Nippon Steel Corporation

Nippon Steel Sumitomo Metal Corporation

Ryosuke Komami

Hiroyuki Kawata

Satoshi Uchida

Yuji Yamaguchi

Takeshi Yasui

Naoki Maruyama

Kohei Ueda

Toyomitsu Nakamura

Hayato Arai

Akinobu Murasato

Yasuhiro Nakashima

A hot-dip galvanized steel sheet includes a base steel sheet and a hot-dip galvanized layer formed on at least one surface of the base steel sheet, in which the hot-dip galvanized layer includes Fe in a content of more than 0% to 5% or less, Al in a content of more than 0% to 1.0% or less, and columnar grains formed by a &#x3b6; phase on the surface of the steel sheet, further, 20% or more of the entire interface between the hot-dip galvanized layer and the base steel sheet is coated with the &#x3b6; phase, and a ratio of an interface formed between &#x3b6; grains in which coarse oxides are present among grains and the base steel sheet with respect to the entire interface between the &#x3b6; phase and the base steel sheet in the hot-dip galvanized layer is 50% or less, the base steel sheet has predetermined chemical components and a refined layer in direct contact with the interface between the base steel sheet and the hot-dip galvanized layer, an average thickness of the refined layer is 0.1 to 5.0 &#x3bc;m, an average grain size of ferrite in the refined layer is 0.1 to 3.0 &#x3bc;m, one or two or more of oxides of Si and Mn are contained in the refined layer, and a maximum size of the oxide is 0.01 to 0.4 &#x3bc;m, and a volume fraction of residual austenite in a range of &#x215b; thickness to &#x215c; thickness centered at a position of &#xbc; thickness from the surface of the base steel sheet is 1% or more.

Hot-dip galvanized steel sheet

A hot-dip galvanized steel sheet includes a base steel sheet and a hot-dip galvanized layer formed on at least one surface of the base steel sheet, in which the hot-dip galvanized layer includes Fe in a content of more than 0% to 5% or less, Al in a content of more than 0% to 1.0% or less, and columnar grains formed by a &#x3b6; phase on the surface of the steel sheet, further, 20% or more of the entire interface between the hot-dip galvanized layer and the base steel sheet is coated with the &#x3b6; phase, and a ratio of an interface formed between &#x3b6; grains in which coarse oxides are present among &#x3b6; grains and the base steel sheet with respect to the entire interface between the &#x3b6; phase and the base steel sheet in the hot-dip galvanized layer is 50% or less, the base steel sheet has predetermined chemical components and a refined layer in direct contact with the interface between the base steel sheet and the hot-dip galvanized layer, an average thickness of the refined layer is 0.1 to 5.0 &#x3bc;m, an average grain size of ferrite in the refined layer is 0.1 to 3.0 &#x3bc;m, one or two or more of oxides of Si and Mn are contained in the refined layer, and a maximum size of the oxide is 0.01 to 0.4 &#x3bc;m.

A high-strength hot-dip galvanized steel sheet excellent in impact resistance and worked portion corrosion resistance including a hot-dip galvanized plating layer on a steel sheet base material whose tensile strength is 590 MPa or more, wherein the plating layer includes projecting alloy layers being in contact with the steel sheet base material, a number density of the projecting alloy layers is 4 pieces/mm or more, wherein the steel sheet base material includes: a miniaturized layer being directly in contact with the interface between the steel sheet base material and the plating layer; a decarburized layer being in contact with the miniaturized layer; and an inner layer other than the miniaturized layer and the decarburized layer, and one or more kinds of oxides of Si and Mn are contained in layers of the miniaturized layer, the decarburized layer, and the projecting alloy layers.

High-strength hot-dip galvanized steel sheet excellent in impact peeling resistance and worked portion corrosion resistance

A hot-dip galvanized steel sheet wherein the hot-dip galvanized steel sheet comprises a base steel sheet and a hot-dip galvanized layer, a ferrite phase is, by volume fraction, 40% or more and 97% or less in a range of &#x215b; thickness to &#x215c; thickness centered at a position of &#xbc; thickness from the surface of the base steel sheet, a hard structure is 3% or more in total, wherein the hot-dip galvanized steel sheet has the hot-dip galvanized layer in which Fe is 5.0% or less and Al is 1.0% or less, and columnar grains formed of a &#x3b6; phase is 20% or more in an entire interface between the plated layer and the base steel sheet on the surface of the base steel sheet in which a ratio of a volume fraction of the hard structure in a surface layer range of 20 &#x3bc;m depth in a steel sheet direction from an interface between the hot-dip galvanized layer and the base steel sheet is 0.10 times or more to 0.90 times or less of a volume fraction of the hard structure in the range of &#x215b; thickness to &#x215c; thickness, and wherein the hot-dip galvanized steel sheet has a refined layer at the side of the interface in the base steel sheet, and wherein an average thickness of the refined layer, an average grain size of ferrite in the refined layer and a maximum size of the oxide included in the refined layer are defined respectively.

A hot-dip galvanized steel sheet having a base steel sheet and a hot-dip galvanized layer, a ferrite phase is, by volume fraction, 50% or less in a range of &#x215b; thickness to &#x215c; thickness centered at a position of &#xbc; thickness from the surface of the base steel sheet, a hard structure is 50% or more, wherein the hot-dip galvanized steel sheet has the hot-dip galvanized layer in which Fe is 5.0% or less and Al is 1.0% or less, and columnar grains formed of a &#x3b6; phase is 20% or more in an entire interface between the plated layer and the base steel sheet. On the surface of the base steel sheet, a volume fraction of a residual austenite is 3% or less.

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Kimitsu, Japan

Ryosuke Komami