|TURCZYN Stanislaw||AGH University of Science and Technology|
|Spoluautoři DZIEDZIC Michal, KUZMINSKI Zbigniew|
In recent years, the increasing demand for ribbed and not-ribbed bars of the smallest diameters can be observed on the market of rolled products. This results from the tendency of reinforcing new concrete constructions with bars of smaller diameters, but made from steels showing higher mechanical properties. In order to be up to marked demand single or multiple longitudinal slitting is applied during small bars rolling. This method as applied to rolling mills enables production of two, three, four or even five bars from one billet. The slitting process uses special passes and guides to prepare, shape and longitudinally separate the rolled stock into two or more individual strands, which will then be further rolled into finished profiles. The essence of this method is the application of two or three consecutive cutting-in passes, in which deformations of metal considerably differ from those occurring in conventional stretching passes. Although the described technology is well known, the slitting grooves and the shape of “knives” are continuously investigated and improved. The deciding factor is metal flow inside the slitting grooves and its symmetrical filling by incoming stock. In order to assess metal flow in the slitting passes, finite element method (FEM) was selected to be applied in the essential part of the analysis. The computations were based on the assumption of thermomechanical model of deformation. The analysis of the influence of shape and width of slitting “knives” was performed with varying technological parameters. In particular, three values of relative height of slitting “knife”, three different shapes of “knife” as well as three different widths were analysed. Furthermore, physical modelling of the process of deformation in both slitting passes was realized with application of Gleeble simulator. The stress-strain characteristic of steel at relatively high strain rate condition was obtained. As a result of calculations, the complete metal flow patterns in the slitting passes were determined. The graphs presenting the distributions of stresses, strains and temperature in the deformation zone allow direct analysis, which gives better information about the phenomena in the roll gap, especially close to the slitting “knives”. The obtained results allowed, in consequence, to design slitting passes more precisely and to better use slit rolling method in rolling mill.