0001]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 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. These pin and box are the ends of the tube, both of which are tubular.
[0005]
　The threaded joint for steel pipes, pressure from internal fluid (hereinafter, also referred to as "internal pressure") and the pressure fluid from the outside (hereinafter, also referred to as "external pressure") excellent sealing performance for is required. Therefore, the threaded joint, a metal - seal part due to metal contact is provided. Metal - sealing portion by the metal contact is composed of a pin seal surface, the box sealing surface having a slightly smaller diameter than the diameter of the pin seal surface. When the screw joint is fastened seal faces are fitted by interference amount which is the difference between the diameters of the box sealing surface pin seal surface, 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 contact pressure on the seal surface all around closely occurring, sealing performance is exhibited.
[0006]
　Some of the threaded joint, in order to further improve the sealing performance of the seal portion, there is one having a structure called a nose portion. Nose portion is provided adjacent to pin seal surface at the tip of the pin. Nose because it does not interfere with the box, to amplify the elastic recovery force of the pin seal surface. Since the adhesion force between the sealing surface by the nose portion is amplified, to improve sealing performance of the sealing portion.
[0007]
　The International Publication No. 2009/060552 and JP-T 2012-506000, a threaded joint for steel pipes having a nose portion between the Pinshoruda surface and pin seal surface is disclosed. In the screw joint, the outer peripheral surface, and a portion corresponding to the nose portion of the inner peripheral surface of the box of the nose portion of the pin, the noncontacting region which does not contact each other in the engaged state is present. Each non-contact region is constituted by a tapered surface or a cylindrical surface.
[0008]
　In JP-T-2013-524116 is a threaded joint for steel pipes pin seal surface and box seal surfaces are composed of a curved surface of a different curvature it has been disclosed. In the threaded joint, a tapered surface is provided continuously with each of the pin seal surface and the box sealing surface.
SUMMARY OF THE DISCLOSURE
[0009]
　Nose portion when the threaded joint is fitted is fastened and sealed faces, the sealing performance is improved by amplifying the adhesion force between the seal surfaces. However, during fastening, adhesion force by the nose portion (contact force) seizing may occur amplified by disaster each seal surface.
[0010]
　This disclosure, while ensuring a high sealing performance after engagement completion, and an object thereof is to provide a tubular threaded joint which can suppress galling of each seal surface during fastening.
[0011]
　The present disclosure relates to a threaded joint for steel pipes. Threaded joint comprises a pin tubular and a tubular box. Pin is connected to the steel tube body. Box, the pin is fastened to the inserted into the pin. Pin includes a pin lip portion, and a male screw portion. Pin lip portion constitutes a tip portion of the pin. Male screw portion than pin lip portion on the outer circumference of the pin is provided on the steel pipe body side. Male screw portion is composed of a taper screw. Pin lip portion includes a first Pinshoruda surface, and a nose portion, and a first pin seal surface. The first Pinshoruda surface is provided at the tip of the pin. Nose portion is provided on the male screw portion side of the first Pinshoruda surface. Nose portion has a pin tapered guide surfaces on the outer peripheral surface. Pin tapered guide surface, the diameter toward the distal end of the pin is reduced. The first pin seal surface is provided on the male screw portion side than the nose portion in the outer peripheral surface of the pin lip portion. The first pin seal surface includes a tapered surface whose diameter toward the tip of the pin is reduced. Box has a first box shoulder surface, and the nose receiving portion, a first box sealing surface, and a buffer surface, and a female screw portion. The first box shoulder surface is provided on the inner end of the box corresponding to the first Pinshoruda surface. The first box shoulder surface is in contact with the first Pinshoruda surface in engagement state. Nose receiving portion is provided corresponding to the nose portion. Nose receiving portion has a box tapered guide surface on the inner peripheral surface. Box tapered guide surface diameter decreases toward the rear end of the box. The first box sealing surface is provided on the inner peripheral surface of the box corresponding to the first pin seal surface. The first box sealing surface includes a tapered surface whose diameter toward the rear end of the box becomes small. The first box sealing surface is in contact with the first pin seal surface in the engagement state. Buffer surface is provided between the tapered surface of the box tapered guide surface and the first box sealing surface on the inner peripheral surface of the box. Internal thread portion is provided on the inner periphery of the box corresponding to the external thread portion. Internal thread portion is composed of a taper screw. Each pin tapered guide surface and the box tapered guide surface, first It has a taper angle. Each of the tapered surface of the first pin seal surface and the first box sealing surface has a second taper angle. The second taper angle, greater than the first taper angle. In a disengaged state, the pin tapered guide diameter of the end portion of the front end side of the pin of the surface Dp1, the diameter of the line of intersection between the extension surface and the extended surface of the tapered surface of the first pin seal surface of the pin tapered guide surface dp2, from the tip of the pin to the line of intersection between the extension surface and the extended surface of the tapered surface of the first pin seal surface of the pin tapered guide surface, the length in the tube axis direction of the threaded joint Lp2, extended surface of the box tapered guide surface When the diameter of the intersection of the first box sealing surface extension plane of the tapered surface of the Db2, from the back end of the box until intersection of the extended plane of the extension surface and the tapered surface of the first box sealing surface of the box tapered guide surface when the length in the tube axis direction and Lb2, satisfies the following formula (1) and (2).
　　Ｄｐ２＞Ｄｂ２＞Ｄｐ１　　　（１）
　　Ｌｂ２＞Ｌｐ２　　　（２）
[0012]
　Buffer surface has a length more than 0.75mm in the tube axis direction. Buffer unit is disposed outside the imaginary plane in the radial direction of the threaded joint. Virtual surfaces are constituted by the extension surface and the extended surface of the first box sealing surface of the box tapered guide surface.
[0013]
　According to a threaded joint for steel pipes according to the present disclosure, while ensuring a high sealing performance after engagement completion, it is possible to suppress the seizure of the sealing surfaces during engagement.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014]
[1] Figure 1 is a longitudinal sectional view showing a schematic configuration of a coupling-type threaded joint for steel pipes according to the first embodiment.
FIG. 2 is a longitudinal sectional view showing a schematic configuration of the integral-type tubular threaded joint according to the first embodiment.
FIG. 3 is an enlarged view of the inner end of the tube axis direction of the threaded joint in the non-engaged state.
[4] FIG. 4 is an enlarged view of the inner end of the tube axis direction of the threaded joint during fastening.
FIG. 5 is an enlarged view of the inner end of the tube axis direction of the threaded joint during engagement completion.
FIG. 6 is a diagram for explaining the shape of the buffer surfaces of the threaded joint.
[7] FIG. 7 is a diagram for explaining another shape of the buffer surfaces of the threaded joint.
[8] FIG. 8 is a diagram for explaining still another form of buffer surface of the threaded joint.
[9] FIG. 9 is a longitudinal sectional view showing a schematic configuration of a tubular threaded joint according to the second embodiment.
[10] FIG 10 is a longitudinal sectional view showing a schematic configuration of a tubular threaded joint according to the third embodiment.
[11] FIG 11 is a longitudinal sectional view showing a schematic configuration of a tubular threaded joint according to the fourth embodiment.
DESCRIPTION OF THE INVENTION
[0015]
　As described above, the nose portion improves the sealing performance of the seal portion. Nose portion has an effect of improving the rigidity against deformation of the tip portion of the pin (pin lip portion). By the action of the nose portion, it is possible to improve the contact surface pressure between the sealing surfaces, also even if a small plastic deformation occurs in the shoulder portion and its vicinity combined load is loaded, stable it can be maintained by the contact surface pressure.
[0016]
　Nose section, although that can ensure excellent sealing performance can also be a factor for generating a burn-in each seal surface during fastening of the threaded joint. The function of the nose portion of increasing the contact surface pressure between the sealing surfaces, the sealing surfaces are in engagement process is because the results in increased contact pressure between the seal surface even when the slide.
[0017]
　As causes of galling during fastening, also it includes contact polarization of the pin seal surface and the box sealing surface. That is, during the engagement, when the pin seal surface and the box sealing surface at the stage where there is a play without Kira tightens the screw portion begins to contact a pin seal surface and the box sealing surface does not uniformly contact over the entire circumference, which may slide with per polarization. In this case, there is a high possibility that seizure occurs at the portion where the contact polarization occurs among the sealing surfaces. Even if not lead to occurrence of seizure, and damage such as scratches may occur on the sealing surface, which may lead to a decrease in sealing performance.
[0018]
　In order to prevent seizure of the sealing surfaces, for example, copper plating or copper - tin - zinc plating, it is conceivable to utilize the excellent surface treatment seizure resistance. However, these surface treatments are expensive, there is a problem of low productivity.
[0019]
　In order to prevent seizure of the sealing surfaces, it is conceivable to use a lubricant. The excellent lubricant seizure resistance, for example, API containing heavy metals (American Petroleum Institute) standard screws compound (API standard dope), and the like. However, in recent years, there is a case where environmentally friendly, is required to use the screws compound containing no heavy metal (yellow dope). Seizure resistance yellow dope is generally inferior galling resistance of API standard dope. Therefore, it is necessary to ensure the resistance seizure resistance by other than the lubricant technology.
[0020]
　The present inventors have, in view of the above circumstances, while able eliminate a seizure during fastening, after engagement completion, discussed how you can benefit from the nose portion of securing high sealing performance. It will be specifically described below.
[0021]
　The present inventors have a tapered guide surface is provided on each of the pin and box, the seal faces thought that sliding causes interference tapered guide faces before starting the slide. Thus, before the sealing faces starts sliding, the tube axis of the pin of the tube axis and the box to match. Therefore, it is possible to prevent the slide in a state of being contact-polarized between the pin seal surface and the box sealing surface. Further, an amount corresponding to the difference between the diameter of the diameter of the pin tapered guide surface and the box tapered guide surface (interference amount), it is possible to seal face each other to shorten the distance that slides. Accordingly, occurrence of seizure in the sealing surface is suppressed.
[0022]
　Tapered guide surfaces each other, although sliding in the engagement, not in contact after engagement completion. The fastening state, the pin tapered guide surface and the box tapered guide surface is opposed with a gap. Therefore, in the engaged state, the tapered guide surface, i.e. the higher the contact pressure between the sealing surfaces by the nose, is exhibited excellent sealing performance.
[0023]
　However, in the case of introducing tapered guide surfaces on each of the pin and box, during fastening, the boundary portion between the box tapered guide surface and the box sealing surfaces will slide strongly pressed against condition the pin tapered guide surface . Therefore, the contact surface pressure of the boundary portion becomes high, even if not enough to generate a seizure, there is a possibility that abrasion damage or plastic deformation of the surface occurs. If the damage or deformation will extend to the region of the box sealing surface, pin seal surface is worn. As a result, or seizure occurs, sealing performance, particularly sealing performance against external pressure is likely to lowered.
[0024]
　The present inventors have to deal with the above problem, it was decided to provide a buffer surface between the box tapered guide surface and the box sealing surface. That is, by forming the buffer surface at the boundary between the box tapered guide surface and the box sealing surface, away box sealing surface of the box tapered guide surface. Thus, damage or deformation of the ends of the box tapered guide surface can be prevented from reaching the box sealing surface.
[0025]
　Tubular threaded joint according to the embodiment, it has been completed based on the above findings.
[0026]
　Tubular threaded joint according to the embodiment includes a pin tubular and a tubular box. Pin is connected to the steel tube body. Box, the pin is fastened to the inserted into the pin. Pin includes a pin lip portion, and a male screw portion. Pin lip portion constitutes a tip portion of the pin. Male screw portion than pin lip portion on the outer circumference of the pin is provided on the steel pipe body side. Male screw portion is composed of a taper screw. Pin lip portion includes a first Pinshoruda surface, and a nose portion, and a first pin seal surface. The first Pinshoruda surface is provided at the tip of the pin. Nose portion is provided on the male screw portion side of the first Pinshoruda surface. Nose portion has a pin tapered guide surfaces on the outer peripheral surface. Pin tapered guide surface, the diameter toward the distal end of the pin is reduced. The first pin seal surface is provided on the male screw portion side than the nose portion in the outer peripheral surface of the pin lip portion. The first pin seal surface includes a tapered surface whose diameter toward the tip of the pin is reduced. Box has a first box shoulder surface, and the nose receiving portion, a first box sealing surface, and a buffer surface, and a female screw portion. The first box shoulder surface is provided on the inner end of the box corresponding to the first Pinshoruda surface. The first box shoulder surface is in contact with the first Pinshoruda surface in engagement state. Nose receiving portion is provided corresponding to the nose portion. Nose receiving portion has a box tapered guide surface on the inner peripheral surface. Box tapered guide surface diameter decreases toward the rear end of the box. The first box sealing surface is provided on the inner peripheral surface of the box corresponding to the first pin seal surface. The first box sealing surface includes a tapered surface whose diameter toward the rear end of the box becomes small. The first box sealing surface is in contact with the first pin seal surface in the engagement state. Buffer surface is provided between the tapered surface of the box tapered guide surface and the first box sealing surface on the inner peripheral surface of the box. Internal thread portion is provided on the inner periphery of the box corresponding to the external thread portion. Internal thread portion is composed of a taper screw. Each pin tapered guide surface and the box tapered guide surface, having a first taper angle That. Each of the tapered surface of the first pin seal surface and the first box sealing surface has a second taper angle. The second taper angle, greater than the first taper angle. In a disengaged state, the pin tapered guide diameter of the end portion of the front end side of the pin of the surface Dp1, the diameter of the line of intersection between the extension surface and the extended surface of the tapered surface of the first pin seal surface of the pin tapered guide surface dp2, from the tip of the pin to the line of intersection between the extension surface and the extended surface of the tapered surface of the first pin seal surface of the pin tapered guide surface, the length in the tube axis direction of the threaded joint Lp2, extended surface of the box tapered guide surface When the diameter of the intersection of the first box sealing surface extension plane of the tapered surface of the Db2, from the back end of the box until intersection of the extended plane of the extension surface and the tapered surface of the first box sealing surface of the box tapered guide surface when the length in the tube axis direction and Lb2, satisfies the following formula (1) and (2).
　　Ｄｐ２＞Ｄｂ２＞Ｄｐ１　　　（１）
　　Ｌｂ２＞Ｌｐ２　　　（２）
[0027]
　Buffer surface has a length more than 0.75mm in the tube axis direction. Buffer unit is disposed outside the imaginary plane in the radial direction of the threaded joint. Virtual surfaces are constituted by the extension surface and the extended surface of the first box sealing surface of the box tapered guide surface.
[0028]
　In the above embodiments, larger than the taper angle of the taper angle each tapered guide surface of the tapered surface included in the seal surface, and the equation (1) and (2) are constituted each tapered guide surface so as to satisfy there. Thus, before the sealing faces starts sliding, and the tube axis of the interfering tapered guide faces pin tube axis and the box to match. Therefore, it is possible to prevent the contact polarization between the seal surfaces. Further, the amount corresponding interference level of the tapered guide surface, it is possible to seal face each other to shorten the distance that slides. Therefore, it is possible to prevent the seizure of the sealing surfaces during engagement.
[0029]
　In the above embodiment, the buffer surface between the box tapered guide surface and the box sealing surface is interposed. As a result, the box sealing surface is separated from the box tapered guide surface. Therefore, even if the box tapered guide surface during fastening is damaged or deformed, it is possible the damage or deformation is prevented from extending to the box sealing surface. Therefore, it is possible to prevent wear of the pin seal surface by box sealing surface, it is possible to suppress the occurrence of seizing.
[0030]
　In the above embodiment, by satisfying the above expression (1) and (2), after engagement completion, the pin tapered guide surface is opposed at a box tapered guide surface and the gap. Therefore, in the engaged state, the pin tapered guide surface by the amplified elastic recovery force of the pin seal surface, the contact surface pressure between the sealing surfaces is improved. Therefore, it is possible to ensure the high sealing performance.
[0031]
　Thus, according to the above embodiment, while ensuring a high sealing performance after engagement completion, it is possible to suppress the seizure of the sealing surfaces during engagement.
[0032]
　The first Pinshoruda surface includes a pin main shoulder surface may comprise a pin sub shoulder surface. Pin sub shoulder surface is disposed on the outer peripheral side of the pin main shoulder surface. The first box shoulder surface, and the box main shoulder surface may include a box sub shoulder surface. Box main shoulder surface is provided corresponding to the pin main shoulder surface. Box main shoulder surface is in contact with the pin main shoulder surface in the engaged state. Box sub shoulder surface is provided corresponding to the pin sub shoulder surface. Box sub shoulder surface is contactable with the pin sub shoulder surface in the engaged state. However, the pin sub shoulder surface and the box sub shoulder surface may not contact with each other in a fastened state.
[0033]
　The pin may further include a second pin seal surface. The second pin seal surface is the outer peripheral surface of the pin, provided at the end of the central portion or the steel main body of the tube axis direction. The box may further comprise a second box sealing surfaces. The second box sealing surface is provided on the inner peripheral surface of the box corresponding to the second pin seal surface. The second box sealing surface contacts the second pin seal surface in the engaged state.
[0034]
　The pin may further include a second Pinshoruda surface. The box may further comprise a second box shoulder surface. The second Pinshoruda surface is provided on an end of the central portion or the steel main body of the tube axis direction. The second Pinshoruda surface intersects the tube axis direction. The second box shoulder surface is disposed corresponding to the second Pinshoruda surface. The second box shoulder surface contacts the second Pinshoruda surface in engagement state.
[0035]
　It said at least one of the first pin seal surface and the first box sealing surface may further include a curved surface. The curved surface is provided continuously to the tapered surface. The curved surface has a curvature of 1 or more.
[0036]
　The buffer surface may include a curved surface. The curved surface is provided continuously with each of the box tapered guide surface and the first box sealing surface. The curved surface has a curvature of 1 or more.
[0037]
　The buffer surface may have a length of less than 2mm in the tube axis direction.
[0038]
　It will be specifically described with reference to the drawings embodiment. 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.
[0039]
　
　[Configuration of the threaded joint]
　(Overall Configuration)
　Figs. 1 and 2, respectively, a threaded joint for steel pipes 1A according to the first embodiment, is a longitudinal sectional view showing a schematic configuration of 1B. Threaded joint 1A shown in FIG. 1 is a coupling type of threaded joint. Threaded joint 1B shown in FIG. 2 is a integral type threaded joint. In the following description, when no particular distinction threaded joint 1A, and 1B are collectively referred to as threaded joint 1.
[0040]
　As shown in FIGS. 1 and 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.
[0041]
　Pin 10 is connected to the steel tube body. The steel body, refers to a portion in the steel pipe comprising a pin 10 not inserted into the box 20. For convenience of explanation, in the tube axis direction of the threaded joint 1, there is a case where the inner or front tip end of the pin 10, a steel body called outer or rear.
[0042]
　Pin 10 includes a pin lip portion 11, and a male screw portion 12. Pin lip portion 11 constitutes a leading end portion of the pin. Male screw portion 12 is arranged on the steel pipe main body side than the pin lip portion 11.
[0043]
　Pin lip portion 11 includes a Pinshoruda surface 111, the nose portion 112, and a pin seal surface 113. Pinshoruda surface 111, the nose portion 112, and a pin seal surface 113 toward the inside of the tube axis direction to the outside, are arranged in this order.
[0044]
　Pinshoruda surface 111 is provided on the tip of the pin 10. Pinshoruda surface 111 may include a pin main shoulder surface and the pin sub-shoulder surface will be described later.
[0045]
　The nose portion 112 is provided on the male screw portion 12 than Pinshoruda surface 111. The nose portion 112 has a pin tapered guide surface 112a on the outer peripheral surface. Pin tapered guide surface 112a is a tapered surface whose diameter toward the tip of the pin 10 is reduced. That is, the pin tapered guide surface 112a is configured to tube axis CL in truncated cone side to axis.
[0046]
　Pin seal surface 113 is provided on the male screw portion 12 than the nose portion 112. Pin seal surface 113 includes a tapered surface whose diameter toward the tip of the pin 10 is reduced. For the tapered surface of the pin seal surface 113 will be described in detail later.
[0047]
　Male thread portion 12 is positioned outside of the pin lip portion 11 in the tube axis direction. Male thread portion 12 is provided on the outer circumference of the pin 10. Male thread portion 12 is composed of a tapered thread.
[0048]
　Box 20 includes a box shoulder surface 21, the nose receiving section 22, the box sealing surface 23, a buffer surface 24, and a female thread portion 25.
[0049]
　Box shoulder surface 21, corresponding to Pinshoruda surface 111 is provided on the inner end of the box 20. Box shoulder surface 21 contacts the Pinshoruda surface 111 in engagement state, to form a shoulder portion with Pinshoruda surface 111. Pinshoruda surfaces 111 and box shoulder surface 21 is responsible stopper for limiting the screwing of the pin 10. Pinshoruda surfaces 111 and box shoulder surface 21, inside the joint, responsible for generating a clamping axial force of the screw.
[0050]
　The nose receiving section 22 is provided in the box 20 corresponding to the nose portion 112 of the pin 10. The nose receiving section 22 is provided outside the box shoulder surface 21 in the tube axis direction. The nose receiving section 22 has a box tapered guide surface 22a on the inner peripheral surface.
[0051]
　Box tapered guide surface 22a is a tapered surface whose diameter toward the rear end of the box 20 is reduced. That is, the box tapered guide surface 22a is composed of an inner surface of the truncated cone to the tube axis CL as the axis.
[0052]
　Box tapered guide surface 22a and the pin tapered guide surface 112a has an interference amount. Box tapered guide surface 22a is while fastening the pin 10 and the box 20, in contact with the pin tapered guide surface 112a. After engagement completion, boxes tapered guide surface 22a does not contact the pin tapered guide surface 112a.
[0053]
　Box sealing surface 23 is disposed outside the nose receiving section 22 in the tube axis direction. Box sealing surface 23, corresponding to the pin seal surface 113 is provided on the inner peripheral surface of the box 20. Box sealing surface 23 and the pin seal surface 113 has an interference amount. Pin seal surface 113 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 113 and the box sealing surface 23, the metal in the engaged state - to form a sealing portion by the metal contact.
[0054]
　Buffer surface 24 is provided on the inner peripheral surface of the box 20. Buffer surface 24, the inner circumferential surface of the box 20, constitutes the boundary between the box tapered guide surface 22a and the box sealing surface 23.
[0055]
　Female screw portion 25 corresponding to the male screw portion 12 is provided on the inner periphery of the box 20. Internal thread portion 25 is composed of a tapered thread that meshes with tapered threads constituting the male screw portion 12. In the engaged condition, the internal thread portion 25 forms a threaded portion with the external thread portion 12. Threaded portion is preferably a single-thread screw or double threaded screw.
[0056]
　Pin 10 of the threaded joint 1B shown in FIG. 2 further includes a pin seal surface 13. Pin seal surface 13 at the end of the steel pipe main body of the pin 10, is provided on the outer peripheral surface of the pin 10.
[0057]
　Box 20 of the threaded joint 1B, corresponding to the pin seal surface 13, further comprising a box sealing surface 26. Pin seal surface 13 and the box sealing surface 26 has an interference amount. Thus, pin seal surface 13 and the box sealing surface 26 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 26, the metal in the engaged state - to form a sealing portion by the metal contact.
[0058]
　(Configuration of the inner end portion of the threaded joint)
　Figure 3 is an enlarged view of the inner end of the tube axis direction of the threaded joint 1 shown in FIGS.
[0059]
　As shown in FIG. 3, in the present embodiment, Pinshoruda surface 111 includes a pin main shoulder surfaces 111a, and a pin sub shoulder surface 111b. Box shoulder surface 21 includes a box main shoulder surfaces 21a, and a box sub shoulder surface 21b.
[0060]
　Pin main shoulder surface 111a is an annular surface that intersects the tube axis direction of the threaded joint 1. In this embodiment, the pin main shoulder surface 111a has an outer peripheral portion is inclined so as to be located inside the tube axis direction than the inner peripheral portion.
[0061]
　Pin sub shoulder surface 111b is an annular face provided on the outer peripheral side of the pin main shoulder surface 111a. Pin sub shoulder surface 111b intersects the radial direction of the threaded joint 1. Pin sub shoulder surface 111b has a slope opposite the slope of the pin main shoulder surface 111a. That is, the pin sub-shoulder surface 111b is inclined to be positioned outside of the tube axis direction than the inner peripheral portion is the outer peripheral portion.
[0062]
　Box main shoulder surface 21a and the box sub-shoulder surface 21b, respectively, corresponding to the pin main shoulder surfaces 111a and the pin sub-shoulder surface 111b is an annular face provided on the box 20. Box main shoulder surface 21a, corresponding to the pin main shoulder surface 111a, tilting so as to be positioned inside the tube axis direction than the inner peripheral portion is the outer peripheral portion. Box sub shoulder surface 21b has a slope opposite the slope of the box main shoulder surface 21a. Box sub shoulder surface 21b, corresponding to the pin sub shoulder surface 111b, tilting so as to be located outside the tube axis direction than the inner peripheral portion is the outer peripheral portion.
[0063]
　Pin main shoulder surface 111a and the box main shoulder surface 21a is in contact with one another in the engaged state. On the other hand, the pin sub-shoulder surface 111b and box sub shoulder surface 21b is configured to be contactable in engaged state, may not be in contact in the normal fastening state. Pin sub shoulder surface 111b and box sub shoulder surface 21b, for example, may be in contact with each other when high compressive load on the threaded joint 1 or acts, excessive tightening torque is applied or. By pin sub shoulder surfaces 111b comes into contact with the box sub-shoulder surface 21b, expanded deformation of the pin lip portion 11 is suppressed.
[0064]
　Pinshoruda surface 111 may not have a pin sub shoulder surface 111b. In this case, box shoulder surface 21, no box sub shoulder surface 21b.
[0065]
　Pin seal surface 113 includes a tapered surface 113a. Tapered surface 113a, the diameter toward the tip of the pin 10 is reduced. That is, the tapered surface 113a is configured to tube axis CL in truncated cone side to axis. In a disengaged state, the tapered surface 113a has a larger taper angle than the taper angle of the pin tapered guide surface 112a.
[0066]
　The tapered surface 113a of the pin seal surface 113 is preferably connected between the pin tapered guide surface 112a through a curved surface with one or more curvatures. Similarly, between the tapered surface 113a and the male thread portion 12 (FIGS. 1 and 2), it is preferable that the curved surface having one or more curvatures is provided. In this case, the both ends of the tube axis direction of the pin seal surface 113 is a curved surface. The curved surface having one or more curvatures, in cross-sectional view of a pin 10 which is cut along a plane including the tube axis CL (vertical section), arcs, elliptical arcs, and composed of one or more curves selected from a parabola it is a surface that has been. However, pin seal surface 113 may be constituted only by the tapered surface 113a.
[0067]
　Box sealing surface 23 includes a tapered surface 23a. Tapered surface 23a has a diameter smaller toward the rear end of the box 20. That is, the tapered surface 23a is configured to tube axis CL in truncated cone side to axis. In a disengaged state, the taper angle of the tapered surface 23a is equal to the taper angle of the tapered surface 113a of the pin seal surface 113 is greater than the taper angle of the box tapered guide surface 22a. In a disengaged state, the taper angle of the box tapered guide surface 22a is equal to the taper angle of the pin tapered guide surface 112a.
[0068]
　Tapered surfaces 113a, 23a taper angle of, 2 ° ~ is preferably 25 ° greater than the taper angle of the pin tapered guide surface 112a and the box tapered guide surface 22a, and more preferably from 3 ° ~ 15 °.
[0069]
　Buffer surface 24 is provided between the tapered surface 23a of the box tapered guide surface 22a and the box sealing surface 23. The length of the buffer plane 24 is more than 0.75 mm. The length of the buffer plane 24 is preferably 2mm or less. The length of the buffer plane 24 is the distance in the tube axis direction from the rear end of the box tapered guide surface 22a to the front end of the tapered surface 23a.
[0070]
　Buffer surface 24, in the radial direction of the box 20 is disposed outside the imaginary plane V. Virtual plane V is constituted by extension surface V1, V2. Extension surface V1 is a virtual plane obtained by extending the box tapered guide surface 22a to the box sealing surface 23 side. Extension surface V2 is a virtual plane obtained by extending the tapered surface 23a of the box sealing surface 23 in the box tapered guide surface 22a side. When comparing the size of the virtual plane V and the diameter of the buffer plane 24 at the same position in the tube axis direction, the diameter of the buffer plane 24 is always greater than the diameter of the virtual plane V. The detailed configuration of the buffer plane 24 will be described later.
[0071]
　3, an extension surface which is extended tip end of the pin 10 of the pin tapered guide surface 112a a diameter of (front end) Dp1, pins tapered guide surface 112a on the pin seal surface 113 side, the tapered surface of the pin seal surface 113 the diameter of the intersection line Xp of an extension surface which is extended 113a to pin a tapered guide surface 112a side shown in Dp2. Lp1 is the length of the tube axis direction from the tip of the pin 10 to the front end of the pin tapered guide surface 112a, Lp2 is the tube axis direction from the tip of the pin 10 to the intersection line Xp long. However, in FIG. 3, because it is not shown the curved surface between the pin tapered guide surface 112a and the tapered surface 113a, and the intersection line Xp to the boundary between the pin tapered guide surface 112a and the tapered surface 113a. Dp1, Dp2, Lp1, Lp2, are all dimensioned in disengaged state.
[0072]
　3, the end portion of the box shoulder surface 21 of the box tapered guide surface 22a of the diameter of the (front end) Db1, the diameter of the intersection line Xb of the extended surface V1 with extended surface V2 and Dp2. Lb1 is the length of the tube axis direction from the inner end of the box 20 to the front end of the box tapered guide surfaces 22a, Lb2 is the length of the tube axis direction from the inner end of the box 20 to the line of intersection Xb. Db1, Db2, Lb1, Lb2 are both dimensioned in disengaged state.
[0073]
　Threaded joint 1 according to the present embodiment is configured so as to satisfy the following equation (1) and (2).
　　Dp2>
　　Db2> Dp1 (1) Lb2> Lp2 (2)
[0074]
　When satisfying the above formula (1) and (2), as shown in FIG. 4, in the fastening process, before the pin seal surface 113 and the box sealing surface 23 starts to slide, the pin tapered guide surface 112a and the box taper and the guide surface 22a starts to slide. After fastening is completed, as shown in FIG. 5, while the contact between pin seal surface 113 and the box sealing surface 23, and the pin tapered guide surface 112a and the box tapered guide surface 22a is opposed with a gap.
[0075]
　In the formula (1), Db2 is preferably less than 97% 100% Dp2, and more preferably less than 100% to 99%. Dp1 is preferably less than 97% 100% Db2, and more preferably less than 100% to 99%.
[0076]
　In the formula (2), Lp2 is preferably less than 40% to 100% of the Lb2, and more preferably 60% to 95% or less.
[0077]
　Furthermore, a threaded joint 1 according to the present embodiment preferably satisfies the following expression (3).
　　Lb1> Lp1 (3)
[0078]
　Here, a description will be given of the relationship between the taper guide interference amount δg and seal interference amount .delta.s. Tapered guide interference amount δg is the amount of interference with the pin tapered guide surface 112a and the box tapered guide surface 22a. Seal interference amount δs is the amount of interference with the pin seal surface 113 and the box sealing surface 23.
[0079]
　Tapered guide interference amount δg is the maximum amount of interference with the pin tapered guide surface 112a and the box tapered guide surface 22a is sliding contact. In other words, the tapered guide interference amount δg is just before the pin seal surface 113 and the box sealing surface 23 starts to slide, the interference quantity has been introduced into the pin tapered guide surface 112a and the box tapered guide surface 22a. Interference amount δg is substantially equal to the value obtained by subtracting the Db2 from Dp2 (= Dp2-Db2).
[0080]
　Seal interference amount δs is engagement completion time, i.e. in a state in which the Pinshoruda surface 111 and the box shoulder surface 21 is in contact with a amount of interference introduced into the pin seal surface 113 and the box sealing surface 23. In other words, the seal interference amount δs as reference position the far end of the tip and the box 20 of the pin 10, the diameter of the diameter and the box sealing surface 23 of the pin seal surface 113 in the tube axis direction of distances equal position from the reference position and substantially equal to the difference (non-engagement).
[0081]
　In this embodiment, the tapered guide interference amount δg and seal interference amount δs satisfy the relationship of the following equation (5).
　　δs> δg (5)
[0082]
　Tapered guide interference amount δg is preferably 95% or less than 50% of the seal interference amount .delta.s, and more preferably 70% to 90%.
[0083]
　(Structure of the buffer surface)
　as described above, the buffer surface 24, between the tapered surface 23a of the box tapered guide surface 22a and the box sealing surface 23 is disposed on the outer peripheral side of the virtual plane V. Buffer surface 24 preferably includes a curved surface having one or more curvatures. The curved surface, viewed in cross-section of the box 20 which is cut along a plane including the tube axis CL (vertical section), an arc, elliptic arc, and a surface composed of one or more curves selected from a parabola.
[0084]
　6 to 8 show mutually different shapes buffer surfaces 24A, 24B, and 24C. Buffer surface 24A, 24B, when not particularly distinguished. 24C, collectively referred to as buffer surface 24.
[0085]
　Buffer surface 24A shown in FIG. 6 is a curved surface 24a having a curvature Ra. That is, the buffer surface 24A is viewed in longitudinal section of the box 20, a single arc. Reciprocal of curvature Ra, i.e. the radius of curvature of the curved surface 24a is preferably 1mm or more.
[0086]
　Buffer surface 24A which is composed of a curved surface 24a is continuous with each of the tapered surface 23a of the box tapered guide surface 22a and the box sealing surface 23. That is, the buffer surface 24 is smoothly connected to each of the boxes tapered guide surface 22a and the tapered surface 23a. For example, in a vertical cross section of the box 20, box tapered guide surface 22a and its extension plane V1 has a tangent at the front end of the buffer plane 24. In longitudinal cross section of the box 20, the tapered surfaces 23a and extended surface V2, and it has a tangent at the rear end of the buffer plane 24.
[0087]
　The rear end of the buffer plane 24A may be construed as is also the front end portion of the box sealing surface 22. That is, in the example of FIG. 6, a portion of the curved surface 24a (the rear end), both a curved surface included in the buffer surface 24A, it can be construed as also a curved surface included in the box sealing surface 23.
[0088]
　Buffer surface 24B shown in FIG. 7, two curvature R1b, and is a curved surface 24b having R2b. Curved 24b has a curved surface 241b having a curvature R1b, a complex surface that curved 242b is connected with a curvature R2b. Curvature R1b, each the inverse of R2b, i.e. curved 241b, each radius of curvature 242b is preferably 1mm or more.
[0089]
　Buffer surface 24B, similarly to the buffer surface 24A shown in FIG. 6 are smoothly connected with each of the tapered surface 23a of the box tapered guide surface 22a and the box sealing surface 23. The rear end portion of the curved surface 24b that constitutes the buffer surface 24B may be construed as well as a curved surface included in the buffer surface 24B, it is also the curved surface included in the box sealing surface 23.
[0090]
　Buffer surface 24C illustrated in FIG. 8, a curved surface 241c, and 242c, a complex surface 24c comprised of a tapered surface 243 c. Curved surface 241c has a curvature R1c. Curved 242c have different curvatures R2c the curvature R1c. Curvature R1c, each the inverse of R2c, i.e. curved 241c, each radius of curvature 242c is preferably 1mm or more.
[0091]
　Curved 241c is smoothly connected to the box tapered guide surface 22a. Curved 242c is smoothly connected to the tapered surface 23a of the box sealing surface 23. Some or all of the curved surface 242c is both a curved surface included in the buffer surface 24C, it can be construed as also a curved surface included in the box sealing surface 23. Tapered surface 243c is curved 241c, is disposed between the 242c.
[0092]
　[Effect]
　In the threaded joint 1 according to the present embodiment, the taper angle of the tapered surface 23a of the tapered surface 113a and the box sealing surface 23 of the pin seal surface 113 than the taper angle of the pin tapered guide surface 112a and the box tapered guide surface 22a large. Furthermore, a threaded joint 1 is configured so as to satisfy the above equation (1) and (2). With this configuration, the fastening process, before pin seal surface 113 and the box sealing surface 23 starts to slide, the pin 10 and the pin tapered guide surface 112a and the box tapered guide surface 22a starts to slide tube axis of the box 20 is matched. Therefore, it is possible to prevent during fastening, and a pin seal surface 113 and the box sealing surface 23 to contact polarized. Therefore, it is possible to prevent the seizure of the pin seal surface 113 and the box sealing surface 23 during the fastening.
[0093]
　P the thread pitch of the threaded portion, the slope angle of the sealing portion (= taper angle / 2) theta, when the representative diameter of the sealing portion and Ds, sliding from the case of conventional threaded joint, pin seal surface and the box sealing surface the distance is approximately δs · πDs / 2Ptanθ. On the other hand, in the case of a threaded joint 1 according to the present embodiment, by introducing the pin tapered guide surface 112a and the box tapered guide surface 22a, the sliding distance of the pin seal surface 113 and the box sealing surface 23 (δs-δg) · reduced to πDs / 2Ptanθ. That is, in the threaded joint 1, by the amount of the taper guide interference amount .DELTA.G, sliding distance between the pin seal surface 113 and the box sealing surface 23 in the fastening is shortened.
[0094]
　For example, when the tapered guide interference amount δg set to half of the seal interference amount .delta.s, since the sliding distance of the pin seal surface 113 and the box sealing surface 23 in the fastening is approximately half, reduces the risk of seizure occurs be able to. On the other hand, at the time of engagement completion, between the pin tapered guide surface 112a and the box tapered guide surface 22a is introduced (δs-δg) / 2 of the gap. Thus, as in the threaded joint with a conventional nose portion, it is possible to generate a sealing surface pressure of the seal portion, it is possible to obtain high sealing performance.
[0095]
　In this embodiment, the boundary portion of the box tapered guide surface 22a and the box sealing surface 23 because the buffer surface 24 is interposed, so that the box sealing surface 23 is moved away from the box tapered guide surface 22a. Therefore, even if the box tapered guide surface 22a is damaged or deformed during the fastening can be the damage or deformation is prevented from extending to the box sealing surface 23. As a result, it is possible to prevent wear of the pin seal surface 113 by box sealing surface 23, it is possible to suppress the occurrence of seizing.
[0096]
　Thus, according to the threaded joint 1 according to the present embodiment, while ensuring a high sealing performance after engagement completion, it is possible to suppress the seizure of the pin seal surface 113 and the box sealing surface 23 during the fastening.
[0097]
　In a threaded joint 1 according to the present embodiment, Pinshoruda surface 111 includes a pin main shoulder surface 111a and the pin sub-shoulder surface 111b. Box shoulder surface 21 includes a box main shoulder surface 21a and the box sub-shoulder surface 21b. Pin main shoulder surface 111a and the box main shoulder surface 21a is in contact with each other at the time of engagement completion, to limit the screwing of the pin 10 relative to the box 20. On the other hand, the pin sub-shoulder surface 111b and box sub shoulder surface 21b is not always necessary in contact with clamping state. Pin sub shoulder surface 111b and box sub shoulder surface 21b, because they are arranged so as to intersect the radial direction of the threaded joint 1, for example, to act a high compressive load on the threaded joint 1, the torque with excessive tightening It may be in contact with each other when the pin lip portion 11 is moved radially outward or added. Therefore, it is possible to suppress the deformation of the radially outward of the pin lip portion 11.
[0098]
　
　FIG. 9 is a longitudinal sectional view showing a schematic configuration of a tubular threaded joint 1C according to the second embodiment. Threaded joint 1C shown in FIG. 9 is a integral type threaded joint, it may be a coupling type of threaded joint.
[0099]
　In a threaded joint 1C, the pin 10C and box 20C are respectively provided with Pinshoruda surface 14 and the box shoulder surface 27. Pinshoruda surface 14 is provided at an end portion of the steel pipe main body of the pin 10. Box shoulder surface 27 is provided in the box 20 in response to Pinshoruda surface 14. Pinshoruda surface 14 and the box shoulder surface 27 is an annular surface that intersects the tube axis direction of the threaded joint 1C. Pinshoruda surface 14 and the box shoulder surface 27 forms a shoulder portion in contact with each other in a fastened state.
[0100]
　
　FIG. 10 is a longitudinal sectional view showing a schematic configuration of a tubular threaded joint 1D according to the third embodiment. Threaded joint 1D shown in FIG. 10 is a integral type threaded joint, it may be a coupling type of threaded joint.
[0101]
　Pin 10D of the threaded joint 1D has a male screw portion 12a and the outer male thread portion 12b among each configured with a tapered thread. That is, the external thread portion of the pin 10D is composed of a two-stage screw.
[0102]
　Pin 10D further comprises Pinshoruda surface 15. Pinshoruda surface 15 is provided in a central portion in the tube axis direction of the pin 10D. Pinshoruda surface 15 is disposed between the inner male screw portion 12a and the outer male thread portion 12b. Pinshoruda surface 15 is an annular surface that intersects the tube axis direction of the threaded joint 1D.
[0103]
　Box 20D of the threaded joint 1D, corresponding to each of the inner male screw portion 12a and the outer male thread portion 12b, has an inner female thread portion 25a and the outer internally threaded section 25b. Internal female threaded portion 25a and the outer internally threaded section 25b is configured by a tapered thread that meshes with the male screw portion 12a and the outer male thread portion 12b, respectively.
[0104]
　Box 20D is provided with a box shoulder surface 28 corresponding to the Pinshoruda surface 15. Box shoulder surface 28 is disposed between the inner internally threaded section 25a and the outer internally threaded section 25b. Box shoulder surface 28 is an annular surface that intersects the tube axis direction of the threaded joint 1D. Pinshoruda surface 15 and box shoulder surface 28 forms a shoulder portion in contact with each other in a fastened state.

claims

A threaded joint for steel pipes,
　and the pin of the tubular connected to the steel pipe body,
　a tubular box which pin is fastened to the pin is inserted,
provided with,
　the pin may
　constitute the distal end portion of the pin pin lip and parts,
　in the outer periphery of the pin than the pin lip portion provided on the steel body, and configured male thread portion with tapered thread
has,
　the pin lip portion,
　first Pinshoruda provided at the tip of the pin surface and,
　provided on the male screw portion side of the first Pinshoruda surface, a nose portion having an outer peripheral surface of the pin tapered guide surface whose diameter decreases toward the tip of the pin,
　the outer circumferential surface of the pin lip portion than the nose section is provided on the male screw portion side, a first pin seal surface including a tapered surface whose diameter decreases toward the tip of the pin
has a,
　the box
　Wherein in response to the first Pinshoruda surface provided on the rear end of the box, the first box shoulder surface in contact with the first Pinshoruda surface in engagement state,
　provided corresponding to said nose portion, the back of the box a nose receiving portion having a box tapered guide surface whose diameter toward the end is reduced on the inner circumferential surface,
　Provided on the inner peripheral surface of the box corresponding to the first pin seal surface comprises a tapered surface whose diameter toward the rear end is reduced in the box, first box in contact with the first pin seal surface in engagement state and seal surface,
　a buffer surface that is provided between the tapered surface of the box tapered guide surface and the first box sealing surface on the inner peripheral surface of the box,
　the inner periphery of the box corresponding to the external thread portion provided, and configured internally threaded portion of a tapered screw
has,
　each of the pin tapered guide surface and the box tapered guide surface has a first taper angle,
　said first pin seal surface and the first box each of the tapered surfaces of the sealing surface has a second taper angle larger than the first taper angle,
　in a non-engaged state, the pin of the pin tapered guide surface The diameter of the end portion of the end side Dp1, the pin tapered guide diameter of intersection of the extension surface and the extended surface of the tapered surface of the first pin seal surface of the surface Dp2, the pin tapered guide surface from the tip of the pin said up line of intersection, wherein the length in the tube axis direction of the threaded joint Lp2, the box tapered guide surface of the extended surface and the first box of the extension surface and the extended surface of the tapered surface of the first pin seal surface the diameter of the intersection of the extended plane of the tapered surface of the sealing surface Db2, the intersection of the extended plane of the tapered surface of the extension surface and the first box sealing surface of the box tapered guide surface from the back end of the box when the length in the tube axis direction to the line and Lb2, satisfy the following equation (1) and
　　(2), Dp2>
　　Db2> Dp1 (1) Lb2> Lp2 (2)
　The buffer surface has more than a length 0.75mm in the tube axis direction, the imaginary surface formed by the said extension plane of the extended surface and the first box sealing surface of the box tapered guide surface the are arranged outside in the radial direction of the threaded joint, a threaded joint.
[Requested item 2]
　A tubular threaded joint according to claim 1,
　wherein the first Pinshoruda surface,
　a pin main shoulder surface,
　a pin sub shoulder surface which is disposed on the outer peripheral side of the pin main shoulder surfaces
wherein the
　said first 1 box shoulder surface is
　provided corresponding to the pin main shoulder surface, and the box main shoulder surface in contact with the pin main shoulder surface in the engaged state,
　provided in correspondence with the pin sub shoulder surface, the engagement state , and the box sub shoulder surface capable of contacting with the pin sub shoulder surfaces
including, threaded joint.
[Requested item 3]
　A tubular threaded joint according to claim 1 or 2,
　wherein the pin further
　in the outer peripheral surface of the pin, second pin seal provided at the end of the central portion or the steel pipe body side of the tube axis direction surface,
has,
　the box is further
　in response to the second pin seal surface provided on the inner peripheral surface of the box, the second box sealing surfaces, in contact with the second pin seal surface in the engaged state
with the , screw joint.
[Requested item 4]
　A threaded joint for steel pipes according to any one of claims 1 to 3,
　wherein the pin is further
　provided at the end of the central portion or the steel pipe body side of the tube axis direction, the pipe axis direction second Pinshoruda surface, intersecting the
has,
　the box is further
　arranged corresponding to the second Pinshoruda surface, the second box shoulder surface, in contact with the second Pinshoruda surface in engagement state
having, screw joint.
[Requested item 5]
　A tubular threaded joint according to claim 1, any one of 4,
　the first at least one of the pin seal surface and the first box sealing surface is further
　provided continuously to said tapered surface, curved surface having one or more curvatures,
including, threaded joint.
[Requested item 6]
　A threaded joint for steel pipes according to any one of claims 1 to 5,
　wherein the buffer surface is
　provided continuously with each of the box tapered guide surface and the first box sealing surface, one or more curved surface having a curvature
including a screw joint.
[Requested item 7]
　A threaded joint for steel pipes according to any one of claims 1 to 6,
　wherein the buffer surface has a length less than 2mm in the tube axis direction, the threaded joint.