Effects of cementite dissolution on the mechanical properties of the heavily drawn hyper-eutectoid steel wires used for steel cords

Abstract

The effects of the dissolved cementite on the mechanical properties have been experimentally investigated. The steel wires were fabricated depending on the carbon content of 0.82 and 1.02 wt.% and drawing strain from 4.12 to 4.32. The bending fatigue resistance and torsion ductility were measured by a hunter fatigue tester and torsion tester specially designed for thin-sized wires. The results showed that as the drawing strain and carbon content increased, the fatigue resistance and the torsional ductility of the steel wires decreased, while the tensile strength increased. In order to elucidate this behavior, the microstructure in terms of lamellar spacing (lambda(P)), cementite thickness (t(C)) and morphology of cementite was observed by advanced analysis techniques such as transmission electron microscope (TEM) and 3 dimensional atom probes (3-D AP).