Nisshin Steel Co., Ltd.

Mitsuo Asabuki

Masaya Yamamoto

Hirofumi Taketsu

Shinya Furukawa

Shigeyasu Morikawa

A chemically processed steel sheet comprises a steel base coated with an Al&#x2014;Si alloy plating layer, whose Si content is preferably adjusted to 5&#x2013;13 mass % as a whole and to 7&#x2013;80 mass % at a surface, and a converted layer generated on the surface of the plating layer. The converted layer contains both soluble and scarcely-soluble compounds. The soluble compound, such as a manganese oxide or hydroxide, or a valve metal fluoride, is once dissolved into water in an atmosphere and then re-precipitated as scarcely-soluble compounds at defective parts of the converted layer. The scarcely-soluble compounds act as a barrier for corrosion prevention of a base steel. Due to the re-precipitation, i.e., self-repairing faculty, excellent corrosion resistance of the converted layer is still maintained even after defects are introduced therein during plastic deformation of the steel sheet.

Chemically processed steel sheet excellent in corrosion resistance

A chemically processed steel sheet comprising a steel base coated with an Al&mdash;Si alloy plating layer, whose Si content is preferably adjusted to approximately 5-13 mass % as a whole and to approximately 7-80 mass % at a surface, and a converted layer generated on the surface of the plating layer. The converted layer contains both soluble and scarcely-soluble compounds. The soluble compound such as a manganese oxide or hydroxide or a valve metal fluoride is once dissolved to water in an atmosphere and then re-precipitated as scarcely-soluble compounds at defective parts of the converted layer. The scarcely-soluble compounds act as a barrier for corrosion-prevention of a base steel. Due to the re-precipitation, that is self-repairing faculty, excellent corrosion resistance of the converted layer is still maintained even after defects are introduced therein during plastic deformation of the steel sheet.

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Sakai, Japan

Mitsuo Asabuki