DOUBLE ANNEALED STEEL SHEET HAVING HIGH MECHANICAL STRENGTH AND DUCTILITY CHARACTERISTICS, METHOD OF MANUFACTURE AND USE OF SUCH SHEETS
Abstract:
The invention relates to a double-annealed steel sheet, the composition of which includes, expressed in per cent 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%, the remainder of the composition being constituted of iron and unavoidable impurities resulting from processing, the microstructure being constituted, in area percentages, of 10 to 30% residual austenite, 30 to 60% annealed martensite, 5 to 30% bainite, 10 to 30% fresh martensite and less than 10% ferrite. The invention further relates to its fabrication method and the use of such sheet.
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