To provide a high-strength hot-rolled steel sheet having excellent corrosion resistance of coating and bending fatigue characteristics, which has excellent corrosion resistance after coating even when coating on either surface of a surface with mill scale (with scale) or a surface from which the scale is removed, and further allows control on generation of a decarburized layer on a ferrite surface, the cause of failure of bending fatigue characteristics, in steel with high content of Si and Al, and to provide a method for producing the same.
The high-strength hot-rolled steel sheet has component composition containing, in mass%, 0.05-0.25% of C, the total content of Si and Al of 0.8-2.0%, 1.0-4.0% of Mn, the total content of one or two of Ti and Nb of 0.05-0.2%, 0.0003-0.01% of N, 0.001-0.2% of P, and 0.01% or less of S, with the balance comprising Fe and unavoidable impurities, wherein the thickness of the decarburized layer on the ferrite surface is 5 μm or less, average roughness Ra of the ferrite surface is 2.0 μm or less, and the maximum tensile strength is 540 MPa or more.
HONDA KAZUHIKO
TANAKA YUKIMOTO
TANAHASHI HIROYUKI
ITAMI ATSUSHI
KAWADA HIROYUKI
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Shunta Naito
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