Galvannealed steel sheet having high corrosion resistance after painting

US8906516B2 · kind B2 · utility

Assignee

• JFE Steel Corporation · JP

Inventors

• Yoshitsugu Suzuki · Tokyo, JP
• Mai Miyata · Tokyo, JP
• Yoichi Makimizu · Fukuyama, JP

Key dates

• Filing date: Sep 20, 2012
• Grant date: Dec 9, 2014
• Expiry date: Sep 20, 2032

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10T428/27
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

A galvannealed steel sheet having high corrosion resistance after painting includes, on a mass percent basis, C: 0.05% to 0.15%, Si: 0.1% to 1.0%, Mn: 0.5% to 2.7%, Al: ≦1.00%, P: ≦0.025%, S: ≦0.025%, and Cr: 0% to 0.8% as chemical components, the remainder being Fe and incidental impurities. The galvannealed steel sheet includes a galvannealed layer in an amount of 20 to 120 g/m2 per side, a percentage of exposed zinc metal of the galvannealed layer surface being 20% or more and less than 80%, and an amount of internal oxidation in a region disposed not more than 5 μm from the surface of the steel sheet is 0.02 g/m2 or more and 0.1 g/m2 or less: Si≦0.68%, Cr≦−1.25Si+0.85, and Si>0.68%, Cr=0, wherein Si and Cr denote respective contents (mass %) of Si and Cr.