Cold-rolled steel sheet and galvanized steel sheet, which are excellent in formability, panel shapeability, and dent-resistance, and method of manufacturing the same

US6524726B1 · kind B1 · utility

Assignee

• NKK Co., Ltd. · JP

Inventors

• Fusato Kitano · Fukuyama, JP
• Masaya Morita · Tokyo, JP
• Yoshihiro Hosoya · Tokyo, JP
• Takeshi Fujita · Takarazuka, JP
• Tadashi Inoue · Tokyo, JP
• Masahiro Iwabuchi · Nagano, JP
• Takeo Ishii · Toyota, JP

Key dates

• Filing date: Dec 23, 1999
• Grant date: Feb 25, 2003
• Expiry date: Dec 23, 2019

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10T428/12799
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

Disclosed is a cold-rolled steel sheet excellent in formability, panel shapeability and dent-resistance, comprising 0.005 to 0.015% by weight of C, 0.01 to 0.2% by weight of Si, 0.2 to 1.5% by weight of Mn, 0.01 to 0.07% by weight of P, 0.006 to 0.015% by weight of S, 0.01 to 0.08% by weight of sol. Al, not higher than 0.004% by weight of N (N&lE;0.004%), not higher than 0.003% by weight of O (O&lE;0.003%), 0.04 to 0.23% by weight of Nb, 1.0&lE;(Nb %&times;12)/(C %&times;93)&lE;3.0, and a balance of Fe and unavoidable impurities, said cold-rolled steel sheet meeting the relationship given below:exp(&egr;)&times;(5.29&times;exp(&egr;)&#8722;4.19)&lE;&sgr;/&sgr;0.2&lE;exp(&egr;)&times;(5.64&times;exp(&egr;)&#8722;4.49)where 0.002<&egr;&gE;0.096, &egr; represents a true strain, &sgr;0.2 represents a 0.2% proof stress, and &sgr; represents a true stress relative to &egr;.