Suppression of Delamination in Hyper-eutectoid Steel Wires by Multi Skin-pass Drawing

Abstract

The effect of multi skin-pass drawing on mechanical properties of high carbon steel wires are investigated. 1.0mass%C-0.2mass%Si-0.4mass%Mn-20ppmB steel was used in this study. The tensile strength change in wet drawing was not different between the filament with single skin pass draft condition and that of multi skin-pass draft condition. However torsion property was drastically changed. Delamination did not occur between 0.287 mm and 0.213 mm in diameter under the multi skin-pass draft, which strength was over 4200 MPa. From DSC curve, the first peak (70100°C peak) was observed only in multi skin-passed filament. By analyising Kissinger plot, the activation energy of the first peak was about 90kJ/mol which was close to that of carbon atoms lattice diffusion in ferritic iron. The effect of multi skin-pass on torsion property change is considered originating from alleviation of dynamic strain aging by carbon atoms desorption from dislocation located ferrite/cementite boundaries.