread of the external thread (2) having a first bearing surface (7) and a first guide surface (21), along the axis (20) of the oil casing threaded joint, the first bearing surface (7) and the first guide surface (21) are respectively located on both sides of the external thread, the first bearing surface (7) is arranged perpendicularly to the axis (20) of the oil casing threaded joint, and the first guide surface (21) is arranged obliquely to the axis (20) of the oil casing threaded joint; An internal thread (5) is arranged on the coupling (4), the internal thread teeth of the internal thread (5) having a second bearing surface (13) and a second guide surface (22), along the axis (20) of the oil casing threaded joint, the second bearing surface (13) and the second guide surface (22) are respectively located on both sides of the internal thread teeth, the second bearing surface (13) is arranged perpendicularly relative to the axis (20) of the oil casing threaded joint, and the second guide surface (22) is arranged obliquely relative to the axis (20) of the oil casing threaded joint; The first bearing surface (7) and the second bearing surface (13) are in interference fit, and at least a portion of the first guide surface (21) and at least a portion of the second guide surface (22) are in interference fit.
2. The oil casing threaded joint according to claim 1, characterized in that: From the crest of the external thread to the root of the external thread, the first guide surface (21) comprises a first guide section (9) and a second guide section (10) connected to each other, the angle between the first guide section (9) and the axis (20) of the oil casing threaded joint is greater than or equal to 35° and less than or equal to 55°, and the angle between the second guide section (10) and the axis (20) of the oil casing threaded joint is greater than or equal to 50° and less than or equal to 70°; From the crest of the internal thread to the root of the internal thread, the second guide surface (22) comprises a third guide section (17) and a fourth guide section (16) connected to each other, the angle between the third guide section (17) and the axis (20) of the oil casing threaded joint is greater than or equal to 35° and less than or equal to 55°, and the angle between the fourth guide section (16) and the axis (20) of the oil casing threaded joint is greater than or equal to 50° and less than or equal to 70°; Part of the first guide section (9) and part of the third guide section (17) are interference fit.
3. The oil casing threaded joint according to claim 1, characterized in that: The sum of the interference between the first bearing surface (7) and the second bearing surface (13) and the interference between the first guide surface (21) and the second guide surface (22) is greater than or equal to 0.15 mm and less than or equal to 0.25 mm.
4. The oil casing threaded joint according to any one of claims 1 to 3, characterized in that: The top of the external thread tooth and the bottom of the internal thread tooth are clearance-matched; The tooth bottom of the external thread tooth is clearance-matched with the tooth top of the internal thread tooth.
5. The oil casing threaded joint according to claim 4, characterized in that: Along the radial direction of the oil casing threaded joint, the gap between the crest of the external thread and the bottom of the internal thread is greater than or equal to 0.3 mm and less than or equal to 0.5 mm.
6. The oil casing threaded joint according to claim 4, characterized in that: Along the radial direction of the oil casing threaded joint, the gap between the tooth bottom of the external thread and the tooth top of the internal thread is greater than or equal to 0.2 mm and less than or equal to 0.3 mm.
7. The oil casing threaded joint according to claim 4, characterized in that: The crest of the external thread has a first plane (8), the root of the internal thread has a second plane (14), and the first plane (8) and the second plane (14) are both parallel to the thread generatrix (19); and / or, The tooth bottom of the external thread tooth has a first arcuate surface (11), the tooth top of the internal thread tooth has a second arcuate surface (18), and the first arcuate surface (11) and the second arcuate surface (18) are clearance-matched.
8. The oil casing threaded joint according to any one of claims 1 to 3, characterized in that: The torque bearing portion comprises a first shoulder (3) and a second shoulder (6) which are arranged in sequence along the axis (20) of the oil casing threaded joint, wherein the first shoulder (3) is arranged on the pipe body (1), and the second shoulder (6) is arranged on the coupling (4), and the first shoulder (3) is in contact with the second shoulder (6).
9. The oil casing threaded joint according to claim 8, characterized in that: Along the axis (20) of the oil casing threaded joint, the first shoulder (3) and the second shoulder (6) are interference fit, and the interference between the first shoulder (3) and the second shoulder (6) is greater than or equal to 0.1 mm and less than or equal to 0.2 mm.
10. The oil casing threaded joint according to any one of claims 1 to 3, characterized in that: The oil casing threaded joint comprises two pipe bodies (1), along the axis (20) of the oil casing threaded joint, the two ends of the coupling (4) are provided with the threaded portion and the torque bearing portion, the two torque bearing portions are located between the two threaded portions, and the two pipe bodies (1) are respectively connected to the two ends of the coupling (4) through the two threaded portions.