Technical field
[0001]The present disclosure relates to a threaded joint for steel pipes, and more particularly to a threaded joint for connecting two steel pipes with one another.
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]The format of this type of 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, the external thread is formed on an outer periphery of both end portions of the steel pipe, the internal thread is formed on the inner periphery of both end portions of the coupling. The external thread of the steel pipe is screwed into the female screw 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 external thread is formed on an outer periphery of one end portion of the steel pipe, the internal thread is formed on the inner periphery of the other end. The external thread of one of the steel pipe is screwed into the female screw of the other steel pipe, which both are connected is fastened by.
[0004]Generally, the joint portion of the tube end portion formed with a male, since the containing elements to be inserted into the female screw, referred to as "pin". On the other hand, the joint portion of the female thread is formed tube end, since it contains an element for receiving an external thread, referred to as the "box". These pin and box are the ends of the tube, both of which are tubular.
[0005]Oil wells, as Anakabe during drilling does not collapse, since the burrows with reinforced anti wall OCTG will result in oil well pipes are arranged in multiple structure. Recently, high-depth reduction and ultra deep water of wells are increasingly progress, in such environments, for developing efficient oil well, the connection of the oil well pipe, the joint inner and outer diameters of the steel pipe inner and outer diameter and a threaded joint is comparable to or slightly larger is frequently used. Such threaded joint by using, it is possible to reduce the gap between the oil well pipe with each other are arranged in multiple utmost, deeper in the well of the diameter can be developed efficiently oil well not so large. Under such an inner diameter and an outer diameter restriction, the threaded joint, the fluid pressure from the interior to (hereinafter also referred to as "internal pressure") and fluid pressure from the outside (hereinafter, also referred to as "external pressure"), excellent sealing performance is required. Furthermore, for example, in such a case to be used in the deep oil well due to the thermal expansion of the oil well pipe, such a large tensile load or compressive load on the threaded joint. In such environments, the threaded joint is also required with excellent sealing performance.
[0006]
　As threaded joints for securing the sealing performance, a metal - sealing by metal contact (. Hereinafter, "metal seal" hereinafter) those having known. The metal seal, (referred to as the difference between the diameter "interference amount") slightly larger than the diameter of the sealing surface of the diameter of the sealing surface of the pin box, the seal faces are fitted with fastening the threaded joint If, the amount of interference sealing surface of the pin is reduced in diameter, the larger diameter the sealing surface of the box, the entire circumference the contact pressure on the sealing surfaces occurs respective sealing surfaces by the elastic restoring force of returning to the original diameter coherent, a structure to exhibit sealing performance. Further, as a screw joint for securing the sealing performance, in combination with or metal seal not include the metal seal are also known comprising a structure to have a sealing performance at the threaded portion. Specifically, in a predetermined length or more regions of the threaded portion in the fastening state, the the presence of a lubricant having a viscosity clearance threaded surface each other of the pin and the box are called small doped into the gap, the pin and the box structure remembering contact surface pressure on the threaded surface due to the interference of the thread diameter (hereinafter, the structure of "thread seal (structure)".) is. By providing such a screw seal, also known threaded joint having a sealing performance with respect to pressure and external pressure.
[0007]
　Another performance required for the threaded joint, for example, as described later, the less likely the cross threads and galling can be mentioned during the fastening. In this regard, JP-A-8-303657 is a paragraph 0041, "for ease of introduction and removal of the tool, a larger angle of absolute value to the external thread of the teeth of the engaging flank (Engaging flank or stabbing flank) it is preferable to present. this angle is 45 ° for example, from about 10 ° with respect to a plane perpendicular to the axis of the screw. in addition, introducing the male element into the female housing without damaging the screw by entanglement (catching) to help the, the maximum diameter portion leading to the tip of the tooth of the male thread, it is preferable to provide the engaging flank of an angle. the angle between 30 ° and 70 ° with respect to a plane perpendicular to the axis of the screw It has been described as being advantageous if there is. ".
SUMMARY OF THE DISCLOSURE
[0008]
　Threaded joint disclosed in Japanese Patent Laid-Open No. 8-303657 is provided with the excellent performance. However, the present inventors have studied intensively, as described in detail later, newly found that there is room for improvement in terms of performance in ease and compressive load caused the cross threads have been granted.
[0009]
　Purposes of this disclosure, difficult to cause cross threads, and is to compression load performance provides a good tubular threaded joint.
[0010]
　Tubular threaded joint according to the present disclosure includes a pin tubular and a tubular box. Pin is formed on one of the tip of the steel tube. Box, the pin is fastened to the inserted into the pin. Pins, including a male thread. External thread is formed on the outer circumference of the pin. Box, including a female thread. Internal thread corresponds to the external thread is formed on the inner periphery of the box. External thread and the internal thread are trapezoidal threads, and a tapered thread. At least a portion of the external thread and the internal thread in the fastening state constitutes a thread seal. External thread includes a male thread surface, and the male screw the bottom, and the male screw stabbing surface and a male thread load surface. External thread stabbing flanks is formed on the side closer to the tip of the pin. Male thread load surface is formed from the tip of the pin on the far side. External thread stabbing flanks has a first external thread stabbing stage, and a second external thread stabbing stage. The first external thread stabbing stage is formed on the far side from the tube axis of the steel pipe, having a stabbing angle of -10 to 15 degrees. The second external thread stabbing stage is formed closer to the tube axis, it has a stabbing angle of 20-60 degrees. The second external thread stabbing stage has a 20-60% of the height of the male thread. Female threads, including the internal thread surface, and the female screw the bottom, and the internal thread stabbing surface, and a female thread load surface. Internal thread Yamamen faces the external thread bottom. Internal thread bottom faces the external thread surface. Internal thread stabbing flanks faces the external thread stabbing flanks. Female thread load surface is opposed to the male screw load surface. Internal thread stabbing flanks has a first female thread stabbing stage, and a second female thread stabbing stage. The first female thread stabbing stage is formed on the far side from the tube axis, having the same stabbing angle of the stabbing angle of the first male screw stabbing stage. The second female thread stabbing stage is formed closer to the tube axis, having the same stabbing angle of the stabbing angle of the second external thread stabbing stage.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011]
[1] Figure 1 is a longitudinal sectional view along the tube axis direction of a threaded joint for steel pipes according to the first embodiment.
FIG. 2 is an enlarged vertical sectional view showing the respective shapes of the external thread and internal thread shown in FIG.
FIG. 3 is an enlarged longitudinal sectional view of the male screw and the female screw shown in FIG.
[4] FIG. 4 is an enlarged longitudinal sectional view of the pin shown in Figure 1.
FIG. 5 is a longitudinal sectional view along the tube axis direction of a threaded joint for steel pipes according to the second embodiment.
FIG. 6 is a longitudinal sectional view along the tube axis direction of a threaded joint for steel pipes according to the third embodiment.
[7] FIG. 7 is an enlarged longitudinal sectional view of the external thread and the internal thread in a threaded joint according to the prior art.
[8] FIG. 8 is a diagram showing how to connect the steel pipe on the rig.
[9] FIG. 9 is a longitudinal sectional view for explaining the cross threads which occurs when connecting the steel pipe.
[10] FIG. 10 is an enlarged longitudinal sectional view of the cross-thread occurs in a small external thread and the internal thread of the stabbing angle.
[11] FIG. 11 is an enlarged longitudinal sectional view of the cross threads occurs at a greater external thread and the internal thread of the stabbing angle.
[12] FIG 12 is an enlarged longitudinal sectional view of the cross-thread occurs in the external thread and the internal thread are shown in Figures 2 and 3.
[13] FIG 13 is an enlarged longitudinal sectional view of the cross-thread occurs in the external thread and internal thread shown in FIG.
[14] FIG 14 is an enlarged longitudinal sectional view of the cross-thread occurs when there is a cutting burr at the external thread and internal thread shown in FIG.
[15] FIG 15 is an enlarged longitudinal sectional view of the cross-thread occurs when there is a cutting burr at the external thread and the internal thread are shown in Figures 2 and 3.
[16] FIG 16 is a longitudinal sectional view showing a compressive load test results of a threaded joint having a male thread and female thread are shown in Figures 2 and 3.
[17] FIG 17 is a longitudinal sectional view showing a compressive load test results of a threaded joint having a male thread and female thread are shown in Figure 7.
[18] FIG 18 is a diagram showing an example of a calculation result of the contact stress of the stabbing flanks when the compressive load applied to the male screw shown in FIGS.
[19] FIG 19 is a diagram illustrating an example distribution of calculated results of the contact stress of the stabbing flanks when the compressive load applied to the male screw shown in FIG.
DESCRIPTION OF THE INVENTION
[0012]
　A threaded joint for steel pipes according to the present embodiment is a threaded joint for connecting two steel pipes with one another. This threaded joint is provided with the pin tubular and a tubular box. Pin is formed on one of the tip of the steel tube. Box, the pin is fastened to the inserted into the pin. Pins, including a male thread. External thread is formed on the outer circumference of the pin. Box, including a female thread. Internal thread corresponds to the external thread is formed on the inner periphery of the box. External thread and the internal thread are trapezoidal threads, and a tapered thread. At least a portion of the external thread and the internal thread in the fastening state constitutes a thread seal. External thread includes a male thread surface, and the male screw the bottom, and the male screw stabbing surface and a male thread load surface. External thread stabbing flanks is formed on the side closer to the tip of the pin. Male thread load surface is formed from the tip of the pin on the far side. External thread stabbing flanks has a first external thread stabbing stage, and a second external thread stabbing stage. The first external thread stabbing stage is formed on the far side from the tube axis of the steel pipe, having a stabbing angle of -10 to 15 degrees. The second external thread stabbing stage is formed closer to the tube axis, it has a stabbing angle of 20-60 degrees. The second external thread stabbing stage has a 20-60% of the height of the male thread. Female threads, including the internal thread surface, and the female screw the bottom, and the internal thread stabbing surface, and a female thread load surface. Internal thread Yamamen faces the external thread bottom. Internal thread bottom faces the external thread surface. Internal thread stabbing flanks faces the external thread stabbing flanks. Female thread load surface is opposed to the male screw load surface. Internal thread stabbing flanks has a first female thread stabbing stage, and a second female thread stabbing stage. The first female thread stabbing stage is formed on the far side from the tube axis, having the same stabbing angle of the stabbing angle of the first male screw stabbing stage. The second female thread stabbing stage is formed closer to the tube axis, having the same stabbing angle of the stabbing angle of the second external thread stabbing stage.
[0013]
　In the above embodiment, the external thread stabbing flank is formed on the far side from the tube axis of the steel pipe, a first external thread stabbing stage having a stabbing angle of -10 to 15 degrees, it is formed on the side closer to the tube axis, 20-60 It has a stabbing angle degrees, and the internal thread stabbing flank is formed on the far side from the tube axis, a first internal thread stabbing stage having the same stabbing angle of the stabbing angle of the first male screw stabbing stage, the side close to the tube axis It is formed, and a second female thread stabbing stage having the same stabbing angle of the stabbing angle of the second external thread stabbing stage. As a result, less likely cross threads, and compression load performance is good.
[0014]
　Male screw further includes a first external thread round surface. The first external thread round surface is formed at the corner between the external thread surface and the external thread stabbing flanks. Internal thread further comprises a first internally threaded round surface. The first internally threaded round surface is formed at the corner between the internal thread surface and the female thread stabbing flanks.
[0015]
　In this case, the cross-thread is further less likely to occur than the above.
[0016]
　Male screw further includes a second male threaded round surface, and a third male threaded round surface, and a fourth male threaded round surface. Second male threaded round surface is formed at the corner between the external thread surface and the external thread load surface. The third male threaded round surface is formed at the corner between the external thread bottom and the male screw stabbing flanks. The fourth external thread round surface is formed at the corner between the external thread bottom and the male screw load surface. Internal thread further comprises a second internal thread round surface, and a third internally threaded round surface, and a fourth female threaded round surface. The second internally threaded round surface is formed at the corner between the internal thread surface and the female screw load surface. The third internally threaded round surface is formed at the corner between the female screw bottom and the internal thread stabbing flanks. The fourth female threaded round surface is formed at the corner between the female screw bottom and the internal thread load surface.
[0017]
　In this case, the cross-thread is further less likely to occur than the above.
[0018]
　Male thread load surface has a load angle of -10 to 3 degrees. Female thread load surface has the same load angle and the load angle of the external thread load surface.
[0019]
　In this case, to improve the traction load performance, the so-called jump-out is unlikely to occur.
[0020]
　External thread surface, the external thread bottom, internal thread surfaces, and the internal thread bottom is formed parallel to the tube axis.
[0021]
　In this case, the stabbing performance is improved.
[0022]
　External thread stabbing flanks and female thread stabbing flank has a clearance of 60 ~ 120 [mu] m between them engaged.
[0023]
　In this case, the sealing performance is improved, galling (seizure) does not occur easily.
[0024]
　Male thread surface and the internal thread bottom, a gap of 0 ~ 50 [mu] m between them engaged. External thread bottom and the internal thread Yamamen have a gap of 0 ~ 50 [mu] m between them engaged.
[0025]
　In this case, the sealing performance is improved.
[0026]
　Pin further includes Pinshoruda surface. Pinshoruda surface is formed at the tip of the pin. Box further includes a box shoulder surface. Box shoulder surface contacts the Pinshoruda surface in the engaged state.
[0027]
　In this case, it increased resistance to compression loads performance, and the amount of interference screws to each other is controllable.
[0028]
　Male thread includes a tapered thread with a small a tapered ratio increasing distance from the tip of the pin.
[0029]
　In this case, the contact pressure with distance from the tip of the pin is gradually lowered.
[0030]
　Pin further comprises a pin seal surface. Pin seal surface is arranged between the pin tip and the male thread is formed on the outer circumference of the pin. Box further includes a box sealing surface. Box sealing surface facing the pin seal surface is formed on the inner periphery of the box, close contact with the pin seal surface is engaged. Some of the external thread and the internal thread constituting a screw seal, in the tube axis direction, having more than three times the length of the wall thickness of steel pipe.
[0031]
　In this case, the sealing performance is improved.
[0032]
　Other exemplary tubular threaded joint according to Embodiment is the threaded joint for connecting two steel pipes with one another. This threaded joint is provided with a first pin of the tubular, and a second pin of the tubular, and a coupling. The first pin is formed on one of the tip of the steel tube. The second pin is formed on the other of the tip of the steel tube. Coupling includes a first box tubular, and a second box tubular. The first box, the first pin is engaged with the first pin is inserted. The second box is formed on the opposite side of the first box, the second pin is engaged with the second pin is inserted. Each of the first and second pin comprises a male thread. External thread is formed on the outer circumference of the pin. Each of the first and second box includes internal threads. Internal thread corresponds to the external thread is formed on the inner periphery of the box. External thread and the internal thread are trapezoidal threads, and a tapered thread. At least a portion of the external thread and the internal thread in the fastening state constitutes a thread seal. External thread includes a male thread surface, and the male screw the bottom, and the male screw stabbing surface and a male thread load surface. External thread stabbing flanks is formed on the side closer to the tip of the pin. Male thread load surface is formed from the tip of the pin on the far side. External thread stabbing flanks has a first external thread stabbing stage, and a second external thread stabbing stage. The first external thread stabbing stage is formed on the far side from the tube axis of the steel pipe, having a stabbing angle of -10 to 15 degrees. The second external thread stabbing stage is formed closer to the tube axis, it has a stabbing angle of 20-60 degrees. The second external thread stabbing stage has a 20-60% of the height of the male thread. Female threads, including the internal thread surface, and the female screw the bottom, and the internal thread stabbing surface, and a female thread load surface. Internal thread Yamamen faces the external thread bottom. Internal thread bottom faces the external thread surface. Internal thread stabbing flanks faces the external thread stabbing flanks. Female thread load surface is opposed to the male screw load surface. Internal thread stabbing flanks has a first female thread stabbing stage, and a second female thread stabbing stage. The first female thread stabbing stage is formed on the far side from the tube axis, the same as the stabbing angle of the first male screw stabbing stage stabbing It has a corner. The second female thread stabbing stage is formed closer to the tube axis, having the same stabbing angle of the stabbing angle of the second external thread stabbing stage.
[0033]
　In the above embodiment, the external thread stabbing flank is formed on the far side from the tube axis of the steel pipe, a first external thread stabbing stage having a stabbing angle of -10 to 15 degrees, it is formed on the side closer to the tube axis, 20-60 It has a stabbing angle degrees, and the internal thread stabbing flank is formed on the far side from the tube axis, a first internal thread stabbing stage having the same stabbing angle of the stabbing angle of the first male screw stabbing stage, the side close to the tube axis It is formed, and a second female thread stabbing stage having the same stabbing angle of the stabbing angle of the second external thread stabbing stage. As a result, less likely cross threads, and compression load performance is good.
[0034]
　First pin further includes a first Pinshoruda surface. The first Pinshoruda surface is formed at the tip of the first pin. Second pin further includes a second Pinshoruda surface. The second Pinshoruda surface is formed at the distal end of the second pin, in contact with the first Pinshoruda surface in the engaged state.
[0035]
　In this case, it increased resistance to compression loads performance, and the amount of interference screws to each other is controllable.
[0036]
　[Embodiment 1]
　Hereinafter, with reference to the accompanying drawings, embodiments of the tubular threaded joint. Given the same reference and the corresponding configuration in the figure does not repeat the same description.
[0037]
　Referring to FIG. 1, a tubular threaded joint 10 according to the first embodiment is a threaded joint for connecting two steel pipes 20 to each other. Threaded joint 10 comprises a pin 30 of the tubular, and a tubular box 40. Pin 30 is formed on one of the tip portions 22 of the steel pipe 20. Box 40, the pin 30 is fastened to the pin 30 is inserted.
[0038]
　Here, tubular threaded joint 10 according to the first embodiment is a coupling type, provided with two pins 20, 20, the coupling 50. One pin 30 is formed at the distal end portion 22 of one of the steel pipe 20. The other pin 30 is formed at the distal end portion 22 of the other steel pipe 20. Coupling 50 includes two boxes 40, 40 and an annular projecting portion 52. One box 40 is formed on one end of the coupling 50. The other box 40 is formed at the other end of the coupling 50. Protrusions 52 are formed in the central portion of the coupling 50. One box 40, one pin 30 is fastened to one of the pins 30 are inserted. The other box 40 is formed on the opposite side of one of the boxes 40, the other pin 30 is inserted is fastened to the other pin 30.
[0039]
　Pin 30 includes external threads 31. Male thread 31 is formed on the outer periphery of the pin 30. Box 40 includes an internal thread 41. Internal thread 41 corresponds to the external thread 31, formed on the inner periphery of the box 40. External thread 31 and internal thread 41 are trapezoidal threads, and a tapered thread. That is, the external thread 31 is formed on the outer periphery of the pin 30 in a spiral shape, decreases as the diameter of the helix toward the end of the pin 30. Female thread 41 is formed in a spiral shape on the inner periphery of the box 40, the diameter of the helix increases toward the open end of the box 40. Preferred taper ratio of the tapered thread is 6.0 to 18.0%. Taper ratio is a length of appropriate threaded portion in relation to wall thickness of the steel pipe is designed to be obtained. Taper ratio may be constant, but the taper ratio of the external thread 31, as will be described in detail later on, become smaller with distance from the tip of the pin 30 are preferred.
[0040]
　At least a portion of the external thread 31 and internal thread 41 in engagement condition constitutes a thread seal. Some of the external thread and the internal thread constituting a screw seal, in the tube axis direction, having more than three times the length of the wall thickness of the steel pipe 20. External thread and the internal thread constituting a thread seal is a complete thread. The length of the thread seal is excellent in longer sealing performance. On the other hand, if the length of the thread seal is too long, in addition to cost and time-consuming to thread, galling is likely to easily occur at the time of fastening. The length of thread seal is preferably not more than 5 times the thickness. In FIG 1, a threaded joint 10 has no metal seal.
[0041]
　Referring to FIGS. 2 and 3, the male screw 31 includes a male thread surface 32, a male thread bottom 33, a male thread stabbing flank 34, and a male thread load surface 35. Male thread stabbing flanks 34 are formed on the side closer to the tip of the pin 30. Male thread load surface 35 is formed from the tip of the pin 30 on the far side.
[0042]
　Male thread stabbing flanks 34 has two external thread stabbing stages 341 and 342. External thread stabbing stage 341 is formed on the far side from the tube axis X of the steel pipe 20, having a stabbing angle [alpha] 1. External thread stabbing stage 342 is formed closer to the tube axis X, having a stabbing angle [alpha] 2. Stabbing angle [alpha] 1, [alpha] 2 is an angle male thread stabbing flanks 34 (male thread stabbing stages 341, 342) is inclined with respect to a plane perpendicular Y to the tube axis X. If the stabbing flanks 34 are overhanging, the stabbing angle α1 becomes negative. Stabbing angle α2 is greater than the stabbing angle α1 (α2> α1). Stabbing angle α1 is -10 to 15 degrees, preferably between 8 and 12 degrees, such as about 10 degrees. Stabbing angle α2 is 20 to 60 degrees, preferably from 28 to 32 degrees, for example about 30 degrees. Therefore, male thread stabbing flanks 34 are recessed in the middle substantially.
[0043]
　The height of the male thread stabbing stage 342 (the length from the male thread bottom 33 to the boundary of the external thread stabbing stages 341 and 342) is 25 to 60% of the height of the male screw, for example 35%.
[0044]
　Internal thread 41 includes an internal thread surface 42, a female screw bottom 43, an internal thread stabbing flank 44, and a female thread load surface 45. Internal thread surface 42, facing the male thread bottom 33. Internal thread bottom 43 faces the male thread surface 32. Internal thread stabbing flanks 44 facing the external thread stabbing flank 34. Female thread load surface 45 faces the external thread load surface 35.
[0045]
　Internal thread stabbing flanks 44 has two internal thread stabbing stages 441 and 442. Internal thread stabbing stage 441 is formed on the far side from the tube axis X, have the same stabbing angle α1 and stabbing angle α1 of the external thread stabbing stage 341. Internal thread stabbing stage 442 is formed closer to the tube axis X, have the same stabbing angle α2 with stabbing angle α2 of the external thread stabbing stage 342. Therefore, the internal thread stabbing flanks 44 are bulged in the middle substantially. Stabbing angle α1 of the external thread stabbing stages 341 and 342, the stabbing angle α1 of [alpha] 2 and the internal thread stabbing stages 441 and 442 may not be exactly the same and [alpha] 2, may be substantially the same. That is, the stabbing angle [alpha] 1, [alpha] 2 may have an error caused by cutting.
[0046]
　Internal thread stabbing stage 442 preferably has the same height as that of the external thread stabbing stage 342. Thus, not larger than necessary clearance of the screw surface each other of the pin and the box, can exhibit good sealing performance in thread seal structure. The height of the male thread stabbing stage 342 is the height of the female thread stabbing stage 442 may not be exactly the same, may be substantially the same. That is, these heights may have an error caused by cutting.
[0047]
　Male thread 31 further includes a male thread round surfaces 36-39. Male thread round surface 36 is formed at the corner between the external thread surface 32 and the male screw stabbing flank 34. External thread round surface 37 is formed at the corner between the external thread surface 32 and the male screw load surface 35. External thread round surface 38 is formed at the corner between the external thread bottom 33 and the male thread stabbing flank 34. External thread round surface 39 is formed at the corner between the external thread bottom 33 and the male screw load surface 35.
[0048]
　The internal thread 41, including a female thread round surface 46-49. Internal thread round surface 46 is formed at the corner between the internal thread surface 42 and the female screw stabbing flank 44. Female thread round surface 47 is formed at the corner between the internal thread surface 42 and the female screw load surface 45. Internal thread round surface 48 is formed at the corner between the internal thread bottom 43 and the internal thread stabbing flank 44. Internal thread round surface 49 is formed at the corner between the internal thread bottom 43 and the internal thread load surface 45.
[0049]
　Round surfaces 36 to 39, 46 to 49 is a so-called R-plane (rounded chamfer surface), having a predetermined radius of curvature. Radius of curvature is 0.1 ~ 1.2 mm, preferably 0.3 ~ 0.8 mm.
[0050]
　Male thread load surface 35 has a load angle β. The load angle beta, is the angle at which the male screw load surface 35 is inclined with respect to a plane perpendicular Y to the tube axis X. If the load surface 35 is overhang, the load angle β becomes negative. The load angle beta, is -10 to 3 °, preferably -5 to -1 °, for example about -3 degrees. Female thread load surface 45, have the same load angle β and load angle β of the external thread load surface 35. The load angle β of load angle β and the internal thread loading surface 45 of the male thread load surface 35 may not be exactly the same, may be substantially the same. That is, the load angle β may have an error caused by cutting.
[0051]
　External thread surfaces 32, male thread bottom 33, an internal thread surface 42 and the internal thread bottom 43, is formed parallel to the tube axis X. Specifically, the line of the surface 32,33,42,43 appearing in longitudinal section including the tube axis X is parallel to the tube axis X.
[0052]
　As shown in FIG. 3, the external thread stabbing flanks 34 and female thread stabbing flank 44 has a gap 60 ~ 120 [mu] m between them engaged. Further, the external thread surface 32 and the internal thread bottom 43 has a gap of 0 ~ 50 [mu] m between them engaged. Male thread bottom 33 and the internal thread surface 42 also has a clearance of 0 ~ 50 [mu] m between them engaged.
[0053]
　Referring again to FIG. 1, the pin 30 further includes a Pinshoruda surface 24 formed at the tip of the pin 30. Box 40 also includes a box shoulder surface 54 which contacts the Pinshoruda surface 24 in the engaged state.
[0054]
　Referring to FIG 4, the male screw 31 includes a tapered thread having a taper ratio TR1 ~ TR4 becomes smaller with distance from the tip of the pin 30. For example, TR1 = 12.5%, TR2 = 12.0%, TR3 = 11.5%, a TR4 = 11.0%.
[0055]
　[Embodiment 2]
　As shown in FIG. 5, the screw joint 10 may be provided with a metal seal. Specifically, the pin 30 further includes a pin seal surface 26 formed on the outer periphery of the pin 30 a between the tip and the male thread 31 of the pin 30. Box 50 further faces the pin seal surface 26, formed on the inner periphery of the box 50 includes a box sealing surface 56 in close contact with the pin seal surface 26 in the engaged state. A pin seal surface 26 and the box sealing surface 56 constitutes a metal seal.
[0056]
　[Embodiment 3]
　As shown in FIG. 6, box 50 may not be provided with a protruding portion 52 described above. In this case, the Pinshoruda surface 24 of one of the pins 30, the other pin Pinshoruda surface 24 of contact with each other in a fastened state. The third embodiment has a so-called Pin-to Pin structure.
[0057]
　[Prior art]
　With reference to FIG. 7, in a threaded joint disclosed in JP-A-8-303657, external thread 31p pins, the external thread surface 32p, and the male screw bottom 33p, and the male screw stabbing flank 34p, and a male thread load surface 35p. External thread stabbing flanks 34p has two external thread stabbing stages 341p, a 342p. Stabbing angle α2p of stabbing stage 342p is smaller than the stabbing angle α1p of stabbing stage 341p (α2p <α1p). Therefore, the external thread stabbing flank 34p is swollen in the middle almost.
[0058]
　On the other hand, the female screw 41p of the box, including the internal thread surface 42p, and the female screw bottom 43p, and the internal thread stabbing flank 44p, and a female thread load surface 45p. Female thread stabbing flanks 44p has two internal thread stabbing stage 441P, a 442p. Stabbing angle α1p of the internal thread stabbing stage 441p is the same as the stabbing angle α1p of the external thread stabbing stage 341p. Stabbing angle α2p of the internal thread stabbing stage 442p is the same as the stabbing angle α2p of the external thread stabbing stage 342p. Therefore, the internal thread stabbing flank 44p are recessed in the middle almost.
[0059]
　Cross Threads
　as shown in FIG. 8, when connecting the steel pipe 20 on the rig, hanging coupling 50 with a steel pipe 20, performs stabbing screws. Mating the screw, in the process of tightening by rotating, the position to be fitted without rotating the screw of "stabbing position". In an ideal stabbing position where the tube axis of the steel pipe 20 and the coupling 50 are matched, they are in contact throughout the external thread surface and the inner thread surface. However, at the time of work at sea and on land, since the steel pipe 20, which is suspended under the influence of waves and wind sway, often accompanied by a roll angle of about 1 degree.
[0060]
　As indicated by the dashed line in FIG. 9, when inserting the pin 30 obliquely into the box 40, it becomes an illegal fitting in a state where the screw pitch deviation occurs between the external thread surface and the inner thread surface in the stabbing position , a phenomenon that also rotate the pin 30 will lock bite screw immediately occurs. This phenomenon is called "cross-thread". Undue mating occurs angle of pitch shift of the pitch angle of deviation. Cross thread tends to occur when there is a roll angle that exceeds the pitch deviation angle. When the cross threads occurs, because by reversely rotating the pin 30 must removed from the box 40, time required for connection work of the steel pipe 20 becomes longer.
[0061]
　When the cross threads occurs, as shown in FIG. 10, is between the external thread round surface 36p that is between the stabbing flanks 34p and external threads face 32p of the pin, and the stabbing flanks 44p and inner thread surface 42p of the box and the internal thread round surface 46p to lock each other. When both the stabbing angle of the external thread and the internal thread is small, prone cross thread.
[0062]
　In contrast, as shown in FIG. 11, when both the stabbing angle of the external thread and the internal thread is greater, the lock is easily cross thread does not occur easily disengaged. However, when a large stabbing angle, meshing of the screw is disengaged by the compression load in the tube axis direction, external thread surface is likely to occur is jump-a phenomenon jump over internal thread surface. Further, in order to improve the sealing performance under high external pressure or internal pressure, increasing the amount of interference in the radial direction of the screw, to become high pressure on the stabbing flanks, easily occur galling.
[0063]
　As shown in Table 1, the lower limit of the pitch deviation angle cross thread occurs depends on the outer diameter of the thread pitch and the steel pipe. If larger than 3 crimps / inch thread pitch, thread design becomes difficult. In the steel pipe having an outer diameter greater than 16 inches, the pitch deviation angle cross thread occurs is close to 1 time in 3 crimps / inch. That is, in particular, the outer diameter of the large-diameter steel pipes, such as more than 16 inches is desired to be less likely structure cross threads. Of course, even in steel pipes having an outer diameter of less 16 inches, it may be less likely structure cross threads
[0064]
[Table 1]

[0065]
　This embodiment, as well as less likely to cross the thread by the two stages of the stabbing flanks, and an object thereof is to maintain without reducing the compression load performance and galling performance.
[0066]
　As shown in FIGS. 12 and 13, the stabbing flank in two stages, and, by reducing the clearance of the screw, it is possible to maintain the sealing performance due to the thread surface. In addition, in order to make it difficult to occur cross thread while maintaining the compression load performance and galling performance, it is sufficient to increase the stabbing angle of one stabbing flank of which is in two stages (stabbing stage). By increasing the stabbing angle, the lock is easy to cross thread is less likely to occur out.
[0067]
　Compared with the prior art embodiment shown in FIG. 13, the embodiment shown in Figure 12, because it reduces the stabbing angle of the side of the stabbing stage 441 near the high box body rigidity, stabbing stage 441 a compressive load large receive. Therefore, it is possible to maintain the engagement of the screw to the limit compressive load. Moreover, even if it takes the same time the internal pressure and the compression load, it no gap is formed in the radial direction of the screw, it is possible to maintain the sealing performance. In addition, since the female thread to the limit of a jump-in caused by the critical compressive load is to restrain the male thread, the meshing of the screw is hard to miss.
[0068]
　Pins of the male thread is in the tube axis direction, become fully threaded at the distal end, the incomplete thread at the rear end. As shown in FIGS. 14 and 15, the threaded surfaces 32p, 32 ends of the incomplete thread burr BR is generated by the tool during cutting. There is a case in which the cross-thread occurs this burr BR is locked and the screw surface of the box. If there is a burr BR in incomplete thread, in order to facilitate unlocked by burrs BR, when locking on to return the relative inclination of the external thread relative to the internal thread goes out sequentially, facing the burr BR It faces better larger plane a and the stabbing angle.
[0069]
　As shown in FIG. 14, burrs BR of incomplete thread is not Ika slipped contact with internal thread round surface 46p that is between the internal thread surface 42p and stabbing flanks 44p box. Therefore, in the embodiment shown in FIG. 14, the locking cross thread prone easily disengaged.
[0070]
　On the other hand, as shown in FIG. 15, burrs BR incomplete screw, is large stabbing angle of the stabbing stage 442, it slipped contact with the surface. Therefore, in the embodiment shown in FIG. 15, the lock is easily cross thread does not occur easily disengaged.
[0071]
　As described above, according to this embodiment, the lock is easily cross thread does not occur easily disengaged. Moreover, it can be maintained without reducing the compression load performance and galling performance.
[0072]
　Having described embodiments, the present invention is not limited to the above embodiments and can be variously modified without departing from the spirit.
Example
[0073]
　To confirm the effect of the above embodiment was performed and the actual pipe test, elastoplastic finite element method and numerical simulation analysis by (FEM). Conditions and results of the tests are shown in Table 1.
[0074]
[Table 2]

[0075]
　[Actual tube test]
　as follows, using real steel.
　- Dimensions: 18-5 / 8,136 # (nominal outer diameter 473.08Mm, thickness 14.71Mm)
　- Materials: API (American Petroleum Institute) P110 steel standard (nominal yield strength 862N / mm 2 , modulus of elasticity 205kN / Mm 2 , Poisson's ratio 0.3)
[0076]
　A threaded joint according to the embodiment includes a stabbing flank of the two stages described above. Stabbing angle α1 is 10 °, the stabbing angle α2 is 30 °. Comparative Examples 1 and 2 together, no only usual one step stabbing flanks. Stabbing angle of Comparative Example 1 is 10 degrees, the stabbing angle of Comparative Example 2 is 30 degrees.
[0077]
　Connect the steel tube in examples and threaded joint according to Comparative Example 1 and 2, the stabbing performance of their threaded joint was evaluated by testing the makeup break performance and sealing performance. Specifically, as the stabbing performance test, connect the steel pipe threaded joint before the state in which the interference in the radial direction of the threaded portion in situations simulating the suspended steel tube shake state on the rig occurs during running of the oil well pipe and performs a test to release (stabbing make / stabbing Break test), to evaluate the stabbing performance on whether or not cross-thread occurs. As a make break performance tests, evaluate the makeup break performance whether interference amount in the radial direction of the threaded joint is subjected to tests for returning tightening this tightening the steel pipe to a predetermined amount (Make / Break test), galling occurs did. Further, as the sealing performance test, the threaded joint of the fastening state liquid inside is filled, were tested for imparting a compressive load equivalent to the nominal yield strength of the steel pipe (100%), the sealing performance by the presence or absence of liquid leakage evaluated.
[0078]
　Embodiment has been performed five times stabbing performance test, it did not cause cross thread with 5 times. Further, embodiments have been performed three times make break performance test, did not cause galling with 3 times. In contrast, Comparative Example 1 was performed five times stabbing performance test, caused the cross threads 4 times out of 5 times. Further, Comparative Example 1 is not done makeup break performance test, if made stabbing without causing cross threads, would not cause galling. In Comparative Example 2 was performed three times stabbing performance test, it did not cause cross thread with 3 times. Comparative Example 2 was performed 3 times a make break performance test, it underwent galling the third time.
[0079]
　Further, sealing performance test results, Examples did not cause liquid leakage. In contrast, both Comparative Examples 1 and 2 caused the liquid leakage.
[0080]
　[FEM analysis]
　Similar to the embodiment has a stabbing flank of the male thread and the female thread even two stages of the threaded joint of Comparative Example 3. A threaded joint according to Comparative Example 3 is a threaded joint according to the prior art described above. Stabbing angle α1 of Comparative Example 3 is 30 degrees, the stabbing angle α2 is 10 °.
[0081]
　To a threaded joint according to the examples and comparative examples 3, shows an example of calculation results of simulating a simple compressive load to FIGS. In these figures, in any example and comparative example 3 also, the pin 30 shows a state that caused buckling undergoing excessive compressive load. However, the amount of deformation due to buckling is smaller than in Comparative Example 3 towards the embodiment shown in FIG. 16 is shown in Figure 17. Therefore, it hardly buckled than Comparative Example 3 towards the Example, i.e., were found to have better resistance to compression load performance.
[0082]
　The reason, as shown in FIGS. 18 and 19, will be described an example of a calculation result of the contact stress of the stabbing flanks when the compression load applied. Figure 18 is an example of a contact stress distribution in the Examples. Figure 17 is an example of a contact stress distribution in Comparative Example 3. In any of FIGS. 18 and 19, contact stress stabbing flanks during compressive load applied was higher in terms stabbing angle is small among the stabbing flanks of the two stages. That is, the direction of the embodiment of FIG. 18, to support the high contact stress in the near surface to a higher box body rigidity, it is estimated to have better resistance to compression load performance.

The scope of the claims

[Requested item 1]A threaded joint,
　a pin of the tubular formed on one tip portion of the steel pipe,
　and a tubular box which pin is fastened to the pin is inserted,
　the pin is formed on the outer periphery of the pin includes a male thread,
　said box corresponding to the external thread includes an internal thread formed on the inner periphery of the box,
　said external thread and said internal thread is a trapezoidal thread and a tapered thread,
　wherein at engagement state At least a portion of the external thread and the internal thread constitute a thread seal,
　said male thread,
　and an external thread surface,
　and the male screw bottom,
　a male thread stabbing flank which is formed on the side closer to the tip of the pin,
　distant from the tip of the pin and a male screw load surface formed on a side,
　the external thread stabbing flank is
　formed on the far side from the tube axis of the steel pipe, first Onejisu with stabbing angle of -10 to 15 degrees And Bing stage,
　formed on the side closer to the tube axis, and a second external thread stabbing stage having a stabbing angle of 20 to 60 degrees,
　the second external thread stabbing stage 20 to the height of the external thread 60 % of a height,
　wherein the internal thread has
　a internal thread surface facing the external thread bottom,
　And the internal thread bottom facing the external thread surface,
　a female thread stabbing flank facing the external thread stabbing flanks,
　and a female thread load surface facing the external thread load surface,
　the female thread stabbing flank is
　farther from the tube axis is formed, a first female thread stabbing stage having the same stabbing angle of the stabbing angle of the first external thread stabbing stage,
　formed on the side closer to the tube axis, having the same stabbing angle of the stabbing angle of the second external thread stabbing stage and a second female thread stabbing stage, a threaded joint.
[Requested item 2]
　A threaded joint according to claim 1,
　wherein the external thread further
　comprises a first external thread round surface formed at the corner between the external thread surface and the external thread stabbing flanks,
　the female screw is further
　the female screw the first includes a female thread round surface, a threaded joint which is formed at the corner between the mountain surface and the female thread stabbing flanks.
[Requested item 3]
　A threaded joint according to claim 2,
　wherein the external thread is further
　a second male threaded round surface formed on the corner, between the external thread surface and the external thread load surface
　the said external thread bottom external thread stabbing flanks corner and a third male threaded round surface formed, between
　and a fourth male threaded round surface formed at the corner between the external thread bottom and the male thread load surface,
　wherein the internal thread further
　said internal threads a second internally threaded round surface formed at the corner between the face and the internal thread load surface,
　and a third internally threaded round surface formed at the corner between the female screw bottom and the internal thread stabbing flanks,
　and the female screw bottom and a fourth female threaded round surface formed at the corner between the female screw load surface, a threaded joint.
[Requested item 4]
　A threaded joint according to any one of claims 1 to 3,
　wherein the external thread load surface has a load angle of -10 to 3 °,
　the female screw load surface, the load angle of the external thread load surface It has the same load angle is, the threaded joint.
[Requested item 5]
　A threaded joint according to any one of claims 1 to 4,
　wherein the external thread surface, said external thread bottom, the internal thread surface, and the internal thread bottom is formed parallel to the tube axis, screw joint.
[Requested item 6]
　A threaded joint according to any one of claims 1 to 5,
　wherein the external thread stabbing flank and the internal thread stabbing flank has a clearance of 60 ~ 120 [mu] m between them engaged, the threaded joint.
[Requested item 7]
　A threaded joint according to any one of claims 1 to 6,
　wherein the external thread surface and the female thread bottom, a gap of 0 ~ 50 [mu] m between them engaged, and the external thread bottom and the female screw Yamamen has a gap of 0 ~ 50 [mu] m between them engaged, the threaded joint.
[Requested item 8]
　A threaded joint according to any one of claims 1 to 7,
　wherein the pin further comprises a Pinshoruda surface formed at the tip of the pin,
　the box further said Pinshoruda surface in engagement state including box shoulder surface that contacts, a threaded joint.
[Requested item 9]
　A threaded joint according to any one of claims 1-8,
　wherein the male thread comprises a tapered thread with a small a tapered ratio increasing distance from the tip of the pin, a threaded joint.
[Requested item 10]
　A threaded joint according to any one of claims 1-9,
　wherein the pin further comprises a pin seal surface formed on the outer periphery of the pin be between the male thread and the tip of the pin,
　the box is further said to pin seal surface facing, it is formed on the inner periphery of the box, including the box sealing surface in close contact with the pin seal surface is engaged, the threaded joint.
[Requested item 11]
　A threaded joint according to any one of claims 1 to 10,
　wherein a portion of said external thread and said internal thread constituting a screw seal, in the tube axis direction, three times or more the thickness of the steel pipe having a length, a threaded joint.
[Requested item 12]
　A threaded joint according to any one of claims 1 to 11,
　wherein the steel pipe has an outer diameter greater than 16 inches threaded joint.
[Requested item 13]
　A threaded joint according to any one of claims 1 to 11,
　wherein the steel pipe has an outer diameter of less 16 inches, a threaded joint.
[Requested item 14]
　A threaded joint for connecting two steel pipes with each other,
　a first pin of the tubular formed on one end portion of the steel pipe,
　and a second pin of the tubular is formed in the other end portion of the steel pipe,
　a first box tubular first pin is engaged with the first pin is inserted, is formed on the opposite side of the first box, said second pin is inserted in a tubular to be fastened to the second pin and a coupling and a second box,
　each of said first and second pin comprises a male thread formed on an outer periphery of the pins,
　each of said first and second box, corresponding to the external thread and includes a female thread formed on the inner periphery of the box,
　said external thread and said internal thread is a trapezoidal thread and a tapered thread,
　the external thread and at least a portion thread seal of the internal thread in engagement state configured,
　before Male thread,
　the external thread surface,
　and the male screw bottom,
　a male thread stabbing flank which is formed on the side closer to the tip of the pin,
　and a male thread load surface formed on the side farther from the tip of the pin,
　said male thread stabbing flank is
　formed on the far side from the tube axis of the steel pipe, a first external thread stabbing stage having a stabbing angle of -10 to 15 degrees,
　Formed on the side closer to the tube axis, and a second external thread stabbing stage having a stabbing angle of 20-60 degrees,
　the second external thread stabbing stage, height of 20 to 60% of the height of the external thread has,
　the internal thread,
　the internal thread surface facing the external thread bottom,
　and the internal thread bottom facing the external thread surface,
　a female thread stabbing flank facing the external thread stabbing flanks,
　female thread facing the external thread load surface and a load surface,
　wherein the internal thread stabbing flank is
　formed on the side farther from the tube axis, a first internal thread stabbing stage having the same stabbing angle of the stabbing angle of the first external thread stabbing stage,
　closer to the tube axis It is formed, and a second female thread stabbing stage having the same stabbing angle of the stabbing angle of the second external thread stabbing stage, a threaded joint.
[Requested item 15]
　A threaded joint according to claim 14,
　wherein the first pin further includes a first Pinshoruda surface formed at the tip of the first pin,
　the second pin is further to the distal end of the second pin It is formed, including a second Pinshoruda surface in contact with the first Pinshoruda surface in the engaged state, a threaded joint.