hot deformation behavior of an api x70 steel: a processing map approach

This study investigates the hot deformation behavior of an api x70 microalloyed steel using a processing map approach. cylindrical specimens were subjected to compression tests at temperatures ranging from 950 to 1100 °c and strain rates from 0.001 to 1 s⁻¹. flow curves revealed typical features of work hardening, dynamic recovery, and dynamic recrystallization. power dissipation efficiency and instability criteria were calculated using a dynamic material model to construct processing maps at various strain levels. the maps identified three optimal hot deformation regions at higher strains, with the most favorable zone (efficiency of 25–33%) located at 1075–1100 °c and 0.001–0.005 s⁻¹. microstructural validation confirmed these safe zones, while unstable regions were characterized by crack formation and deformation bands. a constitutive analysis yielded an apparent activation energy for hot deformation of 572.5 kj/mol. the findings provide valuable guidance for optimizing hot working conditions of api x70 steel.