Abstract: The present invention relates to a flat steel product which has good deep-drawing ability, low edge-crack sensitivity and good bending behaviour. To this end, the flat steel product contains a steel which consists of (in wt %) 0.1-0.5% C, 1.0-3.0% Mn, 0.9-1.5% Si, up to 1.5% Al, up to 0.008% N, up to 0.020% P, up to 0.005% S, 0.01-1% Cr and optionally one or more of the following elements: up to 0.2% Mo, up to 0.01% B, up to 0.5% Cu, up to 0.5% Ni and optionally a total of 0.005-0.2% microalloying elements, the remainder being iron and unavoidable impurities, wherein 75<(Mn2+55*Cr)/Cr<3000 where Mn is the Mn content of the steel in wt % and Cr is the Cr content of the steel in wt %. The steel has a structure which consists of at least 80 area % martensite, of which at least 75 area % is tempered martensite and at most 25 area % is non-tempered martensite, at least 5 volume % residual austenite, 0.

Abstract: A hot-rolled flat steel product including (in wt %) C: 0.1-0.3%, Mn: 1.5-3.0%, Si: 0.5-1.8%, Al: ?1.5%, P: ?0.1%, S: ?0.03%, N: ?0.008%, optionally one or more of Cr: 0.1-0.3%, Mo: 0.05-0.25%, Ni: 0.05-2.0%, Nb: 0.01-0.06%, Ti: 0.02-0.07%, V: 0.1-0.3%, and B: 0.0008-0.0020%, the balance being iron and unavoidable impurities. This flat steel product possesses a tensile strength of 800-1500 MPa, a yield strength of >700 MPa, an elongation at break of 7-25%, and a hole expansion of more than 20%. The structure is at least 85 area % martensite, of which at least half is tempered martensite, with the remainder being ?15 vol % residual austenite, ?15 area % bainite, ?15 area % polygonal ferrite, ?5 area % cementite and/or ?5 area % nonpolygonal ferrite, and has a kernel average misorientation of at least 1.50°. Also, a method for producing the flat steel product, wherein the microstructure of the flat steel product is set by the heat treatment.

Abstract: A flat steel product consisting of (in wt %) 0.1-0.5% C, 1.0-3.0% Mn, 0.9-1.5% Si, ?1.5% Al, ?0.008% N, ?0.020% P, ?0.005% S, 0.01-1% Cr and optionally one or more of: ?0.2% Mo, ?0.01% B, ?0.5% Cu, ?0.5% Ni and optionally a total of 0.005-0.2% microalloying elements, the remainder iron and unavoidable impurities. The steel has a structure consisting of ?80 area % martensite, where ?75 area % is tempered and ?25 area % is non-tempered, ?5 volume % residual austenite, 0.5-10 area % ferrite, ?5 area % bainite, and carbides with a length of ?250 nm, wherein in the phase boundary between tempered martensite and residual austenite, there is a low-Mn ferrite seam having a width of 4·12 nm and a Mn content of ?50% of the average Mn content. Also, a method for producing the flat steel in which the structural characteristics of the flat steel product are set by suitable heat treatment.