Research On Quality Of Oil Drilling Tools During Precise Plastic Foring

Oil drilling tools is mainly composed of drill pipe, connecting set, stabilizer and drill collar. With the development of energy industry represented by oil and gas, the demand of drilling tools are more and more huge, so the performance requirements of drilling tools are more and more high. While the tools are working, they are acted on by internal and external enormous pressure and torsion and bending and vibration, ect. So the higher requirements of quality, performance and reliability are put forward. Especially the strength of oil drill pipe rig plays an important role in the safe and stable work of oil drill tools. But in our country oil dill pipe joints is usually manufactured by the process of free die forging and sub-mold forging and horizontal sub-mold subtended hot extrusion, in terms of which, there are many gaps while compared with the advanced world level. Most of enterprises manufacture the oil drill pipe rig by the way of extensive form and labor intensive and capital intensive, the material utilization rate is not high, and the manufacturing technical content is low, the products are difficult to adapt to the complex geological conditions. In order to improve the material utilization rate and the comprehensive mechanical properties after forming, the method of precision plastic forming is used to explore the forming process of oil drill pipe joints.Firstly, the specimens of 37 Cr Mn Mo steel are formed under the thermodynamic condition of temperature 850 ℃, 950 ℃, 1050 ℃, 1150 ℃, 1200 ℃ and strain rate 0.001s-1, 0.01 s-1, 0.1 s-1, 1 s-1, 10 s-1 and quantitative metallographic technique is used to observe the microstructure of the specimens after forming. And analyse the data of experiments, laying the foundation of exploring the process of oil drill pipe joint precise plastic forming.Secondly, macroscopic flow stress is built relationships with micro-grain size by the Zener-hollomon parameter during the forming process of 37 Cr Mn Mo steel, basing on which, establishing the relation between the austenitic grain size and macroscopic flow stress. For the first time, the model of the relation between macroscopic flow stress and austenite grain size after forming, laying a theoretical foundation in exploring the process of oil drill pipe joint precise plastic forming.Based on the analysis of the advantages and disadvantages of the process of oil drill pipe joint traditional forming in terms of formability(maximum load and flow stress and strain) and the forging quality and material utilization, a optimizing process is proposed, called oil drill pipe joint multi-pass forming.Through coupling the orthogonal experiment and finite element analysis technology, exploring how the parameters of forming speed and the billet initial temperature and friction coefficient influence on oil drill pipe joint forming quality during multi-pass forming. And the optimal parameter is the billet initial temperature 1150℃,the forming speed 20mm/s and the friction coefficient 0.1.According to the new oil drill pipe joint multi-pass forming process, embodies its forming process.