The present disclosure relates to a threaded joint for steel pipes.
BACKGROUND
[0002]
　For example, oil wells and natural gas wells and the like exploration or production, the development of unconventional resources such as oil sand and shale gas, the carbon dioxide recovery and storage (CCS (Carbon (hereinafter, also collectively referred to as "oil wells") dioxide Capture and Storage)), in geothermal, or springs or the like, the steel pipe called oil well pipe is used. The connection of steel pipes, threaded joints are used.
[0003]
　Format tubular threaded joint is roughly classified into a coupling-type and integral type. For coupling type, a pair of tubing of consolidated, where one tube is steel, other tubing is coupled. In this case, a male screw portion is formed on an outer peripheral surface of both ends of a steel pipe, the internal thread portion is formed on the inner peripheral surface of both ends of the coupling. Then, the male screw portion of the steel pipe is screwed into the female screw portion of the coupling, which both are connected is fastened by. For integral type, a pair of tubing of consolidated are both steel pipe, without using a separate coupling. In this case, the male screw portion is formed on the outer peripheral surface of the one end portion of the steel pipe, the internal thread portion is formed on the inner peripheral surface of the other end. Then, the male screw portion of one of the steel pipe is screwed into the female screw portion of the other steel pipe, which both are connected is fastened by.
[0004]
　Generally, the joint portion of the male screw portion the tube end portion formed, since the containing elements to be inserted into the female screw portion, it referred to as pin. On the other hand, the joint portion of the pipe end portion a female screw portion is formed, since it contains elements for receiving the external thread portion, referred to as boxes. These pin and box are the ends of the tube, both of which are tubular.
[0005]
　The threaded joint, the pressure of the fluid from the inside (hereinafter, referred to as "internal pressure") the pressure of the fluid to and from the outside (hereinafter, referred to as "external pressure") excellent sealing performance for is required. Therefore, the threaded joint, the sealing portion by the metal contact is provided. Seal portion is composed of a pin seal surface, the box sealing surface having a slightly smaller diameter than the diameter of the pin seal surface. The difference between the diameters of the box sealing surface pin seal surface of the seal interference amount. When the screw joint is tightened it will fit state interference fit sealing faces, diameter and box seal surfaces of the enlarged diameter of the pin seal surface is generated. The elastic recovery force of these sealing surfaces is to return to their original diameter, the seal face in close contact the entire circumference, sealing performance is exhibited. In this case, sealing performance becomes high contact pressure of the seal surface larger the seal interference amount increases.
[0006]
　In recent years, the development of a well of great depth having a high temperature pressure harsh environments has increased. The threaded joint used in these wells, is required particularly good sealing performance.
[0007]
　As a threaded joint to exhibit excellent sealing performance, for example, as disclosed in Patent Document 1, a threaded joint is known having a nose structure. In the threaded joint disclosed in Patent Document 1, the pin is provided in order from the tip side in the steel pipe main body side, Pinshoruda surface, pin seal surface, and a male thread portion. Box includes box shoulder surface, the box sealing surface, and a female threaded portion. The pin nose is provided. Nose portion is positioned between the Pinshoruda surface and pin seal surface. The outer peripheral surface of the nose portion does not contact the box in engagement state. Nose portion increases the rigidity of the periphery of the pin seal surface. Therefore, even when external pressure is exerted on the threaded joint, shrink deformation hardly occurs the pin seal surface, it is possible to suppress a decrease in the seal interference amount of real (actual), improving the sealing performance against external pressure it can be.
[0008]
　In Patent Document 2, a threaded joint having a nose structure is disclosed. Patent Document 2, the length of the pin lip portion L, and the distance from the tip of the male thread portion to sealing position was x, it the x / L is to the 0.2-0.8 is preferred Has been described. In Patent Document 2, the sealing position is a site on the outer peripheral surface of the pin lip portion contacting upon screwed into the box sealing surface and first.
[0009]
　Herein, the following prior art documents are incorporated by reference.
Patent Document 1: JP 4535064 JP
Patent Document 2: Japanese Patent No. 5776222
SUMMARY OF THE DISCLOSURE
[0010]
　The threaded joint described in the above patent documents, thereby improving the sealing performance by the nose structure. However, the sealing performance of these threaded joints is believed that there is room for further improvement.
[0011]
　The present disclosure aims to provide a threaded joint for steel pipes having excellent sealing performance.
[0012]
　Tubular threaded joint according to the present disclosure includes a pin tubular and a tubular box. Pin is provided connected to the steel pipe body. Box, the pin is fastened to the inserted into the pin. Pin includes a nose portion, and Pinshoruda surface, and the male screw portion, and a pin seal surface. Nose constitutes the tip of the pin. Pinshoruda surface is provided on the distal end surface of the nose portion. External thread portion, in the steel pipe main body side than the nose portion, is provided on the outer peripheral surface of the pin. Pin seal surface is between the nose portion and the male screw portion is provided on the outer peripheral surface of the pin. Box has a box shoulder surface, and the female screw portion, and a box seal surface. Box shoulder surface is provided on the inner back of the box corresponding to Pinshoruda surface. Box shoulder surface contacts the Pinshoruda surface in engagement state. Internal thread portion is provided on the inner peripheral surface of the box corresponding to the external thread portion. Box sealing surface is provided on the inner peripheral surface of the box in correspondence with the pin seal surface. Box sealing surface contacts the pin seal surface in the engaged state. The outer peripheral surface of the nose portion is opposed at an inner peripheral surface and the gap between the box in engagement state. Threaded joint satisfies 0.4 ≦ x / L ≦ 0.55. Here, x is the distance in the tube axis direction between the first end of the pin seal face side of the sealing position and the male screw portion is a position in contact with the inner peripheral surface of the box by a fastening process of the pin seal surface, L is the distance in the tube axis direction between the end of the pin seal face side of the front end and the male screw portion of the pin.
[0013]
　According to the present disclosure, it is possible to impart excellent sealing performance threaded joint for steel pipes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014]
[1] Figure 1 is a graph schematically showing the relationship between the value of x / L and external pressure sealing performance.
FIG. 2 is a longitudinal sectional view showing a schematic configuration of a tubular threaded joint according to the first embodiment.
FIG. 3 is a longitudinal sectional view of the distal portion of the pin of a threaded joint shown in Figure 1.
[4] FIG. 4 is a longitudinal sectional view showing a schematic configuration of a tubular threaded joint according to the second embodiment.
FIG. 5 is a longitudinal sectional view of the distal portion of the pin of a threaded joint shown in FIG.
FIG. 6 is for threaded joint according to Examples and Comparative Examples, a graph showing the relationship between the value and the sealing performance of x / L.
DESCRIPTION OF THE INVENTION
[0015]
　The threaded joint described in the above patent documents, in the fastening state, the shoulder portion is formed by contact with the Pinshoruda surface and the box shoulder surfaces, the seal portion is formed by the contact between the pin seal surface and the box sealing surface. Between the shoulder portion and the seal portion, the nose portion is disposed. Therefore, subjected to any excessive compressive load to the screw joint as shoulder is deformed, the influence is not easily reach the seal. As a result, good sealing performance is maintained.
[0016]
　Nose portion increases the rigidity of the seal portion. Therefore, even when external pressure is exerted on the threaded joint, shrink deformation is unlikely to occur in the seal portion, it is possible to suppress the reduction of the real seal interference amount. Therefore, it is possible to obtain a good external pressure sealing performance.
[0017]
　As described above, Patent Document 2, the parameter x / L is to the 0.2-0.8 is described as being preferred. However, in Patent Document 2, the effect of 0.2 to 0.8 x / L is not verified. Patent Document 2, only examples of the threaded joint is x / L = 0.7 is disclosed. Moreover, these examples are not intended to indicate that some effect can be obtained by the x / L = 0.7. Range of x / L as described in Patent Document 2 is a lack concrete evidence.
[0018]
　According to the present inventors and others have examined the change in the value of x / L affects the both the improvement and reduction of external pressure sealing performance. Therefore, the finally obtained sealing performance, the size of the influence values ​​of x / L is on the improvement of the sealing performance, the value of x / L is determined by the balance between the size of the impact on the reduction of the sealing performance Conceivable. It will be specifically described with reference to FIG.
[0019]
　Figure 1 is a graph schematically showing the relationship between the value and the external pressure sealing performance of x / L. Line a1, a2 in Figure 1, for each factor to improve or lower the external pressure sealing performance, shows the relationship between the value of x / L and external pressure sealing performance. Line A of Figure 1 is obtained by integrating the line a1, a2, showing the relationship between the value of x / L and finally obtained external pressure sealing performance.
[0020]
　First, a description will be given of the relationship indicated by the line a1 in Fig.
[0021]
　When the value of x / L increases, the pin lip portion, the length of the relatively nose portion is shortened. Therefore, the rigidity of the seal portion is reduced. When the value of x / L is large, the pin lip portion, the distance from the sealing position to the front end of the male screw portion is relatively long. That is, since the sealing position is moved away from the engagement portion of the screw, the sealing portion tends to shrink-deformed when external pressure is loaded. Thus, as shown by line a1, external pressure sealing performance is considered decreases as the value of x / L increases.
[0022]
　When the value of x / L is small, the length of the nose portion is relatively long, the distance from the sealing position to the front end of the male screw portion is relatively short. This improves the rigidity of the seal portion, shrink deformation of the seal portion sealing position becomes closer to the engagement portion of the screw is less likely to occur. Thus, as shown by line a1, believed to external pressure sealing performance is improved as the value of x / L decreases.
[0023]
　Next, a description will be given of the relationship indicated by the line a2 in Fig.
[0024]
　As described above, when the value of x / L increases, the distance from the sealing position to the front end of the male screw portion is relatively long. Accordingly, since the sealing position becomes farther from the engaging portion of the screw, reducing the substantial amount of interference of the seal portion due to the interference of the threaded portion is less likely to occur. Thus, as shown by line a2, it believed to external pressure sealing performance is improved as the value of x / L increases. If decline in real interference amount of the seal portion due to the interference of the threaded portion is smaller, it is believed also to improve the internal pressure sealing performance.
[0025]
　When the value of x / L is small, the distance from the sealing position to the front end of the male screw portion is relatively short, the sealing position is closer to the engaging portion of the screw. Therefore, decline in real interference amount of the seal portion due to the interference of the threaded portion is liable to occur. Thus, as shown by line a2, external pressure sealing performance is lowered as the value of x / L decreases. At this time, considered to internal pressure sealing performance is also lowered.
[0026]
　Thus, change in the value of x / L is the rigidity of the seal portion, the ease of diameter reducing deformation of the seal portion, and affect the decline in real interference amount of the seal portion. The final sealing performance, as shown by line A in FIG. 1, the influence of x / L for ease of diameter reducing deformation of the rigid and the sealing portion of the sealing portion (line a1), the substantial amount of interference seal portion It will be determined by the influence of x / L for the reduction and (line a2) comprehensively. The present inventors have thought that eventually good range of optimal x / L in order to obtain the sealing performance exists.
[0027]
　The present inventors have studied the optimum range of x / L. As a result, the present inventors have long x / L is 0.4 or more, almost without substantial interference of the seal portion is reduced by the interference of the thread, in particular for pressure, good sealing performance it has been found that can be obtained.
[0028]
　According to the study results of the present inventors, the external pressure sealing performance tends to decrease as x / L increases. The present inventors have, if x / L is 0.55 or less, than the adverse effect the stiffness reduction of the seal portion due to a reduction in the length of the nose portion, suppressing decrease of substantial interference amount of the seal portion due to the interference of the threaded portion it is large effect, particularly found that external pressure sealing performance is improved.
[0029]
　The present inventors have, based on the above findings, and completed the tubular threaded joint according to the embodiment.
[0030]
　Tubular threaded joint according to the embodiment includes a pin tubular and a tubular box. Pin is provided connected to the steel pipe body. Box, the pin is fastened to the inserted into the pin. Pin includes a nose portion, and Pinshoruda surface, and the male screw portion, and a pin seal surface. Nose constitutes the tip of the pin. Pinshoruda surface is provided on the distal end surface of the nose portion. External thread portion, in the steel pipe main body side than the nose portion, is provided on the outer peripheral surface of the pin. Pin seal surface is between the nose portion and the male screw portion is provided on the outer peripheral surface of the pin. Box has a box shoulder surface, and the female screw portion, and a box seal surface. Box shoulder surface is provided on the inner back of the box corresponding to Pinshoruda surface. Box shoulder surface contacts the Pinshoruda surface in engagement state. Internal thread portion is provided on the inner peripheral surface of the box corresponding to the external thread portion. Box sealing surface is provided on the inner peripheral surface of the box in correspondence with the pin seal surface. Box sealing surface contacts the pin seal surface in the engaged state. The outer peripheral surface of the nose portion is opposed at an inner peripheral surface and the gap between the box in engagement state. Threaded joint satisfies 0.4 ≦ x / L ≦ 0.55. Here, x is the distance in the tube axis direction between the first end of the pin seal face side of the sealing position and the male screw portion is a position in contact with the inner peripheral surface of the box by a fastening process of the pin seal surface, L is the distance in the tube axis direction between the end of the pin seal face side of the front end and the male screw portion of the pin (first configuration).
[0031]
　According to the first configuration, x / L is set to 0.4 or more and 0.55 or less. If x / L is in the range of 0.4 to 0.55, while maintaining good pressure sealing performance, it is possible to improve the external pressure sealing performance. Therefore, with respect to a threaded joint, it is possible to impart excellent sealing performance.
[0032]
　In the threaded joint, the cross-sectional area of ​​the pin in the sealing position, may be more than 35% of the cross-sectional area of ​​the steel body (second configuration).
[0033]
　According to the second configuration, it is possible to secure a sufficient cross-sectional area of ​​the formed sealing portion with pin seal surface and the box sealing surface. Therefore, it is possible for the pin lip portion, to maintain a high stiffness. Therefore, it is possible to further improve the external pressure sealing performance.
[0034]
　It will be described below with reference to the accompanying drawings embodiments. Given the same reference and the corresponding configuration in the figure does not repeat the same description. For convenience of explanation, in each figure, or are simplified or schematized configuration, in some cases or are omitted a part of the configuration.
[0035]
　[First Embodiment]
　FIG. 2 is a longitudinal sectional view showing a schematic configuration of a tubular threaded joint 1 according to the first embodiment. The longitudinal section, a cross-section taken along a plane including the tube axis CL of the threaded joint 1. And the transverse plane refers to section cut by a plane perpendicular to the tube axis CL. This embodiment can either be applied to the integral type threaded joint may also be applied to a coupling type of threaded joint.
[0036]
　As shown in FIG. 2, a threaded joint 1 is provided with a pin 10 of the tubular, a tubular box 20. Pin 10 is inserted into the box 20, the pin 10 and the box 20 is fastened.
[0037]
　Pin 10 is provided connected to the steel tube body 2. The steel pipe body 2 is a portion of the steel pipe comprising a pin 10 not inserted into the box 20. Steel pipe is, for example, a steel pipe. For convenience of explanation, in the tube axis direction of the pin 10, the distal end side of the pin 10 forward, may be referred to as rear side steel pipe body 2 side.
[0038]
　Pin 10 has a nose portion 11, a Pinshoruda surface 12, a pin seal surface 13, and a male screw portion 14. Pinshoruda surface 12, the nose portion 11, pin seal surface 13, and the external thread portion 14 is positioned from the front of the pin 10 toward the rear in this order. Of the pin 10, it referred to as a pin lip portion 15 of the forward section than the male screw portion 14. Pin lip portion 15 includes a nose portion 11, Pinshoruda surface 12, and the pin seal surface 13.
[0039]
　The nose portion 11 constitutes a leading end portion of the pin 10. The nose portion 11 forms a cylindrical shape. The shape of the outer peripheral surface of the nose portion 11 can shape corresponding to the outer peripheral surface of the cylindrical, or the outer diameter toward the distal end side of the pin 10 is shaped to correspond to the frustoconical outer peripheral surface of the smaller. The outer peripheral surface of the nose portion 11 is used, the number and the outer peripheral surface and / or frustoconical outer peripheral surface of the cylindrical, the shape of a combination of the outer peripheral surface of the rotary body obtained by rotating the curve of the circular arc or the like around the tube axis CL it may be in.
[0040]
　The distal end surface of the nose portion 11, i.e. the end face of the pin 10, Pinshoruda surface 12 is provided. Pinshoruda surface 12 constitutes a part or all of the front end surface of the pin 10. Pinshoruda surface 12 is an annular surface disposed to intersect the tube axis direction. Pinshoruda surface 12, so as to be located further forward than the inner peripheral portion is the outer peripheral portion are inclined with respect to a plane perpendicular to the tube axis CL. Pinshoruda surface 12 may be substantially perpendicular to the tube axis CL.
[0041]
　Pin seal surface 13 is disposed steel pipe pile body 2 side of the nose portion 11. Pin seal surface 13 is provided on the outer peripheral surface of the pin 10. Pin seal surface 13 is provided adjacent to the nose portion 11.
[0042]
　Pin seal surface 13 includes a tapered surface and / or curved. For example, pin seal surface 13, the shape corresponds to the frustoconical outer peripheral surface of the outer diameter decreases toward the distal end side of the pin 10, or, the rotation of which is obtained by rotating the curve of the circular arc or the like around the tube axis CL having a shape corresponding to the outer peripheral surface. Pin seal surface 13 may have a shape combining an outer peripheral surface of the outer peripheral surface of the truncated cone and the rotor.
[0043]
　The outer peripheral surface of the pin lip portion 15 may be a single tapered surface may include a plurality of tapered surfaces. In embodiments the outer peripheral surface of the pin lip portion 15 comprises a plurality of tapered surfaces, if the pin seal surface 13 is constituted by a substantially tapered surface, the outer peripheral surface of the nose portion 11 is smaller than the taper angle of the pin seal surface 13 ( loose) or large (can be composed of a tapered surface having a steep) taper angle.
[0044]
　In this embodiment, the outer peripheral surface of the pin lip portion 15 is composed of a plurality of tapered surfaces. More specifically, the outer peripheral surface of the nose portion 11 is substantially tapered surface. Pin seal surface 13 is also substantially tapered surface. Taper angle of the outer peripheral surface of the nose portion 11 is smaller than the taper angle of the pin seal surface 13. Slope of the outer peripheral surface of the pin lip portion 15 is changed at the boundary portion between the nose portion 11 and the pin seal surface 13. Pin seal surface 13 may be provided through the outer peripheral surface and the curved surface of the nose portion 11.
[0045]
　Rear portion than pin seal surface 13 of the outer peripheral surface of the pin lip portion 15 is substantially a tapered surface the taper angle is smaller than the pin seal surface 13. Slope of the outer peripheral surface of the pin lip portion 15 is changed at the boundary portion between the rear portion and the pin seal surface 13. Pin seal surface 13 may be provided through the rear portion and the curved surface. Alternatively, the rear portion and the pin seal surface 13 may be a single tapered surface.
[0046]
　The outer peripheral surface, and / or rear part than pin seal surface 13 of the outer peripheral surface of the pin lip portion 15 of the nose portion 11 may be constituted by the outer peripheral surface of the cylinder.
[0047]
　2 represents a tube axis direction of the distance from the sealing position P of the pin seal surface 13 to the front end of the external thread portion 14 x, the distance in the tube axis direction from the tip of the pin 10 to the front end of the external thread portion 14 in L. The distance L is the length of the pin lip portion 15. Sealing position P and the distance x, for L, it will be described in detail later.
[0048]
　External thread portion 14 is disposed behind the pin lip portion 15 in the tube axis direction. External thread portion 14 is provided on the outer peripheral surface of the pin 10. External thread portion 14 is composed of a tapered thread.
[0049]
　Box 20 includes a nose receiving portion 21, the box shoulder surface 22, the box sealing surface 23, and a female thread portion 24. For convenience of explanation, in the tube axis direction of the box 20, the tube end of a steel pipe or coupling box 20 is provided outside, it may be referred to the opposite side of the inner or back side. Box shoulder surface 22, the nose receiving portion 21, the box sealing surface 23, and the internal thread portion 24 are arranged in this order from the inside of the box 20 toward the outside.
[0050]
　The nose receiving portion 21, out of the box 20, a portion corresponding to the nose portion 11 of the pin 10. The nose receiving portion 21 constitutes the octane portion of the box. In the engaged condition, the inner peripheral surface of the nose receiving portion 21 is opposed at a peripheral surface with a gap of the nose portion 11. That is, in the fastening state, the outer peripheral surface of the nose portion 11 does not contact the inner peripheral surface of the box 20.
[0051]
　Shape of the inner peripheral surface of the nose receiving portion 21 is not particularly limited. The inner peripheral surface of the nose receiving portion 21 may be constituted by the inner surface of the cylindrical, or may be composed of a tapered surface whose inner diameter becomes smaller toward the rear side of the box 20. The inner peripheral surface of the nose receiving portion 21 includes an inner peripheral surface and / or the tapered surface of the cylindrical, the shape obtained by combining the inner peripheral surface of the rotary body obtained by rotating the curve of the circular arc or the like around the tube axis CL it may have.
[0052]
　Box shoulder surface 22, in response to Pinshoruda surface 12 is provided on the inner back of the box 20. Box shoulder surface 22, like the Pinshoruda surface 12 is an annular surface disposed to intersect the tube axis direction.
[0053]
　Box shoulder surface 22 contacts the Pinshoruda surface 12 in engagement state, to form a shoulder portion with Pinshoruda surface 12. Pinshoruda surface 12 and box shoulder surface 22 is responsible stopper for limiting the screwing of the pin 10. Pinshoruda surface 12 and box shoulder surface 22, inside the joint, responsible for generating a clamping axial force of the screw.
[0054]
　Box sealing surface 23 is disposed outside the nose receiving portion 21 in the tube axis direction. Box sealing surface 23, corresponding to the pin seal surface 13 is provided on the inner peripheral surface of the box 20.
[0055]
　Pin seal surface 13 and the box sealing surface 23 has an interference amount. That is, in the disengaged state, pin seal surface 13 has a slightly larger diameter than the diameter of the box sealing surface 23. Pin seal surface 13 and the box sealing surface 23 is a fit state interference fit in close contact with the fitting in the engagement state. Pin seal surface 13 and the box sealing surface 23 forms a seal by metal contact at the engagement state.
[0056]
　Box sealing surface 23 has a shape projecting toward the pin seal surface 13. However, the box sealing surface 23 may not protrude toward the pin seal surface 13. Box sealing surface 23 is at least partially in the fastening state may, if possible in close contact with the pin seal surface 13. Box sealing surface 23 can be formed into various shapes.
[0057]
　Internal thread portion 24, corresponding to the external thread portion 14 is provided on the inner peripheral surface of the box 20. Internal thread portion 24 is formed by a tapered thread that meshes with tapered threads constituting the external thread portion 14. In the engaged condition, the internal thread portion 24 forms a threaded portion with the external thread portion 14.
[0058]
　Each load surface of the male screw portion 14 and the internal thread portion 24 has a flank angle of less than 0 °. In particular but not limited to, male threaded portion 14 and the internal thread portion 24 can be configured in a trapezoidal screw. External thread portion 14 and the internal thread portion 24 is preferably composed of a single-thread screw or double threaded screw.
[0059]
　Figure 3 is a longitudinal sectional view showing an enlarged tip portion of the pin 10.
[0060]
　As shown in FIG. 3, in the vertical cross section of the pin 10, the thread of the front end portion of the external thread portion 14 has an incomplete shape with a portion cut away. The said threads, bevel 14a is formed is a surface inclined toward the distal end side and inner peripheral side of the pin 10. In the longitudinal cross section of the pin 10, an extension L14 bevel 14a, the intersection of the extension line L15 of parts 15a adjacent to the bevel 14a of the outer peripheral surface of the pin lip portion 15, is defined as the front end of the male screw portion 14.
[0061]
　Sealing position P, of the pin seal surface 13 is a position of the portion first contacts the inner peripheral surface of the box 20 in the fastening process (Figure 2). As described above, L is a distance in the tube axis direction from the leading edge of the pin 10 to the front end of the male screw portion 14. x is the distance in the tube axis direction from the sealing position P to the front end of the male screw portion 14.
[0062]
　In the present embodiment, the value of x / L is to be within a predetermined range, the length of the pin lip portion 15 L, and the distance x from the sealing position P to the front end of the male screw portion 14 is set. Specifically, x / L is 0.4 or more 0.55 or less, preferably 0.4 or more and less than 0.5. Values ​​of and distance x of the length L, respectively, to a value in the disengaged state.
[0063]
　Cross-sectional area of ​​the pin 10 in the sealing position P is a steel pipe pile body 2 (FIG. 2) is preferably a cross-sectional area of ​​35% or more, more preferably 50% or more. The upper limit of the cross-sectional area of ​​the pin 10 in the sealing position P is, for example, 70% of the cross-sectional area of ​​the steel pipe pile body 2.
[0064]
　[Second Embodiment]
　FIG. 4 is a longitudinal sectional view showing a schematic configuration of a tubular threaded joint 1A according to the second embodiment. Figure 5 is a longitudinal sectional view showing an enlarged tip portion of the pin 10A in the threaded joint 1A. Threaded joint 1A may be a integral type threaded joint, it may be a coupling type of threaded joint.
[0065]
　It threaded joint 1A according to this embodiment, except for a part of the box 20A corresponding to pin lip portion 15A, and the pin lip portion 15A, having the same configuration as the threaded joint 1 according to the first embodiment. In the present embodiment, it will be described focusing on differences from the first embodiment.
[0066]
　As shown in FIGS. 4 and 5, the outer peripheral surface of the pin lip portion 15A is constituted by a convex curved surface 15b. That is, the outer peripheral surface of the pin lip portion 15A is a curved surface convex toward the box 20A side. The outer peripheral surface of the pin lip portion 15A, the curvature does not change abruptly throughout, is a smooth continuous surface. The outer peripheral surface of the pin lip portion 15A is may be a convex surface of a single curvature, it may include a plurality of curved surfaces.
[0067]
　As shown in FIG. 5, in vertical cross section of the pin 10A, the threads of the front end portion of the external thread portion 14 has an incomplete shape with a portion cut away. The said threads, bevel 14a is formed is a surface inclined toward the distal end side and inner peripheral side of the pin 10. In the longitudinal cross section of the pin 10, an extension L14 bevel 14a, the intersection of the extension line L15 of the convex surface 15b of the outer peripheral surface of the pin lip portion 15, it is defined as the front end of the male screw portion 14.
[0068]
　The portion corresponding to the pin lip portion 15A of the inner peripheral surface of the box 20A has a shape corresponding to the outer peripheral surface of the pin lip portion 15A. That is, the portion corresponding to the pin lip portion 15A of the inner peripheral surface of the box 20A, in the fastening state, box sealing surface 23A is in contact with the pin seal surface 13A, and formed into a shape nose receiving portion 21A is not in contact with the nose portion 11A It is.
[0069]
　Box sealing surface 23A has a tapered surface. However, the shape of the box sealing surface 23A is not limited thereto. As described above, the box sealing surface 23A can have a variety of shapes.
[0070]
　Also in threaded joint 1A according to this embodiment, like the first embodiment, x / L is 0.4 or more and 0.55 or less, preferably set to 0.4 or more and less than 0.5.
[0071]
　Cross-sectional area of ​​the pin 10A in the sealing position P is a steel pipe pile body 2 (FIG. 4) is preferably the cross-sectional area of ​​35% or more, more preferably 50% or more. The upper limit of the cross-sectional area of ​​the pin 10A in the sealing position P is, for example, 70% of the cross-sectional area of ​​the steel pipe pile body 2.
[0072]
　[Effect of Embodiment]
　As described above, when the value of x / L is increased, lowering of the rigidity of the seal portion is a length of the nose portion 11,11A is relatively short occurs easily, engagement of the threaded portion diameter reducing deformation of the seal portion becomes the distance to the seal portion is relatively long is likely to occur from the. On the other hand, when the value of x / L is increased, a decrease in real interference amount of the seal portion due to the interference of the thread is less likely to occur. That is, when the value of x / L is large, but in terms of shrink deformation of the rigid and the sealing portion of the sealing portion is considered to external pressure sealing performance is lowered, the external pressure sealing performance and pressure sealing in terms of substantial interference amount of the seal portion It is believed to improve performance.
[0073]
　When the value of x / L is small, shrink deformation of the drop and the sealing portion of the rigidity of the seal portion is less likely to occur, a decrease in real interference amount of the seal portion due to the interference of the threaded portion is liable to occur. If the value of x / L is small, but in terms of shrink deformation of the rigid and the sealing portion of the sealing portion is believed to improve the external pressure sealing performance, in terms of substantial interference amount of the seal portion is external pressure sealing performance and pressure sealing performance It is considered to be reduced.
[0074]
　Thus, change in the value of x / L affects both the improvement and reduction in sealing performance. The final sealing performance is determined by the balance between the effect on the sealing performance deterioration and effect on sealing performance improvement in the value of x / L.
[0075]
　When x / L is smaller than 0.4, the distance x from the front end of the male screw portion 14 to the sealing position P is shortened, the distance between the threaded portion and the seal portion is getting close, interference screw portion of the seal portion cause a decrease in real interference amount. When x / L is less than 0.4, because the influence of the decrease in the substantial amount of interference seal portion due to the interference of the thread portion is large, especially pressure sealing performance is lowered.
[0076]
　When x / L is larger than 0.55, the seal due to the influence of the decrease in the rigidity of the seal portion due to the length of the nose portion 11,11A is relatively short, and the seal portion is moved away from the engagement portion of the screw effect of facilitating the diameter reducing deformation of the parts increases. Thus, in particular external pressure sealing performance is lowered.
[0077]
　Threaded joint 1,1A according to the above embodiments, x / L is configured to be 0.4 to 0.55. Therefore, the value of x / L becomes affected and is preferably balanced on lowering effect and sealing performance on the improvement of sealing performance, it is possible to both improve the external pressure sealing performance and pressure sealing performance.
[0078]
　In a threaded joint 1,1A according to the above embodiments, the cross-sectional area of ​​the pin 10,10A in the sealing position P is preferably not less than 35% of the cross-sectional area of ​​the steel pipe pile body 2. Thereby, since the cross-sectional area of ​​the seal portion can be sufficiently secured, it is possible to maintain high rigidity for pin lip portion 15, 15A. Therefore, it is possible to further improve the external pressure sealing performance.
[0079]
　If the rigidity of the seal portion is too high, possibility of seizure occurs becomes high during fastening. To suppress the occurrence of galling during fastening, the threaded joint 1,1A according to the above embodiments, the cross-sectional area of ​​the pin 10,10A at position P is preferably a 70% or less of the cross-sectional area of ​​the steel pipe pile body 2 It is.
[0080]
　Having described embodiments, the present disclosure is not intended to be limited to the above embodiments but can be variously modified without departing from the spirit.
[0081]
　To confirm the effects of a threaded joint for steel pipes according to the present disclosure was conducted numerical simulation analysis by elasto-plastic finite element method.
[0082]
　[Test Conditions]
　The parameter x / L is different specimens was compared the difference in performance by implementing a finite element analysis. Each specimen is coupling type of threaded joint having the basic structure shown in FIG. A common test conditions are shown below.
(1) the size of the steel pipe
　7 "x29 # (outer diameter: 177.8 mm, wall thickness: 10.4
mm) (2) steel grades
　of API Standards P110 (nominal yield stress of 110ksi carbon
steel) (3) of the screw dimensions (conditions common in all of the screw)
　screw pitch: 5.08 mm, the flank angle of the load surface: -3 °, insert flank angle: 10 °, insertion surface gap: 0.15 mm
[0083]
　In finite element analysis, the elasto-plastic body of isotropic hardening the material, 210 GPa elastic modulus, so the yield strength becomes 110ksi (758.3MPa) as 0.2% proof stress, the a model of each specimen used.
[0084]
　[Evaluation Method]
　After analysis of the tightening of the screw with respect to each specimen, a load simulating the ISO13679 CAL4 Series A test to evaluate the sealing performance against external pressure and internal pressure. Sealing performance against the inner external pressure, respectively, the internal pressure cycle (first, second quadrant) of the load history and external pressure cycle (third, fourth quadrant) of the load history contact force per unit length in the circumferential direction of the seal portion in It was evaluated by the minimum value. Means that enough sealing performance minimum value of the contact force is large is excellent.
[0085]
　Table 1 shows the test conditions and evaluation of each specimen. Figure 6 is a graph plotting the sealing performance for the values ​​and the inner external pressure of each specimen of the x / L.
[0086]
[Table 1]

[0087]
　Sealing performance, using the relative value was 1.00 performance of the specimen # 10 (x / L = 0.7 ), and evaluated according to the following three levels.
　Yu: contact force in pressure cycles (pressure sealing performance) contact force of 1.00 or more and an external pressure cycles (external pressure sealing performance) is 1.10 or more
　, Good: pressure sealing performance is 1.00 or more and external pressure sealing performance 1.05
　- Call: less than the internal pressure sealing performance is 1.00 or external pressure sealing performance is less than 1.05
[0088]
　Specimens # 4-8 are embodiments within the scope of the present disclosure, specimens # 1 to 3,9 to 10 are comparative examples outside the scope of this disclosure. That is, in the specimens # 4 ~ 8, x / L is 0.4 or more and 0.55 or less, the specimen # 1 ~ 3,9 ~ 10, x / L is less than 0.4 or 0.55 greater than.
[0089]
　As shown in Table 1 and Figure 6, the specimens # 1-3, for x / L was less than 0.4, the distance of the threaded portion and the sealing portion is near, substantial interference amount of the interference of the screw seal portion It caused a decrease of. Thus, the specimens # 1-3, the internal pressure sealing performance is less than 1.00, was FuKaoru.
[0090]
　As shown in Table 1 and Figure 6, the specimens # 4-8, for x / L was 0.4 or more, the distance between the threaded portion and the sealing portion is away enough, the interference of the thread seal It did not cause a decrease in the substantial amount of interference part. Thus, the specimens # 4-8, the internal pressure sealing performance becomes 1.00 or more, were good.
[0091]
　Further, the specimens # 4-8, by which the x / L and 0.55 or less, the screw portion is sufficiently meshing in the vicinity of the seal portion, the seal portion be external pressure load was difficult to shrink. Thus, the specimens # 4-8, it is the external pressure sealing performance is 1.05 or more, were good.
[0092]
　x / L is about specimens # 4-6 0.4 or more and less than 0.5, it was possible to obtain a particularly good external pressure sealing performance. In specimens # 4-6, it is the external pressure sealing performance is 1.10 or more, was very good.
[0093]
　As shown in Table 1 and Figure 6, the specimen # 9-10, for x / L is larger than 0.55, the distance of the threaded portion and the sealing portion are sufficiently separated, sealed by the interference of the threaded portion decline in real interference amount of parts does not occur. Therefore, the internal pressure sealing performance of the specimen # 9-10, was no particular problem.
[0094]
　However, the larger specimen # 9-10 than x / L is 0.55, since the large distance between the seal portion and the engaging portion of the screw, diameter reducing deformation of the seal portion is likely to occur when the external pressure is loaded became. Thus, the specimen # 9-10, external pressure sealing performance is less than 1.05, was FuKaoru.
[0095]
　As described above, by setting the x / L to 0.4 to 0.55, it was possible to confirm that for both external pressure and internal pressure, excellent sealing performance is obtained. Further, if the x / L and less than 0.4 or 0.5, and particularly good external pressure sealing performance could be confirmed that the obtained.

WE claims

A threaded joint for steel pipes,
and the pin of the tubular that is provided connected to the steel body,
and a tubular box which the pin is fastened to the pin is inserted,
provided with,
said pin
constituting a front end portion of the pin a nose portion which,
with Pinshoruda surface provided on the distal end surface of the nose portion,
in the steel pipe body side of the nose portion, and a male screw portion provided on an outer peripheral surface of the pin,
　and the male screw portion and the nose portion between, the pin seal surface provided on the outer peripheral surface of the pin
has,
　the box is
　provided corresponding to the Pinshoruda surface innermost of the box, box shoulder in contact with the Pinshoruda surface in engagement state a surface,
　and a female screw portion provided on the inner peripheral surface of the box corresponding to the external thread portion,
　set on the inner peripheral surface of the box in correspondence with the pin seal surface It is, and the box sealing surface in contact with the pin seal surface in the engaged state,
have,
　the outer peripheral surface of the nose portion is opposed at an inner peripheral surface and the clearance of the box in the engaged state,
　The threaded joint satisfies 0.4 ≦ x / L ≦ 0.55, wherein, x is the seal position is a position where the first contact with the inner peripheral surface of the box by a fastening process of the pin seal surface a distance in the tube axis direction between the end of the pin seal surface of the male screw portion, L is is the tube axis direction of the distance between the end of the pin seal surface side of the distal end and the male thread portion of the pin , screw joint.
[Requested item 2]
　A tubular threaded joint according to claim 1,
　the cross-sectional area of said pin in said sealing position is more than 35% of the cross sectional area of the steel pipe body, a threaded joint.