Research On The New Technology For Forming The Large Diamater Lsaw Pipes With Four-point Bending JCO Process And Compression

The advance of global industry processing technologies have not reduced the demandof energy, in particular, the traditional energy of oil and gas. On the contary, it has beenincreased among countires around the world due to the emergence of nuclear and solarenergy. To solve this problem and meet the demand of market, large pipe manufacturingtechnologies have been under rapid development in recent years, especially the JCOE/JCOand the UOE pipe technology that have been extensively researched and applied in theengineering industry. As a representative pipe manufacturing technology, the JCOforming process presents the characteristics of low cost, high efficiency and the similarforming quality of the UOE. Therefore, the JCO forming process has gained worldwiderecognition.Traditional JCO forming process is based on three-point bending theory. It requiresmore forming procedures, bears less productivity and accuracy of the pipe shape andcauses larger residual stress. Another forming process, the UOE forming process, hashigher efficiency, but the mold that mathces the pipe diameter requires high cost. In thecurrent studies of manufacturing engineering, both forming processes need to bepre-curved to the blank before forming. In addition, expanding and setting round iscommonly used in the follow-up setting round process to correct the pipe shape, with thedrawback of expanding the organization of internal defects. This study, based onthree-point bending JCOE forming process research, uses four-point bending springbackas the theoretical framework, aiming at establishing the longitudinal-seam submerged arcwelded(LSAW) pipe of four-point bending JCO forming by combining it withcompression to set round. The pipe of this forming process have the followingadvantagess: a. circular cross section; b. high shape precision; c. low forming steps; and d.high productivity. Furthermore, pre-bending of plate edge is not required, thus reduces theequipment cost. In addition, the facts that the residual stress is lower and evenlydistributed and the mold number is small with a higher flexible degree prevent theexpansion of defects, therefore the ideal circular degree of forming is achieved. The methodologies and procedures of the study include:First, based on the assumptions of flat section, uniaxial stress, stress neutral layer,strain neutral layer and the geometric of neutral layer coincide as well as the smalldeformation and bilinear hardening model, the study established the mechanical model ofboard blank four-point bending and springback by integrating the classical elastoplasticmechanical theories, theoretical verified the model, and examined the relationship betweencurvate radius of blank neutral layer, bending trip and die geometry parameters afterdeduced the before-and after-bending springback.Second, the study designed the board blank four-point bending mold and conductedexperiments to verify the theoretical analyses. Furthermore, it simulated the process offour-point bending using finite element analysis software ABAQUS. The results oftheoretical analyses have been verified by numerical simulation and experiments. Thestudy also analyzed the impact of the mold and process parameters on shaping law, suchas fillet radius of the punch, fillet radius of the die, coefficient of friction, punch span anddie span.Third, this study proposed the formulation of the process parameters of four-pointbending JCO. It analyzed the impact of blank width, forming step, feeding step, punchspan, die span, forming force, bending trip and other key parameters on forming process.Reliable rules of forming parameter to four-point bending JCO haven been achieved. Inaccordance with the rules established by the process parameters and the fact that theprototype pipe of X80steel level is widely used in the current market, the studyimplemented numerical simulation according to the principle of geometric similarity. As aresult, the experiment received better roundness pipe, with the specification of.Last, based on the theories of plane bending and springback, the study analyzed theprinciple of compression to make round. It designed the mold of compression to makeround to the pipe of four-point JCO forming and the ascertain process parameters. Itgained an ideal pipe through experiments, with the compression rate of1%and thespecification of, thus confirmed the feasibility and advantages of four-point bendingJCO forming combined with compression to make round using in the longitudinal-seamsubmerged arc welded pipe production. In conclusion, this study established initially longitudinal-seam submerged arcwelded pipe four-point bending JCOC forming process route, proposed the relatedregulations and methodologies, thus providing theoretical and experimental foundationprocess parameter formulation and mold design in the practice of engineering.