Steel sheet, the composition of the steel of which comprises, the contents being expressed by weight: 0.08%≦C≦0.23%, 1%≦Mn≦2%, 1≦Si≦2%, Al≦0.030%, 0.1%≦V≦0.25%, Ti≦0.010%, S≦0.015%, P≦0.1%, 0.004%≦N≦0.012%, and, optionally, one or more elements chosen from: Nb≦0.1%, Mo≦0.5%, Cr≦0.3%, the balance of the composition consisting of iron and inevitable impurities resulting from the smelting.