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: Disclosed herein is a water-dispersion-type hot-rolling lubricant for the production of seamless steel pipes. This lubricant features the inclusion of a salt of a polybasic high molecular acid in addition to fine graphite powder, a water-insoluble fine particulate synthetic resin and water as principal components and fine gilsonite powder as an optional component. Even when the surface temperature of a mandrel bar is in a high temperature range of 100.degree.-400.degree. C., this lubricant can form a uniform and thick coating film on the surface of the bar so that the lubricant can exhibit extremely good hot-rolling lubrication performance.