Hot-dip galvanized steel sheet with zero-spangle having excellent age-flaking resistance, and hot-dip galvanizing process and composition of molten zinc bath therefor
AssigneeNippon Steel Corporation
InventorsYoshio Shindo, Teppei Tamura, Motoo Kabeya, Mitsumasa Nagahisa, Hidejirou Asano
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Abstract
Hot-dip galvanized steel sheet, wherein said coating layer is characterized by being highly resistant to flaking either in a high-temperature humid atmosphere or in long-term indoor aging. The coating comprises 0.1 to less than 0.2 wt % Al, 0.1-0.5 wt % Sb, the remainder being Zn and unavoidable impurities, the total of the unavoidable impurities other than Fe, namely Pb, Cd and Sn being less than 0.02 wt %, the ratio of Sb/Pb being 10-250, and the Al present in the coating layer being in the form of an Al-Sb eutectic.
Claims13
An improved zero-spangle galvanized steel sheet having excellent resistance to age-flaking of its galvanized coating comprising a steel sheet provided at least on one side thereof with a hot-dip galvanized coating of a novel composition consisting of 0.1 to less than 0.2 weight % Al, 0.1-0.5 weight % Sb, unavoidable impurities including Pb, Cd and Sn but not including Fe in a total amount of less than 0.02 weight % and the remainder Zn, the ratio of Sb/Pb in said coating being 10-250, and the Al existing in said coating being present as an Al-Sb eutectic.
An improved hot-dip galvanizing bath comprising 0.1 to less than 0.2 weight % Al, 0.1-0.5 weight % Sb, unavoidable impurities including Pb, Cd and Sn but not including Fe in a total amount of less than 0.2 weight % and the remainder Zn, the ratio of Sb/Pb in said bath being 10-250.
A method for the manufacture of a zero-spangle hot-dip galvanized steel sheet having excellent resistance to an age-flaking of said galvanized coating which comprises the steps of hot-dipping a steel sheet in a hot-dip galvanizing bath consisting of 0.1 to less than 0.2 weight % Al, 0.1-0.5 weight % Sb, unavoidable impurities including Pb, Cd and Sn but not including Fe in a total amount of less than 0.02 weight %, the ratio of Sb/Pb being 10-250, and the remainder Zn, and subsequently processing said hot-dipped steel sheet by a zero-spangled treatment.
Dependencies are inferred from the claim text.