Rotary-forged, heavy wall drill pipe is composed of a homogeneous one-piece forging of AISI 4145 Modified low alloy steel. This integral forging eliminates the weld at the tool joint, has high strength steel pipe and has a center upset the same diameter as the connection upsets. Continuous-line heat treating increases the depth of hardening to enhance the mechanical properties of the integrally forged material. Whether used in compression, in tension or at the neutral point for drilling vertical or directional holes, this new drill string member will increase fatigue life and reduce stress corrosion-cracking tendencies over commonly used lower strength welded pipe.
The precision rotary-forging process has begun a revolution in the traditional forging industry. A major cannon use is for forging artillery cannon barrels and was recently used to forge the leg segments for the Conoco Hutton tension-leg platform. This rotary-forging process is now computer platform. This rotary-forging process is now computer controlled to automatically produce precisionforged, heavy wall drill pipe that has reliable precisionforged, heavy wall drill pipe that has reliable dimensions, superior material quality and exceptional forged surface finish. This paper will cover the properties of 4-1/2 in. [11-cm] diameter and 5 in. [13-cm] diameter heavy wall drill pipe. Connection upsets and center upsets are integrally formed on the bars by the forging hammers. There are no welded joints at the tool joints and the pipe portion has the same composition and high pipe portion has the same composition and high strength as the threaded connections. Figures 1 and 2 are photographs comparing the tapered area construction of the rotary-forged to the welded heavy wall drill pipe. The fibrous texture of the rotary-forged upset is seen to flow smoothly through the reducing section of the taper. Whereas an abrupt change in flow is seen at the weld line where the dissimilar pipe and tool joint material meet in the welded pipe taper area.
The homogeneous forging is full length heat-treated by the continuous-line method to achieve a uniform fine-grained microstructure of fully quenched and tempered martensite. This further enhances the fatigue resistance and stress corrosion resistance properties of the material. properties of the material. There are many advantages of using this rotary-forged heavy wall drill pipe over welded designs in everyday drilling practices. These advantages include reduced susceptibility to pipe and thread fatigue cracking and to stress corrosion cracking in the welded zone of standard designs. The larger center upset reduces peak bending loads and is easily rebuilt if worn down. The taper area is easily remachined without worrying about reducing the section area of a weaker welded zone. The pertinence of these advantages to the end user generally depends on its in-hole application. whether the pipe is used in tension, in compression or at the string's neutral point; whether it is used for drilling vertical or directional holes and whether drilling hard or soft formations, the different levels of stress encountered will best be accommodated by this more fatigue-resistant material. It is important to understand the task that heavy wall drill pipe performs in the drill string and how it is used in order to understand how the improved properties of rotary-forged pipe apply.
Heavy wall drill pipe is generally used as a replacement either for some of the drill pipe or the drill collars in the section of the string where they are joined.