CN216767298U

CN216767298U - Thread tooth-shaped structure and threaded connection structure

Info

Publication number: CN216767298U
Application number: CN202121938011.6U
Authority: CN
Inventors: 刘国辉; 张海燕; 胡海青; 姜涛; 米永峰; 姜海龙; 石晓霞; 张行钢
Original assignee: Baotou Iron and Steel Group Co Ltd
Current assignee: Baotou Iron and Steel Group Co Ltd
Priority date: 2021-08-18
Filing date: 2021-08-18
Publication date: 2022-06-17
Anticipated expiration: 2031-08-18

Abstract

The utility model discloses a thread tooth profile structure and a thread connection structure, wherein the tooth profile of the thread tooth profile structure is in a buttress shape, and a first distance H1 between the tooth crest and the middle diameter surface and a second distance H2 between the tooth bottom surface and the middle diameter surface meet the following requirements: H2-H1 is 0.03 mm-0.05 mm; and the arc transition radius between the bearing surface and the tooth crest surface of the thread tooth-shaped structure is equal to the arc transition radius between the bearing surface and the tooth bottom surface, and the arc transition radius between the guide surface and the tooth crest surface is equal to the arc transition radius between the guide surface and the tooth bottom surface. The thread connecting structure which is meshed with each other by utilizing the thread tooth-shaped structures has a tiny gap between the tooth top and the tooth bottom, the bearing surfaces or the guide surfaces are contacted with each other, the sealing capability can be improved, the gap can not change along with the increase of tensile load, the sealing performance can be ensured to be unchanged under the tensile load, and the tensile capability is higher.

Description

Thread tooth-shaped structure and threaded connection structure

Technical Field

The utility model belongs to the technical field of threaded connection in the petroleum industry, particularly relates to a threaded tooth-shaped structure and a threaded connection structure, and particularly relates to a threaded connection structure with high connection strength.

Background

The oil pipe in API (American Petroleum institute) 5CT standard mainly has two structures, namely an un-thickened oil pipe (NU) and an external thickened oil pipe (EU), and is widely applied to the oil well pipe industry.

As shown in figure 1, the threaded connection structure of the non-thickened oil pipe is characterized in that external threads are processed on the outer surface of a pipe end, internal threads are processed on the inner surface of a coupling, and the coupling and the pipe are connected through threads to form a pipe column. The tooth profile of the thread is as shown in fig. 2, the tooth profile is an equilateral triangle, H is 0.866p, the tooth top and the tooth bottom are processed into transition arcs with different radiuses, the radiuses of the two arcs have a certain difference, the two tooth sides are contacted with each other after the thread is meshed, and a gap exists between the tooth top and the tooth bottom. As the tightening torque increases, the flank contact pressure increases, and the sealing performance of the threaded connection also increases. However, when the threaded connection has an axial tensile load, as shown in fig. 3, the thread tends to slip in the flank direction, and the thread slips with an increase in the axial load, so that there is a drawback that the threaded connection has a lower tensile resistance than the pipe body.

The threaded connection structure of the external thickened oil pipe (EU) is characterized in that the outer diameter of the pipe is enlarged and the inner diameter of the pipe is unchanged by upsetting the end of the pipe, and then threads are processed on the outer surface of the upset part. Its advantage is high tension-resisting power of joint, and can reach or exceed the tension-resisting level of main body of pipe. However, the disadvantages include the following:

1. the manufacturing process of the pipe is complex;

2. the unqualified product of thread processing needs to be upset again;

3. the overall weight of the pipe column is improved;

4. the coupling outer diameter is increased, and a larger wellhead diameter is required;

5. the user cannot repair the damaged threads autonomously.

The prior art also has a buttress thread connection structure, as shown in fig. 4, which is characterized in that the bearing surfaces of the tooth top and the tooth bottom are parallel to the axis, and an interdental gap is arranged between the guide surfaces, when the thread is subjected to an axial load, the interdental gap becomes larger or smaller, and thread grease in the gap cannot effectively block pressure, so that sealing failure is caused. In order to improve the sealing performance of the joint, an air-tight seal threaded joint is also provided in the field of oil pipes, a metal seal structure is added, but the requirements on machining precision are high, the machining difficulty is high, and the cost is high.

SUMMERY OF THE UTILITY MODEL

In view of the problems in the prior art, it is an object of the present invention to provide a threaded connection structure having higher connection strength, good sealing performance, and good workability. The method solves the problems that the connection strength of the non-thickened oil pipe is low, the external thickened oil pipe needs upsetting, the sealing performance of the buttress thread is low and the cost of the special buckle is high.

In one aspect, the utility model provides a thread tooth profile structure, wherein the tooth profile of the thread tooth profile structure is in a partial trapezoid shape, the bearing surface of the thread tooth profile structure is at an angle of 3 degrees, and the guide surface of the thread tooth profile structure is at an angle of 45 degrees; wherein the tooth width and the groove width at the middle diameter surface (1) of the thread tooth-shaped structure are the same, and a first distance H1 between the tooth crest (2) and the middle diameter surface (1) of the thread tooth-shaped structure and a second distance H2 between the tooth bottom surface (3) and the middle diameter surface (1) of the thread tooth-shaped structure satisfy the following conditions: H2-H1 is 0.03 mm-0.05 mm; and the bearing surface and the guide surface of the thread tooth-shaped structure and the tooth top surface (2) and the tooth bottom surface (3) of the thread tooth-shaped structure are in arc transition, the requirement that the arc transition radius R1 between the bearing surface and the tooth top surface (2) is equal to the arc transition radius R2 between the bearing surface and the tooth bottom surface (3) is met, and the arc transition radius R3 between the guide surface and the tooth top surface (2) is equal to the arc transition radius R4 between the guide surface and the tooth bottom surface (3) is met.

In another aspect, the present invention provides a threaded connection structure, which includes an external thread and an internal thread that are matched with each other to be in threaded connection, wherein the external thread and the internal thread have the same tooth form and are both the thread tooth form structure described above.

The thread connecting structure provided by the utility model comprises an external thread and an internal thread which have the same tooth forms and are in partial trapezoidal shape and are matched with each other for threaded connection, the tooth forms of the external thread and the internal thread meet the requirement that the distance between a tooth crest and a middle diameter surface and the distance between a tooth bottom surface and the middle diameter surface are different by 0.03 mm-0.05 mm, the arc transition radius between the bearing surface and the tooth crest surface is equal to the arc transition radius between the bearing surface and the tooth bottom surface, and the arc transition radius between the guide surface and the tooth crest surface is equal to the arc transition radius between the guide surface and the tooth bottom surface, so that after the external thread and the internal thread of the thread connecting structure are mutually meshed, a gap of 0.03 mm-0.05 mm exists between the tooth crest and the tooth bottom surface, the bearing surface or the guide surface is mutually contacted, the surface contact pressure is increased along with the increase of the thread passing amount, the sealing capacity can be improved, and the surface pressure of the bearing surface or the guide surface of the thread connecting structure is increased under the axial tensile load, axial load is counteracted, and the possibility of mutual sliding between the inner thread and the outer thread does not exist, so that the sealing capability cannot be reduced; in addition, the small gap between the tooth top and the tooth bottom can be filled with thread grease, the gap cannot change along with the increase of the tensile load, and the sealing performance under the tensile load can be ensured to be unchanged. The threaded connection structure provided by the utility model also has higher tensile strength and can exceed the tensile strength of the pipe body. The thread precision requirement of the threaded connection structure is lower than that of an airtight joint, and the control requirements of the threaded connection structure for screwing on and screwing off the well in the field are equivalent to those of the API buttress thread no matter in factory processing, so that the processing and using difficulty can be reduced; moreover, the internal and external thread structures of the threaded connection structure are completely the same, and the internal and external threads can be simultaneously processed by adopting the same thread chasers.

Drawings

FIG. 1 is a schematic view of a threaded connection structure of an API non-thickened tubing;

FIG. 2 is a schematic view of a thread profile structure of an API non-thickened oil pipe;

FIG. 3 is a schematic diagram of the movement tendency of an API non-thickened tubing under tensile load;

FIG. 4 is a schematic view of the profile structure of an API buttress thread;

FIG. 5 is a schematic view of a thread profile configuration provided by one embodiment of the present invention;

FIG. 6 is a schematic diagram illustrating a threaded connection according to an embodiment of the present invention after engagement of internal and external threads;

FIG. 7 is a schematic view of a threaded connection provided by one embodiment of the present invention;

in the figure:

H. tooth profile height; p, thread pitch;

h1, distance between the tooth crest and the middle diameter surface; h2, distance between the tooth bottom surface and the middle diameter surface;

r1, the transition arc radius of the tooth top surface and the bearing surface; r2, the transition arc radius of the tooth bottom surface and the bearing surface; r3, the transition arc radius of the tooth crest and the guide surface; r4, the transition arc radius of the tooth bottom surface and the guide surface;

1. a medium diameter surface; 2. tooth crest; 3. the tooth bottom surface.

Detailed Description

The detailed description below is described in conjunction with the appended drawings.

Fig. 5 is a schematic view of the thread profile structure provided by the present invention, wherein 1 is a pitch diameter surface, 2 is a crest surface, and 3 is a root surface. As shown in fig. 5, the surface of the thread tooth profile structure connected to the bottom land 3 on the left side of the crest 2 is a bearing surface, and the surface of the thread tooth profile structure connected to the bottom land 3 on the right side of the crest 2 is a guide surface. Assuming that the distance H between the tooth crest 2 and the tooth bottom surface 3 is the tooth height, the distance H1 between the tooth crest 2 and the intermediate diameter surface 1 is the upper half tooth height, and the distance H2 between the tooth bottom surface 3 and the intermediate diameter surface 1 is the lower half tooth height, H, H1 and H2 satisfy the following relationships: (a) H-H1 + H2; (b) H2-H1 is 0.03 mm-0.05 mm. In the thread tooth-shaped structure, the horizontal distance P between the intersection point of the middle diameter surface 1 and two adjacent bearing surfaces is a thread pitch, and the horizontal distance between the intersection point of the middle diameter surface 1 and the two adjacent bearing surfaces and the intersection point of the guide surface between the two adjacent bearing surfaces is P/2, namely the tooth width and the groove width at the middle diameter surface 1 of the thread tooth-shaped structure are the same. The transition arc radius R1 of the tooth top surface 2 and the bearing surface, the transition arc radius R2 of the tooth bottom surface 3 and the bearing surface, the transition arc radius R3 of the tooth top surface 2 and the guide surface, and the transition arc radius R4 of the tooth bottom surface 3 and the guide surface satisfy the following relations: (c) r1 ═ R2; (d) r3 ═ R4.

Fig. 6 shows a schematic structural diagram of the threaded connection structure provided by the utility model after the internal threads and the external threads are meshed, wherein the internal threads and the external threads of the threaded connection structure have the same tooth form and are all buttress tooth forms shown in fig. 5. When the internal thread and the external thread are meshed, the guide surfaces of the internal thread and the external thread are contacted with each other, the bearing surfaces are also contacted with each other, a small gap exists between the tooth crest of the external thread and the tooth bottom of the internal thread, and the size of the gap is H2-H1 which is 0.03 mm-0.05 mm. Because the bearing surface or the guide surface are mutually contacted, the surface contact pressure is increased along with the increase of the interference of the threads, the sealing capacity can be improved, the surface pressure of the bearing surface or the guide surface is increased under the axial tensile load of the threaded connection structure, the axial load is offset, the possibility of mutual sliding between the inner threads and the outer threads does not exist, and the sealing capacity cannot be reduced; in addition, the small gap between the tooth top and the tooth bottom is filled with thread grease, and the gap cannot change along with the increase of the tensile load, so that the sealing performance under the tensile load can be ensured to be unchanged.

Fig. 7 is a schematic view of a threaded connection provided by the present invention, which employs the external thread and the internal thread shown in fig. 6. As shown in fig. 7, the threaded connection is a tapered thread with a 1:16 taper consistent with the API thread, the pitch P is 3.175mm, and the external thread tail-out naturally disappears. The adoption of the taper thread can provide better screwing torque, the taper is too small, the thread length is increased, the screwing process is lengthened, and if the taper is too large, the thread length is reduced, and the connection strength is insufficient, so that the utility model adopts 1:16 of API standard. The advantage of the tail buckle being naturally eliminated is that the joint strength is increased and the internal thread completely covers the external thread, i.e. all external threads participate in the engagement.

Screw connection structure (i.e. screw connection joint)) The sealing capability of the screw thread is determined by two main aspects, namely the first aspect is the contact pressure of the thread surface, the sealing capability is stronger when the surface contact pressure is larger, the surface contact pressure can be improved by improving the interference of the thread, but the consideration is simultaneously that the surface pressure cannot exceed the yield strength of the material, otherwise, the thread sticking is easily caused. Therefore, the most direct means for improving the sealing performance of the joint is to reasonably improve the interference of the threads. On the other hand, the sealing capacity of the joint depends on the leakage path between the tooth profiles, which, according to a known consensus, is proportional to the ratio of the length of the leakage path to the cross-sectional area of the sealing path. The sectional area of the tooth-shaped leakage channel is 0.0278mm²Less than 0.0490mm cross-sectional area of 8 threads per inch and 10 threads per inch round threads²And 0.0411mm²。

Examples

For example, 88.9 × 6.45N80Q, the thread taper is 1:16, P is 3.175mm, H is 1.24mm, H1 is 0.605mm, H2 is 0.635mm, the bearing face angle is 3 °, the guide face angle is 45 °, R1 — R2 is 0.25mm, R3 — R4 is 0.64mm, and the thread interference is 0.45 mm. The total length of the external thread is 65mm, and the length of the coupling is 156 mm. The specification joint was subjected to a tensile to failure test with a failure load of 1098.6KN, greater than the minimum 922KN of the API 5C3 standard.

Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art will understand that various changes, modifications and substitutions can be made without departing from the spirit and scope of the utility model as defined by the appended claims. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A thread tooth-shaped structure is characterized in that the tooth shape of the thread tooth-shaped structure is a partial trapezoid, the bearing surface of the thread tooth-shaped structure is at an angle of 3 degrees, and the guide surface of the thread tooth-shaped structure is at an angle of 45 degrees;

wherein the tooth width and the groove width at the middle diameter surface (1) of the thread tooth-shaped structure are the same, and a first distance H1 between the tooth crest (2) and the middle diameter surface (1) of the thread tooth-shaped structure and a second distance H2 between the tooth bottom surface (3) and the middle diameter surface (1) of the thread tooth-shaped structure satisfy the following conditions: H2-H1 =0.03 mm-0.05 mm; and is

The bearing surface and the guide surface of the thread tooth-shaped structure and the tooth top surface (2) and the tooth bottom surface (3) of the thread tooth-shaped structure are in circular arc transition, the circular arc transition radius R1 between the bearing surface and the tooth top surface (2) is equal to the circular arc transition radius R2 between the bearing surface and the tooth bottom surface (3), and the circular arc transition radius R3 between the guide surface and the tooth top surface (2) is equal to the circular arc transition radius R4 between the guide surface and the tooth bottom surface (3).