Abstract: The invention relates to a cold-rolled flat steel product which, despite high strength values, has a high level of deformability characterized by a high elongation at break and a good hole expansion ratio ?M. For this purpose the flat steel product is produced from a steel that is composed of (in % by weight) C: 0.12-0.19%, Mn: 1.5-2.5%, Si: >0.60-1.0%, Al: ?0.1%, Cr: 0.2-0.6%, Ti: 0.05-0.15% with the remainder being iron and unavoidable impurities caused by the production process, and which comprises a perlite- and bainite-free structure having 4-20% by vol. martensite, 2-15% by vol. residual austenite, remainder ferrite, an elongation at break A80 of at least 15%, a tensile strength Rm of at least 880 MPa, a yield strength ReL of at least 550 MPa and a hole expansion ratio ?M of more than 6%. The invention also relates to a method which easily enables production of a flat steel product according to the invention.

Abstract: The invention relates to a steel and to a flat steel product produced therefrom that have optimized mechanical properties and at the same time can be produced at low cost, without having to rely for this on expensive alloying elements that are subject to great fluctuations with regard to their procurement costs. The steel and the flat steel product have for this purpose the following composition according to the invention (in % by weight): C: 0.11-0.16%; Si: 0.1-0.3%; Mn: 1.4-1.9%; Al: 0.02-0.1%; Cr: 0.45-0.85%; Ti: 0.025-0.06%; B: 0.0008-0.002%, the remainder Fe and impurities that are unavoidable for production-related reasons, which include contents of phosphorus, sulfur, nitrogen or molybdenum as long as the following respectively apply for their contents: P: ?0.02%, S: ?0.003%, N: ?0.008%, Mo: ?0.1%. Similarly, the invention relates to a method for producing a flat steel product that consists of a steel according to the invention.

Abstract: A multi-phase steel including in % wt. C: 0.14-0.25%, Mn: 1.7-2.5%, Si: 0.2-0.7%, Al: 0.5-1.5%, Cr: <0.1%, Mo: <0.05%, Nb: 0.02-0.06%, S: up to 0.01%, P: up to 0.02%, N: up to 0.01% and optionally at least one of Ti, B, and V according to the following stipulation: Ti: up to 0.1%, B: up to 0.002%, V: up to 0.15%, with the remainder iron and unavoidable impurities, wherein the microstructure has at least 10% vol. ferrite and at least 6% vol. residual austenite and the steel has a tensile strength Rm of at least 950 MPa, a yield point ReL of at least 500 MPa and an elongation at break A80 measured in the transverse direction of at least 15%. A method of producing the multi-phase steel.

Abstract: The invention relates to a steel and to a flat steel product produced therefrom that have optimized mechanical properties and at the same time can be produced at low cost, without having to rely for this on expensive alloying elements that are subject to great fluctuations with regard to their procurement costs. The steel and the flat steel product have for this purpose the following composition according to the invention (in % by weight): C: 0.11-0.16%; Si: 0.1-0.3%; Mn: 1.4-1.9%; Al: 0.02-0.1%; Cr: 0.45-0.85%; Ti: 0.025-0.06%; B: 0.0008-0.002%, the remainder Fe and impurities that are unavoidable for production-related reasons, which include contents of phosphorus, sulfur, nitrogen or molybdenum as long as the following respectively apply for their contents: P: ?0.02%, S: ?0.003%, N: ?0.008%, Mo: ?0.1%. Similarly, the invention relates to a method for producing a flat steel product that consists of a steel according to the invention.

Abstract: The invention relates to a cold-rolled flat steel product which, despite high strength values, has a high level of deformability characterised by a high elongation at break and a good hole expansion ratio A. For this purpose the flat steel product is produced from a steel that is composed of (in % by weight) C: 0.12-0.19%, Mn: 1.5-2.5%, Si: >0.60-1.0%, Al: ?0.1%, Cr: 0.2-0.6%, Ti: 0.05-0.15% with the remainder being iron and unavoidable impurities caused by the production process, and which comprises a perlite- and bainite-free structure having 4-20% by vol. martensite, 2-15% by vol. residual austenite, remainder ferrite, an elongation at break A80 of at least 15%, a tensile strength Rm of at least 880 MPa, a yield strength ReL of at least 550 MPa and a hole expansion ratio ?M of more than 6%. The invention also relates to a method which easily enables production of a flat steel product according to the invention.

Abstract: A multi-phase steel including in % wt. C: 0.14-0.25%, Mn: 1.7-2.5%, Si: 0.2-0.7%, Al: 0.5-1.5%, Cr: <0.1%, Mo: <0.05%, Nb: 0.02-0.06%, S: up to 0.01%, P: up to 0.02%, N: up to 0.01% and optionally at least one of Ti, B, and V according to the following stipulation: Ti: up to 0.1%, B: up to 0.002%, V: up to 0.15%, with the remainder iron and unavoidable impurities, wherein the microstructure has at least 10% vol. ferrite and at least 6% vol. residual austenite and the steel has a tensile strength Rm of at least 950 MPa, a yield point ReL of at least 500 MPa and an elongation at break A80 measured in the transverse direction of at least 15%. A method of producing the multi-phase steel.

Abstract: A multi-phase steel which in addition to iron and unavoidable impurities includes (in % wt.) C: 0.14-0.25%, Mn: 1.7-2.5%, Si: 1.4-2.0%, Al: <0.1%, Cr: <0.1%, Mo: <0.05%, Nb: 0.02-0.06%, S: up to 0.01%, P: up to 0.02%, N: up to 0.01% and optionally one of Ti, B, and V according to the following stipulation: Ti: ?0.1%, B: ?0.002%, V: ?0.15%. A cast semi-finished product, is hot rolled starting at an initial temperature of 1100-1300° C. and ending at a final temperature of 820-950° C., coiled at 400-750° C., cold rolled into the cold flat product at degrees of 30-80%, and subjected to a heat treatment including continuous annealing at 20° C.+Ac1-Ac3 and overageing at 350-500° C.

Abstract: A dual-phase steel, a flat product and processes for the production thereof. The dual-phase steel having a strength of at least 950 MPa, good deformability, and good surface finish. It is possible, when a simple production process is used, for the flat product produced from this steel to be formed into a complexly formed component, such as part of a car body, either uncoated or provided with an anti-corrosion coating. The steel according to the invention has a structure comprising 20-70% martensite, up to 8% retained austenite and the remainder ferrite and/or bainite and has the following composition (in % by weight): C: 0.050-0.105%, Si: 0.20-0.60%, Mn: 2.10-2.80%, Cr: 0.20-0.80%, Ti: 0.02-0.10%, B: <0.0020%, Mo: <0.25%, Al: <0.10%, Cu: up to 0.20%, Ni: up to 0.10%, Ca: up to 0.005%, P: up to 0.2%, S: up to 0.01%, N: up to 0.012%, remainder iron and unavoidable impurities.

Abstract: A dual-phase steel, a flat product produced therefrom and a process for the production thereof. The dual-phase steel has, in addition to a strength of at least 950 MPa and good deformability, a surface finish which, when a simple production process is used, makes it possible for the flat product produced from this steel to be formed into a complexly formed component, such as a part of a car bodywork, in an uncoated state or in a state provided with an anti-corrosion coating. The steel according to the invention comprises 20-70% martensite, up to 8% retained austenite and the remainder ferrite and/or bainite and comprises (in % by weight): C: 0.10-0.20%, Si: 0.10-0.60%, Mn: 1.50-2.50%, Cr: 0.20-0.80%, Ti: 0.02-0.08%, B: <0.0020%, Mo: <0.25%, Al: <0.10%, P: ?0.2%, S: ?0.01%, N: ?0.012%, the remainder iron and unavoidable impurities.