Jfe Steel Corporation

Taro Kanayama

Masaki Yoshikawa

Takamasa Kawai

Jun Takano

Tsuyoshi Yoneyama

Kazunari Takahashi

Takuya Nagahama

Masateru Ueta

Seigo Goto

Haruhiko Seki

A threaded joint with excellent tensile strength, comprising: a pin having an externally threaded part comprising a first and second externally threaded sections across a step on an outer periphery on a distal-end side of a first steel pipe or tube; and a box having an internally threaded part comprising a first and second internally threaded sections across the step on an inner periphery on a distal-end side of a second steel pipe or tube, the externally threaded part being screwed to the internally threaded part to join the pin and the box. The threaded joint has a first and second thread sequence with lengths Land Lrespectively, and cross-sectional areas PPBand Bat end positions 4, 5, 6, and 7, respectively, satisfying Formulas (1) and (2): (PB)&#x2264;P{L/(L+L)}(1) and (PB)&#x2264;B/{L/(L+L)}(2), where (PB)represents Por Bwhichever is smaller.

Threaded joint

A threaded joint for oil well steel pipe is provided. The threaded joint includes a pin provided with a male thread, and a box provided with a female thread threadedly engaged with the male thread, and at an outer periphery side sealing portion, a cross-sectional area S1 of the pin at a seal point, and a cross-sectional area S0 of a pipe body portion, which is an unprocessed pin portion, satisfy an expression (S1/S0)&#xd7;100&#x2265;15(%), at an inner periphery side sealing portion, a cross-sectional area S2 of the box at a seal point, and a cross-sectional area S0' of a pipe body portion, which is an unprocessed box portion satisfy an expression (S2/S0&#x2032;)&#xd7;100&#x2265;20(%), and a surface area S3 of a contact portion of an intermediate shoulder between thread rows and the cross-sectional area S0 satisfy the expression (S3/S0)&#xd7;100&#x2265;10(%).

Threaded joint for oil well steel pipe

Provided is a threaded joint for an oil well tubing which possesses sufficient sealability when the external pressure is applied to the threaded joint by suppressing the plastic deformation of a nose portion and sufficient galling resistance. The sufficient galling resistance is provided by preventing the occurrence of galling at the time of making up the threaded joint during verification test performed in accordance with ISO13679:2002 even when the threaded joint for an oil well tubing has a small thickness. Parameters including sizes of the threaded joint at positions of a seal point and shoulder portions satisfy formula 1 ((Ds1&#x2212;Ds0)/(D1&#x2212;D0)&#x2265;0.30), formula 2 (tan &#x3b8;&#x3e;(&#x394;D+&#x3b4;)/{2(Lt&#x2212;Ls)}), and Ls/Ln is set to 0.2 to 0.6.

Threaded joint for oil well tubing

A threaded pipe joint, when acted upon by a tensile load, does not break on the female thread-side of a first thread section of a second thread series that extends from an intermediate shoulder. The threaded pipe joint reliably undergoes tensile rupture on the female thread-side of a first thread section of a first thread series, which is the original critical cross-section site. The threaded pipe joint is configured so that when the male and female threads of the intermediate shoulder are screwed together, the load flank-side thread gaps L1G and L2G of a first thread series, which is the radially inward thread series, and a second thread series, which is the radially outward thread series, on the two sides of the intermediate shoulder always satisfy the relationship L1G&#x3c;L2G.

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Tokyo, Japan

Taro Kanayama