Numerical Simulation And Experimental Study On Closed-die Extrusion Process Of Oil Drill Pipe Joint

Drill pipe joint is the important part, it is used to connect drill pipes and protect drill pipe from wearing in drilling operations. During drilling, the joint works in the environment of harsh conditions, and bearing a variety of complex load as tension force,bending force, torsional force etc. The joint must have good mechanical properties, fatigue resistance, corrosion resistance and so on. Therefore, the study of joint forming process has important significance.At present, the common forging process of drill pipe joint is single-direction extrusion,a few companies use horizontal double-direction extrusion for joints figuration. The former has more forming processes, thus lower efficiency, the latter has higher production efficiency, but more investment in equipment. In this paper, according to the structure characteristics of oil drill pipe joint and floating-die principle, the vertical closed-die forging process was proposed and used in the general press. The special die closing tool was used to achieve double-direction extrusion process of drill pipe joint.In this paper, the three-dimensional solid model of drill pipe joint was built on the basis of the software UG. The thermo-mechanical analysis of the forging process of the oil drill pipe joint was performed by DEFORM-3D. The law of metal flow, the distribution of stress field, strain field and temperature field, the relationship between extrusion force,closing die’s force and stroke in different stages of deformation were analyzed. Moreover,the influence of the preheating temperature, friction coefficient, extrusion speed on forming force were analyzed. The forming rule and process parameters of double-direction extrusion of the drill pipe joint have been obtained.The actual forming process can be reflected by the combination of experiment and numerical simulation analysis. So the laboratory experiment of drill pipe joints is necessary.Based on similarity theory, the experiment of vertical double-direction extrusion process of drill pipe joint was designed using pure lead as simulation material. Forming quality and forming force were analyzed. In addition, the correctness of numerical simulation and the feasibility of the technology were verified. A strong basis for practical production was provided.