Effects of Nb Solute and Precipitates on the Continuous Cooling and Isothermal Transformation of Pearlite in High‐Carbon Steel Wire Rods

To investigate the influence mechanism of Nb solute and precipitates on pearlite transformation, the effects of Nb content and heat‐treatment process on pearlite transformation and microstructure in high‐carbon steel wire rods are analyzed in this article. During the austenite deformation stage, the increase in solute Nb and strain‐induced precipitates (SIPs) suppresses austenite recrystallization, while the decrease in prior austenite grain size promotes the reduction of refined pearlite colonies size. During the continuous cooling transformation process, an increase in Nb content and cooling rate increases the supercooling of pearlite transformation and refines the interlamellar spacing (ILS) of pearlite. During the isothermal transformation process, the increase in isothermal temperature increases the incubation period of pearlite transformation and slows down the rate of pearlite transformation. With the increase in Nb content, the incubation period of pearlite transformation lengthens. But uneven distribution of C in austenite is caused by the SIP, which promotes interface migration, and shorts the pearlite transformation time. In high‐carbon steel wire rods, the refinement of pearlite colonies and pearlite ILS is achieved by increasing the Nb content, raising the cooling rate, and lowering the isothermal temperature, thereby increasing the content of precipitates and improving their mechanical properties.