Formation of ultra-fine ferrite microstructure in warm rolled and annealed C–Mn steel

Laboratory simulations of warm rolling followed by intercritical annealing of a low carbon 0.15%C–1.39%Mn steel have been performed. The effects of austenitising temperature, amount of deformation and annealing time on microstructure and mechanical properties have been investigated. The results have shown that the homogeneous ultra-fine ferrite grain microstructure (∼1.1–1.2 μm average grain size) has been achieved after austenitising at 900 °C, warm rolling with 3 passes of 20% reduction each at 700 °C and annealing at 800 °C for 60 min. This correlates to the 20% improvement in mechanical properties compared to traditional industrial hot rolled steel.