Patent ID: 6957834

Claim:
A threaded joint for pipes having a metal-to-metal seal portion and comprising a male thread and an unthreaded sealing surface formed on an end of a steel pipe, and a female thread and an unthreaded sealing surface formed on the inner surface of a coupling, the female thread threadingly engaging with the male thread and the unthreaded sealing surface of the coupling abutting against the sealing surface of the steel pipe and forming an annular contact portion, characterized in that the surface roughness Ry of the unthreaded sealing surfaces of the steel pipe and the coupling is at most 25 μm, and upon make-up of the threaded joint, a metal-to-metal seal portion can be formed in which the average pressure Pm of the annular contact portion satisfies Pm/Py≧3, and the width in the axial direction of the portion which receives a pressure Ps which satisfies Ps/Py≧1 in the annular contact portion is at least 1 mm, with the yield pressure of the inner surface of the pipe being Py.