Modeling of longitudinal welded pipe forming in open rolling pass unit of electric weld pipe mill

Abstract

The results of theoretical and physical modeling of pipes forming process are described. Experiments on strip billets forming were carried out on 10-50 pipe-welding mill for a pipe 50 mm in diameter with 1mm wall. Forming of pipe billets was carried out at unit of forming horizontal and vertical stands with estimation of geometrical parameters. Roll drafting is one-radial. Energy-power parameters of the process that affect quality of billet geometry were determined and measured. Analysis of geometric parameters of resulting billet has revealed defects of buckling type on the billet’s right edge between the second edger and the third molding stand. Similar defect was detected at the left edge of the billet at a distance of the third molding and edger stands. To eliminate defects in forming section, shaping stands were rebuilt so that forces on drive cells were identical. Energy-force parameters of the process were sequentially determined: pulling forces of drive stands, resistance to strip movement and vertical molding forces. Calculations for determining energy-force parameters were performed taking into account the main technical parameters using two methods. The first technique takes into account geometric parameters of molded billet and parameters of working zone with the zone of non-contact deformation. The second method is based on consideration of contact interaction between the billet and shaped instrument along the deformation section. Discrepancy between calculated and experimental data was 8 – 12 %. After adjusting technical parameters of the molding process and the passes re-adjusting, a defect-free pipe billet was formed. Comparative analysis of calculated and experimental edge trajectories along the height and width of the cages showed discrepancy in results in range of 6 – 9 %. While studying geometric parameters of the focus of deformation, contact and non-contact zones of working zone and area of sprinkling were taken into account. Parameters of the pipe billet shaping in monotonous and roll forming centers have been calculated. Analysis of the results has shown that change in billet’s geometry in shaping stand corresponds to the accepted statements of billet’s geometry changes in rolling pass.