Nippon Steel Corporation

Takuma Kawanaka

Masahiro Nakata

Satoshi Uchida

Kunio Hayashi

Yuji Yamaguchi

Takafumi Yokoyama

A high-strength hot-dip galvanized steel sheet contains predetermined amounts of C, Si, Mn, P, S, N, O, sol. Al, Ti, and B, 0.1 to 1.5 mass % of Cr+2&#xd7;Mo, and a balance in a form of Fe and inevitable impurities. A steel structure includes, in area %, ferrite: 1 to 50%, martensite: 20 to 70%, residual austenite: 0 to 5%, pearlite: 0 to 5%, MA and cementite having 0.2 &#x3bc;m or more grain size: 0 to 5% in total, and a balance in a form of bainite. A number density of MA or cementite having 0.2 &#x3bc;m or more grain size and isolated in ferrite or bainite grains is 100 pcs/1000 &#x3bc;mor less, and an average hardness of martensite is in a range from 330 to 500 Hv.

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Tokyo, Japan

Takuma Kawanaka