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: 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 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 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 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.