High-strength hot-dip galvanized steel sheet, high-strength alloyed hot-dip galvanized steel sheet excellent in bake hardenability, and manufacturing method thereof

US9162422B2 · kind B2 · utility

Assignee

• NIPPON STEEL & SUMITOMO METAL CORPORATION · JP

Inventors

• Hiroyuki Kawata · Tokyo, JP
• Naoki Maruyama · Utsunomiya, JP
• Akinobu Murasato · Tokyo, JP
• Akinobu Minami · Tokyo, JP
• Takeshi Yasui · Kandanghaur, ID
• Takuya Kuwayama · Tokyo, JP
• Hiroyuki Ban · Ebeye, US
• Kaoru Hiramatsu · Tokyo, JP

Key dates

• Filing date: Sep 28, 2012
• Grant date: Oct 20, 2015
• Expiry date: Sep 28, 2032

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10T428/265
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

Steel contains each of C, Si, Mn, P, S, Al, N, O, at a range from ⅛ thickness centered around a ¼ sheet thickness from a surface to ⅜ thickness centered around the ¼ sheet thickness from the surface at a base steel sheet, a structure of the base steel sheet contains, in volume fraction, 3% or more of a retained austenite phase, 50% or less of a ferrite phase, and 40% or more of a hard phase, average dislocation density is 5×1013/m2 or more, solid-solution C amount contained in the retained austenite phase is in mass % 0.70 to 1.00%, X-ray random intensity ratio of FCC iron in an texture of the retained austenite phase is 3.0 or less, ratio between a grain diameter relative to a rolling direction and a grain diameter relative to a sheet width direction of the retained austenite phase is 0.75 to 1.33.