Nippon Steel Nisshin Co., Ltd.

Nippon Steel Corporation

Nisshin Steel Co., Ltd.

Shin Ueno

Tadashi Nakano

Masaya Yamamoto

Hiromasa Shoji

Masanori Matsuno

Atsuo Shimizu

Yoshikatsu Nishida

A surface-treated steel sheet includes: a base steel sheet; a plated layer formed on the base steel sheet and containing 50 mass % or more of Zn and 0.3 mass % or more of Mg; and a chemical conversion coating formed on the plated layer. The chemical conversion coating contains a silicon compound, P and F, and Mg, an average Si concentration of the chemical conversion coating is 10 mass % or more, the chemical conversion coating includes an F—Mg concentrated layer having an Mg concentration of 1.50 mass % or more and 40.00 mass % or less and an F concentration of 0.50 mass % or more and 5.00 mass % or less in a region in contact with an interface between the chemical conversion coating and the plated layer, a thickness of the F—Mg concentrated layer is 1.0 nm or more, and an average Mg concentration is less than 0.50 mass % and an average F concentration is less than 0.50 mass % in a region of the chemical conversion coating excluding the F—Mg concentrated layer.

Surface-treated steel sheet

The purpose of the present invention is to provide a water-based treatment solution which makes it possible to form a chemical-conversion-treated coating film having further improved corrosion resistance. The present invention relates to a water-based treatment solution for a chemical conversion treatment of a steel sheet or a plated steel sheet. The water-based treatment solution contains an organic resin including a fluororesin, a Group-4A metal compound, and at least one binding promoter selected from the group consisting of dimethyl adipate, diethyl adipate, di(iso)propyl adipate, di(iso)butyl adipate, dimethyl phthalate, diethyl phthalate, di(iso)propyl phthalate and di(iso)butyl phthalate.

Water-based treatment solution, chemical conversion treatment method, and chemical-conversion-treated steel sheet

The present invention provides a method for evaluating the quality of steam-treated products, allowing easy, quick and precise evaluation of the quality of oxide films in steam-treated products such as black coated steel sheets. Specifically, the present invention provides a method for evaluating the quality of steam-treated products with a surface oxide film formed during steam treatment, wherein test pieces () are cut out from said steam-treated products to measure the amount of oxygen in said test pieces () as a basis for evaluating the brightness of the surface(s) of said test pieces and/or the thickness of the oxide film of said test pieces.

Method for evaluating the quality of steam-treated products

The purpose of the present invention is to provides a method for manufacturing a black plated steel sheet that is capable of more evenly blackening the area of the plated steel sheet to be blackened. The present invention relates to a method for manufacturing a black plated steel sheet by bringing a plated steel sheet with an Al- and Mg-containing hot-dip galvanized layer into contact with water vapor inside a sealed vessel. This method performs, in the following order: a first step for heating a plated steel sheet disposed inside a sealed vessel in the presence of a gas, the dew point of which is always less than the plated steel sheet temperature; a second step for evacuating the heated ambient gas inside the sealed vessel to make the pressure of the gas inside the sealed vessel to be 70 kPa or less; and a third step for introducing water vapor inside the sealed vessel in which the pressure of the gas therein has been reduced to 70 kPa or less to blacken the galvanized layer.

Method for manufacturing black plated steel sheet, apparatus for manufacturing black plated steel sheet, and system for manufacturing black plated steel sheet

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Osaka, Japan

Shin Ueno