IRON-ZINC ALLOY PLATED STEEL SHEET HAVING TWO PLATING LAYERS AND EXCELLENT IN PRESS-FORMABILITY AND ELECTROPAINTABILITY AND METHOD FOR MANUFACTURING SAME

摘要

An iron-zinc alloy plated steel sheet having two plating layers and excellent in press-formability and electropaintability, which comprises: a steel sheet; an alloying-treated iron-zinc alloy dip-plating layer as a lower layer formed on at least one surface of the steel sheet; and an iron alloy electroplating layer as an upper layer formed on the alloying-treated iron-zinc alloy dip-plating layer as the lower layer. The alloyingtreated iron-zinc alloy dip-plating layer as the lower layer, which has an iron content of 7 to 15 wt.% and a plating weight of 30 to 120 g/m2 per surface of the steel sheet, is formed by subjecting the steel sheet to a conventional zinc dip-plating treatment followed by a conventional alloying treatment by heating. The iron alloy electroplating layer as the upper layer, which has an iron content of at least 60 wt.%, a content of silica particles of 0.01 to 2 wt.% and a plating weight of 1 to 10 g/? per surface of the steel sheet, is formed by electroplating the steel sheet, on which the alloyingtreated iron-zinc alloy dip-plating layer has been formed, in an iron alloy electroplating bath containing silica particles of 0.1 to 10 g/? and nitric acid ions of 100 to 20,000 ppm.