High tensile strength hot rolled steel sheet having excellent formability and method for manufacturing the same

US9068238B2 · kind B2 · utility

Assignee

• JFE Steel Corporation · JP

Inventors

• Tamako Ariga · Tokyo, JP
• Katsumi Nakajima · Tokyo, JP
• Tetsuya Mega · Chiba, JP

Key dates

• Filing date: Mar 30, 2011
• Grant date: Jun 30, 2015
• Expiry date: Apr 14, 2032

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C21D2211/005
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

Described is a high tensile strength hot rolled steel sheet having high strength and formability, and a manufacturing method. It has tensile strength ≧980 MPa and excellent formability, and specifically identified ranges by mass % of C, Si, Mn, P, S, N, Al, Ti, V, Solute V, and Solute Ti; (ii) microstructure with fine carbides dispersion precipitated therein, the fine carbides containing Ti and V and having the average particle diameter <10 nm, as well as volume ratio with respect to the entire microstructure ≧0.007; and matrix as ferrite phase having area ratio with respect to the entire microstructure ≧97%. C, Ti, V, S and N satisfy (1) Ti≧0.08 +(N/14×48+S/32×48) and (2) 0.8≦(Ti/48+V/51)/(C/12)≦1.2, where “C”, “Ti”, “V”, “S” and “N” represent contents (mass %) of corresponding elements, respectively.