Posco

Dong-Seoug Sin

Jai-Hyun Kwak

Kyoo-Young Lee

Joo-Hyun Ryu

Min-Seo Koo

Hang-Sik Cho

Se-Don Choo

Provided are a high-strength cold-rolled steel sheet and a hot-dip galvanized steel sheet comprising in % by weight: 0.05 to 0.3% of carbon (C); 0.6 to 2.5% of silicon (Si); 0.01 to 0.5% of aluminum (Al); 1.5 to 3.0% of manganese (Mn); and the remainder being Fe and unavoidable impurities, the steel sheet has a microstructure comprised of, in an area fraction, ferrite in an amount of 60% or less, lath-type bainite of 25% or more, martensite of 5% or more, and lath-type retained austenite in an amount of 5%, wherein the ferrite has an average grain diameter of 2 &#x3bc;m or less and the ferrite satisfies Fn2, defined by relational expression 1, is 89% or more and Fa5, defined by relational expression 2, is 70% or less.

High strength cold-rolled steel sheet and hot-dip galvanized steel sheet having excellent hole expansion, ductility and surface treatment properties, and method for manufacturing same

The present invention relates to: a high-strength steel sheet used for construction materials and transportation means such as vehicles and trains and, more specifically, to a high-strength cold rolled steel sheet having excellent ductility, a hot-dip galvanized steel sheet, and a method for manufacturing the same.

High-strength cold rolled steel sheet having excellent ductility, hot-dip galvanized steel sheet and method for manufacturing same

The present invention relates to a lightweight steel sheet and a method of manufacturing the same, wherein high strength and ductility can be achieved in the lightweight steel sheet even when a small amount of carbon and manganese is added, by preventing loss of austenite due to decarburizing through inhibiting decarburization, which occurs during a heat treatment step of a steel sheet containing austenite.

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Gwangyang-si, South Korea

Dong-Seoug Sin