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AssigneesNippon Steel & Sumitomo Metal Corporation, Vallourec Oil and Gas France
InventorsKunio Goto, Yuji Tanaka, Yasuhiro Yamamoto
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A tubular threaded joint is constituted by a pin and a box each having a contact surface comprising an unthreaded metal contact portion including a seal portion and a shoulder portion and a threaded portion. Of the contact surface of at least one of the pin and the box, the surfaces of the seal portion and the shoulder portion has a first lubricating coating in the form of a solid lubricating coating, and the surface of the threaded portion or the entire surface of the contact surface has a second lubricating coating selected from a viscous liquid lubricating coating and a solid lubricating coating. The first lubricating coating has a coefficient of friction which is higher than that of the second lubricating coating, and the second lubricating coating is positioned on top in a portion where both the first lubricating coating and the second lubricating coating are present.
A tubular threaded joint constituted by a pin and a box each having a contact surface comprising an unthreaded metal contact portion including a seal portion and a shoulder portion and a threaded portion, characterized in that the contact surface of at least one of the pin and the box has a first lubricating coating and a second lubricating coating, the first lubricating coating being a solid lubricating coating formed on the unthreaded metal contact portion of the contact surface, the second lubricating coating being selected from a viscous liquid lubricating coating and a solid lubricating coating and formed on at least the portion of the contact surface where the first lubricating coating is not present, the first lubricating coating having a coefficient of friction which is higher than that of the second lubricating coating, the second lubricating coating being positioned on top if there is a portion of the contact surface in which both the first lubricating coating and the second lubricating coating are present.
Dependencies are inferred from the claim text.