Threaded connection for pipes or tubes and method for producing the threaded connection for pipes or tubes
This invention provides a threaded connection for pipes or tubes having high over-torque performance, and a method for producing the threaded connection for pipes or tubes. A threaded connection for pipes or tubes according to the present embodiment includes a pin and a box. The pin and the box include a contact surface including a threaded portion and a metal contact portion. The threaded connection for pipes or tubes includes a solid lubricant coating layer on at least one of the contact surfaces of the pin and the box, the solid lubricant coating layer including a resin, a solid lubricant powder, and Cr 2 O 3 .
1. A threaded connection for pipes or tubes comprising a pin and a box,
the pin and the box each comprising a contact surface having a threaded portion and an unthreaded metal contact portion,
the threaded connection for pipes or tubes comprising a solid lubricant coating layer on at least one of the contact surfaces of the pin and the box,
and the solid lubricant coating layer containing:
one or more types of resin selected from the group consisting of epoxy resin, phenol resin, polyamide-imide resin, and polyamide resin in a range of 60.0 to 90.0 mass %,
one or more types of solid lubricant powder selected from the group consisting of graphite and polytetrafluoroethylene in a range of 5.0 to 25.0 mass %, and
Cr 2 O 3 in a range of 5.0 to 19.2 mass %.
2. A method for producing the threaded connection for pipes or tubes according to claim 1 , comprising the steps of:
applying a composition containing the one or more types of resin selected from the group consisting of epoxy resin, phenol resin, polyamide-imide resin, and polyamide resin in a range of 60.0 to 90.0 mass %, the one or more types of solid lubricant powder selected from the group consisting of graphite and polytetrafluoroethylene in a range of 5.0 to 25.0 mass % and 5.0 to 19.2 mass % of the Cr 2 O 3 to at least one of the contact surfaces of the pin and the box; and
solidifying the composition applied to the contact surface to form a solid lubricant coating layer.
3. The method for producing the threaded connection for pipes or tubes according to claim 2 , the method further comprising the step of:
before applying the composition,
forming a Zn alloy plating layer by electroplating on at least one of the contact surfaces of the pin and the box.
4. The method for producing the threaded connection for pipes or tubes according to claim 3 , the method further comprising the step of:
before forming the Zn alloy plating layer,
forming surface roughness on at least one of the contact surfaces of the pin and the box.