Patent ID: 8857857

Claim:
A threaded joint for steel pipes comprising a pin and a box each having a threaded portion and an unthreaded metal-to-metal contact portion serving as contact surfaces of the joint when tightened without using a compound grease, characterized in that the contact surfaces of at least one of the pin and the box are coated with a multi-layer structure comprising: from the bottom, a first layer formed from a first metal or alloy, a second layer, which contains tin, the second layer being formed from a second metal or alloy, which is softer than the first metal or alloy, and a solid lubricating coating as an uppermost layer, the solid lubricating coating having a composition based on a lubricating powder and a binder comprised of an organic resin or inorganic polymeric compound, wherein the first layer has a coating thickness of 2-15 micrometers, the second layer has a coating thickness of 5-30 micrometers, and the solid lubricating coating has a coating thickness of 5-40 micrometers, wherein the first layer has a hardness in the range of Hv 100-500, and the second layer has a hardness in the range of Hv 10-150, provided that the hardness of the second layer is lower than the hardness of the first layer.