Thyssenkrupp Steel Europe Ag

Voestalpine Stahl Gmbh

Dorothea Mattissen

Thomas Heller

Roland Sebald

Andreas Pichler

Brigitte Hammer

Daniel Krizan

Günter Stich

Sigrun Ebest

Ekaterina Bocharova

Ekatherina Bocharova

Silke Strauss

Stefan Follner

Thomas Nickels

Sigrun Voß

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 &#x3bb;. 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: &#x3e;0.60-1.0%, Al: &#x2264;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 &#x3bb;of more than 6%. The invention also relates to a method which easily enables production of a flat steel product according to the invention.

Cold-rolled flat steel product and method for its production

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: &#x2264;0.02%, S: &#x2264;0.003%, N: &#x2264;0.008%, Mo: &#x2264;0.1%. Similarly, the invention relates to a method for producing a flat steel product that consists of a steel according to the invention.

Steel, sheet steel product and process for producing a sheet steel product

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: &#x3c;0.1%, Mo: &#x3c;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 Rof at least 950 MPa, a yield point Rof at least 500 MPa and an elongation at break Ameasured in the transverse direction of at least 15%. A method of producing the multi-phase steel.

Multi-phase steel, cold-rolled flat product produced from such a multi-phase steel and method for producing it

Growing community of inventors

Mulheim, Germany

Dorothea Mattissen