Thyssenkrupp Steel Europe Ag

Jfe Steel Corporation

Frank Hisker

Thomas Heller

Brigitte Hammer

Shinjiro Kaneko

Rudolf Kawalla

Fusae Shiimori

Richard Georg Thiessen

Grzegorz Korpala

Almir Dzafic

Richard Thiessen

Rudolf ProfDr-Ing Kawalla

A method for producing a cold-rolled steel strip with a yield ratio Re/Rm of at least 0.7, the cold-rolled steel product including iron, unavoidable impurities and (in wt. %) C: 0.05-0.20%, Si: 0.25-1.00%, Mn: 1.0-3.0%, Al: 0.02-1.5%, Cr: 0.1-1.5%, N: &#x3c;0.02%, P: &#x3c;0.03%, S: &#x3c;0.05% and optionally one or more of Ti, Mo, Nb, V, and B, Ti: up to 0.15%, Mo: &#x3c;2%, Nb: &#x3c;0.1%, V: &#x3c;0.12%, and B: 0.0005-0.003%. The cold-rolled flat steel product undergoes heat treatment for 4.5-24 hours at a temperature of 150-400&#xb0; C. Also, a cold rolled flat steel product discussed above having a structure including at least two phases, selected from (in vol. %) at least 10% tempered martensite, &#x3c;10% bainite, &#x3c;10% residual austenite and remainder ferrite, a yield ratio of at least 0.7, a tensile strength of &#x2265;750 MPa and a hole expansion of at least 18%.

Method for producing a cold-rolled flat steel product with high yield strength and flat cold-rolled steel product

A complexly formed steel component may have a tensile strength Rm of greater than 1200 MPa and an elongation at break A50 of greater than 6%. Example methods for producing such components comprise providing a flat steel product, which in addition to iron and unavoidable impurities, contains in percent by weight 0.10-0.60% C, 0.4-2.5% Si, up to 3.0% Al, 0.4-3.0% Mn, up to 1% Ni, up to 2.0% Cu, up to 0.4% Mo, up to 2% Cr, up to 1.5% Co, up to 0.2% Ti, up to 0.2% Nb, and up to 0.5% V. At least 10% by volume of a microstructure of the flat steel product may consist of residual austenite comprising globular residual austenite islands with a grain size of at least 1 &#x3bc;m. Before being cooled, the flat steel product may be heated to a forming temperature of 150-400&#xb0; C. and formed into a component with a degree of forming that is at most equal to uniform elongation Ag.

Method for producing a steel component

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Bottrop, Germany

Frank Hisker