Abstract: Disclosed herein are embodiments of a drill pipe tool joint and a drill pipe which are optimized for repeated make-up/break-out operations without the use of screw grease. Embodiments of the disclosure are environment friendly as well as having improved operating efficiency. In particular, the box and pin can be formed from different materials having different hardness.

Abstract: A drill pipe tool joint comprising: a pin including a male threaded portion at an outer surface; and a box including a female threaded portion at an inner surface, the female threaded portion to be screwed and fastened to the male threaded portion in a contacting zone consisting of a male threaded contacting surface and a female threaded contacting surface, wherein at least a portion of the male threaded contacting surface or a portion of the female threaded contacting surface is a surface layer consisting of a hard metal and respectively at least a portion of the female threaded contacting surface or a portion of the male threaded contacting surface is a surface layer consisting of a soft material and where said both surface portions are contacting surfaces after screwing.

Abstract: The present invention relates to an austenitic stainless steel tube for boiler, used for superheater or reheater in thermal power plant, giving excellent resistance to high temperature steam oxidation, in particular to an austenitic stainless steel tube containing 16 to 20% Cr by weight, and being cold-worked at the inner surface of the tube. The Cr concentration in the vicinity of the inner surface of the steel tube is 14% by weight or larger, and the hardness at 100 ?m depth from the inner surface of the steel tube is 1.5 times or larger the average hardness of the mother material or is HV 300 or larger.

Abstract: The present invention relates to an austenitic stainless steel tube for boiler, used for superheater or reheater in thermal power plant, giving excellent resistance to high temperature steam oxidation, in particular to an austenitic stainless steel tube containing 16 to 20% Cr by weight, and being cold-worked at the inner surface of the tube. The Cr concentration in the vicinity of the inner surface of the steel tube is 14% by weight or larger, and the hardness at 100 ?m depth from the inner surface of the steel tube is 1.5 times or larger the average hardness of the mother material or is HV 300 or larger.