The Drill Pipe Tube End Upsetting Forming Numerical Simulation Studies

Drill pipe plays an important role in the exploration of oil and gas. Since drill pipe at work is subject to the combined effects of bending, twisting, pulling and eroding, high demand is needed for the strength, toughness, corrosion resistance and fatigue characteristics of drill pipe in practice. Numerous studies have shown that:service life of drill pipe is determined by the length of the internal transition section (Miu) and the radius of curvature (R) there to a large extent. For industries home and abroad, researching new and powerful design methods, adopting advanced forming process and improving the shape at internal transition section have become the key work to enhance the competitiveness of product. In this paper, based on experimental study on thermoplastic deformation characteristics of grade 105 oil drill pipe, using finite element method, the process of internal-external end upsetting onΦ114.3×10.92 mm drill pipe was researched.Using rigid visco-plastic model and coupled thermo-mechanical finite element method, the model of end upsetting on drill pipe was established. Secondly, the process of end upsetting on drill pipe was simulated to study and master the influence of die and temperature on the forming quality of drill pipe, especially at the internal transition part.Firstly, the study shows that the shape of die at the transition part plays an important role in the end upsetting. It can be seen from the simulation that the end upsetting couldn't be made because of too small resistance arising from the transition location of die. So it can be concluded that different values of b will result in the metal moving at different proportion in each direction. A too short transition part of die will cause a too steep slope at the internal transition part of drill pipe, weakening the mechanical properties of it.Moreover, the fully heated length in the first step was 600～650 mm; In order to avoid bulges at the junction of fully heated part and transition temperature part, respectively, the fully heated length in the second and third step was move back for 50 mm.Based on similarity theory, using clay as the model material, the physical simulation of end upsetting on oil drill pipe was performed. The experiment shows that there is a same result with the numerical simulation.The simulation results show that not only it is continuous and smooth but also long (up to about 200 mm) at the internal transition section of the oil drill pipe by adopting the process designed in this paper. In this investigation, the productive use of finite element technique disclosed the influence of die and temperature on making upset on oil drill pipe, which helps us understand some typical problems in forming process we should pay special attention to. What we have done in this paper is of great significance in designing of the forming process and improving the performance of drill pipe.