Abstract: Steel for which the composition is, in weight percentages: 0.35%?C?0.50%; 0.30%?Mn?1.50%; trace amounts ?Cr?1.50%; 0.05%?Mo?0.50%; 0.15?Si?1.20%; trace amounts ?Ni?1.0%; trace amounts ?Cu?1.0%; trace amounts ?V?0.35%; trace amounts ?Al?0.10%; trace amounts ?B?0.005%; trace amounts ?Ti?0.10%; trace amounts ?Nb?0.10%; trace amounts ?S?0.15%; trace amounts ?Ca?0.010%; trace amounts ?Te?0.030%; trace amounts ?Se?0.050%; trace amounts ?Bi?0.050%; trace amounts ?Pb?0.100%; trace amounts ?N?0.020%; the remainder being iron and impurities resulting from the elaboration, and the C, Mn and Cr contents being such that 830-270 C %-90 Mn %-70 Cr %)?620.

Abstract: A mechanical steel part in steel with high characteristics, characterized in that its composition, comprising in weight percentages, is 0.05%?C?0.25%; 1.2%?Mn?2%; 1%?Cr?2.5%; wherein the contents of C, Mn and Cr are such that (830-270C %-90 Mn %-70Cr %)?560; 0<Si?1.55; 0<Ni?1%; 0<Mo?0.5%; 0<Cu?1%; 0<V?0.3%; 0<Al?0.1%; 0<B?0.005%; 0<Ti?0.03%; 0<Nb?0.06%; 0<S?0.1%; 0<Ca?0.006%; 0<Te?0.03%; 0<Se?0.05%; 0<Bi?0.05%; 0<Pb?0.1%; the remainder of the steel part being iron and impurities resulting from processing, and wherein the in that its structure of the steel is bainitic and contains no more than a total of 20% of martensite and/or pro-eutectoid ferrite and/or pearlite.