SCREW JOINT FOR STEEL PIPE

摘要

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 DEG C and below 40 DEG C and an upper lubricant layer which is in solid form at 40 DEG C, or (2) a coating which is semi-solid or solid at 40 DEG C and is formed of a mixture comprising a lubricating oil which is in liquid form in the temperature range of above 0 DEG C and below 40 DEG C and a wax which is in solid form at 40 DEG C, the mixture preferably having been heated so as to liquefy the wax and dissolve in each other the wax and lubricant oil.