Research On The Technology And CAPP System For Foming The Large Diameter Longitudinal-seam Submerged ARC Welded Pipes With JCOE Process

With China’s social and economic development, there is a substantial increase indemand for oil, natural gas and other energy. With the construction of the long-distanceoil and gas pipelines, the demand of large-diameter, high-strength, high toughnesslongitudinal-seam submerged arc welded (LSAW) pipes is growing day by day. Thisprovides an unprecedented opportunity of development for steel pipe manufacturing, alsopresents a greater challenge to the large-diameter LSAW manufacturing technology. Thecommon forming way of large-diameter LSAW pipes tube is JCOE and UOE. JCOE isthe most common forming way because of the characteristics such as less investment,strong adaptability and other etc.The JCOE forming process of large-diameter LSAW pipes consists of board edgepre-bending, JCO forming and mechanical expanding. JCO forming is a typicalprogressive multi-pass compression molding process. Mechanical expanding is acomplex elastic and plastic deformation process with the characteristics of obviouspartial small deformation. Because of the springback of sheet metal bending, accuratelyforecasting the JCOE forming process parameters is a difficult engineering problem.Currently, JCOE forming process parameters are formulated and adjusted mainly rely onexperience or trial and error methods in the actual production. By this way, there are suchproblems that the parameters adjustment error is large, the cycle of setting processparameters is long, Fluctuation of product quality is large. Therefore, it is necessary tosystematically research the tube JCOE forming process. It provides theoretical basis andtechnical support to design process for actual production.Firstly, based on conventional elastic-plastic theory and small curvature planebending theory, The board edge pre-bending, sheet metal three-point bending andmechanical expanding process are systematically analyzed by the theory. The bendingangle theory expressions of board edge pre-bending after springback and the finalpre-bending force, the corner and the deflection theory expressions of any particle in thesheet deformation zone at the different formative stage of the three-point bending, thetheoretical analytical expressions of the upper die stroke and pressure, the cross-section shape parameters of the tube, the expanding force and the expanding stroke aftermechanical expanding are derived.Secondly, the physical experimental systems of board edge pre-bending, three-pointbending of sheet metal and mechanical expanding are designed to verify the theoryanalytical results of the tube JCOE forming process. Experimental results consistent withthe theoretical analysis results, The relative errors are within the range that is permitted inthe field of engineering. It proves that the board edge pre-bending, JCO formingsingle-pass three-point bending and mechanical expanding process theory analyticalmodel is correct and reliable. It also provides a theoretical basis to predict the formingprocess parameters for actual production accurately.Again, based on the theoretical results of JCOE forming process, the functionalrequirements for the CAPP system of the large-diameter LSAW pipes JCOE forming areproposed, the structure and function realization process of the system are designed.Combined with the actual pipes production and based on the software developmentplatform of VC++6.0, the theory predicting functional modules of board edgepre-bending, the tube JCO forming and mechanical expanding forming processparameters are researched and developed. And the JCOE forming CAPP system forlarge-diameter LSAW pipes has been established.Finally, the forming process parameters of X70steel grade specifications forΦ1067mm×19.1mm LSAW pipe on the actual production are predicted by the CAPPsystem of JCOE forming in this article. According to the process parameters that arepredicted by the system, the simulation experiment of tube JCOE forming is done. Thereasons that cause the errors between the simulation and theoretical prediction results offorming process parameters are analyzed, the adjustment rules.of the JCO formingprocess parameters are summarized.It provides a theoretical basis and technical support to formulate the forming processparameters of large-diameter LSAW pipes for the plant on actual production by theresults of this study. It is possible to reduce the cycle of developing the forming processparameters and to improve quality and production efficiency of large-diameter LSAWpipes forming for the actual production. Therefore, there is a certain value of the practical application and promotion on the results of this study.