SURFACE-TREATED STEEL PLATE OF EXCELLENT MACHINABILITY AND CORROSION RESISTANCE OF MACHINED PART, AND MANUFACTURING METHOD THEREOF

摘要

PROBLEM TO BE SOLVED: To provide a non-chromate surface-treated steel plate exhibiting excellent machinability and corrosion resistance of machined part in which an Al-Zn hot-dipped steel plate with 20 to 95% Al contained in a plating film constitutes a base steel plate. SOLUTION: The plating film is obtained through a heat history in which a hot-dipping metal is solidified, and the steel plate is heated to a temperature T(°C) in a range between 130 and 300°C, and the mean cooling rate from the temperature T(°C) to 100°C is≤C(°C/hr) expressed by the formula C=(T-100)/2 (1), and/or a heat history in which the mean cooling rate from the temperature T(°C) in a range between 130 and 300°C to 100°C after the hot-dipping metal is solidified is≤C(°C/hr) expressed by the formula (1). A specified non-chromate coating layer is provided on the surface of the plating film. COPYRIGHT: (C)2003,JPO