Patent ID: 11353144

Abstract:
A threaded joint with excellent tensile strength, comprising: a pin having an externally threaded part comprising a first and second externally threaded sections across a step on an outer periphery on a distal-end side of a first steel pipe or tube; and a box having an internally threaded part comprising a first and second internally threaded sections across the step on an inner periphery on a distal-end side of a second steel pipe or tube, the externally threaded part being screwed to the internally threaded part to join the pin and the box. The threaded joint has a first and second thread sequence with lengths L1 and L2, respectively, and cross-sectional areas P1, P2, B1, and B2 at end positions 4, 5, 6, and 7, respectively, satisfying Formulas (1) and (2): (P2, B2)min≤P1/{L1/(L1+L2)}(1) and (P2, B2)min≤B1/{L2/(L1+L2)}(2), where (P2, B2)min represents P2 or B2, whichever is smaller.