The Semi-floating Mandrel Rolling Tubes Forming The Finite Element Analysis And Roller Pass Improvements

Seamless pipes are widely applied to ducting, thermal engineering equipment, machinery manufacturing, petrolic and geological rig, chemical high pressure container, and so on. Quality of pipes is intimately relative to rolling mill, and the technology of semi-floating mandrel pipe mill is an important procedure of pipe deformation in hot rolling process. Determining rolling parameters reasonably is a key problem to be resolved both in design and production, and it is also hot spot of research at present. Surrounding improvement of hole shape of mandrel pipe mill, some works were performed.Firstly, some theories of pipe milling were illustrated, based on the technology process and rolling mill procedure of semi-floating mandrel pipe mill, hole shape of rolling mill were designed.Secondly, in order to simulate pipe material more truly, mechanical experiment at high temperature was designed and introduced. Curvesσ-εof steel 20# were studied in different temperatures and strain rates. Based on it, constitutive relation of elastic viscoplastic thermal material was founded at high temperature by software MATLAB. The constitutive function was effective and noticeable at conditions of temperatures and strain rates in experiment.Thirdly, Finite element dynamic model was established on deformation of 6-stand semi-floating mandrel pipe mill by ANSYS/LS-DYNA at 3D thermosetting coupling, and the standardΦ109mm×6mm was simulated. Based on the comparison between simulated results and shell object, conclusions were reached that variational regularities of their hole shapes were similar in circumferential direction. It was validated that reliability of the model and feasibility of the method.Finally, formative causation of irregular shape of shell section were analysed:shapes incongruity between rolling mill and pipe caused contact did not occur at one time, character that contact boundary was a spatial curve caused asymmetrical distribution of shell exterior diameters indirectly; it indirectly cased asymmetrical distribution of shell thickness that inverse directions of friction at hole top area and lateral wall area. Shell shape was improved obviously after adjusting eccentricity and rolling mill gap. Data displayed:average relative tolerance beteeen exterior diameter and its target 109mm was decreased from 1.680% to 0.861%; average relative tolerance beteeen thickness and its target 6mm was decreased from 3.569% to 2.722%.