Effect of processing parameters on the ductility of high-carbon steel wire

Abstract

High-carbon steel (or patent) wire is an indispensable technology in many industries. Great effort has been expended to improve the strength of patent wire by strain hardening through cold drawing. The largest challenge for this effort is improving wire's workability, a quality that is curtailed by the presence of defects. Several variables pertinent to the evolution of these defects were investigated via finite element modeling in DEFORM, a forging environment. An investigation of a wide portion of die geometry space found a strong and friction-independent correlation between local longitudinal stress and normalized damage at the wire centerline. Rigid inclusions were found to amplify the damaging effects of drawing stresses in their immediate vicinities, but do so independently of their size. It was found that the damage caused by one pass through a die with flawed geometry has lasting effects that cannot be recovered in subsequent passes. Simulations supplemented with physical testing determined that carburized AISI 1080 steel wires experience a small reduction in damage compared to uncarburized wires under similar drawing conditions. This thesis suggests that carburization, coupled with proper die selection, can permit larger overall area reductions and produce thinner, stronger patent wire.