Threaded joint for steel pipes
AssigneesNippon Steel & Sumitomo Metal Corporation, Vallourec Mannesmann Oil & Gas Grance
InventorsKunio Goto, Ryuichi Imai
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Abstract
A threaded joint for steel pipes for use in an oil well which has galling resistance and which is protected from rusting comprises a pin and a box each having a contact surface including a threaded portion and an unthreaded metal contact portion. The contact surface of at least one of the pin and the box has a lower layer of a viscous liquid or semisolid lubricating coating comprising at least wax and a fatty acid alkaline earth metal salt and not containing a harmful heavy metal such as lead and an upper layer of a dry solid coating formed from an aqueous resin coating composition, an organic solvent type coating composition, or an ultraviolet curing coating composition.
Claims9
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.
Dependencies are inferred from the claim text.