Vallourec Oil and Gas France

Nippon Steel Corporation

Nippon Steel Sumitomo Metal Corporation

Shin Ugai

Masaaki Sugino

Keita Inose

Suguru Yamaguchi

Fumio Ota

Takashi Okada

Masayoshi Sasaki

Yousuke Oku

Masahiro Oshima

Hikari Nakano

Yoshinori Ando

A two-step threaded connection for steel pipe includes an intermediate seal and intermediate shoulders. A pinhas an inner male-threaded sectionand an outer male-threaded sectionA boxhas an inner female-threaded sectionand an outer female-threaded sectionThe pinhas a pin intermediate critical cross section PICCS located near an end of the first male-threaded sectionThe boxhas a box critical cross section BCCS located near an end of the inner female-threaded sectionand a box intermediate critical cross section BICCS located near an end of the outer female-threaded section The pinand the boxsatisfy the following relationships:PICCSA+BICCSA&#x3e;BCCSA, and0.70&#x2264;PICCSA/BICCSA&#x2264;0.95.

Threaded connection for steel pipe

The threaded joint includes a pin and a box. The pin includes a taper male thread part, and the box includes a taper female thread part to be engaged with the taper male thread part. The male thread part is divided into a first region on the free end side of the pin, and a second region on the tubular side of the pin along a tube axis direction. The taper ratio of the first region is greater than the taper ratio of the second region. The taper ratio of the first region is greater than the taper ratio of the female thread part. The taper ratio of the second region is equal to or greater than the taper ratio of the female thread part.

Threaded joint for steel pipes

A threaded connection for steel pipe is provided that prevents galling on the sealing surfaces during make-up while providing high sealing performance after completion of make-up. The pin () includes a nose () including a pin taper guide surface () and a pin sealing surface () including a taper surface (). The box () includes a nose-receiving portion () including a box taper guide surface (), a box sealing surface () including a taper surface (), and a buffer surface (). The taper angle of the taper surfaces () includes a second taper angle larger than the taper angle of the taper guide surfaces (). The threaded connection () is constructed so as to satisfy Dp2&#x3e;Db2&#x3e;Dp1 and Lb2&#x3e;Lp2. The buffer surface (), located between the box taper guide surface () and taper surface (), has a length of 0.75 mm or larger, and is located outward of an imaginary plane (V) determined along radial directions.

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.

A threaded joint for pipes comprises a pin and a box, each having a threaded and unthreaded portion metal contact surface. The unthreaded metal contact portion includes a sealing surface and a shoulder surface, the shoulder surface of the pin located on the pin end surface. A non-contacting region where the pin and the box do not contact each other exists between the sealing surfaces and the shoulder surfaces of the pin and the box. One or more grooves is formed in at least one of the pin and the box shoulder surfaces and extending to the non-contacting region and to the interior of the joint. At least one of the contact surfaces has a solid lubricating coating exhibiting plastic or viscoplastic rheological behavior. A total volume V (mm) of the grooves and coating weight W (g) of the solid lubricating coating satisfy the equation V/W&#x2267;24 (mm/g).

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Tokyo, Japan

Shin Ugai