The Anisotropy of Ductility in Carbon Steel

Abstract

The anisotropy of ductility of O.46% carbon steel is examined by using small tensile specimens. The axial ductilities increase with increasing cooling rates in the heat-treatments, but the transverse ductilities are not improved by heat-treatment. Thus, a remarkable anisotropy of ductility is produced when the material is subjected to a high cooling rate. The anisotropy of ductility is caused by the sulphide inclusions which are elongated in the axial direction of steel bars, and the anisotropy can be eliminated by reducing the sulphur content or spheroidizing the inclusions. Based on the observations of fracture surfaces by the SEM, a model of crack-propagation is proposed and the mechanism of the anisotropy of ductility is explained.