Threaded connection for pipe or tube and method for producing the threaded connection for pipe or tube
The present invention has an objective to provide a threaded connection for pipe or tube including a pin and a box, having excellent galling resistance, torque property, and anticorrosion property, and still having an excellent adhesiveness with a lubricating coating even when being repeatedly exposed to high temperature and very low temperature, and to provide a method for producing the threaded connection for pipe or tube. The threaded connection for pipe or tube according to the present embodiment includes a pin and a box. The pin and the box have contact surfaces including a thread portions and and unthreaded metal contact portions, respectively. The threaded connection for pipe or tube comprises an electroplating layer consisting of a Zn—Ni alloy, a mechanical plating layer consisting of Zn or a Zn alloy, and a lubricating coating, on the contact surface of at least one of the pin and the box, in this order from a contact surface side.
1. A threaded connection for pipe or tube comprising a pin and a box, the pin and the box each including a contact surface that includes a thread portion and an unthreaded metal contact portion, the threaded connection for pipe or tube comprising:
on the contact surface of at least one of the pin and the box,
a first plating layer consisting of a Zn—Ni alloy;
a second plating layer on the first plating layer, the second plating layer consisting of Zn or a Zn alloy, and being porous; and
a lubricating coating on the second plating layer.
2. The threaded connection for pipe or tube according to claim 1 , wherein the lubricating coating is a solid lubricant coating.
3. The threaded connection for pipe or tube according to claim 1 , wherein the porosity of the second plating layer is 5 to 80%.
4. The threaded connection for pipe or tube according to claim 3 , wherein the first plating layer has a thickness of 1 to 20 μm, the second plating layer has a thickness of 2 to 30 μm, and the lubricating coating has a thickness of 5 to 50 μm.
5. The threaded connection for pipe or tube according to claim 4 , wherein the lubricating coating is a solid lubricant coating.
6. The threaded connection for pipe or tube according to claim 3 , wherein the lubricating coating is a solid lubricant coating.
7. The threaded connection for pipe or tube according to claim 1 , wherein the first plating layer has a thickness of 1 to 20 μm, the second plating layer has a thickness of 2 to 30 μm, and the lubricating coating has a thickness of 5 to 50 μm.
8. The threaded connection for pipe or tube according to claim 7 , wherein the lubricating coating is a solid lubricant coating.
9. A method for producing a threaded connection for pipe or tube that includes a pin and a box, the pin and the box each including a contact surface that includes a thread portion and an unthreaded metal contact portion, the method comprising the steps of:
on the contact surface of at least one of the pin and the box,
forming a first plating layer consisting of a Zn—Ni alloy by performing electroplating treatment;
forming a second plating layer consisting of Zn or a Zn alloy by performing mechanical plating treatment after forming the first plating layer; and
forming a lubricating coating after forming the second plating layer.