High strength multiphase steel, production method and use

US10612107B2 · kind B2 · utility

Assignee

• ArcelorMittal · LI

Inventors

• Dongwei Fan · Hammond, US
• Hyun Jo Jun · Clinton, US
• John A. Rotole · East Chicago, US

Key dates

• Filing date: Jun 3, 2015
• Grant date: Apr 7, 2020
• Expiry date: Feb 11, 2036

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C21D2211/008
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

The invention deals with a cold rolled and hot dip steel sheet, with a tensile strength of at least 980 MPa, with yield strength above or equal to 500 MPa, with total elongation above or equal to 8%, the composition consisting by weight percent: 0.05<C<0.15%, 2<Mn≤3%, Al<0.1%, 0.3<Si<1.5%, 0.01%<Nb<0.05%, N<0.02%, 0.1<Cr+Mo<1%, 0.0001<B<0.0025, Ti<0.5%, V<0.01%, S<0.01%, P<0.05% the remainder of the composition being iron and unavoidable impurities resulting from the smelting and the microstructure contains, in surface fraction: between 50 and 95% of martensite and between 5 and 50% of the sum of ferrite and bainite, wherein the ferrite grain size is below 10μιτι, and wherein the aspect ratio of the ferrite grain size is between 1 and 3. The steel according to the invention is oxidized and subsequently reduced during heating, soaking and cooling steps of the annealing.