Technical field
[0001]
The present invention relates to a threaded joint for connecting a pair of tube.
BACKGROUND
[0002]
Conventionally, oil wells and natural gas wells and the like (hereinafter, also collectively referred to as "oil wells"), in order to mine underground resources casing, oil well pipes such as tubing is used. OCTG is constituted by a steel pipe which are sequentially connected. 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 to be connected, in which one tube is steel, other tubing is coupled. Male screw portion is provided on the outer periphery of both ends of a steel pipe. Internal thread portion is provided on the inner periphery of both end portions of the coupling. By the male screw portion of the steel pipe is screwed into the female screw portion of the coupling, and a steel pipe and a coupling are connected is fastened.
[0004]
　For integral type, both of the pair of the tubing being linked are steel pipes, the coupling is not used. In each steel pipe, a male screw portion is provided on the outer periphery of one end portion, the internal thread portion is provided on the inner periphery of the other end. By the male screw portion of one of the steel pipe is screwed into the female screw portion of the other steel pipe, two steel pipes are connected are fastened.
[0005]
　In general, a portion externally threaded portion in the tube material consolidated is provided, from being inserted into the female screw portion, it referred to as pin. Portion a female screw portion in the tube material consolidated is provided from accepting an external thread portion, it referred to as boxes. Pin and box are part of the tube, forming a respective tubular.
[0006]
　As a type of tubular threaded joint, thread width and thread root widths are known to have a threaded portion that changes at a constant rate. Threaded joint having such a structure includes a high torque. In this type of threaded joint, typically, stab lead and load leads has a respective constant throughout the threaded portion. However, stub lead and load lead do not match.
[0007]
　Patent No. 4087798 discloses a threaded joint for stab lead and / or load leads to changes in the middle of the threaded portion. That is, in the threaded joint of Japanese Patent No. 4087798, and the rate of change of the thread width and thread root width is changed in the middle of the threaded portion. Thus, relates the type of threaded joint thread width and thread root width changes, it is possible to improve the resistance to tensile and compressive stresses.
Summary of the Invention
[0008]
　Generally, the machining of the threaded portion, the cutting tool size to fit the smallest thread root widths used. Therefore, when cutting a thread root having a larger thread root width, cutting the number of passes in the tube axis direction is inevitably increased. The threaded joint of Patent No. 4087798 publication, screws Tanihaba, although the rate of change is not constant, but varies across the threaded portion. Therefore, a large difference between the minimum thread root width and maximum thread root width. Thus, cutting the number of passes in the tube axis direction of the thread root having the greatest thread root width becomes particularly large, the processing time of the entire threaded portion is increased. Also, if the thread width changes throughout the threaded portion, inevitably thread width endmost quite small. Its thread width becomes smaller than that or height about the same thread, if the tensile load is applied in the axial direction of the tube, the shear fracture is likely to occur at the root of the thread with a minimum thread width.
[0009]
　The present disclosure aims to provide a threaded joint which can shorten the processing time of the threaded portion while having a high torque.
[0010]
　Tubular threaded joint according to the present disclosure is intended to connect the pair of tubes. Threaded joint comprises a pin and a 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. Box is fastened to the pin. External thread portion includes a screw having a constant width portion, and a screw variable width portion. Screw constant width portion of the external thread portion has a constant thread root width. Screw width variable portion of the external thread portion has a gradually larger thread root width toward a the thread root width or more screws constant width portion of the male thread portion from the thread width constant portion of the external thread portion at the tip of the pin. Internal thread portion includes a screw having a constant width portion, and a screw variable width portion. Screw constant width portion of the female screw portion has a constant thread width. Screw width variable portion of the internal thread portion has a gradually larger thread width toward a the thread width or more screws constant width portion of the female screw portion from the screw constant width portion of the female thread portion in the middle of the box.
[0011]
　According to a threaded joint for steel pipes according to the present disclosure, it is possible to shorten the processing time of the threaded portion with a threaded joint having a high torque.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012]
[1] Figure 1 is a longitudinal sectional view schematically showing the threaded joint according to the first embodiment.
[Figure 2A] Figure 2A is a longitudinal sectional view of an enlarged threaded constant width portion of the threaded joint shown in Figure 1.
[Figure 2B] Figure 2B is a longitudinal sectional view of an enlarged threaded width variable portion of the threaded joint shown in Figure 1.
FIG. 3 is a longitudinal sectional view showing an enlarged part of the threaded joint shown in Figure 1.
[Figure 4A] Figure 4A is a graph showing the stab lead and load lead of the threaded joint shown in Figure 1.
[Figure 4B] Figure 4B is a longitudinal sectional view of an enlarged threaded portion of the threaded joint shown in Figure 1.
FIG. 5 is in threaded joint according to the first embodiment, is a longitudinal sectional view showing a state where the distal ends of the pins are in contact.
FIG. 6 is a longitudinal sectional view schematically showing the threaded joint according to the second embodiment.
[7] FIG. 7 is a longitudinal sectional view schematically showing the threaded joint according to the third embodiment.
[8] FIG. 8 is a longitudinal sectional view schematically showing the threaded joint according to the fourth embodiment.
[9] FIG. 9 is a longitudinal sectional view schematically showing the threaded joint according to the embodiment.
[10] FIG 10 is a longitudinal sectional view schematically showing the threaded joint of the comparative example.
[11] FIG 11 is a graph showing the processing time of the threaded joint according to Examples and Comparative Examples.
DESCRIPTION OF THE INVENTION
[0013]
　A threaded joint according to the embodiment is for connecting a pair of tube. Threaded joint comprises a pin and a 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. Box is fastened to the pin. External thread portion includes a screw having a constant width portion, and a screw variable width portion. Screw constant width portion of the external thread portion has a constant thread root width. Screw width variable portion of the external thread portion has a gradually larger thread root width toward a the thread root width or more screws constant width portion of the male thread portion from the thread width constant portion of the external thread portion at the tip of the pin. Internal thread portion includes a screw having a constant width portion, and a screw variable width portion. Screw constant width portion of the female screw portion has a constant thread width. Screw width variable portion of the female screw portion is a in the thread width or more screws constant width portion of the female screw portion having a gradually larger thread width toward the center of the box from the screw constant width portion of the female screw portion (the first configuration).
[0014]
　In the first configuration, the external thread portion and the internal thread portion includes a threaded constant width portion and a threaded variable width portion. Thread root width and thread width is threaded width varying section varies but, thread root width and thread width is not changed by the screw constant width portion. By providing a screw constant width portion to the male screw portion and the female screw portion, as compared with the case where thread root width throughout the external thread portion and the internal thread portion is gradually changed, the maximum and minimum thread root width at the male thread portion and the female threaded portion the difference between the screw valley width is reduced of. Therefore, the external thread portion and the internal thread portion, cutting the number of passes in the tube axis direction of the thread root having the greatest thread root width is reduced, it is possible to reduce the total cutting pass count in the tube axis direction. As a result, it is possible to shorten the processing time of the threaded portion including a male thread portion and the internal thread portion. Further, by providing the threaded constant width portion to the male screw portion and the female screw portion, a male screw portion and as compared with the case of gradually changing the thread width throughout the internal thread portion, the minimum of the thread width at the male thread portion and the female threaded portion the difference between the maximum of the thread width is reduced. Accordingly, the male screw portion or internally threaded portion, if the tensile load is applied in the axial direction of the tube, shear fracture at the root of the thread is less likely to occur with a minimum thread width. Preferably, both the external thread portion and the female screw portion, a minimum of screws Yamahaba is greater than the height of each thread.
[0015]
　In the first configuration, the screw-width variable regions thread root width changes is provided in the externally threaded portion, the screw width variable portion of the female screw portion so as to correspond to the screw width variable portion of such male screw portion is formed ing. Therefore, a threaded joint having a first configuration can have a high torque.
[0016]
　Maximum screw Tanihaba the external thread portion and the internal thread portion may be less than twice the minimum thread root width of the external thread portion and the female screw portion (the second configuration).
[0017]
　For example, patent in threaded joints described in No. 4,087,798 Publication throughout the threaded portions the screw trough width is changed, the maximum of the thread root width is more than 3 times the minimum thread root width, the thread root cutting pass number is required more than three paths. On the other hand, if the threaded joint having the second configuration, it is possible to suppress the cutting path number of thread root below 2 path. Therefore, it is possible to shorten the processing time of the threaded portion more reliably.
[0018]
　In screwing the pin into the box, the tip of the pin, at the time when both the insertion surface and the load flanks of the thread width variable portion is in contact with the box, without touching the tip of the other pins that are fastened to the box, thread width before both the insertion surface and the load surface of the variable portion is a male screw portion even after the contact with the box yields, it may be in contact with the tip of the other pins (third configuration).
[0019]
　According to a third configuration, it is possible to increase the further torque if necessary.
[0020]
　That is, when the high torque performance threaded joint is not required, the screwing of the pin relative to the box, both the insertion surface and the load flanks of the thread width variable portion of the male threaded portion terminates the fastening at the time of contact with the box. At this time, the tip of the pin screwed into the box, not in contact with the tip of the other pins that are fastened to the box.
[0021]
　On the other hand, if the high torque performance is required in the screw joint, further screwing the pin, the tip of the pin contacting the tip of the other pins before the male thread portion is yield. Axial force is applied to each pin by the tip ends of the two pin contacts, it is possible to increase the torque.
[0022]
　Pin may further have a shoulder surface. Box is further provided corresponding to the shoulder surface of the pin can have a shoulder surface capable of contacting the shoulder surfaces of the pin in the engaged state (fourth configuration).
[0023]
　According to a fourth configuration, when the shoulder surfaces of the pin and box are in contact, axial force is imparted to the pin. Therefore, it is possible to improve the torque.
[0024]
　In screwing the pin into the box, the shoulder surface of the pin, at the time when both the insertion surface and the load flanks of the thread width variable portion is in contact with the box, without contacting the shoulder surface of the box, the insertion surface of the screw width variable portion and before both of the load surface is externally threaded portion even after the contact with the box yields, it may be in contact with the shoulder surface of the box (fifth configuration).
[0025]
　Even the fifth configuration, it is possible to increase the torque as required.
[0026]
　That is, when the high torque performance threaded joint is not required, the screwing of the pin relative to the box, both the insertion surface and the load flanks of the thread width variable portion of the male threaded portion terminates the fastening at the time of contact with the box. In this case, shoulder surfaces of the pin and box are not in contact.
[0027]
　On the other hand, if the high torque performance is required in the screw joint, further screwing the pin contacting the shoulder surfaces of the pin and box before the male screw part is yield. Thus, the axial force is applied to the pin, it is possible to increase the torque.
[0028]
　The length of the tube axis direction of the screw width variable portion of the internal thread portion may be longer than the length in the tube axis direction of the threaded width variable portion of the male screw portion (sixth configuration).
[0029]
　According to the configuration of the sixth, the screw thread of the male screw portion tends fits into thread root of the female screw portion, it is easy to screw the pin into the box.
[0030]
　
　Hereinafter, will be described with reference to the drawings the embodiments. Given the same reference and the corresponding configuration in the figure does not repeat the same description.
[0031]
　[First Embodiment]
　(Overall Configuration)
　FIG. 1 is a longitudinal sectional view showing a threaded joint 1 according to the first embodiment. Threaded joint 1 according to the present embodiment is a coupling type of threaded joint. However, the configuration of the threaded joint described in this embodiment can also be applied to the integral type threaded joint.
[0032]
　As shown in FIG. 1, a threaded joint 1 is provided with two pins 10, and a box 20. Two pins 10 and box 20 forms a respective tubular. Box 20 is fastened to each pin 10. The box 20 is inserted one pin 10 of the one end of the tube axis direction, the other pin 10 is inserted from the other end of the tube axis direction.
[0033]
　Each pin 10 has a male thread portion 11 on the outer periphery. Box 20 has a female screw portion 21 corresponding to the male screw portion 11 on the inner periphery. Each male thread portion 11 and the internal thread portion 21 is configured by a tapered screw meshing with each other. Thread form of each of male thread portions 11 and the internal thread portion 21 is a dovetail shape.
[0034]
　External thread portion 11 of each pin 10 includes a threaded constant width portion 111, and a screw variable width portion 112. Each internal thread portion 21 of the box 20 includes a threaded constant width portion 211, and a screw variable width portion 212. In threaded constant width portion 111, 211 thread width and thread root width is constant, the screw-width variable portion 112, 212 in the thread width and thread root width changes. This point will be described in detail later.
[0035]
　Figure 2A is a longitudinal sectional view of an enlarged threaded constant width portion 111, 211. Figure 2B is a longitudinal sectional view of an enlarged threaded variable width portion 112, 212.
[0036]
　As shown in FIGS. 2A and 2B, when viewed from the cross section obtained by cutting the threaded joint 1 in a plane passing through the tube axis CL, the external thread portion 11, a plurality of screws crest surface 11a, a screw trough bottom 11b, insertion surface 11c, and a load surface 11d. Each insertion surface 11c and the load surface 11d connects the screw crest surface 11a and the thread valley bottom 11b. Each insertion surface 11c is a surface that precedes by screwing of the pin 10 relative to the box 20. Each load surface 11d is positioned opposite the corresponding insertion face 11c.
[0037]
　Viewed from a cross section taken along the threaded joint 1 in a plane passing through the tube axis CL, the internal thread portion 21 has a plurality of screw crest surfaces 21a, thread root bottom surface 21b, insertion face 21c, and the load surface 21d. Each thread crest surface 21a faces the thread root bottom surface 11b of the external thread portion 11. Each thread root bottom surface 21b faces the thread crest surface 11a of the male threaded portion 11. Each insertion surface 21c faces the insertion face 11c of the externally threaded portion 11. Each load surface 21d faces the load surface 11d of the external thread portion 11.
[0038]
　Insertion face 11c, 21c and the load surface 11d, 21d each flank angle are both negative angle of less than 0 °. Here, the flank angle say is that the angle between a plane perpendicular to the tube axis CL insertion face 11c, 21c or load surface 11d, and the 21d. 2A and 2B, the insertion surface 11c, flank angles of 21c is counterclockwise is positive, the load surface 11d, 21d flank angle of the clockwise and positive.
[0039]
　Viewed from a cross section taken along the threaded joint 1 in a plane passing through the tube axis CL, the external thread portion 11 preferably has a plurality of chamfer surfaces 11e. Each chamfer surface 11e is an inclined surface connecting the insertion face 11c and the screw trough bottom 11b. Angle θ of chamfer surfaces 11e for screw trough bottom 11b is preferably in the range of 25 ° ~ 75 °.
[0040]
　If the male screw portion 11 has a chamfer surface 11e, the female screw portion 21 has a chamfer surface 21e corresponding to each chamfer surface 11e of the external thread portion 11. Each chamfer surface 21e of the internal thread portion 21 is opposed to each chamfer surface 11e of the external thread portion 11.
[0041]
　As shown in FIG. 2A, the fastening state, the thread constant width portion 111 and 211, the load surface 11d of the external thread portion 11 are in contact with each other with the load surface 21d of the internal thread portion 21. Further, the threaded constant width portion 111 and 211, the screw crest surface 11a and the screw trough bottom 11b of the external thread portion 11, respectively, in contact with the thread root bottom surface 21b and the screw crest surface 21a of the internal thread portion 21. However, the threaded constant width portion 111 and 211, insertion surface 11c, 21c do not contact each other. Male threaded portion 11 and the internal thread portion 21 of each chamfer surface 11e, when having 21e, the threaded constant width portion 111, 211, chamfer surfaces 11e, 21e also do not contact each other. That is, in the screw constant width portion 111 and 211, a gap is formed between the external thread portion 11 and the internal thread portion 21 in the engaged state.
[0042]
　On the other hand, as shown in Figure 2B, the screw variable width portion 112 and 212, no gap is formed between the external thread portion 11 and the internal thread portion 21 in the engaged state. That is, in the fastening state, the thread width variable portion 112 and 212, the load surface 11d, 21d and between the insertion face 11c, is 21c to each other in contact. Further, the threaded variable width portion 112 and 212, thread root bottom surface 21b of the thread crest surface 11a and the internal thread portion 21 of the male thread portion 11 are in contact with each other, and thread crest surface of the screw trough bottom 11b and the internal thread portion 21 of the male thread portion 11 21a are in contact with each other. Male threaded portion 11 and the internal thread portion 21 of each chamfer surface 11e, when having 21e, the threaded variable width portion 112 and 212, chamfer surfaces 11e, also 21e with each other in contact.
[0043]
　Figure 3 is a longitudinal sectional view of an enlarged portion of the threaded joint 1. In Figure 3, as one pin 10 of one of the two pins 10, and the portion corresponding to the pin 10 of the one out of the box 20 is shown.
[0044]
　As described above, the external thread portion 11 of the pin 10 includes a threaded constant width portion 111 and a threaded variable width portion 112. Screw constant width portion 111 is located proximal of the pin 10 (main pipe side) in the external thread portion 11. Screw constant width portion 111 has a constant thread root width and thread width.
[0045]
　Screw width variable portion 112, the external thread portion 11 is disposed on the distal end side of the pin 10 than the threaded constant width portion 111. Screw width variable portion 112 is continuously provided with threaded constant width portion 111. Screw width variable portion 112 has a thread root width or more thread root width of the thread constant width portion 111. Screw Tanihaba of thread width variable portion 112 gradually increases toward the threaded constant width portion 111 at the tip of the pin 10. Therefore, the screw Yamahaba of thread width variable section 112 gradually decreases toward the tip of the pin 10.
[0046]
　In the external thread portion 11, the maximum thread root width W11max is preferably the minimum of less than twice the thread root width W11min. Screw Tanihaba of thread width variable portion 112 varies from not less than thread root width of the thread constant width portion 111. Therefore, thread width variable portion 112 has a maximum thread root width W11max the male threaded portion 11. The minimum of the thread root width W11min the external thread portion 11 is a thread root width of the thread constant width portion 111.
[0047]
　The internal thread portion 21 of the box 20 so as to correspond to each of the threaded constant width portion 111 and a threaded variable width portion 112 of the male threaded portion 11, threaded constant width portion 211 and a threaded variable width portion 212 is provided.
[0048]
　Screw constant width portion 211, opposite the threaded constant width portion 111 of the male threaded portion 11. Screw constant width portion 211 has a constant thread width and thread root width. Thread width and thread Tanihaba screws constant width portion 211, respectively, corresponding to the thread root width, and the thread width of the thread constant width portion 111 of the male threaded portion 11.
[0049]
　Screw width variable portion 212, opposite the threaded variable width portion 112 of the male threaded portion 11. Thread width and thread Tanihaba screws width variable section 212, respectively, corresponding to the thread root width, and the thread width of the thread width variable portion 112 of the male threaded portion 11. That is, the screw Yamahaba of thread width variable portion 212, corresponds to the thread root width of the thread width variable portion 112 of the external thread portion 11, the center of the screw constant width portion 211 of the box 20 (the distal end opposite the box 20) gradually increases toward the. Screw Tanihaba of thread width variable portion 212, corresponds to the thread width of the thread width variable portion 112 of the male thread portion 11 gradually decreases toward the threaded constant width portion 211 at the center of the box 20.
[0050]
　In the internal thread portion 21, the maximum thread root width W21max is preferably the minimum of less than twice the thread root width W21min. Screw Tanihaba of thread width variable portion 212 changes in a range not exceed the thread root width of the thread constant width portion 211. Therefore, thread width variable portion 212 has a minimum thread root width W21min the internal thread portion 21. The maximum of the thread root width W21max the internal thread portion 21 is a thread root width of the thread constant width portion 211.
[0051]
　The male thread portion 11 and the internal thread portion 21, and contributes mainly to improve thread width variable portion 112 and 212 of the torque. The ratio of the screw variable width portion 112 to the entire of the external thread portion 11, in consideration of the required torque can be appropriately determined. Similarly, the ratio of the thread width variable portion 212 for the entire female threaded portion 21, in consideration of the required torque can be appropriately determined. For example, the length of the external thread portion 11 across the tube axis direction L11, and the length in the tube axis direction of the threaded variable width portion 112 and L112, may be 0 1.05. If completely matched the position between the pin and the box, the threads of the external thread portion is less likely fits into thread root of the female thread portion, with the result that it becomes difficult to screw the pin into the box.
[0058]
　(Method of fastening the pin and the box)
　will be described fastening method of the pin 10 and the box 20.
[0059]
　As described above, a threaded joint 1 according to the present embodiment is a coupling type of threaded joint. Thus, the box 20, the pin 10 is screwed from both ends of each of the tube axis direction.
[0060]
　Referring to FIGS. 1 and 2B, when screwed one pin 10 from one end of the tube axis direction of the box 20, and the internal thread portion 21 of the male thread portion 11 and the box 20 of the pin 10 interfere external thread at some point load surface 11d and the insertion face 11c of the screw-width variable portion 112 of the part 11 is in contact with the box 20. More specifically, each of the load surface 11d and the insertion face 11c of the screw-width variable portion 112 contacts the load surface 21d and the insertion face 21c of the corresponding female thread portion 21. Similarly, when screwing the tube axis direction other pin 10 from the other end of the box 20, for the other pin 10 is also the load surface 11d and the insertion face 11c of the screw-width variable portion 112 of the external thread portion 11 at a certain point each in contact with the load surface 21d and the insertion face 21c of the corresponding female thread portion 21 (Figure 2B). At this point, the tip ends of the pin 10 as shown in FIG. 1 is not in contact.
[0061]
　For example, if the threaded joint 1 in the horizontal digging or the like of the shale well is utilized, high torque performance is required for a threaded joint 1. In this case, it screwed the pins 10 further from the state of FIG. 1 in the box 20. That is, after the loading surface 11d and the insertion face 11c of the screw-width variable portion 112 is in contact with the box 20 (FIG. 2B), further threading the pins 10 in the box 20, the leading ends of the pin 10 as shown in FIG. 5 Contact. Tips of pins 10, each male threaded portion 11 is in contact before the breakdown. Thus, the axial force is applied to each pin 10, the torque is increased. To impart reliably axial force to the pin 10, the tip of each pin 10 is preferably formed of a substantially vertical annular surface to the tube axis CL.
[0062]
　(Effects of First Embodiment)
　As described above, in the threaded joint 1 according to the present embodiment, the external thread portion 11 has a threaded constant width portion 111 and a threaded variable width portion 112. Screw Tanihaba of thread width variable portion 112 is increased toward the threaded constant width portion 111 at the tip of the pin 10, screw Tanihaba the threaded constant width portion 111 does not change. By providing such a screw constant width portion 111 to the external thread portion 11, as compared with the case where gradually changing the thread root width throughout the external thread portion, to reduce the difference between the thread root width caused by the external thread portion 11 can. Therefore, when processing the external thread portion 11 with the cutting tool of suitable size for the smallest thread root width, it is possible to reduce the cutting path number in the tube axis direction.
[0063]
　Internal thread portion 21 is provided in correspondence with the external thread portion 11. That is, the internal thread portion 21 has a threaded constant width portion 211 corresponding to the screw constant width portion 111 of the male threaded portion 11. Therefore, it is possible to reduce the difference in thread root width at the internal thread portion 21, it is possible to reduce the cutting path number in the tube axis direction.
[0064]
　Thus, according to the threaded joint 1 according to the present embodiment, it is possible to reduce the cutting path number in the tube axis direction in the external thread portion 11 and the internal thread portion 21. Therefore, it is possible to shorten the processing time of the formed threaded portion with the external thread portion 11 and the internal thread portion 21.
[0065]
　Further, the external thread portion 11 and the internal thread portion 21, and a threaded constant width portion 111 and 211 and threaded variable width portion 112 and 212. By providing such a screw constant width portion 111 and 211 to the external thread portion 11 and the internal thread portion 21, as compared with the case where the thread width across the male thread portion 11 or the internally threaded portion 12 is gradually changed, the external thread portion 11 or the difference between the minimum of the thread width and the maximum thread width of the internal thread portion is reduced. Therefore, the external thread portion and the female screw portion, if the tensile load is applied in the axial direction of the tube, shear fracture at the root of the thread is less likely to occur with a minimum thread width.
[0066]
　As described above, the external thread portion 11 is threaded variable width portion 112 which thread root width increases toward the tip of the pin 10 is provided. The female screw portion, a screw variable width portion 212 which thread root width varies in correspondence with the thread width variable portion 112 of the male thread portion 11 is provided. Therefore, a threaded joint 1 according to the present embodiment may also have a high torque.
[0067]
　Here, if only to reduce the difference between the maximum thread root width and minimum thread root width of the difference and the internal thread portion of the largest thread root width and minimum thread root width of the male screw portion, a male screw portion or internally threaded over the entire length of the section, each have a smaller threaded width variable portion of the rate of change of the thread root width, and the thread width may be in the form having no screw constant width portion. However, both the external thread portion and the female screw portion, a thread root width, and the thread width thread width variable portion 111 and 211 a large ratio of change of each is the mutual form having a threaded constant width portion 112 and 212, high torque it is advantageous to provide for the.
[0068]
　In the external thread portion 11, the maximum thread root width W11max is preferably, more than twice the minimum thread root width W11min. Therefore, the external thread portion 11, it is possible to suppress the cutting path number of thread root below 2 path.
　In the internal thread portion 21, the maximum thread root width W21max is preferably, more than twice the minimum thread root width W21min. Therefore, the internal thread portion 21, it is possible to suppress the cutting path number of thread root below 2 path.
[0069]
　If the tensile load is applied in the axial direction of the tube, in order to suppress rise to shear fracture at the root of the thread, the external thread portion 11 and the internal thread portion 21, the minimum of the screw Yamahaba is more than the height of the screw thread preference is.
[0070]
　In screwing of the pin 10 against the box 20, tip ends of the pin 10, at the time when both the insertion surface and the load flanks of each thread width variable portion 112 is in contact with the box 20, do not contact each other. Especially if not much required large high torque performance, a threaded joint 1, tips of the pin 10 is used in a state not in contact.
[0071]
　When a large high torque performance is required in the screw joint 1, by further screwing the pin 10 into the box 20 can be the male threaded portion 11 is brought into contact with tip ends of the pins 10 before breakdown. Thus, each pin 10 to impart axial force, it is possible to increase the torque. Thus, the threaded joint 1 according to the present embodiment, it is possible to increase the torque as required.
[0072]
　In a threaded joint 1 according to the present embodiment, the external thread portion 11 and the internal thread portion 21, respectively, not only the threaded constant width portion 111, 211 includes a threaded variable width portion 112, 212. Therefore, it is possible to ensure the necessary torque.
[0073]
　In the engaged state, contact with the screw crest surface of the screw trough bottom and the internal thread portion of the male screw portion, and when the thread root bottom surface of the thread crest surface and the internal thread portion of the male screw portion is not in contact, it is constituted by the male screw portion and the female threaded portion ball screw section does not have a sealing performance. On the other hand, in the fastening state of the threaded joint 1 according to the present embodiment, the screw-width variable portion 112 and 212, contact with the screw crest surface 21a of the thread root bottom surface 11b and the internal thread portion 21 of the male thread portion 11, and the external thread portion 11 screw crest surface 11a of and the thread root bottom surface 21b of the female thread portion 21 are in contact. According to such a configuration, it is possible to impart sealing performance composed threaded portion with the external thread portion 11 and the internal thread portion 21.
[0074]
　[Second Embodiment]
　FIG. 6 is a longitudinal sectional view showing a threaded joint 1A according to the second embodiment. Threaded joint 1A is in that the pins 10A and box 20A has a respective shoulder surfaces 12, 22 and the sealing surface 13 and 23, differs from the threaded joint 1 according to the first embodiment. Other configurations of the threaded joint 1A may be similar to the threaded joint 1 according to the first embodiment.
[0075]
　Pins 10A includes a shoulder surface 12 and the sealing surface 13. Shoulder surface 12 is disposed at the proximal end of the pin 10A. Shoulder surface 12 may be substantially perpendicular annular surface to the tube axis CL. Sealing surface 13 is provided on the outer circumference of the pin 10A. Sealing surface 13, at pin 10A, it is disposed between the male thread portion 11 and the shoulder surface 12.
[0076]
　Box 20A includes a shoulder surface 22 and seal surface 23. Shoulder surface 22 is provided corresponding to the shoulder surface 12 of the pin 10A. Shoulder surface 22 may be substantially perpendicular annular surface to the tube axis CL. Sealing surface 23, corresponding to the seal surface 13 of the pin 10A, it is provided on the inner periphery of the box 20A. Sealing surface 23 is arranged between the internal thread portion 21 and the shoulder surface 22.
[0077]
　Sealing surface 13, 23 contact each other with the screwing of the pin 10A with respect to the box 20A, a fit state interference fit in close contact with the fitting in the engagement state. Thus, the sealing surface 13 and 23, to form a seal by metal contact. As a result, improved sealing performance of the threaded joint. 1A. Seal portion composed of a sealing surface 13 and 23 is particularly excellent sealing performance against external pressure.
[0078]
　Shoulder surface 12, 22 is pressed in contact with each other with the screwing of the pin 10A with respect to the box 20A. By shoulder surfaces 12 and 22 contact each other, the axial force is applied against the pin 10A, the torque is increased.
[0079]
　Although not shown, the external thread portion 11 of the pin 10A, similarly to the first embodiment has a threaded variable width portion. Shoulder surface 12 and 22, the screwing of the pin 10A with respect to the box 20A, to load flanks and the stabbing flanks of the thread width variable portion of the male screw portion 11 may contact each other at the time of contact with the box 20A, to each other in the time it is not necessary to contact.
[0080]
　If the load surface and the insertion side of the thread width variable portion of the male threaded portion 11 does not contact the shoulder surfaces 12 and 22 with each other at the time of contact with the box 20A, by further screwing the pin 10A in the box 20A, shoulder surfaces 12 and 22 to each other it can be brought into contact with. That is, after the load flanks and the stabbing flanks of the thread width variable portion of the male threaded portion 11 is in contact with the box 20A, further screwing the pin 10A in the box 20A, contacting the shoulder surfaces 12 and 22 to each other before the male thread portion 11 yields . Thereby, axial force is imparted to the pin 10A, the torque is increased as compared with the state between shoulder surfaces 12 and 22 are not in contact. With such a configuration, similarly to the first embodiment, it is possible to increase the torque as required.
[0081]
　In the second embodiment, the pin 10A has a shoulder surface 12 and the sealing surface 13, the pin 10A may have only one of the shoulder surface 12 and the sealing surface 13. In this case, box 20A includes a sealing surface 23 corresponding to the sealing surface 13 of the shoulder surface 22, or pins 10A corresponding to the shoulder surface 12 of the pin 10A.
[0082]
　[Third Embodiment]
　FIG. 7 is a longitudinal sectional view showing a threaded joint 1B according to the third embodiment. Threaded joint. 1B, in that the pins 10B and box 20B has a respective sealing surface 14 and 24, it differs from the threaded joint 1 according to the first embodiment. Other configurations of the threaded joint. 1B, may be similar to the threaded joint 1 according to the first embodiment.
[0083]
　Pin 10B includes a sealing surface 14. Sealing surface 14 is provided on the outer circumference of the pin 10B. Sealing surface 14 is disposed at the distal end portion of the pin 10B.
[0084]
　Box 20B includes a sealing surface 24. Sealing surface 24, corresponding to the sealing surface 14 of the pin 10B, provided on the inner periphery of the box 20B.
[0085]
　Sealing surface 14, 24 contact each other with the screwing of the pin 10B with respect to box 20B, the fit state interference fit in close contact with the fitting in the engagement state. Thus, the sealing surface 14, 24 to form a seal by metal contact. As a result, improved sealing performance of the threaded joint. 1B. Seal portion composed of a sealing surface 14 and 24, particularly excellent sealing performance against the pressure.
[0086]
　In a threaded joint 1B according to the third embodiment, the pin 10B may further have a similar sealing face 13 (FIG. 6) and the second embodiment. In this case, box 20B has a seal surface 23 corresponding to the sealing surface 13 (FIG. 6). According to this structure, it improves the sealing performance for the internal pressure by sealing section consisting of a sealing surface 14 and 24, to improve the sealing performance against external pressure by a sealing portion made of a sealing surface 13 and 23 it can.
[0087]
　[Fourth Embodiment]
　FIG. 8 is a longitudinal sectional view showing a threaded joint 1C according to the fourth embodiment. In a threaded joint 1C, each of the pins 10C and box 20C is a third embodiment similar to the sealing surface 14, 24. The pin 10C and box 20C each have a shoulder surface 15, 25.
[0088]
　Shoulder surface 15 is provided on the tip of the pin 10C. Shoulder surface 25, corresponding to the shoulder surface 15 of the pin 10C, are provided in the box 20C. Shoulder surface 15, 25 is preferably constructed of a substantially vertical annular surface to each tube axis CL.
[0089]
　Shoulder surface 15 and 25 is pressed in contact with each other with the screwing of the pin 10C with respect to the box 20C. By shoulder surfaces 15 and 25 contact each other, the axial force is applied to the pin 10C and torque is increased.
[0090]
　External thread portion of the pin 10C 11 has a threaded width variable portion as in the first embodiment. Shoulder surface 15 and 25, the screwing of the pin 10C with respect to box 20C, to load flanks and the stabbing flanks of the thread width variable portion of the male screw portion 11 may contact each other at the time of contact with the box 20C, each other in the time it is not necessary to contact.
[0091]
　If the load surface and the insertion side of the thread width variable portion of the male threaded portion 11 does not contact the shoulder surfaces 15 and 25 with each other at the time of contact with the box 20C, by further screwing the pin 10C into the box 20C, shoulder surfaces 15 and 25 to each other it can be brought into contact with. That is, after the load flanks and the stabbing flanks of the thread width variable portion of the male threaded portion 11 is in contact with the box 20C, further screwing the pin 10C into the box 20C, contacting the shoulder surfaces 15 and 25 to each other before the male thread portion 11 yields . Thus, the axial force is applied against the pin 10C, torque rises as compared with the state between shoulder surfaces 15 and 25 are not in contact. According to this structure, similarly to the first embodiment, it is possible to increase the torque as required.
[0092]
　In the fourth embodiment, the pin 10C has a shoulder surface 15 and sealing surface 14, the pin 10C may have only one of the shoulder surface 15 and sealing surface 14. In this case, box 20C has a shoulder surface 25 or the seal surface 24 corresponding to the sealing surface 14 of the pin 10C, corresponding to the shoulder surface 15 of the pin 10C.
[0093]
　Pin 10C may further have the same shoulder surfaces 12 and the second embodiment. That is, the pin 10C may have a shoulder surface 12, 15 in the proximal and distal ends. In this case, box 20C has a shoulder surface 22, 25 corresponding to each of the shoulder surfaces 12, 15 of the pin 10C.
[0094]
　[Modification]
　While there have been described the embodiments, the present invention is not limited to the above embodiments and can be variously modified without departing from the spirit.
[0095]
　In the above embodiment, the external thread portion and the female screw portion is configured by one screw constant width portion and one threaded variable width portion. However, the external thread portion and the internal thread portion may also include a plurality of threaded constant width portion and / or a plurality of threaded variable width portion. When the external thread portion and the female threaded portion comprises a plurality of threaded constant width portion, the threaded constant width portion may have a different thread root widths. When the external thread portion and the female threaded portion comprises a plurality of screws width variable portion, the rate of change of thread root width at each thread width variable portion may be the same or different from each other.
[0096]
　In the above embodiment, the external thread portion and the female threaded portion is constituted by a screw of dovetail shape. However, thread forms of the male screw portion and the female screw portion is not limited thereto. External thread portion and the internal thread portion may be, for example, consist of trapezoidal threads.
[0097]
　In the above embodiment, the external thread portion and the internal thread portion, which had been composed of one stage of the screw, may be composed of multiple stages of screws. Also, threaded portion constituted by the male screw portion and the female threaded portion may be a single-thread screw, it may be a double threaded screw.
[0098]
　In the second and fourth embodiments, the pin has a shoulder surface at the tip and / or proximal end. However, the pin may have an intermediate shoulder surface provided on the intermediate portion. The box intermediate shoulder surface is provided corresponding to the intermediate shoulder surface of the pin. Pin and box may each have two or more intermediate shoulder surfaces. In this case, the external thread portion and the internal thread portion is composed of a plurality of stages of screws sandwiching intermediate shoulder surface.
[0099]
　In the third embodiment (FIG. 7), the front end portion of the pin male sealing surface 14 is arranged, the female sealing surface 24 is arranged in the corresponding part of the box. However, instead of this structure, or in combination with this structure, it is disposed male sealing surface to the tip of one of the pins, the tip of the other pin sealing surface of the female may be disposed. Thus, the sealing surfaces of both the pin forms a sealing portion by the metal contact. As a result, improved sealing performance of the threaded joint.
Example
[0100]
　To confirm the effects of a threaded joint according to the present disclosure, the following test was conducted.
[0101]
　(Example)
　FIG. 9 is a longitudinal sectional view of a threaded joint according to the embodiment. Conduct machining of the external thread portion 11 of the threaded joint shown in FIG. 9, and measuring the processing time.
[0102]
　A thread root width is constant thread width constant portion 111, to form a thread width variable portion 112 thread root width gradually increases toward the threaded constant width portion 111 at the tip of the pin 10. Tube axis direction of the length of the thread constant width portion 111 and a threaded variable width portion 112 are equal. That is half screw constant width portion 111 of the male threaded portion 11. As a result, the external thread portion 11, the maximum thread root width W11max became twice the minimum thread root width W11min.
[0103]
　Machining of the external thread portion 11 was performed using the cutting tool of a size appropriate to the minimum thread root width W11min. As described above, the external thread portion 11, the maximum thread root width W11max is twice the minimum thread root width W11min. Therefore, as one of the cutting path number in the tube axis direction of the screw trough having a minimum thread root width W11min, up the tube axis direction of the cutting path number of thread root having a thread root width W11max (maximum cutting pass number) is 2 It became. The total cutting pass count in the tube axis direction became 14.
[0104]
　(Comparative Example)
　FIG. 10 is a longitudinal sectional view of a threaded joint according to the comparative example. Conduct machining of the male thread portion 31 of the threaded joint shown in FIG. 10, and measures the processing time.
[0105]
　The threaded joint according to the comparative example, changing the thread root width throughout the external thread portion 31. Screw Tanihaba of the male screw portion 31 is gradually increased from the base to the tip of the pin 30. The length of the tube axis direction of the external thread portion 31 is approximately equal to the length of the tube axis direction of the external thread portion 11 according to the embodiment. Rate of change of the thread root width of the male thread portion 31 was also substantially the same as the rate of change of thread root width of the thread width variable portion 112 according to the embodiment. As a result, the external thread portion 31, the maximum screw Tanihaba became 4 times the minimum thread root width.
[0106]
　Machining of the external thread portion 31 was performed using the cutting tool of a size appropriate to the minimum thread root width. In the external thread portion 31, since the maximum of the screw Tanihaba is four times the minimum thread root width, maximum cutting pass count became 4. The total cutting pass count in the tube axis direction became 28.
[0107]
　(Evaluation)
　FIG. 11 shows a graph of the machining time according to Examples and Comparative Examples each of the threaded joint. Maximum cutting pass number and total cutting pass number of the external thread portion 11 in the embodiment are respectively the half of the maximum cutting pass number and total cutting pass number of the external thread portion 31 according to a comparative example. Accordingly, as shown in FIG. 11, also the processing time of the external thread portion 11 according to the embodiment, which is approximately half of the processing time of the external thread portion 31 according to a comparative example.
[0108]
　As described above, by providing a threaded constant width portion 111 to the external thread portion 11, as compared to the male thread portion 31 that does not include a threaded constant width portion, it was confirmed that can shorten the processing time of the external thread portion 11. For internal thread portion 21 having a corresponding configuration as the male thread portion 11 can also be expected a similar effect.
Industrial Applicability
[0109]
　The present invention is applied to a threaded joint.

The scope of the claims
[Requested item 1]
　A threaded joint for connecting a pair of tube,
　a pin having a male threaded portion on the outer periphery,
　has a female screw portion corresponding to the external thread portion inner circumference, and a box to be fastened to the pin
provided with,
　said male thread portion ,
　a screw constant width portion, having a constant thread root width
　becomes gradually larger toward the a at thread root width or more screws constant width portion of the male thread portion from the thread width constant portion of the male screw portion at the tip of the pin a screw variable width portion having a thread root width
comprises,
　the female screw portion,
　a screw constant width portion having a constant thread width,
　said there is thread width or more screws constant width portion of the female screw portion internal thread a screw constant width portion of the parts, and the thread width variable portion having a gradually larger thread width toward the center of the box
containing the screw joint.
[Requested item 2]
　A threaded joint according to claim 1,
　the maximum screw Tanihaba of the external thread portion is less than twice the minimum thread root width of the male thread portion, a threaded joint.
[Requested item 3]
　A threaded joint according to claim 1 or 2,
　in screwing of the pin relative to the box, the tip of the pin, when both the insert surface and the load flanks of the thread width variable portion is in contact with the box , without touching the tip of the other pins that are fastened to the box, before the male screw portion yields both insertion surface and the load flanks of the thread width varying portions even after being in contact with the box, contacts to the free end of the other pin, a threaded joint.
[Requested item 4]
　A threaded joint according to claim 1 or 2,
　wherein the pin further comprises a shoulder surface,
　the box is further provided corresponding to the shoulder surface of the pin, the pin in the engaged state having a shoulder surface capable of contacting the shoulder surface, a threaded joint.
[Requested item 5]
　A threaded joint according to claim 4,
　in screwing of the pin relative to the box, the shoulder surface of the pin, when both the insert surface and the load flanks of the thread width variable portion is in contact with said box, not in contact with the shoulder surface of the box, the external thread portion both insertion surface and the load flanks of the thread width varying portions even after being in contact with the box before the breakdown, in contact with the shoulder surface of the box , screw joint.
[Requested item 6]
　A threaded joint according to any one of claims 1 to 5,
　the length of the tube axis direction of the screw width variable portion of the internal thread portion has a length in the tube axis direction of the threaded width variable portion of the male screw portion long, threaded joints than of.