Thyssen Krupp Ag

Thyssenkrupp Steel Europe Ag

Thorsten Rösler

Liuyi Zhang

Jörg Mertens

A flat steel product and a method of making a flat steel product having a hole expansion of at least 60%, a yield strength of at least 660 MPa, a tensile strength of at least 760 MPa, and an elongation at break of at least 10%. The flat steel product is made from a complex-phase steel, which includes (in wt %) C: 0.01-0.1%, Si: 0.1-0.45%, Mn: 1-2.5%, Al: 0.005-0.05%, Cr: 0.5-1%, Mo: 0.05-0.15%, Nb: 0.01-0.1%, Ti: 0.05-0.2%, N: 0.001-0.009%, P: &#x3c;0.02%, S: &#x3c;0.005%, Cu: &#x2264;0.1 %, Mg: &#x2264;0.0005 %, O: &#x3c;0.01 %, optionally one or more of Ni, B, V, Ca, Zr, Ta, W, REM, and Co, where Ni: &#x2264;1%, B: &#x2264;0.005%, V: &#x2264;0.3%, Ca: 0.0005-0.005%, Zr, Ta, W: in total &#x2264;2%, REM: 0.0005-0.05%, and Co: &#x3c;1%, and iron and unavoidable impurities as the remainder, where % Ti&#x3e;(48/14)% N+(48/32)% S and % Nb&#x3c;(93/12)% C+(45/14)% N+(45/32)% S. The structure of the flat steel product includes (in area %) &#x2265;80% bainite, &#x3c;15% ferrite, &#x3c;15% martensite, &#x3c;5% cementite, and &#x3c;5 vol % retained austenite.

Hot rolled flat steel product consisting of a complex-phase steel with a largely bainitic microstructure and method for manufacturing such a flat steel product

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Muelheim an der Ruhr, Germany

Thorsten Rösler