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AssigneeNKK Corporation
InventorsToshihiko Ooi, Takafumi Yamaji, Keiji Yoshida, Yuichiro Tanaka, Junichi Inagaki, Masaaki Yamashita, Yasuhiro Majima, Nobuyuki Ishida, Yuichi Fukushima, Norio Inoue, Shinji Hori
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The method for manufacturing coated steel sheet has the steps of: immersing a steel sheet in a hot-dip coating bath to form an Al—Zn base coating layer containing 20 to 95 mass % Al on the steel sheet, forming a passivated layer on the coating layer; and applying thermal history to the coating layer. The thermal history is applied immediately after the steel sheet left the hot-dip coating bath or in a temperature range of from T(° C.) between 130° C. and 300° C. to 100° C.
In a method for manufacturing a coated steel sheet, comprising the steps of forming an Al—Zn base coating layer containing 20 to 95 mass % Al on a steel sheet by immersing the steel sheet in a hot-dip coating bath, and forming a passivated layer on the coating layer,
A coated steel sheet having an Al—Zn base coating layer containing 20 to 95 mass % Al and a passivated layer formed on the coating layer, the coating layer being subjected to a first thermal history of less than 11° C./sec of an average cooling rate during the first 10 seconds after the steel sheet left a hot-dip coating bath, and to a second thermal history of 0.5×(T−100)(° C./hr) or less of average cooling rate in a temperature range of from T(° C.) between 130° C. and 300° C. to 100° C.
Dependencies are inferred from the claim text.