| 摘要 |
PROBLEM TO BE SOLVED: To provide an advantageous manufacturing method of a molten-zinc/aluminum/magnesium alloy plated steel sheet having corrosion resistance and good surface appearance.SOLUTION: In a manufacturing method of a molten-Zn/Al/Mg alloy plated steel sheet, there is prepared a molten-zinc/aluminum/magnesium alloy plating bath containing about 6 mass% of Al, about 3 mass% of Mg, 0.02 mass% of Si, 0.05 mass% of Ti, and 0.01 mass% of B in zinc. A low-carbon cold-rolled steel strip of various thickness is passed through the plating bath to manufacture a molten-zinc/aluminum/magnesium alloy plated steel sheet. The temperature of the plating bath is 430°C and the cooling rate after plating is 7°C/sec. The temperature of the steel sheet at the outlet of an air jet cooler 5 is controlled to be 330°C or lower, which is lower than about 340°C, the solidification point of the plate layer of this composition. The steel sheet is cooled to 230°C or lower immediately before a top roll 6. |
