Relationship between mesoscale structure and ductility of drawn high carbon steel wire

Abstract

This study describes the evolution of a mesoscale structure that was characterized using fiber textures and mechanical properties versus drawing strain up to the drawing limit: the wire was drawn without causing rupturing, for the drawn high carbon steel wires (initial diameters: 0.276, 0.444 and 0.936 mm). Crystal orientation analysis using an electron backscatter diffraction pattern showed that the evolution of the mesoscale structure followed four steps with increasing drawing strain, regardless of the initial wire diameter. First, the wire consisted of only a primary fiber texture {100}<110>−{111}<110>. Second, the wire had primary and secondary {110}<110>−{111}<110> fiber textures in the outer and inner sides, respectively. Third, the wire had subprimary {100}<110>−{111}<110> and secondary fiber textures in its outer and inner sides, respectively. Fourth, the wire only consisted of a subprimary fiber texture. Results obtained through tensile testing showed that uniform elongation increased but the reduction of area decreased as the initial diameter increased over the entire drawing strain range, when there were no differences in lamellar spacing and tensile strength for the patented wires. Furthermore, uniform elongation decreased but the reduction of area increased when the ratio of thickness of secondary fiber texture to the wire radius increased. This study suggested that maintaining the thickness of secondary fiber texture in a large drawing strain region contributes to the improvement of drawability.