The relation between microstructure and mechanical properties of carbide-free bainitic steel 0.2% C – 1.53% Mn – 1.1% Si – 1% Cr – 0.3% Mo – 0.5% N under thermomechanical treatment is studied under isothermal conditions and under continuous air cooling. Impact tests of Charpy specimens, metallographic and x-ray diffraction analyses of the steel deformed by different variants are conducted. The size of the initial austenite grains and the Vickers hardness of the steel are determined. The hot plastic deformation is shown to affect positively the impact toughness of the steel treated for bainite. © 2021, Springer Science+Business Media, LLC, part of Springer Nature.