Thyssenkrupp Steel Europe Ag

Thyssen Krupp Ag

Voestalpine Stahl Gmbh

Roland Sebald

Thomas Heller

Andreas Pichler

Richard Georg Thiessen

Karsten Machalitza

Dorothea Mattissen

Sigrun Ebest

Daniel Krizan

Ekaterina Bocharova

Andreas Bongards

Sigrun Voβ

Hans Ferkel

Ekatherina Bocharova

Stefan Follner

Sigrun Voss

Annette BÄUMER

Karoline Drewes

Fabian Nowara

Sigrun Voß

Sebastian Feldhaus

Udo Paul

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

A cold-rolled flat steel product may have a yield strength Rp0.2 of not more than 320 MPa, a fracture elongation A80 of at least 20% and a microstructure having by percent area 62%-82% ferrite, 10%-30% martensite, 1.5%-8% residual austenite, and a sum total of not more than 10% other microstructure constituents. The flat steel product may comprise a steel alloy containing in percent by weight 0.06%-0.1% C; 0.15%-0.4% Si; 1.5%-2% Mn; 0.2%-0.5% Cr; not more than 0.1% Al; wherein the sum total of C, Si, Mn, and Cr is at least 2.3% and not more than 2.8%; wherein the sum total of Si and Al is not more than 0.4%; not more than 0.03% P; not more than 0.006% S; not more than 0.008% N; unavoidable impurities including not more than 0.0006% B, not more than 0.02% V, and not more than 0.01% each of Nb and Ti, and not more than 0.1% each of Mo, Ni, and Cu; as well as iron. For production of such a flat steel product, a cold-rolled flat steel product may first be produced and then brought to 760-860&#xb0; C. in a continuous run and kept at that temperature over an annealing period Gt for which, depending on the thickness D of the flat steel product, Gtu&#x2264;Gt&#x2264;Gto with[s]=3.56*[s/mm]&#x2212;5.1*[s/mm]+9.8 s[s]=&#x2212;21.4*[s/mm]+132.8*[s/mm]+47 s.

Cold-rolled flat steel product and method for the production thereof

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

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Geldern, Germany

Roland Sebald