| 摘要 |
PROBLEM TO BE SOLVED: To provide a screw joint in which a thread part is capable of sufficiently resisting both of tensile force and compressive force in a pipe axial direction to maintain sealability.SOLUTION: A screw joint for steel pipe comprises a pin 1 including a taper male thread part 11 and a non-threaded part 3 provided at a tip side from the taper male thread part 11, and a box 2 including a taper female thread part 21 and a non-threaded part 3 corresponding to the taper male thread part 11 and the non-threaded 3, respectively. The pin 1 and the box 2 are screw-jointed to bring the non-threaded part 3 of the pin 1 and the non-threaded part 3 of the box 2 into metal-to-metal contact with each other in a circumferential direction at one or more portions in a pipe axial direction so that fluid in a pipe will be blocked. In the screw joint, a contact surface 7 between bottom of thread of the pin and thread ridge of the box tapers in a direction opposite to a thread tapered surface 8 with respect to a pipe axial direction 4 to form a tapered surface 14 (or 14A), and a counter surface 10 between thread ridge of the pin and bottom of thread of the box forms a surface 9 parallel to the tapered surface 8. |
