HIGH SILICON BEARING DUAL PHASE STEELS WITH IMPROVED DUCTILITY

摘要

A process for producing a dual phase steel sheet are described. The processcomprising steps of: providing a dual phase hot rolled steel sheet comprisingacomposition comprising: 0.1 - 0.3 wt.% C; 1.5 - 2.5 wt.% Si; 1.75-2.5 wt.% Mn;0-1wt.% Al; 0-0.1 total of one or more of Nb, Ti and V; and 0-0.3wt% Mo; and theremainder being Fe and inevitable residuals; annealing said hot rolled sheetfrom 750to 875°C; water quenching said hot rolled sheet from 400 to420°C; and overagingsaid sheet from 400 to 420°C to convert the martensite in said hotrolled steel sheet totempered martensite. The sheet comprising a microstructure containing ferriteandtempered martensite and comprising a tensile strength of at least 980 MPa, atotalelongation of at least 15%, and a hole expansion ratio of at least 15%.