A threaded connection with good internal-pressure and external-pressure sealability while preventing galling is provided. A threaded connection 1 includes a pin 10 and a box 20. The pin 10 includes a pin lip 11, a pin metal seal 13, and a cylindrical inner machined surface 14. The pin metal seal 13 includes a pin seal taper surface 16 and a pin seal curvature surface 17. The box 20 includes a box metal seal 22 parallel to the pin seal taper surface 16. The pin metal seal 13 sealingly contacts the box metal seal 22 at a seal point SP. The threaded connection satisfies the following expressions, (1) and (2),

L>Lm>Ls  (1), and

tb/tp>1.6  (2).

L is the length of the pin lip 11; Lm is the distance between the tip AP of the pin and the end point of the cylindrical inner machined surface 14; Ls is the distance between the tip AP of the pin 10 and the seal point SP; tb is the wall thickness of the box 20 as measured at the seal point SP when the connection is made up; and tp is the wall thickness of the pin 10 as measured at the seal point SP.

A screw joint has a tubular element with a female thread and a tubular element with a male thread, wherein the male thread and the female thread have first contact surfaces that cooperate with each other, and the tubular elements optionally have second contact surfaces adjacent to the female thread and/or the male thread, wherein the first contact surfaces and the optional second contact surfaces each have a coating including a first and a second layer, wherein the first layer is formed as a conversion layer in each case, one of the first contact surfaces that cooperate with each other has a second layer made of ceramic material with a friction reducing effect and the other of the two contact surfaces that cooperate with each other has, as a second layer, a varnish layer with a binding agent made of an organic polymer throughout which solid lubricant particles are distributed.

An object of the present invention is to provide a threaded connection that has high torque and still requires reduced machining time for the thread. A threaded connection (1) connects a pair of pipes. The threaded connection (1) includes a pin (10) and a box (20). The pin (10) has a male thread (11) on its outer diameter. The box (20) has a female thread (21) on its inner diameter, the female thread corresponding to the male thread (11). The box (20) and the pin (10) are made up. The male thread (11) includes a constant-thread-width portion (111) and a varying-thread-width portion (112). The constant-thread-width portion (111) has a constant thread-groove width. The varying-thread-width portion (112) has a thread-groove width equal to or larger than the groove width of the constant-thread-width portion (111) and gradually increasing, going from the constant-thread-width portion (111) toward the tip of the pin (10). The female thread (21) includes a constant-thread-width portion (211) and a varying-thread-width portion (212). The constant-thread-width portion (211) has a constant thread-ridge width. The varying-thread-width portion (212) has a thread-ridge width equal to or larger than the thread-ridge width of the constant-thread-width portion (211) and gradually increasing, going from the constant-thread-width portion (211) toward the center of the box (20).

An object of the present invention is to provide a threaded connection that has high torque and still requires reduced machining time for the thread. A threaded connection (1) connects a pair of pipes. The threaded connection (1) includes a pin (10) and a box (20). The pin (10) has a male thread (11) on its outer diameter. The box (20) has a female thread (21) on its inner diameter, the female thread corresponding to the male thread (11). The box (20) and the pin (10) are made up. The male thread (11) includes a constant-thread-width portion (111) and a varying-thread-width portion (112). The constant-thread-width portion (111) has a constant thread-groove width. The varying-thread-width portion (112) has a thread-groove width equal to or larger than the groove width of the constant-thread-width portion (111) and gradually increasing, going from the constant-thread-width portion (111) toward the tip of the pin (10). The female thread (21) includes a constant-thread-width portion (211) and a varying-thread-width portion (212). The constant-thread-width portion (211) has a constant thread-ridge width. The varying-thread-width portion (212) has a thread-ridge width equal to or larger than the thread-ridge width of the constant-thread-width portion (211) and gradually increasing, going from the constant-thread-width portion (211) toward the center of the box (20).

A threaded connection between adjacent drill string components comprises a threaded female connection end adapted to receive a correspondingly threaded male connection end, the two ends each having first and second portions of different tapers. Tubular members, drill string tools and other drill string components comprising the female or male ends described herein are also provided.

A threaded connection between adjacent drill string components comprises a threaded female connection end adapted to receive a correspondingly threaded male connection end, the two ends each having first and second portions of different tapers. Tubular members, drill string tools and other drill string components comprising the female or male ends described herein are also provided.

A threaded coupling comprising a first end, a second end, a first portion of the threaded coupling defining a first thread profile, a second portion of the threaded coupling defining a second thread profile different from the first thread profile, where at least two threads of the second thread profile proximate to the second end are reduced in height according to an extra machining angle.

A threaded coupling comprising a first end, a second end, a first portion of the threaded coupling defining a first thread profile, a second portion of the threaded coupling defining a second thread profile different from the first thread profile, where at least two threads of the second thread profile proximate to the second end are reduced in height according to an extra machining angle.

A threaded connection for steel pipe is provided that prevents cross-threading and provides good compression load resistance. A threaded connection (10) includes a pin (30) and a box (40). The male thread stabbing flank (34) of the pin (30) includes two male thread stabbing flank portions (341) and (342). The male thread stabbing flank portion (341) is located farther from the pipe axis (X) of the steel pipe (20) and has a stabbing flank angle (α1) of −10 to 15 degrees. The male thread stabbing flank portion (342) is located closer to the pipe axis (X) and has a stabbing flank angle (α2) of 20 to 60 degrees. The female thread stabbing flank (44) of the box (40) includes two female thread stabbing flank portions (441) and (442). The female thread stabbing flank portion (441) is located farther from the pipe axis (X) and has a stabbing flank angle (α1) equal to the stabbing flank angle (α1) of the male thread stabbing flank portion (341). The female thread stabbing flank portion (442) is located closer to the pipe axis (X) and has a stabbing flank angle (α2) equal to the stabbing flank angle (α2) of the male thread stabbing flank portion (342).

A threaded connection for steel pipe is provided that prevents cross-threading and provides good compression load resistance. A threaded connection (10) includes a pin (30) and a box (40). The male thread stabbing flank (34) of the pin (30) includes two male thread stabbing flank portions (341) and (342). The male thread stabbing flank portion (341) is located farther from the pipe axis (X) of the steel pipe (20) and has a stabbing flank angle (α1) of −10 to 15 degrees. The male thread stabbing flank portion (342) is located closer to the pipe axis (X) and has a stabbing flank angle (α2) of 20 to 60 degrees. The female thread stabbing flank (44) of the box (40) includes two female thread stabbing flank portions (441) and (442). The female thread stabbing flank portion (441) is located farther from the pipe axis (X) and has a stabbing flank angle (α1) equal to the stabbing flank angle (α1) of the male thread stabbing flank portion (341). The female thread stabbing flank portion (442) is located closer to the pipe axis (X) and has a stabbing flank angle (α2) equal to the stabbing flank angle (α2) of the male thread stabbing flank portion (342).