Patent ID: 8409718
Filing Date: 2013-04-02
Classification: C10M,C10N,E21B,F16L,Y10T

Abstract:
1. A threaded joint for oil well steel pipes comprising a pin and a box each having a contact surface in contact with each other including a threaded portion and an unthreaded metal contact portion, wherein the contact surface of at least one of the pin and the box has a viscous liquid or semisolid lubricating coating and a dry solid coating formed atop the lubricating coating, and the viscous liquid or semisolid lubricating coating comprises wax and a fatly acid alkaline earth metal salt, the dry solid coating is dry at 50° C., the thickness of the viscous liquid or semisolid lubricating coating is 10-200 μm, the thickness of the dry solid coating is 5-50 μm, and the thickness of the lubricating coating is greater than the thickness of the dry solid coating, wherein the dry solid coating is made from an aqueous coating composition comprising a water soluble or water dispersible polymeric compound and one or more additional components selected from silica, calcium stearate, calcium hydroxide, and calcium carbonate as a film-forming component.