High deformation effects on the plasticity of ultra-high carbon steel wires

Abstract

Steel wires under severe cold drawing deformation, develop high strength (5-6 GPa) and ductility. For these reasons it is relevant to increase the knowledge on the structural evolution and deformation mechanisms involved during wire drawing process, due to their critical applications such as bridges, cranes and tire cord. This paper presents a comparative study of steel wires (0.84%C) at different deformation stages. The product presents a normal behaviour under torsion test, the mentioned test is normally used to corroborate the wire aptitude. The main objective of the study is to increase the knowledge on the structural evolution after cold drawn considering the deformation mechanisms, cementite dissolution, and epsilon carbide precipitation. The microstructural study was carried out applying light and scanning electron microscopy (SEM-EBSD). The structural information was correlated with results of differential thermal analysis (DTA) and FactSage simulation. The structural study verified the presence of curling phenomenon in the wires. The interlaminar spacing (l) and the thickness of cementite lamellae in wires cold drawn from 8 mm up to 2 mm of diameter was determined. Finally, the dynamic strain aging, which is promoted by cementite destabilization and the precipitation of epsilon carbide was studied.