Formation Mechanism And Simulation Of Roll Trace In Stretch Reducing Process

With the continuous development of modern industry,the application of seamless steel tubes in petroleum,nuclear power,automotive,aviation and other industries has become more and more extensive,and the demand is also increasing year by year.With the increasingly fierce competition,the quality level for seamless steel tubes is also increasing.In the process of tension reduction of seamless steel tubes,steel tubes often produce defects such as roll trace,scar,internal hexagon,thickened tube end,and so on,which greatly affect the quality of finished product tubes.At present,there are relatively few researches on the roll trace,which mainly analyzes and summarizes the conditions of individual roll trace appearing in the actual production process.There is a lack of systematic exploration.Therefore,it is of great practical significance to explore the causes and formation mechanism of the roll trace by the finite element method.Firstly,based on the metal deformation mechanics,this paper introduces the basic tension reduction theory and the basic calculation method of process parameters.After deriving the 14-stand tension reducing process,the size of the obsolete pipe required for the (?)88.90mm×6.45 mm finished pipe,and the diameter,wall thickness,tension distribution,etc.,of each frame are obtained,which lays a foundation for the later study.Secondly,the finite element model of the 14-stand tension reducing unit was established.At the same time,the micro-model of the tension reducing unit was established by shortening the distance between the stands.DEFORM was used for simulation and comparing the simulation results between the standard stand-to-stand strain reduction unit model and the miniature model from the wall thickness distribution,equivalent stress distribution,equivalent strain distribution,etc.,and the scope of application of the miniature model of tension reduction was determined.On the basis of ensuring the accuracy of the calculation results,in order to speed up the calculation,a miniature model with a rack spacing of 150 mm was selected as a model for subsequent studies.Finally,through the method of setting variables,the influence of the axial deviation of the roller,the centerline error of the machine assembly,the error of the roll radius and other factors on the roll trace is explored.The change law and formation mechanism of the roll trace are analyzed by measuring the shape of the roll trace through the surface of the steel tubes.It is found that all three factors can produce the roll trace on the surface of the steel pipe.The axial migration of the roll and the assembly error of the center line of the machine will produce the wrong roll trace,and the cross of the roll corner will produce the scratched roll trace.