Threaded steel pipe or tube and production method therefor
AssigneeJfe Steel Corporation
InventorsHiroshi OKANO, Kazuki MATSUBARA, Shusaku TAKAGI, Nobuyuki ISHIKAWA
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Abstract
To alleviate stress exerted on a thread portion of a threaded steel pipe or tube during use to prevent fatigue fracture, there is provided a threaded steel pipe or tube having a female thread portion on an inner peripheral surface of at least one end, wherein a maximum value of residual compressive stress at a position of 0.4 mm in a depth direction from a thread bottom of the female thread portion is 100 MPa or more and less than or equal to tensile strength of a material of the threaded steel pipe or tube.
Claims8
A threaded steel pipe or tube having a female thread portion on an inner peripheral surface of at least one end,
- wherein a maximum value of residual compressive stress at a position of 0.4 mm in a depth direction from a thread bottom of the female thread portion is 100 MPa or more and less than or equal to tensile strength of a material of the threaded steel pipe or tube.
A production method for a threaded steel pipe or tube, the production method comprising:
- attaching a lid having a male thread portion on an outer peripheral surface to a threaded steel pipe or tube having a female thread portion on an inner peripheral surface of at least one end so that the male thread portion is screwed into the female thread portion;
- and
- applying an internal pressure to the threaded steel pipe or tube with the lid attached thereto, under the following conditions (A), (B), and (C):
- (A) thread bottom stress of the female thread portion is more than yield stress of a material of the threaded steel pipe or tube;
- (B) axial stress of the threaded steel pipe or tube is less than or equal to tensile strength of the material of the threaded steel pipe or tube;
- and
- (C) circumferential stress of the threaded steel pipe or tube is less than or equal to the tensile strength of the material of the threaded steel pipe or tube.
A production method for a threaded steel pipe or tube, the production method comprising:
- attaching a jig having a male thread portion on an outer peripheral surface to a threaded steel pipe or tube having a female thread portion on an inner peripheral surface of at least one end so that the male thread portion is screwed into the female thread portion;
- and
- applying a load to the threaded steel pipe or tube using the jig, under the following conditions (A) and (B):
- (A) thread bottom stress of the female thread portion is more than yield stress of a material of the threaded steel pipe or tube;
- and
- (B) axial stress of the threaded steel pipe or tube is less than or equal to tensile strength of the material of the threaded steel pipe or tube.
Dependencies are inferred from the claim text.