In this study, we are interested in a preliminary characterization of the NV10 steel for the thermochemical treatment. A spectral analysis was done to determine the chemical composition of two NV10 nuances rich and poor in micro-alloying elements. Metallographic characterization allows us to examine the structures and the evaluation of the mean grain diameter. XRD is introduced a supplementary basis for the study of the structure the hardness measurements have been developed in addition to the impact tests at low temperature and traction in both directions of the transverse and longitudinal rolling.