Threaded connection for steel pipe

Patent metadata

Field	Value
Publication number	US-11067205-B2
Application number	US-201816495420-A
Country	US
Kind code	B2
Filing date	Mar 2, 2018
Priority date	Mar 31, 2017
Publication date	Jul 20, 2021
Grant date	Jul 20, 2021

Abstract

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).

First claim

What is claimed is:

1. A threaded connection comprising:
a tubular pin located on one end of a steel pipe; and
a tubular box, the pin being inserted into the box such that the box and pin are made up,
wherein the pin includes a male thread provided on an outer periphery of the pin,
the box includes a female thread corresponding to the male thread and provided on an inner periphery of the box,
the male thread and the female thread are trapezoidal threads and tapered threads,
when the connection has been made up, at least a portion of the male thread and at least a portion of the female thread serve as a thread seal,
the male thread includes:
a male thread crest;
a male thread root;
a male thread stabbing flank located closer to a tip of the pin; and
a male thread load flank located farther from the tip of the pin,
the male thread stabbing flank includes:
a first male thread stabbing flank portion located farther from a pipe axis of the steel pipe and having a stabbing flank angle of −10 to 15 degrees; and
a second male thread stabbing flank portion located closer to the pipe axis and having a stabbing flank angle of 20 to 60 degrees,
the second male thread stabbing flank portion has a height of 20 to 60% of that of the male thread,
the female thread includes:
a female thread crest facing the male thread root;
a female thread root facing the male thread crest;
a female thread stabbing flank facing the male thread stabbing flank; and
a female thread load flank facing the male thread load flank,
the female thread stabbing flank includes:
a first female thread stabbing flank portion located farther from the pipe axis and having a stabbing flank angle equal to the stabbing flank angle of the first male thread stabbing flank portion; and
a second female thread stabbing flank portion located closer to the pipe axis and having a stabbing flank angle equal to the stabbing flank angle of the second male thread stabbing flank portion.

2. The threaded connection according to claim 1 , wherein the male thread further includes a first male thread round surface located on a corner between the male thread crest and the male thread stabbing flank, and
the female thread further includes a first female thread round surface located on a corner between the female thread crest and the female thread stabbing flank.

3. The threaded connection according to claim 2 , wherein the male thread further includes:
a second male thread round surface located on a corner between the male thread crest and the male thread load flank;
a third male thread round surface located on a corner between the male thread root and the male thread stabbing flank; and
a forth male thread round surface located on a corner between the male thread root and the male thread load flank, and
the female thread further includes:
a second female thread round surface located on a corner between the female thread crest and the female thread load flank;
a third female thread round surface located on a corner between the female thread root and the female thread stabbing flank; and
a fourth female thread round surface located on a corner between the female thread root and the female thread load flank.

4. The threaded connection according to claim 1 , wherein the male thread load flank has a load flank angle of −10 to 3 degrees, and
the female thread load flank has a load flank angle equal to the load flank angle of the male thread load flank.

5. The threaded connection according to claim 1 , wherein the male thread crest, the male thread root, the female thread crest, and the female thread root are parallel to the pipe axis.

6. The threaded connection according to claim 1 , wherein the male thread stabbing flank and the female thread stabbing flank have a clearance therebetween of 60 to 120 μm when the connection has been made up.

7. The threaded connection according to claim 1 , wherein the male thread crest and the female thread root have a clearance therebetween of 0 to 50 μm when the connection has been made up, and the male thread root and the female thread crest have a clearance therebetween of 0 to 50 μm when the connection has been made up.

8. The threaded connection according to claim 1 , wherein the pin further includes a pin shoulder surface located on the end of the pin, and the box further includes a box shoulder surface in contact with the pin shoulder surface when the connection has been made up.

9. The threaded connection according to claim 1 , wherein the male thread includes a tapered thread having a taper ratio decreasing away from the tip of the pin.

10. The threaded connection according to claim 1 , wherein the pin further includes a pin sealing surface located between the tip of the pin and the male thread and on the outer periphery of the pin, and
the box further includes a box sealing surface facing the pin sealing surface and located on the inner periphery of the box, the box sealing surface adhering to the pin sealing surface when the connection has been made up.

11. The threaded connection according to claim 1 , wherein the portions of the male thread and the female thread serving as the thread seal have a length as measured in a pipe-axis direction three times a wall thickness of the steel pipe or more.

12. The threaded connection according to claim 1 , wherein the steel pipe has an outer diameter above 16 inches.

13. The threaded connection according to claim 1 , wherein the steel pipe has an outer diameter of 16 inches or below.

14. A threaded connection for connecting two steel pipes to each other, comprising:
a tubular first pin located on an end of one pipe of the steel pipes;
a tubular second pin located on an end of the other pipe of the steel pipes; and
a coupling including a tubular first box, the first pin being inserted into the first box such that the first box and first pin are made up, and a tubular second box located opposite to the first box, the second pin being inserted into the second box such that the second box and second pin are made up,
wherein each of the first and second pins includes a male thread provided on an outer periphery of the pin,
each of the first and second boxes includes a female thread corresponding to the male thread and provided on an inner periphery of the box,
the male thread and the female thread are trapezoidal threads and tapered threads,
when the connection has been made up, at least a portion of the male thread and at least a portion of the female thread serve as a thread seal,
the male thread includes:
a male thread crest;
a male thread root;
a male thread stabbing flank located closer to a tip of the pin; and
a male thread load flank located farther from the tip of the pin,
the male thread stabbing flank includes:
a first male thread stabbing flank portion located farther from a pipe axis of the steel pipe and has a stabbing flank angle of −10 to 15 degrees; and
a second male thread stabbing flank portion is located closer to the pipe axis and has a stabbing flank angle of 20 to 60 degrees,
the second male thread stabbing flank portion has a height of 20 to 60% of that of the male thread,
the female thread includes:
a female thread crest facing the male thread root;
a female thread root facing the male thread crest;
a female thread stabbing flank facing the male thread stabbing flank; and
a female thread load flank facing the male thread load flank,
the female thread stabbing flank includes:
a first female thread stabbing flank portion located farther from the pipe axis and having a stabbing flank angle equal to the stabbing flank angle of the

Assignees

• Nippon Steel Corp

Inventors

• Iwamoto Michihiko
• Takeda Yusuke
• Kochi Yasuhiro
• Maruta Satoshi
• Toyota Yusuke

Classifications

• E21B17/042

  Threaded · CPC title

• F16L15/04

  with additional sealings · CPC title

• F16L15/06 Primary

  characterised by the shape of the screw-thread · CPC title

• F16L15/004 Primary

  with axial sealings having at least one plastically deformable sealing surface (with sealing rings F16L15/003) · CPC title