A steel plate, the chemical composition of which includes, the contents being expressed by weight: 0.010%≤C≤0.20%, 0.06%≤Mn≤3%, Si≤1.5%, 0.005%≤Al≤1.5%, S≤0.030%, P≤0.040%, 2.5%≤Ti≤7.2%, (0.45×Ti)−0.35%≤B≤(0.45×Ti)+0.70%, and optionally one or more elements chosen from: Ni≤1%, Mo≤1%, Cr≤31, Nb≤0.1%, V≤0.1%, the balance of the composition consisting of iron and inevitable impurities resulting from the smelting.