Patent number: 11220721
Abstract: 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: <0.02%, S: <0.005%, Cu: ?0.1 %, Mg: ?0.0005 %, O: <0.01 %, optionally one or more of Ni, B, V, Ca, Zr, Ta, W, REM, and Co, where Ni: ?1%, B: ?0.005%, V: ?0.3%, Ca: 0.0005-0.005%, Zr, Ta, W: in total ?2%, REM: 0.0005-0.05%, and Co: <1%, and iron and unavoidable impurities as the remainder, where % Ti>(48/14)% N+(48/32)% S and % Nb<(93/12)% C+(45/14)% N+(45/32)% S. The structure of the flat steel product includes (in area %) ?80% bainite, <15% ferrite, <15% martensite, <5% cementite, and <5 vol % retained austenite.
Type:
Grant
Filed:
January 16, 2018
Date of Patent:
January 11, 2022
Assignees:
THYSSENKRUPP STEEL EUROPE AG, THYSSENKRUPP AG
Inventors:
Thorsten Rösler, Liuyi Zhang, Jörg Mertens
Publication number: 20190338384
Abstract: 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: <0.02%, S: <0.005%, Cu: ?0.1 % , Mg: ?0.0005 % , O: <0.01 % , optionally one or more of Ni, B, V, Ca, Zr, Ta, W, REM, and Co, where Ni: ?1%, B: ?0.005%, V: ?0.3%, Ca: 0.0005-0.005%, Zr, Ta, W: in total ?2%, REM: 0.0005-0.05%, and Co: <1%, and iron and unavoidable impurities as the remainder, where % Ti>(48/14)% N+(48/32)% S and % Nb<(93/12)% C+(45/14)% N+(45/32)% S. The structure of the flat steel product includes (in area %) >80% bainite, <15% ferrite, <15% martensite, cementite, and <5 vol % retained austenite.
Type:
Application
Filed:
January 16, 2018
Publication date:
November 7, 2019
Inventors:
Thorsten Rösler, Liuyi Zhang, Jörg Mertens