Patent ID: 7494159
Filing Date: 2009-02-24
Classification: E21B,F16L

Abstract:
1. A threaded joint for a steel pipe having a pin member having a tapered male thread, a metal seal-forming portion, and a torque shoulder-forming portion, and a box member having a tapered female thread, a metal seal-forming portion, and a torque shoulder-forming portion corresponding to those of the pin portion, characterized in that the threads which constitute the tapered male thread and the tapered female thread have a first trapezoidal thread portion which does not have simultaneous contact at the load flanks and the stabbing flanks, and a second trapezoidal thread portion which has contact at the load flanks and stabbing flanks and which has gaps at the thread root surfaces and the thread crest surfaces, wherein the first trapezoidal thread portion has contact at the load flanks and the thread root surface, and gaps at the thread crest surface and the stabbing flanks.