Research On Numerical Simulation Of The Hot Rolling Deformation-Defects Control In Large-Scale Round Bar

As an important structural length products, the large-scale round bar has been widelyused in heavy equipment, metallurgical machinery, bridge architecture, etc., and mainlyused as shaft parts and Trolley parts withstanding complex overload, which requires itshigh mechanical properties and internal quality. However, the porosity, holes, non-metallicinclusions and other metallurgical cast defects spread in the large size alloy billet heartwidely, the higher requirements on the rolling mill practice have been put forward in orderto meet the strict industrial requirements of the large-scale round bar internal quality andproperties. Funded by the National Science Foundation of China (51005197), the paperhas carried out numerical simulation studies on the hot rolling defects control and hassolved the morphological evolution and elimination of the mechanism during hot rollingcaused by porosity, shrinkage, inclusions and other large billet internal defects, which isgood for establishing reasonable rolling process.Thinking of large-scale round bar hot continuous rolling units, the paper hasprogramed a Large-scale Round Bar Computer-aided Roll Pass Design System(RB-CARD) by Visual Basic to obtain analytic calculation of the structural parameters,process parameters, mechanics parameters, etc and rolling simulation. Based on the rollingparameters, the parametric finite element model of the deformation in hot rolling has beenbuilt by DEFORM secondary development. In order to investigate the compaction law ofporosity defects in the large billet during hot rolling process, the porosity defect wastreated as a compressible porous material in this paper, and the compressible rigid-plasticelement method was used to establish the three-dimensional non-linear finite elementmodel of the hot rolling compaction process of central porous in the42CrMo alloy billet.By the varying-parameter numerical simulation to explore the effect law of the heartporous compaction of different process parameters, the paper has proposed to attach themicro negative tension between the rack for rolling process to effectively solving theporosity compaction problems of porous defects, and has analyzed compaction and rollingforce with different tension, as well as the feasibility of the negative tension rollingaccording to the simulation results, which has laid the foundation of optimizing the rolling parameters.According to the physical characteristics, the internal nonmetallic inclusions havebeen divided into two major categories of plastic and rigid ones. And the study ofnumerical simulation on the compatible deformation of the plastic inclusions and the holesand cracks defects of the rigid inclusions during hot rolling. The three-dimensional closureevolution and the effects on the surrounding matrix during large-scale round bar rollingprocess have been studied by presetting goals shaped holes in the rectangular billet core tosimulate and analyze the pore defect, and the void closure has been analyzedquantitatively by combining the three-dimensional size of the pore. Besides, by using leadas the workpiece material to carry out the physical simulation experiment of the internalpore-rolling closure process on the five rack rolling units of Yanshan University rollinglaboratory, the finite element simulation results have been verified.