STEEL SHEET VERSATILE BY HIGH MECHANICAL STRENGTH, BY PLASTICITY AND BY PLIABILITY, PROCESS FOR PRODUCING AND USE OF SUCH SHEETS

摘要

1. The cold-rolled and annealed steel sheet with a mechanical strength greater than or equal to 1000 MPa and a uniform elongation greater than or equal to 12%, which composition comprises, in weight percent, 0.15% 1.8% ≤C≤0,25 % ≤Mn≤3,0% 1,2% ≤Si≤2% Al≤0,10% 0% ≤Cr≤0,50% 0% ≤Cu≤1% 0% ≤Ni≤1% S≤0,005% P≤0,020% Nb≤0,015% Ti≤0,020% V≤0,015% Co≤1% N≤0,008% B≤0,001% with Mn + Ni + Cu≤3%, the remainder being iron and unavoidable impurities resulting from the manufacturing , the microstructure consists in fractions of area of ​​5-20% of polygonal ferrite, 10-15% of residual austenite, martensite, 5-15%, with the remainder Toit of bainite in the form of plates narrow and comprises between these narrow plates carbides, so that the number N interlamellar carbides having a size greater than 0.1 micrometers per unit surface area of ​​less than or equal to 50000 / mm.2. The steel sheet according to claim 1, which composition comprises, in mass% ≤C≤0,22% protsentah0,18 3. Steel sheet according to any one of claims 1-2, the composition of which comprises, in mass% ≤Mn≤2,6% percentage2 4. Steel sheet according to any one of claims 1-2, the composition of which comprises, in mass% ≤Si≤1,8% protsentah1,4 5. Steel sheet according to any one of claims 1-2, the composition of which comprises, in mass% ≤Cr≤0,35% protsentah0 6. Steel sheet according to any one of claims 1-2, wherein the V-angle bend at which cracks occur, is greater than or equal to 90 ° 90 ° .7. Steel sheet according to any one of claims 1-2, further comprising a coating of zinc or zinc splava.8. A method of manufacturing a cold rolled and annealed sheet steel with a strength greater than or equal to 1000 MPa and elongation greater than or equal to 12%, comprising the following steps in which: - a steel composition according to any one of claims 1-5, zatem- this steel is cast into a billet continuous casting, for