HIGH-STRENGTH HOT-DIP ZINCED STEEL SHEET EXCELLENT IN MOLDABILITY AND SUITABILITY FOR PLATING, HIGH-STRENGTH ALLOYED HOT-DIP ZINCED STEEL SHEET, AND PROCESSES AND APPARATUS FOR PRODUCING THESE

摘要

A high-strength hot-dip zinced steel sheet excellent in moldability and suitability for plating which comprises a high-strength steel sheet containing, in terms of mass%, 0.05-0.25% C, 0.3-2.5% Si, 1.5-2.8% Mn, up to 0.03% P, up to 0.02% S, 0.005-0.5% Al, and up to 0.0060% N, with the remainder being iron and unavoidable impurities and, formed thereon, a zinc deposit layer containing 0.05-10 mass% Al and 0.05-3 mass% Fe, with the remainder being zinc and unavoidable impurities, characterized in that the crystal grain boundaries and crystal grains in the steel sheet which are located in a part ranging from the interface between the high-strength steel sheet and the deposit layer to a depth of 5 µm have an average content of silicon-containing oxides of 0.6-10 mass% and that an Fe-Zn alloy having an average particle diameter of 0.5-3 µm is present in the deposit layer.