HIGH STRENGTH THIN STEEL SHEET, HIGH STRENGTH GALVANNEALED STEEL SHEET AND MANUFACTURING METHOD THEREOF

摘要

A high strength thin steel sheet which comprises 0.01 to 0.20 wt % of C, 1.0 wt % or less of Si, 1.0 to 3.0 wt % of Mn, 0.10 wt % or less of P, 0.05 wt % or less of S, 0.10 wt % or less of Al, 0.010 wt % or less of N, 1.0 wt % or less of Cr, and 0.001 to 1.00 wt % of Mo, the residue of the sheet being comprised of Fe and obligatory impurities, and has a band structure consisting of two layers and having a thickness satisfying the relationship: Tb/T0.005, wherein Tb represents a mean thickness of the band structure in the thickness direction of the sheet and T represents a thickness of the sheet, and a method for producing the steel sheet; and a high strength hot-dip zinc-coated steel sheet or a high strength alloyed hot-dip zinc-coated steel sheet which is produced by subjecting the high strength thin steel sheet to zinc plating or alloying and zinc plating. The above high strength thin steel sheet is excellent in workability and capability of being metal-plated, and the above high strength hot-dip zinc-coated steel sheet or high strength alloyed hot-dip zinc-coated steel sheet has excellent workability and strength, and also can be excellent in capability of being metal-plated, intimate contact of a plating and resistance to corrosion.