Effects of deformation temperature and strain rate on hot deformation behaviour and optimisation of processing maps of SWRH82B high-carbon steel

Isothermal hot compression tests were performed on surface and centre specimens cut from SWRH82B high-carbon steel continuously cast billets at 950–1100 °C and 0.01–7 s−¹. Arrhenius-type constitutive equations and hot processing maps based on the Dynamic Materials Model were developed to characterise and optimise hot working behaviour. Results reveal that flow stress decreases with increasing temperature and rises with higher strain rate for both regions. The centre shows 5–10 MPa lower flow stress than the surface under identical conditions, with hot deformation activation energies of 382.60 and 381.60 kJ/mol for the surface and centre, respectively. Flow instability occurs in the surface at 1100 °C and strain rates ≥7 s−¹, whereas no instability domain is observed in the centre within the tested range. These differences arise from solidification-induced microstructural heterogeneity. The centre has more uniform initial structure and better hot workability, indicating that region-specific parameters are required for uniform deformation control.