| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a high-tensile strength hot-dip galvanized steel sheet excellent in surface plating quality and having a tensile strength of 590 MPa or more. <P>SOLUTION: The steel raw material having the composition containing 0.03-0.20% C, 0.5-1.8% Si, 1.5-3.5% Mn, 0.1% or less P, 0.01% or less S, 0.02-0.1% Al and 0.005% or less N, by mass%, is subjected to hot-rolling comprising rough rolling and finish rolling to obtain a hot-rolled steel sheet. The hot-rolled steel sheet is wound up at the temperature within the range of 540-640°C, and then, pickling treatment having an amount of dissolution of 80-200 g/m<SP POS="POST">2</SP>is applied. Thereafter, cold rolling, annealing treatment, and hot dip galvanizing treatment are applied to make the hot-dip galvanized steel. In this way, reduction of cold rollability can be prevented, a cold rolled steel sheet can be manufactured, and an intergranular corrosion layer causing surface plating defect, such as poor plating and black stain, can be removed. Thus, the high-tensile strength hot-dip galvanized steel sheet having excellent surface plating quality can be easily and stably manufactured. <P>COPYRIGHT: (C)2012,JPO&INPIT |
