Jfe Steel Corporation

Seisuke Tsuda

Masaki Koba

Tatsuya Nakagaito

Hiroyuki Masuoka

Takuya Hirashima

Hiromi Yoshitomi

Shotaro Terashima

Yasuhiro Nishimura

Kyoko Naito

Katsuya Hata

Provided is a steel sheet having excellent workability while ensuring excellent strength. The steel sheet comprises: a predetermined chemical composition; and a steel microstructure that contains ferrite: 45% to 90%, martensite: 5% to 30%, bainite: 1% to 25%, and retained austenite: 3% or more and in which [Mn]/[Mn] is 1.00 to 1.15 and [Mn]/[Mn]is 1.00 to 1.30, wherein TS×El is 16000 MPa·% or more.

Steel sheet and production method therefor

Provided are a high-yield-ratio high-strength galvanized steel sheet and a method for manufacturing thereof. The high-yield-ratio high-strength galvanized steel sheet has a steel sheet having a specified chemical composition and a metallographic structure including, in terms of area ratio, in terms of area ratio, 15% or less of ferrite, 20% or more and 50% or less of martensite, and bainite and tempered martensite in a total amount of 30% or more, and a galvanized layer formed on the steel sheet having a coating weight of 20 g/mto 120 g/mper side, in which a yield strength ratio is 65% or more, a tensile strength is 950 MPa or more, and Mn oxides are contained in the galvanized layer in an amount of 0.015 g/mto 0.050 g/m.

High-yield-ratio high-strength galvanized steel sheet and method for manufacturing the same

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Tokyo, Japan

Seisuke Tsuda