COLD-ROLLED FLAT STEEL PRODUCT AND METHOD FOR THE PRODUCTION THEREOF

The invention relates to a cold-rolled flat steel product and to a method for the production thereof. The flat steel product has a proof stress Rp0.2 of = 320 MPa, an elongation at break A80 of = 20% and a microstructure comprising (in % by unit area) 62-82% ferrite, 10-30% martensite, 1.5-8% residual austenite and in total = 10% other microstructural constituents. The flat steel product in this case consists of a steel alloy containing (in % by weight) C: 0.06-0.1%, Si: 0.15-0.4%, Mn: 1.5-2%, Cr: 0.2-0.5%, Al: = 0.1%, the sum total of the contents of C, Si, Mn and Cr being = 2.3% and = 2.8% and the sum total of the contents of Si and Al being = 0.4%, P: = 0.03%, S: = 0.006%, N: = 0.008%, and further technically unavoidable impurities, including = 0.0006% B, = 0.02% V and also in each case = 0.01% Nb, Ti and also in each case = 0.1% Mo, Ni and Cu, remainder iron. To produce such a flat steel product, firstly a cold-rolled flat steel product is produced, and this is then brought in a continuous pass to 760 - 860°C, at which it is held for an annealing period Gt, for which the following holds true depending on the thickness D of the flat steel product: Gtu = Gt = Gto, where Gtu [s] = 3.56*D2 [s/mm2] - 5.1*D [s/mm] + 9.8 s Gto [s] = -21.4*D2 [s/mm2] + 132.8*D [s/mm] + 47 s. The invention relates to a cold-rolled flat steel product and to a method for the production thereof. The flat steel product has a proof stress Rp0.2 of = 320 MPa, an elongation at break A80 of = 20% and a microstructure comprising (in % by unit area) 62-82% ferrite, 10-30% martensite, 1.5-8% residual austenite and in total = 10% other microstructural constituents. The flat steel product in this case consists of a steel alloy containing (in % by weight) C: 0.06-0.1%, Si: 0.15-0.4%, Mn: 1.5-2%, Cr: 0.2-0.5%, Al: = 0.1%, the sum total of the contents of C, Si, Mn and Cr being = 2.3% and = 2.8% and the sum total of the contents of Si and Al being = 0.4%, P: = 0.03%, S: = 0.006%, N: = 0.008%, and further technically unavoidable impurities, including = 0.0006% B, = 0.02% V and also in each case = 0.01% Nb, Ti and also in each case = 0.1% Mo, Ni and Cu, remainder iron. To produce such a flat steel product, firstly a cold-rolled flat steel product is produced, and this is then brought in a continuous pass to 760 - 860°C, at which it is held for an annealing period Gt, for which the following holds true depending on the thickness D of the flat steel product: Gtu = Gt = Gto, where Gtu [s] = 3.56*D2