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1. (WO2018037781) THREADED JOINT FOR OIL WELL PIPE

Pub. No.:    WO/2018/037781    International Application No.:    PCT/JP2017/026245
Publication Date: Fri Mar 02 00:59:59 CET 2018 International Filing Date: Fri Jul 21 01:59:59 CEST 2017
IPC: F16L 15/04
Applicants: JFE STEEL CORPORATION
JFEスチール株式会社
Inventors: YAMAGUCHI Masao
山口 正男
Title: THREADED JOINT FOR OIL WELL PIPE
Abstract:
Provided is a threaded joint, for an oil well pipe, having excellent sealing properties. This threaded joint for the oil well pipe is provided with: a pin having an annular outer peripheral surface part located at the leading end side of the steel pipe, and a male thread part provided toward the center of the steel pipe in the steel pipe axial direction from the annular outer peripheral surface part; and a box having a cavity accommodating the pin inside thereof, having a female thread part and being screwed to the male thread part in the cavity, and having an annular inner peripheral surface part that is in contact with and collides with the annular outer peripheral surface part, wherein the pin and the box are joined with each other by screwing of the male thread part and the female thread part, whereby the annular outer peripheral surface part and the annular inner peripheral surface part are in contact with each other, so that the contact part forms a sealing part. The annular outer peripheral surface part that forms the sealing part of the pin is formed in a projected arc shape, and the annular inner peripheral surface part that forms a sealing part of the box is formed in a recessed arc shape. The difference, in curvature radius, of the arc of the annular inner peripheral surface part of the box from the arc of the annular outer peripheral surface part of the pin is set within ±10%, and the difference of distance in the pipe axial direction between the center position of the arc of the annular outer peripheral surface part of the pin and the center position of the arc of the annular inner peripheral surface part of the box is not more than 2 mm.