Abstract: Part comprising a steel material whose constituent grains comprise a matrix in which precipitates are incorporated, the precipitates comprising at least one metallic element selected from a metallic element M, a metallic element M?, a metallic element M? or mixtures thereof; the microstructure of the steel being such that the grains are equiaxed and the average grain size being such that the average of their largest dimension “D max” and/or the average of their smallest dimension “D min” is comprised between 10 ?m and 50 ?m. The steel material has optimised, stable and isotropic mechanical properties, in particular so that the steel material can best withstand mechanical and/or thermal stresses.