Abstract: A pin (10) includes, in order from a free end of the pin (10), a shoulder surface (11), a first sealing surface (12), a first male threaded portion (13), a second sealing surface (14), and a second male threaded portion (15). A box (20) includes a shoulder surface (21), a first sealing surface (22), a first female threaded portion (23), a second sealing surface (24), and a second female threaded portion (25). The flank angles of load flanks (13d and 23d) of the first male threaded portion (13) and the first female threaded portion (23) are each less than 0 degrees. The first male threaded portion (13) is composed of, in order from near the second sealing surface (14), an incomplete thread section (31b) and a complete thread section (31a). The incomplete thread section (31b) 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 (31a).

Abstract: A threaded joint for steel pipe is provided that ensures good sealing performance and reduces crevice corrosion. A threaded joint includes a pin (10) and a box (20). The pin (10) includes a first shoulder surface (11), a first male thread (14), a second shoulder surface (18), and a second male thread (17). The box (20) includes a first shoulder surface (21), a first female thread (24), a second shoulder surface (28), and a second female thread (27). Supposing that the distance between the shoulder surfaces of the pin (10) is represented as Lpin and the distance between the shoulder surfaces of the box (20) is represented as Lbox, and the interference ?shld is defined by Equation (1) given below, then, the threaded joint is constructed such that Equations (2) and (3) given below are satisfied.

Abstract: 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.

Abstract: 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.