Effects of post-deformation annealing conditions on the behavior of lamellar cementite and the occurrence of delamination in cold drawn steel wires

The effects of post-deformation annealing temperature and time on mechanical properties and the occurrence of delamination in cold drawn steel wires were investigated. For the low temperature annealing, the carbon dissolution into lamellar ferrite due to strain aging would enhance not only the increase of strength but also the occurrence of delamination. However, as annealing temperatures and annealing time increase further, age softening, including such as the break-up and the spheroidization of lamellar cementite, starts to operate. Consequently, the reduction of carbon content dissolved in lamellar ferrite would result in the decrease of tensile strength and suppress the occurrence of delamination. The voids formed at the surface of globular cementite particle, which were produced during post-deformation annealing at high temperatures for a long time, would act as one of the origins for delamination during torsion.