HOT DIP ZN-AL COATED STEEL SHEET HAVING EXCELLENT APPEARANCE, AGE BLACKENING RESISTANCE AND CORROSION RESISTANCE

摘要

PURPOSE: To produce the hot dip Zn-Al coated steel sheet having excellent appearance, age blackening resistance and corrosion resistance by forming hot dip Zn-Al plating films contg. specific ratios of Al and Ti and having the spangle size of the surfaces of a specific value on the steel sheet. ;CONSTITUTION: The plating films of about 100 to 120g/m² per surface of coating weight of plating are formed on the steel sheet by immersing the steel sheet into a hot dip coating bath (about 440°C bath temp.) consisting of 3 to 10wt.% Al, 0.01 to 1wt.% Ti and the balance Zn and inevitable impurities. The cooling rate of the steel sheet is adjusted to about 15 to 100°C/sec during the transition from about 400°C to 380°C to reduce the spangle size on the plating surfaces to ≤0.5mm at the time of cooling the steel sheet. As a result, the hot dip Zn-Al coated steel sheet having the excellent appearance, age blackening resistance and corrosion resistance is obtd.;COPYRIGHT: (C)1994,JPO&Japio