Loading patent…
AssigneesSumitomo Metal Industries, Ltd., Vallourec Mannesmann Oil & Gas France
InventorsKeishi Matsumoto, Kunio Goto, Toshiro Anraku, Shigeo Nagasaku, Hideo Yamamoto
Estimating the term…
A threaded joint for steel pipes comprising a pin 1 and a box 2 each having a contact surface comprising a threaded portion 3 or 4 and an unthreaded metal contact portion 8 is provided with improved anti-galling propertied by forming a lubricating coating on the contact surface of at least one of the pin and the box, the lubricating coating exhibiting a self-repairing function by liquid lubrication and having a decreased greasiness. The lubricating coating is (1) a coating which comprises a lower lubricant layer which is in liquid form in the temperature range of above 0° C. and below 40° C. and an upper lubricant layer which is in solid form at 40° C., or (2) a coating which is semi-solid or solid at 40° C. and is formed of a mixture comprising a lubricating oil which is in liquid form in the temperature range of above 0° C. and below 40° C. and a wax which is in solid form at 40° C., the mixture preferably having been heated so as to liquefy the wax and dissolve in each other the wax and lubricant oil.
A pin adapted for use in a threaded joint for steel pipes, the pin having a contact surface including a threaded portion and an unthreaded metal contact portion and which has a lubricating coating on the contact surface, characterized in that the lubricating coating comprises an upper lubricant layer which is in solid form at 40° C. and appears as an outer surface for the contact surface of the pin, and a lower lubricant layer which is in liquid form in the temperature range of above 0° C. and below 40° C., the lower lubricant layer disposed between the contact surface and the upper lubricant layer.
A box adapted for use in a threaded joint for steel pipes, the box having a contact surface including a threaded portion and an unthreaded metal contact portion and which has a lubricating coating on the contact surface, characterized in that the lubricating coating comprises an upper lubricant layer which is in solid form at 40° C. and appears as an outer surface for the contact surface of the box, and a lower lubricant layer which is in liquid form in the temperature range of above 0° C. and below 40° C., the lower lubricant layer disposed between the contact surface and the upper lubricant layer.
Dependencies are inferred from the claim text.