Corrosion-resistant screwed joint

Abstract

The utility model belongs to the field of oil casing processing and manufacturing, and particularly relates to a corrosion-resistant screwed joint which comprises a male end and a coupling, and the outer surface of the male end is provided with a male thread, a pipe end cylindrical surface, a male end sealing surface and a male end shoulder; coupling shoulders and coupling threads which are symmetrically distributed are manufactured on the inner surface of the coupling, coupling tool withdrawal grooves and coupling sealing faces are manufactured between the coupling shoulders and the coupling threads, the male end is provided with a pipe body upsetting section, and the male threads, the pipe end cylindrical surface, the male end sealing faces and the male end shoulders are manufactured on the pipe body upsetting section. The male threads and the coupling threads are all full-top complete tooth-shaped threads, and the coupling shoulder is of a wedge-shaped shoulder structure. According to the threaded connector, the full-top complete tooth-shaped threads are designed, and a cone-to-cone metal sealing structure and a wedge-shaped shoulder structure are designed in the connector, so that the bearing surface of the shoulder of the connector is wider, the over-twisting resistance is high, the corrosion-resistant period is longer, and the using economical efficiency is better.

Description

Technical Field

[0001] The utility model belongs to the field of petroleum casing processing and manufacturing, and relates to a corrosion-resistant threaded joint. Background Art

[0002] According to the special needs of oil field users, in the field of oil casing manufacturing and processing, a variety of non-API threaded joint connection structures have been born, especially special threaded joints with air sealing capabilities. A structure with interference fit is designed inside the joint to achieve the air sealing function of the joint.

[0003] In the case of high concentration H2S, CO2 and other corrosive media, designers can only use expensive nickel-based, 13Cr, composite pipes and other pipes to deal with corrosion. In general corrosive environments, designers comprehensively consider the corrosion rate and use cost of the casing, and choose thicker casing to make ordinary carbon steel casing have better cost performance.

[0004] In order to extend the service life of carbon steel casing and avoid local corrosion on the inner wall of the casing, the inner wall of the casing is usually surface treated to achieve uniform corrosion as much as possible. However, due to the processing of threads, a weak area of ​​wall thickness is naturally formed at the casing joint. During the service of the casing, the weak area of ​​wall thickness becomes the concentrated area of ​​casing corrosion failure.

[0005] Chinese patent CN204266942U discloses a BHC quick sleeve threaded joint, such as Figure 7 As shown, the structure is provided with a tapered pipe external thread that gradually shrinks from the outside to the inside on the outer diameter of the casing joint, and an external shoulder transition surface and an external torque shoulder are provided in sequence. The inner diameter of the coupling is provided with a tapered pipe internal thread that gradually shrinks from the outside to the inside and matches the tapered pipe external thread, and a back-off groove, an internal shoulder transition surface and an internal torque shoulder are provided in sequence. Although this structure strengthens the compression and bending resistance of the thread and improves the connection strength, the wall thickness of the threaded casing part gradually decreases from the outside to the inside, the wall thickness of the end portion decreases significantly, the thread tooth height of the end portion decreases significantly, and the shoulder surface is a vertical surface, and the internal corrosive pressure medium can easily enter the thread area, resulting in poor corrosion resistance in the weak area, which is very likely to cause corrosion failure.

[0006] Therefore, it is necessary to develop a threaded joint with good corrosion resistance. Utility Model Content

[0007] The purpose of the utility model is to overcome the shortcomings of the prior art and provide a corrosion-resistant threaded joint. By roughing and thickening the pipe end, a full-top complete toothed thread can be designed in the rough section of the pipe body, and the pipe end cylindrical wall thickness at the thread end of the rough section of the pipe body can be made not less than 80% of the pipe body wall thickness. The ordinary carbon steel casing of the threaded joint of the utility model is used in a general corrosive environment, which can increase the service life of the threaded joint in the corrosive environment.

[0008] The technical solution adopted by the utility model to solve the technical problem is:

[0009] A corrosion-resistant threaded joint comprises a male end and a coupling, wherein the outer surface of the male end is provided with a male thread, a pipe end cylindrical surface, a male end sealing surface and a male end shoulder; the inner surface of the coupling is provided with a symmetrically distributed coupling shoulder and coupling thread, a coupling back-cut groove and a coupling sealing surface are provided between the coupling shoulder and the coupling thread, the tooth top of the coupling thread is meshed with the tooth bottom of the male thread, the pipe end cylindrical surface, the male end sealing surface and the male end shoulder constitute a male end sealing structure, and the coupling back-cut groove, the coupling sealing surface and the coupling shoulder constitute a coupling The male end sealing structure and the coupling sealing structure are cone-to-cone sealing forms, the male end sealing surface fits with the coupling sealing surface, and the coupling shoulder fits with the male end shoulder; the male end has a pipe body pier section, the male thread, the pipe end cylindrical surface, the male end sealing surface, and the male end shoulder are made on the pipe body pier section, the male thread and the coupling thread are both full-top complete toothed threads, the male end shoulder and the coupling shoulder are wedge-shaped shoulder structures, and the angle β between the shoulder surface and the vertical plane is 10°~20°.

[0010] Furthermore, the roughening transition angle α of the roughening section of the pipe body is 5-15°, the roughening coefficient e is 2-5%, and the wall thickness coefficient k of the cylinder at the pipe end is ≥80%.

[0011] Furthermore, the overall length of the male end sealing structure is 15 to 20 mm, wherein the sealing length of the male end sealing surface is 5 to 10 mm, and the sealing taper is 1 / 10 to 1 / 3.

[0012] Furthermore, the overall length of the coupling sealing structure is 20 to 25 mm, wherein the sealing length of the coupling sealing surface is 10 to 15 mm, and the sealing taper is 1 / 10 to 1 / 3.

[0013] Furthermore, the pitch of the male thread and the coupling thread are both 5 to 8 teeth per inch, the tooth height is 1.0 to 2.0 mm, and the thread taper is 1 / 12 to 1 / 16.

[0014] Furthermore, considering the safety of the joint under load, the thread bearing area of ​​the male thread is not less than 1.2 times the cross-sectional area of ​​the pipe body; the cross-sectional area of ​​the coupling retreat groove is not less than 1.2 times the cross-sectional area of ​​the pipe body.

[0015] The advantages and positive effects of the utility model are:

[0016] (1) The corrosion-resistant threaded joint of the utility model has a casing pipe end that has been roughened and thickened, and the processed male threads are all full-top complete toothed threads. The thickness of the pipe end cylinder at the thinnest part of the pipe end wall can reach more than 80% of the pipe body wall thickness, and a metal interference sealing structure and a wedge-shaped shoulder structure are designed inside the joint. Compared with the traditional non-roughened and thickened threaded joint, the male end shoulder bearing surface is wider and its anti-torque ability is stronger.

[0017] (2) The threaded joint of the utility model adopts a roughening and post-processing method, which effectively increases the thickness of the joint end and can effectively extend the service life in a corrosive environment. Taking into account the use cost and corrosion rate of the casing, the utility model joint enables ordinary carbon steel casing to have a better cost-effectiveness in dealing with general corrosive environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the structure of the corrosion-resistant threaded joint of the utility model;

[0019] Figure 2 This is a first schematic diagram of the male end of the corrosion-resistant threaded joint of the utility model;

[0020] Figure 3 This is a second schematic diagram of the male end of the corrosion-resistant threaded joint of the utility model;

[0021] Figure 4 This is a third schematic diagram of the male end of the corrosion-resistant threaded joint of the utility model;

[0022] Figure 5 It is a schematic diagram of a coupling of the corrosion-resistant threaded joint of the utility model;

[0023] Figure 1 to Figure 5 The following figure marks are included: 1 is a male end, 1-1 is a male thread, 1-2 is a male end sealing surface, 1-3 is a male end shoulder, 1-4 is a pipe end cylindrical surface, 1-5 is a pipe body pier rough section, 2 is a coupling, 2-1 is a coupling thread, 2-2 is a coupling sealing surface, 2-3 is a coupling shoulder, and 2-4 is a coupling back cutter groove.

[0024] Figure 6 This is a schematic diagram of a specific embodiment of the corrosion-resistant threaded joint of the utility model;

[0025] Figure 7 This is a schematic diagram of the structure of Chinese patent CN204266942U;

[0026] Figure 7The following figure marks are included: 1-casing joint, 2-coupling, 3-taper tube internal thread, 4-knife groove, 5-inner shoulder transition surface, 6-inner torque shoulder, 7-taper tube external thread, 8-smooth inner wall transition surface, 9-external torque shoulder, 10-external shoulder transition surface. DETAILED DESCRIPTION

[0027] The present invention will be further described in detail below through specific embodiments. The following embodiments are merely descriptive and not restrictive, and the protection scope of the present invention cannot be limited by them.

[0028] like Figure 1 A corrosion-resistant threaded joint shown includes a male end 1 and a coupling 2. The ordinary carbon steel sleeve of the threaded joint is used in a general corrosive environment and can increase the service life of the threaded joint in the corrosive environment.

[0029] like Figure 1-Figure 4 The outer surface of the male end 1 shown is provided with a male thread 1-1, a male end sealing surface 1-2, a male end shoulder 1-3, and a pipe end cylindrical surface 1-4; the male end 1 has a pipe body pier section 1-5, the pier transition angle α of the pipe body pier section 1-5 is 5° to 15°, the pier coefficient is 2 to 5%, and the wall thickness coefficient of the pipe end cylindrical surface 1-4 is ≥80%. The male thread 1-1, the male end sealing surface 1-2, the male end shoulder 1-3, and the pipe end cylindrical surface 1-4 are formed on the pipe body pier section 1-5, and the male thread 1-1 and the coupling thread 2-1 are both full-top complete tooth-shaped threads. The male end shoulder bearing surface of the threaded joint of the utility model is wider, and the joint has a higher anti-torque capacity. The pitch of the male thread 1-1 and the coupling thread 2-1 is 5 to 8 teeth per inch, the tooth height is 1.0 to 2.0 mm, and the thread taper is 1 / 12 to 1 / 16.

[0030] like Figure 1 and Figure 5 The coupling 2 shown has symmetrically distributed coupling shoulders 2-3 and coupling threads 2-1 formed on the inner surface of the coupling, coupling backing grooves 2-4 and coupling sealing surfaces 2-2 formed between the coupling shoulders 2-3 and the coupling threads 2-1, and the tooth tops of the coupling threads 2-1 mesh with the tooth bottoms of the male threads 1-1.

[0031] The male end sealing surface 1-2, the male end shoulder 1-3 and the pipe end cylindrical surface 1-4 constitute the male end sealing structure, and the overall length of the male end sealing structure is 15 to 20 mm, of which the sealing length of the male end sealing surface 1-2 is 5 to 10 mm, and the sealing taper is 1 / 10 to 1 / 3. The coupling sealing surface 2-2, the coupling shoulder 2-3 and the coupling backing groove 2-4 constitute the coupling sealing structure, and the overall length of the sealing structure is 20 to 25 mm, of which the sealing length of the coupling sealing surface 2-2 is 10 to 15 mm, and the sealing taper is 1 / 10 to 1 / 3. The male end sealing structure and the coupling sealing structure are cone-to-cone sealing forms, the coupling shoulder 2-3 fits with the male end shoulder 1-3, the coupling shoulder 2-3 is a wedge-shaped shoulder structure, and the angle β between the shoulder surface and the vertical plane is 10° to 20°. The male end sealing surface 1-2 fits with the coupling sealing surface 2-2, which can ensure good sealing of the end of the threaded joint, thereby improving the corrosion resistance of the joint. When the joint is tightened, the male end fits with the sealing surface of the coupling and is in an interference contact state. The length of the male end sealing surface 1-2 is less than the length of the coupling sealing surface 2-2. The entire male end sealing surface is in a compressed state. The wedge-shaped shoulder structure increases the radial contact stress under the action of the axial force, which strengthens the sealing performance of the joint.

[0032] The threaded joint is pre-roughened before processing. The calculation parameters of the roughened outer diameter and length include thread tooth height, taper, thread length, etc. The casing end is roughened and thickened, and its roughened outer diameter D1 is calculated according to the formula: D1=D-2*t+2*k*t+L*T+2*H+Δd, where the casing diameter is D, the wall thickness is t, the thread taper is T, and the thread tooth height is H.

[0033] The casing end upsetting coefficient e satisfies e=(D1-D) / D=2-5%. Considering the machining allowance and ellipse, the casing end upsetting diameter adjustment amount Δd=1-3 mm.

[0034] The cross-sectional area of ​​the pipe body S0 = π*t*(Dt), the thread load area S1 and the thread length L, pitch p, load tooth height h, equivalent mid-diameter D p Related factors,

[0035]

[0036] Among them, D p is the equivalent diameter of the tapered thread, D a , D b They are respectively the middle diameters of the large end and small end of the full top thread.

[0037]

[0038] The bearing area S2 of the coupling 2 refers to the cross-sectional area of ​​the coupling undercut 2 - 4 , which is calculated based on the annular area formed by the undercut d and the outer diameter W of the coupling 2 .

[0039] S2=π*(W 2 -d 2 ) / 4

[0040] Taking into account the safety of the joint under load, the thread bearing area of ​​the male thread 1-1 is not less than 1.2 times the cross-sectional area of ​​the pipe body; the cross-sectional area at the coupling recess 2-4 is not less than 1.2 times the cross-sectional area of ​​the pipe body.

[0041] Taking the pipe body specification of 177.8*10.36mm as an example, the roughening transition angle α of the pipe body roughening section 1-5 is 10°, the roughening coefficient is 3%, and the wall thickness coefficient of the end of the pipe body roughening section 1-5 is 80%. According to the above formula, if Figure 6 As shown, the wall thickness t of the male end 1 is 10.36 mm, and the end wall thickness t1 is 10.36*80%=8.29 mm. The outer diameter D of the male end 1 is 177.8 mm, and the outer diameter D1 of the tube body pier section 1-5 is 177.8*1.03=183.1 mm.

[0042] The minimum thread length L of the pipe body pier rough section 1-5 is 96mm. The pitch is 5 teeth per inch, the tooth height is 1.50mm, the effective load-bearing tooth height is 1.30mm, the thread taper T is 1 / 12, the sealing length is 8mm, and the sealing taper is 1 / 10. According to the safety principle of thread and coupling load, considering the sealing length and other processing factors, the minimum length of the pipe end pier rough section is 118mm.

[0043] The diameter d of the coupling recess 2-4 is 177.26 mm, the outer diameter W of the coupling 2 is 199.40 mm, the length of the hole in the coupling 2 is 38 mm, and the length of the coupling 2 is 278 mm.

[0044] The use of the utility model:

[0045] When the corrosion-resistant threaded joint of the utility model is screwed together, part of the male thread 1-1 enters the coupling backing groove 2-4 without interference, and the male end sealing surface 1-2 slides against the coupling sealing surface 2-2 and generates radial contact stress. This process continues until the male end shoulder 1-3 contacts the coupling shoulder 2-3, and the torque surges to reach the set value and stops.

[0046] The above is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several modifications and improvements without departing from the concept of the present invention, which all fall within the scope of protection of the present invention.

Claims

1. A corrosion-resistant threaded joint, comprising a male end (1) and a coupling (2), wherein the outer surface of the male end (1) is provided with a male thread (1-1), a male end sealing surface (1-2), a male end shoulder (1-3), and a pipe end cylindrical surface (1-4); the inner surface of the coupling (2) is provided with symmetrically distributed coupling shoulders (2-3) and coupling threads (2-1), a coupling undercut groove (2-4) and a coupling sealing surface (2-2) are provided between the coupling shoulders (2-3) and the coupling threads (2-1), and the tooth top of the coupling threads (2-1) is aligned with the male thread. The tooth bottoms of the groove (1-1) are meshed and matched, the male end sealing surface (1-2), the male end shoulder (1-3) and the pipe end cylindrical surface (1-4) constitute a male end sealing structure, the coupling retreat groove (2-4), the coupling sealing surface (2-2) and the coupling shoulder (2-3) constitute a coupling sealing structure, the male end sealing structure and the coupling sealing structure are cone-to-cone sealing forms, the male end sealing surface (1-2) is in contact with the coupling sealing surface (2-2), the coupling shoulder (2-3) is in contact with the male end shoulder (1-3), and the characteristics are: The male end (1) has a pipe body pier section (1-5), the male thread (1-1), the pipe end cylindrical surface (1-4), the male end sealing surface (1-2), and the male end shoulder (1-3) are formed on the pipe body pier section (1-5), the male thread (1-1) and the coupling thread (2-1) are both full-top complete toothed threads, the male end shoulder (1-3) and the coupling shoulder (2-3) are wedge-shaped shoulder structures, and the angle β between the shoulder surface and the vertical plane is 10° to 20°.

2. The corrosion-resistant threaded joint according to claim 1, characterized in that: The roughening transition angle α of the pipe body roughening section (1-5) is 5° to 15°, the roughening coefficient is 2 to 5%, and the wall thickness coefficient of the pipe end cylinder (1-4) is ≥80%.

3. The corrosion-resistant threaded joint according to claim 1, characterized in that: The overall length of the male end sealing structure is 15 to 20 mm, wherein the sealing length of the male end sealing surface (1-2) is 5 to 10 mm, and the sealing taper is 1 / 10 to 1 / 3.

4. The corrosion-resistant threaded joint according to claim 1, characterized in that: The overall length of the coupling sealing structure is 20 to 25 mm, wherein the sealing length of the coupling sealing surface (2-2) is 10 to 15 mm, and the sealing taper is 1 / 10 to 1 / 3.

5. The corrosion-resistant threaded joint according to claim 1, characterized in that: The pitch of the male thread (1-1) and the coupling thread (2-1) are both 5 to 8 teeth per inch, the tooth height is 1.0 to 2.0 mm, and the thread taper is 1 / 12 to 1 / 16.

6. The corrosion-resistant threaded joint according to claim 1, characterized in that: The thread bearing area of ​​the male thread (1-1) is not less than 1.2 times the cross-sectional area of ​​the pipe body; and the cross-sectional area at the coupling backcut groove (2-4) is not less than 1.2 times the cross-sectional area of ​​the pipe body.

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