Abstract: A threaded connection for steel pipe is provided in which galling does not easily occur on any of the inner and outer threads. A threaded connection for steel pipe 1 includes a pin 10 and a box 20. The pin 10 includes: a nose 12; a tapered inner male thread 14; a tapered outer male thread 17; a pin inner sealing surface 13; a pin intermediate shoulder surface 18; and a pin intermediate sealing surface 16. The box 20 includes: a tapered inner female thread 24; a tapered outer female thread 27; a box inner sealing surface 23; a box intermediate shoulder surface 28; and a box intermediate sealing surface 26. Each of the inner male thread 14, outer male thread 17, inner female thread 24 and outer female thread 27 includes a perfect thread portion 141, 171, 241, 271. Each perfect thread portion includes an inner end located relatively close to the tip of the pin 10 and an outer end located relatively close to the end of the pin 10 opposite to its tip.

Abstract: A disclosed threaded connection for steel pipes includes a pin and a box. The pin includes, in order from a front end of the pin toward a pipe body of the pin, an annular shoulder surface, an annular sealing surface located adjacent to the shoulder surface, and a male thread part. The box includes, in order from a pipe body of the box toward a front end of the box, an annular shoulder surface, an annular sealing surface located adjacent to the shoulder surface, and a female thread part. The pin shoulder surface and the box shoulder surface incline from a plane perpendicular to a pipe axis in a direction of screwing the pin. A diameter of an inner circumferential edge of the pin shoulder surface is smaller than a diameter of an inner circumferential edge of the box shoulder surface.

Abstract: A two-step threaded connection for steel pipe includes an intermediate seal and intermediate shoulders. A pin 2 has an inner male-threaded section 23 and an outer male-threaded section 26. A box 3 has an inner female-threaded section 33 and an outer female-threaded section 36. The pin 2 has a pin intermediate critical cross section PICCS located near an end of the first male-threaded section 23. The box 3 has a box critical cross section BCCS located near an end of the inner female-threaded section 33 and a box intermediate critical cross section BICCS located near an end of the outer female-threaded section 36. The pin 2 and the box 3 satisfy the following relationships: PICCSA+BICCSA>BCCSA, and 0.70?PICCSA/BICCSA?0.95.

Abstract: A threaded connection with good internal-pressure and external-pressure sealability while preventing galling is provided. A threaded connection 1 includes a pin 10 and a box 20. The pin 10 includes a pin lip 11, a pin metal seal 13, and a cylindrical inner machined surface 14. The pin metal seal 13 includes a pin seal taper surface 16 and a pin seal curvature surface 17. The box 20 includes a box metal seal 22 parallel to the pin seal taper surface 16. The pin metal seal 13 sealingly contacts the box metal seal 22 at a seal point SP. The threaded connection satisfies the following expressions, (1) and (2), L>Lm>Ls??(1), and tb/tp>1.6??(2).

Abstract: An object of the present disclosure is to ensure good sealability in a threaded connection for steel pipe of a two-step thread construction including an intermediate seal and intermediate shoulders. The pin 2 includes an intermediate seal section 22, an inner male-threaded section 23, an intermediate shoulder 24, an intermediate seal section 25 and an outer male-threaded section 26. The box 3 includes an intermediate seal section 32, an inner female-threaded section 33, an intermediate shoulder 34, an intermediate seal section 35 and an outer female-threaded section 36. The pin 2 has a pin intermediate critical cross section PICCS located near an end of the first male-threaded section 23. The box 3 has a box critical cross section BCCS located near an end of the first female-threaded section 33 and a box intermediate critical cross section BICCS located near an end of the second female-threaded section 36. The pin 2 and the box 3 satisfy the following relationships: PICCSA+BICCSA>BCCSA, and 0.

Abstract: A threaded connection for steel pipes having improved sealing performance is provided. A threaded connection (10) for steel pipes includes a pin (10) and a box (20). The pin (10) includes a nose (11), a pin shoulder surface (12), a pin sealing surface (13) and a male thread (14). The box (20) includes a box shoulder surface (22), a box sealing surface (23) and a female thread (24). When the position of the portion of the pin sealing surface (13) that first contacts the inner periphery of the box (20) during make-up defines a seal position (P), the distance between the seal position (P) and the end of the male thread (14) adjacent to the pin sealing surface (13) as measured in the pipe-axis direction is denoted by x, and the distance between the tip of the pin (10) and the end of the male thread (14) adjacent to the pin sealing surface (13) as measured in the pipe-axis direction is denoted by L, then, x/L is not smaller than 0.4 and not larger than 0.55.

Abstract: A threaded connection for steel pipe is provided that improves its internal-pressure sealability while maintaining the high external-pressure sealability of a threaded connection having a nose used in a steel pipe with large diameter and large wall thickness. In a threaded connection for connecting steel pipe bodies each having an outer diameter equal to or larger than 7 inches and a wall thickness equal to or larger than 0.7 inches, Expression (1) in the description is satisfied and tB/tL>1.

Abstract: A threaded connection for steel pipes is provided that exhibits improved sealability against the external pressure while maintaining the sealability against the internal pressure. A threaded connection for steel pipes includes a pin and a box. The pin includes a nose, a tapered inner male thread, a tapered outer male thread, a pin inner sealing surface, a pin intermediate shoulder surface, a pin intermediate sealing surface, and a pin annular portion. The box includes a recess corresponding to the nose, a tapered inner female thread, a tapered outer female thread, a box inner sealing surface, a box intermediate shoulder surface, a box intermediate sealing surface, and a box annular portion. The threaded connection satisfies expressions (1) and (2), provided below. ?1 is a taper slope of the inner male thread, and ?2 is a taper slope of the outer male thread. ? ? 1 > ?2 , and ( 1 ) 0.5 ? L ? ? 1 ? ?1 L ? ? 2 ? ?2 ? 1.

Abstract: A threaded connection for steel pipe is provided in which galling does not easily occur on any of the inner and outer threads. A threaded connection for steel pipe 1 includes a pin 10 and a box 20. The pin 10 includes: a nose 12; a tapered inner male thread 14; a tapered outer male thread 17; a pin inner sealing surface 13; a pin intermediate shoulder surface 18; and a pin intermediate sealing surface 16. The box 20 includes: a tapered inner female thread 24; a tapered outer female thread 27; a box inner sealing surface 23; a box intermediate shoulder surface 28; and a box intermediate sealing surface 26. Each of the inner male thread 14, outer male thread 17, inner female thread 24 and outer female thread 27 includes a perfect thread portion 141, 171, 241, 271. Each perfect thread portion includes an inner end located relatively close to the tip of the pin 10 and an outer end located relatively close to the end of the pin 10 opposite to its tip.

Abstract: A threaded connection with good internal-pressure and external-pressure sealability while preventing galling is provided. A threaded connection 1 includes a pin 10 and a box 20. The pin 10 includes a pin lip 11, a pin metal seal 13, and a cylindrical inner machined surface 14. The pin metal seal 13 includes a pin seal taper surface 16 and a pin seal curvature surface 17. The box 20 includes a box metal seal 22 parallel to the pin seal taper surface 16. The pin metal seal 13 sealingly contacts the box metal seal 22 at a seal point SP. The threaded connection satisfies the following expressions, (1) and (2), L>Lm>Ls??(1), and tb/tp>1.6??(2).

Abstract: High sealing performance is provided in a threaded connection used for pipes for oil wells with large wall thickness and with a connection efficiency smaller than 1. A threaded connection (10) connects pipes for oil wells (1). The threaded connection (10) includes two pins (11) and a tubular coupling. Each of the pins (11) is provided on an end of the pipe for oil wells (1) and is in continuity with the pipe body (12), which has a wall thickness not smaller than 12 mm. The coupling (2) includes two boxes (21) and a recess portion (22). The box (21) is provided on both ends of the coupling (2). The recess portion (22) has a length not smaller than 10 mm. The threaded connection (10) has a connection efficiency smaller than 1.

Abstract: A disclosed threaded connection for steel pipes includes a pin and a box. The pin includes, in order from a front end of the pin toward a pipe body of the pin, an annular shoulder surface, an annular sealing surface located adjacent to the shoulder surface, and a male thread part. The box includes, in order from a pipe body of the box toward a front end of the box, an annular shoulder surface, an annular sealing surface located adjacent to the shoulder surface, and a female thread part. The pin shoulder surface and the box shoulder surface incline from a plane perpendicular to a pipe axis in a direction of screwing the pin. A diameter of an inner circumferential edge of the pin shoulder surface is smaller than a diameter of an inner circumferential edge of the box shoulder surface.

Abstract: 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.

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: A threaded connection for steel pipes is provided that exhibits improved sealability against the external pressure while maintaining the sealability against the internal pressure. A threaded connection for steel pipes includes a pin and a box. The pin includes a nose, a tapered inner male thread, a tapered outer male thread, a pin inner sealing surface, a pin intermediate shoulder surface, a pin intermediate sealing surface, and a pin annular portion. The box includes a recess corresponding to the nose, a tapered inner female thread, a tapered outer female thread, a box inner sealing surface, a box intermediate shoulder surface, a box intermediate sealing surface, and a box annular portion. The threaded connection satisfies expressions (1) and (2), provided below. ?1 is a taper slope of the inner male thread, and ?2 is a taper slope of the outer male thread. ? ? 1 > ?2 , and ( 1 ) 0.5 ? L ? ? 1 ? ?1 L ? ? 2 ? ?2 ? 1.

Abstract: A threaded connection for steel pipe is provided that improves its internal-pressure sealability while maintaining the high external-pressure sealability of a threaded connection having a nose used in a steel pipe with large diameter and large wall thickness. In a threaded connection for connecting steel pipe bodies each having an outer diameter equal to or larger than 7 inches and a wall thickness equal to or larger than 0.7 inches, Expression (1) in the description is satisfied and tB/tL>1.

Abstract: A threaded connection for steel pipes having improved sealing performance is provided. A threaded connection (10) for steel pipes includes a pin (10) and a box (20). The pin (10) includes a nose (11), a pin shoulder surface (12), a pin sealing surface (13) and a male thread (14). The box (20) includes a box shoulder surface (22), a box sealing surface (23) and a female thread (24). When the position of the portion of the pin sealing surface (13) that first contacts the inner periphery of the box (20) during make-up defines a seal position (P), the distance between the seal position (P) and the end of the male thread (14) adjacent to the pin sealing surface (13) as measured in the pipe-axis direction is denoted by x, and the distance between the tip of the pin (10) and the end of the male thread (14) adjacent to the pin sealing surface (13) as measured in the pipe-axis direction is denoted by L, then, x/L is not smaller than 0.4 and not larger than 0.55.

Abstract: High sealing performance is provided in a threaded connection used for pipes for oil wells with large wall thickness and with a connection efficiency smaller than 1. A threaded connection (10) connects pipes for oil wells (1). The threaded connection (10) includes two pins (11) and a tubular coupling. Each of the pins (11) is provided on an end of the pipe for oil wells (1) and is in continuity with the pipe body (12), which has a wall thickness not smaller than 12 mm. The coupling (2) includes two boxes (21) and a recess portion (22). The box (21) is provided on both ends of the coupling (2). The recess portion (22) has a length not smaller than 10 mm. The threaded connection (10) has a connection efficiency smaller than 1.

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: 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.