Special thread structure capable of improving machining yield

Abstract

The utility model belongs to the field of oil casing threads, and particularly relates to a special thread structure capable of improving the machining yield. A special thread structure capable of improving the machining yield comprises an external thread located at the front end of a pipe body and an internal thread located at the front end of a coupling, the sections of the external thread and the internal thread are both large-chamfer polygons, the angle of the guide face of the sections of the external thread and the internal thread is 45 degrees, the angle of the bearing face of the sections of the external thread and the internal thread is-3 degrees, and the angle of the bearing face of the sections of the external thread and the internal thread is 45 degrees. And the front end of the external thread and the rear end of the internal thread are respectively provided with a sealing surface and a circular bead which are matched with each other. According to the utility model, through the design of the sealing surface and the large-chamfer polygonal threaded section, the connection strength of the oil casing in a complex oil gas well can be ensured, and the air-tight sealing performance of the oil casing can be ensured; under the condition that the geometric dimension of the appearance of the pipe blank is not changed, black leather buckles are controlled, the numerical control machining quality and the production efficiency are improved, and the production cost is reduced.

Description

Technical Field

[0001] The utility model belongs to the field of oil casing threads, and particularly relates to a special thread structure which can improve the processing yield rate. Background Art

[0002] In the research and development of special thread structures, both air tightness and thread connection strength must be ensured. However, during the CNC machining process, due to factors such as the ovality of the pipe, structural design, and the non-straightness of the pipe end, the turning from the pipe end to the full top thread Lc is not thorough, and there are a large number of "black buckles". According to the API 5B standard, "black buckles" are not allowed to exist after the complete thread machining of the pipe end connection part, because the existence of "black buckles" directly affects the connection strength of the joint, and in severe cases, the casing will break and fall into the well, causing oilfield quality accidents or even safety accidents. In the mass production process of oil casing, the existence of "black buckles" causes the product scrap rate to be too high, the processing is difficult, and the yield rate is only 50%, which seriously affects production efficiency and product benefits.

[0003] At present, Chinese patent ZL 20090045683.7 "Thickened oil pipe capable of improving the processing yield rate of connecting threads" increases the radial size of the connecting threads, and uses the increased outer diameter to compensate for the incomplete cutting threads caused by insufficient roundness or non-straightness of the pipe end, thereby avoiding the generation of black buckles. However, this method requires increasing the outer diameter of the oil pipe, and only ensures the reduction of "black buckles", but does not explain whether the oil pipe can still ensure the airtight seal and the connection strength of the threads after the "black buckles" are reduced. An additional pipe end heating and roughening process is added, which reduces the processing efficiency of the oil pipe and increases the production cost. Utility Model Content

[0004] In view of the above problems, the purpose of the utility model is to provide a special thread structure that can improve the processing yield rate. By designing a special thread sealing surface and a large chamfered polygonal thread section, the position of the mid-diameter point of the internal and external threads is changed, which can not only ensure the connection strength of the oil casing in complex oil and gas wells, but also ensure its airtight performance; without changing the external geometric dimensions of the pipe blank, the generation of "black buckles" is controlled, the quality of CNC processing and production efficiency are improved, and the one-time pass rate of CNC processing is increased from 50% to more than 90%, thereby reducing production costs.

[0005] The technical solution of the utility model is: a special thread structure that can improve the processing yield rate, including an external thread located at the front end of the pipe body and an internal thread located at the front end of the coupling, the cross-sectional shapes of the external thread and the internal thread are both large chamfered polygons, the angle of the guide surface of the cross-sectional area of ​​the external thread and the internal thread is 45°, the angle of the bearing surface of the cross-sectional area of ​​the external thread and the internal thread is -3°, and the front end of the external thread and the rear end of the internal thread are respectively provided with matching sealing surfaces and shoulders.

[0006] The sealing surface includes a spherical surface and a conical surface connected in sequence, the radius of the spherical surface is 5-10 mm, and the angle between the conical surface and the horizontal plane is 14°.

[0007] A gap of 0.1 to 0.2 mm is provided at the tooth height and tooth width of the matching external thread and internal thread.

[0008] The end of the tube body is provided with a conical necking, and the angle of the conical necking is 5°.

[0009] The mid-diameter point of the external thread is the first mid-diameter point, and the diameter of the tube body at the first mid-diameter point is reduced by 0.2-0.3 mm.

[0010] The mid-diameter point of the internal thread is the second mid-diameter point, and the diameter of the coupling at the second mid-diameter point is reduced by 0.2-0.3 mm.

[0011] The technical effect of the utility model is that: the utility model changes the mid-diameter point positions of the internal and external threads through the design of special thread sealing surfaces and large chamfered polygonal thread sections, which can not only ensure the connection strength of the oil casing in complex oil and gas wells, but also ensure its gas sealing performance; without changing the external geometric dimensions of the tube blank, the generation of "black buckles" is controlled, the quality of CNC machining and production efficiency are improved, the one-time pass rate of CNC machining is increased from 50% to more than 90%, and the production cost is reduced.

[0012] The following is a further description with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The utility model is a schematic diagram of a special thread structure capable of improving the processing yield rate.

[0014] Figure 2 It is an enlarged schematic diagram of the connection between the internal thread and the external thread of the utility model.

[0015] Figure 3 This is a comparison chart of the processing yield rate of the utility model.

[0016] Figure numerals: 1-external thread; 2-internal thread; 3-sealing surface; 4-shoulder; 5-conical necking; 6-tube body; 7-coupling; 8-first mid-diameter point; 9-second mid-diameter point; 10-guide surface; 11-bearing surface. DETAILED DESCRIPTION Example 1

[0017] like Figure 1 , Figure 2As shown, a special thread structure that can improve the processing yield rate includes an external thread 1 located at the front end of a pipe body 6 and an internal thread 2 located at the front end of a coupling 7, the cross-sectional shapes of the external thread 1 and the internal thread 2 are both large chamfered polygons, the angle of the guide surface 10 of the cross-sectional area of ​​the external thread 1 and the internal thread 2 is 45°, the angle of the bearing surface 11 of the cross-sectional area of ​​the external thread 1 and the internal thread 2 is -3°, and the front end of the external thread 1 and the rear end of the internal thread 2 are respectively provided with a matching sealing surface 3 and a shoulder 4.

[0018] The cross-sectional shapes of the external thread 1 and the internal thread 2 of the utility model are both large chamfered polygons, the angle of the guide surface 10 of the cross-sectional shape of the external thread 1 and the internal thread 2 is 45°, the angle of the bearing surface 11 of the cross-sectional shape of the external thread 1 and the internal thread 2 is -3°, and the front end of the external thread 1 and the rear end of the internal thread 2 are respectively provided with a matching sealing surface 3 and a shoulder 4. The utility model can not only ensure the connection strength of the oil casing in complex oil and gas wells, but also ensure its gas sealing performance through the design of special thread sealing surface and large chamfered polygonal thread cross-sectional shape; without changing the appearance geometric dimensions of the tube blank, the generation of "black leather buckle" is controlled, the quality and production efficiency of CNC machining are improved, and the one-time pass rate of CNC machining is increased from 50% to more than 90%, reducing production costs. Example 2

[0019] On the basis of Example 1, in this embodiment, preferably, the sealing surface 3 includes a spherical surface and a conical surface connected in sequence, the radius of the spherical surface is 5-10 mm, and the angle between the conical surface and the horizontal plane is 14°.

[0020] The sealing surface 3 of the utility model includes a spherical surface and a conical surface connected in sequence. The radius of the spherical surface is 5-10mm, and the angle between the conical surface and the horizontal plane is 14°. The "spherical surface + conical surface" combined sealing structure is adopted at the sealing surface. The radius of the spherical surface at the external thread sealing surface is 5-10mm. Both the internal thread and the external thread sealing surfaces are conical surfaces, and the angle between them and the horizontal plane is 14°, thereby ensuring the sealing effect. Example 3

[0021] On the basis of Example 1 or Example 2, in this embodiment, preferably, a gap of 0.1-0.2 mm is provided at the tooth height and tooth width of the matching external thread 1 and internal thread 2.

[0022] The utility model provides a gap of 0.1-0.2 mm at the tooth height and tooth width of the matched external thread 1 and internal thread 2, which effectively solves the problems of insufficient thread connection strength and easy sticking. Example 4

[0023] On the basis of Example 1 or Example 3, in this embodiment, preferably, a conical necking 5 is provided at the end of the tube body 6, and the angle of the conical necking 5 is 5°.

[0024] The end of the tube body 6 of the utility model is provided with a conical necking 5, and the angle of the conical necking 5 is 5°. This design effectively improves the inner flatness of the tube body and eliminates the influence of the ovality of the tube body. Example 5

[0025] On the basis of Example 1 or Example 4, in this embodiment, preferably, the mid-diameter point of the external thread 1 is the first mid-diameter point 8, and the diameter of the tube body 6 at the first mid-diameter point 8 is reduced by 0.2-0.3 mm.

[0026] The mid-diameter point of the external thread 1 described in the utility model is the first mid-diameter point 8, and the diameter of the tube body 6 at the first mid-diameter point 8 is reduced by 0.2-0.3mm, which increases the length of the complete thread, i.e., Lc, reduces the probability of "black buckle" generation, effectively improves the thread matching accuracy, and further improves the connection strength of the thread. Example 6

[0027] On the basis of Example 1 or Example 5, in this embodiment, preferably, the mid-diameter point of the internal thread 2 is the second mid-diameter point 9, and the diameter of the coupling 7 at the second mid-diameter point 9 is reduced by 0.2-0.3 mm.

[0028] The mid-diameter point of the internal thread 2 of the utility model is the second mid-diameter point 9, and the diameter of the coupling 7 at the second mid-diameter point 9 is reduced by 0.2-0.3mm, which increases the length of the complete thread, i.e., Lc, reduces the probability of "black buckle" generation, effectively improves the thread matching accuracy, and further enhances the connection strength of the thread.

[0029] according to Figure 1 , Figure 2 A special thread structure that can improve the processing yield rate. Set the processing parameters, adjust the processing parameters after trial processing, and then complete the processing process by rough turning and fine turning. After mass production, the processing yield rate has increased from 50% to more than 90%. Figure 3 As shown. The thread structure can realize the processing of limit specimens within the tolerance range. According to the designed tolerance parameters, by adjusting the load-bearing surface, guide surface, thread taper, and thread height parameters, the limit specimens that appear in the API5C5 evaluation are processed as shown in Table 1. The limit specimens within the tolerance range are used to simulate the downhole working conditions of the oil field. According to the API 5C5-2017 "Test Procedures for Threaded Connections of Casing and Tubing in the Petroleum and Natural Gas Industry" standard, after the make-up and make-up test, the sealing surface is smooth and there is no sticking phenomenon. Tensile, compression, bending, internal and external pressure composite load loading tests are carried out. There is no breakage at the thread and the connection strength is high.

[0030] Table 1 API5C5 limit specimen selection principles

[0031] Using the standard medium bubble method internal pressure leakage detection system and the limit specimen processed by the utility model, an air tightness test is carried out. After experiencing tension, compression, bending, and internal and external pressure composite loads, there are no bubbles in the measuring cylinder of the bubble method internal pressure leakage detection system, and the airtightness performance is good.

[0032] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the present invention should be included in the protection scope of the present invention.

Claims

1. A special thread structure that can improve the processing yield rate, characterized by: The invention comprises an external thread (1) located at the front end of a pipe body (6) and an internal thread (2) located at the front end of a coupling (7), wherein the cross-sectional shapes of the external thread (1) and the internal thread (2) are both large chamfered polygons, the angle of the guide surface (10) of the cross-sectional shape of the external thread (1) and the internal thread (2) is 45°, the angle of the bearing surface (11) of the cross-sectional shape of the external thread (1) and the internal thread (2) is -3°, and the front end of the external thread (1) and the rear end of the internal thread (2) are respectively provided with a matching sealing surface (3) and a shoulder (4).

2. A special thread structure capable of improving the processing yield rate according to claim 1, characterized in that: The sealing surface (3) comprises a spherical surface and a conical surface which are connected in sequence, the radius of the spherical surface is 5-10 mm, and the angle between the conical surface and the horizontal plane is 14°.

3. A special thread structure capable of improving the processing yield rate according to claim 1, characterized in that: A gap of 0.1 to 0.2 mm is provided at the tooth height and tooth width of the matching external thread (1) and internal thread (2).

4. A special thread structure capable of improving the processing yield rate according to claim 1, characterized in that: The end of the tube body (6) is provided with a conical necking opening (5), and the angle of the conical necking opening (5) is 5°.

5. The special thread structure capable of improving the processing yield rate according to claim 1, characterized in that: The mid-diameter point of the external thread (1) is a first mid-diameter point (8), and the diameter of the tube body (6) at the first mid-diameter point (8) is reduced by 0.2-0.3 mm.

6. The special thread structure capable of improving the processing yield rate according to claim 1, characterized in that: The mid-diameter point of the internal thread (2) is a second mid-diameter point (9), and the diameter of the coupling (7) at the second mid-diameter point (9) is reduced by 0.2-0.3 mm.

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