| 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 an end 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 is formed into an undulated surface shape including one or more sets consisting of two parts 7A and 7B that are inclined in directions opposite to each other with respect to the pipe axial direction. |
