| 摘要 |
PROBLEM TO BE SOLVED: To provide a hot-dip Zn-Al-Mg-Si-plated steel sheet which has superior surface appearance with few black spots, and to provide a manufacturing method therefor. SOLUTION: The method for manufacturing the hot-dip Zn-Al-Mg-Si-plated steel sheet comprises the steps of: reducing a base steel sheet while heating it; cooling it; hot-dipping it in a bath including 2.8% or more Mg, 10.5% or more Al, 0.01-0.5% Si and the balance Zn with unavoidable components; adjusting a coating mass of the plated layer on the steel sheet appearing from a hot dipping pot, with a gas wiping technique; and cooling and solidifying the plated layer in a molten state at a cooling rate of 10°C/s or higher in a temperature range of 340±10°C and at a cooling rate of 7°C/s or lower in a temperature range of 330 to 310°C. Thus obtained steel sheet has a Zn-alloy-plated layer of which the X-ray intensity ratio of Mg<SB>2</SB>Zn<SB>11</SB>/MgZn<SB>2</SB>is 0.5 or lower, and shows a uniform appearance. COPYRIGHT: (C)2006,JPO&NCIPI
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