Forming Feasibility of High-Strength and Toughness Drill Pipe Joint Based on Plastic Deformation Mechanism.

In view of the severe performance requirements of high-strength drill pipe joint in deep drilling engineering, 130 ksi high-strength and toughness drill pipe joint is taken as the research object. Thermal deformation behavior and precision forming process of a new composition system joint are investigated. Wire-cut specimens (ϕ10 × 15 mm) are tested on a Gleeble-3500 machine under 900-1200 °C and 0.01-10 s-1, with EBSD for microstructure observation. Results show that the small- and large-angle grain boundary cooperate to obtain the mixed structure of high dislocation density, fine substructure and fine grain, which makes the phase transformation products more fine and uniform. Combined with the finite element numerical simulation and experimental verification system, the effects of billet temperature, strain rate and die temperature on the microstructure and macro properties of the joint are analyzed, and the optimal combination of parameters is determined, including 880 °C billet temperature, 20 mm/s punch speed and 300 °C die temperature. The optimization scheme aims to achieve grain refinement and flow stress control, obtain fine and uniform tempered sorbite structure with grain size grade 10.0, and also achieve the optimal comprehensive strength and toughness, which can provide a theoretical basis and technical path for the industrial production of high-performance drill pipe joints.