Nippon Steel Corporation

Vallourec Oil and Gas France

Nippon Steel Sumitomo Metal Corporation

Fumio Ota

Masaaki Sugino

Yousuke Oku

Suguru Yamaguchi

Keita Inose

Shin Ugai

A threaded joint is constructed of a pin and a box. The pin includes, in order from an end of the pin toward the tubular body: a first male threaded portion, a first sealing surface, a shoulder surface, a second sealing surface, and a second male threaded portion. The box includes a first female threaded portion, a first sealing surface, a shoulder surface, a second sealing surface, and a second female threaded portion. A length from a boundary of the first sealing surfaces to a position of the shoulder surfaces and a length from a boundary of the second sealing surfaces to a position are each at least 15 mm, and the total length which is a sum of the length and the length is at least 50 mm. Thus, the threaded joint is capable of providing excellent sealing performance.

Threaded joint for steel pipes

A pin includes, in order from a free end thereof, a shoulder surface, a first sealing surface, a first male threaded portion, a second sealing surface, and a second male threaded portion. A box includes a shoulder surface, a first sealing surface, a first female threaded portion, a second sealing surface, and a second female threaded portion. The flank angles of load flanks of the first male threaded portion and the first female threaded portion are each less than 0 degrees. The first male threaded portion is composed of, in order from near the second sealing surface, an incomplete thread section and a complete thread section. The incomplete thread section has a length of at least three times the thread pitch thereof and has a thread height lower than the thread height of the complete thread section. The incomplete thread section is provided with clearances between crests and roots.

Threaded joint for steel pipe

A threaded joint is constructed of a pin and a box. The pin includes, in order from an end thereof, a shoulder surface, a nose portion, a first sealing surface, a first male threaded portion, an annular portion, a second sealing surface, and a second male threaded portion. The box includes a shoulder surface, a recessed portion, a first sealing surface, a first female threaded portion, an annular portion, a second sealing surface, and a second female threaded portion. In the threaded joint, in a fastened state, the shoulder surfaces are in contact with each other, the first sealing surfaces are in contact with each other, the second sealing surfaces are in contact with each other, a clearance is provided between the nose portion and the recessed portion, a clearance is provided between the annular portions.

The load flanks in the male threaded portion of the pin and the load flanks in the female threaded portion of the box have a flank angle of less than 0 degrees. The female threaded portion is divided into, in order from near the seal surface, an incomplete thread section and a complete thread section. In the female threaded portion, over the entire area including the two thread sections, roots collectively define a single tapered periphery. The incomplete thread section has a length of at least three times the thread pitch and has a thread height lower than a thread height of the complete thread section. The shoulder surfaces are in contact with each other, the seal surfaces are in contact with each other, and in the incomplete thread section, clearances are provided between the roots of the male threaded portion and the crests of the female threaded portion.

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Tokyo, Japan

Fumio Ota