A double-annealed steel sheet is provided. The composition of which includes, expressed in percent by weight, 0.20%≤C≤0.40%, 0.8%≤Mn≤1.4%, 1.60%≤Si≤3.00%, 0.015≤Nb≤0.150%, Al≤0.1%, Cr≤1.0%, S≤0.006%, P≤0.030%, Ti≤0.05%, V≤0.05%, B≤0.003%, N≤0.01%. A remainder of the composition includes iron and unavoidable impurities resulting from processing. The microstructure of the steel sheet includes, in area percentages, 10 to 30% residual austenite, 30 to 60% annealed martensite, 5 to 30% bainite, 10 to 30% fresh martensite and less than 10% ferrite A fabrication method and vehicle parts are also provided.