The present disclosure relates to a threaded joint for use in connecting steel pipes.
BACKGROUND
[0002]
　Oil wells, natural gas wells and the like in (hereinafter collectively referred to as "oil wells"), a casing, an oil well pipe such as tubing are used to mine underground resources. OCTG are made are sequentially connected steel pipes, threaded joints are used for the connection.
[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, a short tube the other tube called coupling. In this case, a male screw portion is formed on an outer periphery of both end portions of the steel pipe, the internal thread portion is formed on the inner periphery of both end portions 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, a male screw portion is formed on an outer periphery of one end portion of the steel pipe, the internal thread portion is formed on the inner periphery 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. Pin and box are the ends of the tube, both of which are tubular.
[0005]
　Recently, for example, with the new technology development such horizontal drilling and directional drilling, etc., with respect to a threaded joint, so that the high torque resistance performance and sealing performance is required. In order to achieve both anti-torque performance and sealing performance, for example, it is effective to apply a taper screws referred dovetail shape with wedge thread on the threaded portion. The threaded joint having a wedge-shaped thread, the thread width of the male screw portion (pin) is narrower tapers in the direction of travel of the right screw along the helical line of the thread, even thread root width of the opposed female threaded portion (box) narrows in tapered in the direction of travel of the right screw along the screw chord winding. The wedge screw, load flank surface (hereinafter, also referred to as "load surface") and insert flank (hereinafter, also referred to as "insertion surface") both are negative angle, the contact load faces and insert faces to each other to. Thus, the entire threaded portion fit Mari firmly fitted, exhibits high resistance to torque performance. Further, in the engaged state, since the thread crest surface and the thread root bottom surface of the threaded portion are in contact with each other, it is possible to secure the sealing performance.
[0006]
　On the other hand, Patent Documents 1 and 2, without using a wedge-type screw, a threaded joint has been disclosed with improved torque resistance performance.
[0007]
　In Patent Document 1 of the threaded joint, load flanks and the stabbing flanks of each of the cross-sectional shape of the screw portion is formed on the Z-shaped. In this threaded joint, by contacting the load surface and between the insertion faces of such a shape, controls the tightening of the tube axis direction and the radial direction in the screw portion.
[0008]
　The threaded joint described in Patent Document 2, the cross-sectional shape of each load surface of the screw portion is formed in a hook shape. Therefore, at the time of fastening, mate to each other hook-like load surface. Thus, it is possible to share part of the twisting torque is a torque shoulder to bear on the threaded portion, a high torque resistance performance with plastic deformation of the torque shoulder is reduced can be exhibited.
[0009]
　Herein are incorporated by reference prior art documents described below.
Patent Document 1: U.S. Patent Application Publication No. 2008/0073909 Pat
Patent Document 2: JP 2002-81584 JP
SUMMARY OF THE DISCLOSURE
[0010]
　Incidentally, in the applied threaded joint a wedge thread on the threaded portion, the screw trough width of the internal thread portion which corresponds to the thread width and its male thread portion is changed. Therefore, it is difficult cutting threaded portion, and since it takes cutting time, production cost is increased. From the viewpoint of reducing the manufacturing cost, it is conceivable to apply the API (American Petroleum Institute (American Petroleum Institute)) buttress thread (trapezoidal thread) standard to the screw portion. However, a threaded joint according to the buttress thread, if the torque amplification mechanism such as a torque shoulder is not provided, it is not possible to exert a high torque resistance performance.
[0011]
　The present disclosure aims to provide a tubular threaded joint which can achieve both reduction of securing and manufacturing cost of the torque resistance performance.
[0012]
　Tubular threaded joint according to the present disclosure includes a pin tubular and a tubular box. Pin has a male thread portion on the outer periphery. Box has on the inner circumferential internal threads corresponding to the male screw portion is fastened to the pin. External thread portion includes a main external thread, and a sub-male screw. The main external thread is comprised of trapezoidal threads having a constant thread width and thread root width. Sub male screw is disposed thread root of the main external thread has a smaller thread width and thread height than the thread width and thread height of the main external thread. The main external thread and secondary male screw each have an insertion flank, a load flank surface disposed on the opposite side of the insertion flank. In the tube axis direction of the cross-section of the pin, the flank angle of the load flank surface of the flank angle and the sub-male screw insertion flank of the main adjacent external thread is greater than 0 degrees.
[0013]
　According to a threaded joint for steel pipes according to the present disclosure, while ensuring the anti-torque performance, it is possible to reduce the manufacturing cost.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014]
[1] Figure 1 is a longitudinal sectional view of a tubular threaded joint according to the embodiment.
FIG. 2 is a longitudinal sectional view of a threaded portion of a threaded joint for steel pipes shown in Figure 1.
FIG. 3 is a longitudinal sectional view of a tubular threaded joint according to the prior art (Comparative Example).
[4] FIG. 4 is a graph showing the yield torque of the threaded joint for steel pipes according to the examples and comparative examples.
FIG. 5 is a graph showing the minimum seal contact force tubular threaded joint according to the examples and comparative examples.
DESCRIPTION OF THE INVENTION
[0015]
　Inventor, etc. of a threaded joint for steel pipes according to the embodiment mainly considered trying to exert anti-torque performance in the screw portion, API standard buttress thread (trapezoidal thread) was changed thread shape based.
[0016]
　Tubular threaded joint according to the embodiment includes a pin tubular and a tubular box. Pin has a male thread portion on the outer periphery. Box has on the inner circumferential internal threads corresponding to the male screw portion is fastened to the pin. External thread portion includes a main external thread, and a sub-male screw. The main external thread is comprised of trapezoidal threads having a constant thread width and thread root width. Sub male screw is disposed thread root of the main external thread has a smaller thread width and thread height than the thread width and thread height of the main external thread. The main external thread and secondary male screw each have an insertion flank, a load flank surface disposed on the opposite side of the insertion flank. In the tube axis direction of the cross-section of the pin, the flank angle of the load flank surface of the flank angle and the sub-male screw insertion flank of the main adjacent external thread is greater than 0 degrees.
[0017]
　The external thread portion of the threaded joint, a thread root of the main external thread, the main sub male screw thread width and thread height is less than the external thread is arranged. Internal thread portion is configured so as to correspond to the external thread portion. According to this configuration, the engagement area between the male thread portion and the internal thread portion may be larger than a conventional buttress thread. Therefore, it is possible to secure a high torque resistance performance.
[0018]
　Further, the external thread portion of the threaded joint, the thread width and thread root width is constituted mainly male thread by a constant trapezoidal thread. Therefore, as compared with the wedge-type screw, it is possible to cut the threaded portion in a short time. Therefore, it is possible to reduce the manufacturing cost.
[0019]
　[Embodiment]
　Hereinafter will be described with reference to the accompanying drawings embodiments. Given the same reference and the corresponding configuration in the figure does not repeat the same description.
[0020]
　(Configuration of a threaded joint for steel pipes)
　FIG. 1 is a longitudinal sectional view showing a threaded joint for steel pipes 1 according to the present embodiment (cross-sectional view of a plane including the tube axis CL). Threaded joint 1 may be a integral type threaded joint, it may be a coupling type of threaded joint. Threaded joint 1 is provided with a pin 10 and a box 20.
[0021]
　Pin 10 includes a male screw portion 11, and the sealing surface 12, and a shoulder surface 13. Male thread portion 11 includes a main male screw 111 and the sub male screw 112. Male thread portion 11 and the sealing surface 12 is provided on an outer periphery of the pin 10. Sealing surface 12 is disposed on the distal end side of the pin 10 than the male threaded portion 11. Shoulder surface 13 is provided on the distal end of the pin 10.
[0022]
　Box 20 includes a female threaded portion 21, a sealing surface 22, and a shoulder surface 23. Internal thread portion 21, the sealing surface 22, and the shoulder surface 23, respectively, male threaded portion 11 of pin 10 is provided corresponding to the sealing surface 12, and the shoulder surface 13.
[0023]
　Male threaded portion 11 and the internal thread portion 21, fit to each other in the engaged state, the interference fit state.
[0024]
　Sealing surface 12, 22 contact each other with the screwing of the pin 10 relative to the box 20, fit in the fastening state, the interference fit state. Thus, between the sealing surfaces 12 and 22, to form a seal by metal contact.
[0025]
　Shoulder surface 13 and 23, with the screwing of the pin 10 relative to the box 20 are pressed in contact with each other. Shoulder surface 13 and 23, as well as limiting the screwing of the pin 10 relative to the box 20, the load of the screwing direction opposite to the traveling direction, that is, the fastening axial force of the screw imparts to the external thread portion 11.
[0026]
　Figure 2 is a longitudinal sectional view of a threaded portion of a threaded joint 1 (cross-sectional view of a plane including the tube axis CL). In Figure 2, for convenience of explanation, it is shown apart the male thread portion 11 and the internal thread portion 21.
[0027]
　As described above, the external thread portion 11 includes a main male screw 111 and the sub male screw 112. The main external thread 111 is formed by a trapezoidal screw having a constant thread width and thread root width throughout the external thread portion 11. The main external thread 111, in longitudinal section, each plurality of screws crest surfaces 111a, thread root bottom surface 111b, the insertion flank surfaces (hereinafter, also referred to as "insertion surface") 111c, and load flank surface (hereinafter, also referred to as "load surface" having a) 111d. Each insertion surface 111c is located on the distal end side of the pin 10. Each load surface 111d is located on the opposite side of the insertion surface 111c with respect to each thread of the main external thread 111.
[0028]
　Each insertion surface 111c and the load surface 111d of the main external thread 111 is inclined in the same direction. Specifically, the flank angle of the insertion face 111c is a conformal greater than 0 degrees. Flank angle of the load surface 111d is a negative angle slightly less than 0 °. Here, the flank angle refers, is the angle between a plane perpendicular VP to the tube axis CL and each insert surface 111c or the load surface 111d. 2, the flank angle of the insertion surface 111c is the counterclockwise direction is positive, the flank angle of the load surface 111d to the clockwise and positive.
[0029]
　Sub male screw 112 is disposed thread root of the main external thread 111. That is, the thread of the sub-male screw 112, in longitudinal section, are provided on the threads of the main external thread 111. Sub male screw 112 has a screw thread width and thread less than the height thread width and thread height of the main external thread 111. For example, longitudinal area of ​​the threads of the sub-male screw 112 is 50% or less of a longitudinal area of ​​the threads of the main external thread 111.
[0030]
　Sub male screw 112 has in longitudinal section, each plurality of screws crest surfaces 112a, insert flank surfaces (hereinafter, also referred to as "insertion surface") 112c, and load flank surface (hereinafter, also referred to as "load surface") and 112d. Each insertion surface 112c is located on the distal end side of the pin 10. Each load surface 112d is located on the opposite side of the insertion surface 112c with respect to each thread of the sub-male screw 112. Each insertion surface 112c of the sub-male screw 112, facing the load surface 111d of the main external thread 111. Each load surface 112d of the sub-male screw 112, facing the insertion surface 111c of the main external thread 111.
[0031]
　Each insertion surface 112c and the load surface 112d of the sub-male screw 112 is inclined in the opposite direction. In other words, the flank angle of the insert surfaces 112c and respective load surface 112d, respectively, has a large positive angle than 0 °. Here, the flank angle refers, is the angle between a plane perpendicular to the tube axis CL and each insert surface 112c or the load surface 112d. 2, the flank angle of the insertion surface 112c is the counterclockwise direction is positive, the flank angle of the load surface 112d to the clockwise and positive.
[0032]
　Longitudinal section of the pin 10 in (tube axis direction of the cross section), the flank angle θ111c and flank angle θ112d the load surface 112d of the sub-male screw 112 of the insertion surface 111c of the main adjacent external thread 111, respectively, conformal greater than 0 degrees it is. Although not shown particularly, the flank angle of the load surface 111d of the main external thread 111 is negative angle less than 0 degrees. Flank angle of insertion surface 112c of the sub-male screw 112 is conformal greater than 0 degrees. But are not limited to, the absolute value of flank angle of the load surface 111d is smaller than the absolute value of flank angle of the insert surface 112c.
[0033]
　Internal thread portion 21, in a longitudinal section, say each plurality of screws crest surfaces 21a, thread root bottom surface 21b, insertion flank surfaces (hereinafter, also referred to as "insertion surface") 21c, and load flank surface (hereinafter, also referred to as "load surface" having a) 21d. The threads of the internal thread portion 21, the sub screw groove 21e is formed.
[0034]
　Screw crest surface 21a of the female screw portion 21, the screw trough bottom 21b, insertion face 21c, and the load surface 21d, respectively, thread root bottom surface 111b of the main external thread 111, thread crest surfaces 111a, insertion surface 111c, and the load surface 111d facing to. Secondary screw groove 21e of the female screw portion 21 accepts the threads of the sub-male screw 112.
[0035]
　In the engaged state, the screw crest surface 21a and the load surface 21d of the internal thread portion 21, respectively, in contact with the thread root bottom surface 111b and the load surface 111d of the main external thread 111. The bottom and the side surface of the sub screw groove 21e of the female screw portion 21, the screw crest surface 112a of the sub-male screw 112, insertion surface 112c, and the load surface 112d contacts.
[0036]
　The width of the sub screw groove 21e provided on the threads of the internal thread portion 21 W2 is slightly smaller than the width W1 of the threads of the sub-male screw 112. In the thread of the internally threaded portion 21, the insertion surface 21c tube axial direction length L21 to the side wall surface of the sub screw groove 21e from the insertion surface 111c of the main external thread to load surface 112d of the sub-male screw 112 tube axis direction of slightly larger than the length L11. Also, in the thread of the internal thread portion 21, a tube axial length L22 from the load surface 21d to the side wall surface of the sub screw groove 21e is the tube axis from the load surface 111d of the main male screw to the insertion surface 112c of the sub-male screw 112 slightly larger than the direction of the length L12. With this configuration, it is possible to sub-male screw 112 is mutually tightening Toka internal thread portion 21, to increase the engagement strength of the formed threaded portion with a male thread portion 11 and the internal thread portion 21.
[0037]
　(Effects of Embodiment)
　As described above, in the threaded joint 1 according to the present embodiment, the thread root of the main external thread 111 is disposed sub male screw 112 threads width and thread height smaller than the main external thread 111 there. Thread sub male screw 112, the fastening state, is received in the sub screw groove 21e of the internal thread portion 21. Therefore, the engagement area between the male thread portion 11 and the internal thread portion 21 can be made larger than conventional buttress thread, it is possible to ensure a high torque resistance performance.
[0038]
　Further, in the present embodiment, the thread width and thread root width of the main external thread 111 at the male thread portion 11, and the thread width and thread Tanihaba of the internal thread portion 21 corresponding to the external thread portion 11 is constant over the entire threaded portion is there. Therefore, as compared with the wedge screw cuts the thread portion in a short time. As a result, it is possible to reduce the manufacturing cost.
[0039]
　In the present embodiment, the width W2 of the sub screw groove 21e of the female threaded portion 21 for receiving a sub-male screw 112 is slightly smaller than the width W1 of the threads of the sub-male screw 112. In the thread of the internal thread portion 21, a tube axial length L21 from the insertion face 21c to (opposite side to the insertion face 21c) 21f load flanks of the secondary thread groove 21e, vice male thread from the insertion surface 111c of the main external thread 112 slightly larger than the tube axis direction of the length L11 to the load surface 112d of. Also, in the thread of the internal thread portion 21, a tube axial length L22 from the load surface 21d up (opposite to the side load surface 21d) 21g insertion face of the secondary thread groove 21e from the load surface 111d of the main external thread slightly larger than the tube axis direction of the length L12 to insertion surface 112c of the sub-male screw 112. Thereby, since the sub-male screw 112 and the female screw portion 21 fits caulking, it is possible to increase the engagement strength of the threaded portion. As a result, it is possible to further improve the torque resistance performance.
[0040]
　As described above, in the present embodiment, by the sub-male screw 112 provided on the male thread portion 11 engages the area and engagement strength of the screw portion is increased. Accordingly, even when the external pressure is loaded to the threaded portion, the external pressure of the osmotic against screw portion and the sealing portion is suppressed. Therefore, it is possible to improve the sealing performance against external pressure.
Example
[0041]
　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.
[0042]
　[Test conditions]
　As an example, to prepare a model of the threaded joint 1 having a secondary male thread 112 on the thread root of the main male screw 111 (Fig. 1). As prior art (Comparative Example) for comparison was produced a model of a threaded joint 2 employing the buttress thread (Fig. 3). It threaded joint 2 according to the comparative example, except that it does not include the sub-male screw 112 has the same configuration as the threaded joint 1 according to the embodiment. The size of the steel tube 5 "18 # (tube body outer diameter: 127.00mm, the tube body inner diameter: 108.61mm), material P110 (nominal yield stress (YS): 758 MPa) of API carbon steel and the.
[0043]
　[Evaluation Method]
　The analysis for each model produced, continue to increase the fastening turns after the shoulder 13, 23 of the pin 10 and box 20 are in contact with each other, and the yield torque the point at which the slope of the tightening torque diagram is changed defined and evaluated the anti-torque performance in the value of the breakdown torque. Furthermore, for each model produced by the minimum value of the seal contact force obtained by the load conditions simulating the Series A test ISO13679 (minimum seal contact force) to evaluate the sealing performance.
[0044]
　4 and 5, respectively, show the resulting yield torque and minimum seal contact force. As shown in FIGS. 4 and 5, the threaded joint 1 is significantly greater yield torque and minimum seal contact force than threaded joint 2 towards (Fig. 1) is according to the comparative example (FIG. 3) according to the embodiment. Thus, by providing the sub-male screw 112 into the screw trough of the main external thread 111, it was found that is caused to remarkably improve the torque resistance performance and sealing performance.
[0045]
　Range provisions]
　vertical area of the threads of the sub-male screw 112, it is better to ensure a certain size. With increasing contact area of the threaded portion at the time of fastening, in order to significantly improve in comparison with torque resistance performance to the conventional. It is also true with respect to external pressure sealing performance described above. And Sankounisuru this embodiment, to increase the external pressure sealing performance is considered to be desirable thread of a longitudinal area S1 of the sub-male screw 112 is 15% or more of the threads of the longitudinal area S2 of the main external thread 111 . However, if too large a thread of a longitudinal area S1 of the sub screw 112, since there may occur a problem in the manufacture and the fastening of the threaded portion, the thread of a longitudinal area S1 of the sub-male screw 112, the main external thread 111 it is better to 40% or less of the threads of the longitudinal area S2. Here, the thread of a longitudinal area S1 of the sub-male screw 112, as shown in FIG. 2, the longitudinal section of the screw thread of the sub-male screw 112, the contour of the thread of the sub-male screw 112, the screw trough bottom 111b to each other is the area enclosed by the straight line L connecting. Furthermore, the threads of the longitudinal area S2 of the main external thread 111, as shown in FIG. 2, the longitudinal section of the screw thread of the main external thread 111, and the thread profile of the main male screw 111, connecting thread root bottom surface 111b to each other is the area surrounded by the straight line L.
DESCRIPTION OF SYMBOLS
[0046]
1: a threaded joint for steel pipes
10: Pin
11: external thread portion
111: Main male thread
111c: insert flanks
111d: load flank surfaces
112: secondary male thread
112c: insert flanks
112d: load flank face
20: box
21: female thread part

WE claims

A threaded joint for steel pipes,
and a pin tubular having an external thread portion on the outer periphery,
has a female screw portion corresponding to the external thread portion inner periphery, a tubular box to be fastened to the pin
provided with,
　said male thread portion ,
　the main external thread consists of trapezoidal threads having a constant thread width and thread root width,
　the main is located thread root of the external thread, the main male screw thread width and small thread width and thread than the thread height , a sub-male screw having a crest height
comprises,
　the main external thread and the sub male screw each have an insertion flank, a load flank surface disposed opposite the insertion flank,
　the tube of the pin in axial section, the flank angle of the main flank angle of the insert flanks of the external thread and the load flanks of the sub-male screw adjacent to each other is greater than 0 degrees, a threaded joint for steel pipes.
[Requested item 2]
　A tubular threaded joint according to claim 1,
wherein the threads of the sub-male screw has a longitudinal area of 15-40% of a longitudinal area of the thread of the main external threads adjacent to the sub-male screw, tubular threaded joint.