Threaded joint for steel pipes
AssigneesSumitomo Metal Industries, Ltd., Vallourec Mannesmann Oil & Gas France
InventorsKunio Goto, Ryuichi Imai
Life of this patent
Estimating the term…
Abstract
A threaded joint for steel pipes for use in an oil well which has enhanced 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.
Claims11
A threaded joint for steel pipes comprising a pin and a box each having a contact surface including a threaded portion and an unthreaded metal contact portion, characterized in that 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 fatty acid alkaline earth metal salt, the dry solid coating is formed of a solidified material having a resistance to softening at 50 degrees 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 ultraviolet curing resin and the dry solid coating contains a lubricant.
Dependencies are inferred from the claim text.