Microstructure and mechanical properties of heavily cold drawn pearlitic steel wires: effects of low temperature annealing

Abstract

Heavily cold drawn pearlitic steel wires prepared with drawing strains (ε) of 4.5, 5.1 and 5.3 were annealed at low temperatures for different durations. Microstructural characteristics and mechanical properties of the annealed wires were investigated and determined. The tensile strength of cold drawn pearlitic steel wires was found to increase, due to low temperature annealing treatment. For example, for the cold drawn wires (ε = 5.3) annealed at 60 °C for 1 h, the tensile strength is enhanced from about 4920 MPa to 5020 MPa. Counterintuitively, the ductility shows little decrease. With the increase of annealing temperature and time, the tensile strength decreases. For the annealed wires, carbon atoms were observed to segregate at subgrain boundaries (SGBs), and particle precipitation can also be observed. Substitutional solid solution atoms, such as Cr, Mn and Si, remain locked in their original positions. Exothermic peaks in differential scanning calorimetry (DSC) curves were found to shift to higher temperatures for the annealed wires.