ArcelorMittal S.A.
METHOD FOR PRODUCING HIGH SILICON DUAL PHASE STEELS WITH IMPROVED DUCTILITY

Abstract:

A method for producing a dual phase steel sheet is provided. The method includes providing a dual phase hot rolled steel sheet having a microstructure including ferrite and martensite and a composition including 0.1 to 0.3 wt. % C, 1.5 to 2.5 wt. % Si and 1.75 to 2.5 wt. % Mn. The steel sheet is annealed at a temperature from 750 to 875.degree. C., water quenched to a temperature from 400 to 420.degree. C. and subject to overaging at the temperature from 400 to 420.degree. C. to convert the martensite in the hot rolled steel sheet to tempered martensite. The overaging is sufficient to provide the hot rolled steel sheet with a hole expansion ratio of at least 15%.