BR-112023008942-B1 - METAL SHEET WITH SURFACE TREATMENT

Abstract

METAL SHEET WITH SURFACE TREATMENT. This metal sheet with surface treatment comprises: a steel sheet; a galvanizing layer that is formed on the steel sheet and contains zinc; and a coating film that is formed on the galvanizing layer. With respect to this metal sheet with surface treatment, the coating film contains an organosilicon compound, a phosphoric acid compound, and a fluorine compound. Regarding the surface roughness of a 1 μm square area of the coating film surface, if Sa is the arithmetic mean height, Sz is the maximum height, and Sq is the square root of the mean roughness, one or more of the following conditions are satisfied: the arithmetic mean height Sa is from 0.1 nm to 10 nm; the maximum height Sz is from 1 nm to 1000 nm; and the root mean square roughness Sq is from 0.1 nm to 100 nm.

Inventors

• Hiromasa Shoji
• Kohei Ueda
• Satoru Yonetani
• Tomokazu Sugitani
• Nobuki Shiragaki

Assignees

• NIPPON STEEL CORPORATION

Dates

Publication Date

20260317

Application Date

20211111

Priority Date

20201113

Claims (4)

1. 1. Metal sheet with surface treatment (1), comprising: a steel sheet (11); a coating layer (12) containing zinc formed on the steel sheet (11); a conversion coating (13) formed on the coating layer (12), wherein the amount of zinc in the coating layer (12) is 50% by mass or more, characterized in that the conversion coating (13) contains a zirconium compound, a vanadium compound, an organosilicon compound, a phosphate compound and a fluorine compound, wherein, when the average value of F/Si, which is a ratio between the mass of the solid content of F derived from a fluorine compound and the mass of the solid content of Si derived from an organosilicon compound, is from 0.01 to 0.15, wherein, when the average value of Zr/Si, which is a ratio between the mass of the solid content of Zr derived from a zirconium compound and the mass of the solid content of Si derived from an organosilicon compound, is from 0.06 to 0.15, wherein, when the average value of V/Si, which is a ratio between the mass of the content solid V derived from a vanadium compound and the mass of solid Si content derived from an organosilicon compound, is from 0.010 to 0.200, wherein, when the surface roughness in a rectangular area with a side of 1 μm on the surface of the conversion coating (13) is represented by an arithmetic mean height of the scale-limited surface Sa, a maximum height of the scale-limited surface Sz and a quadratic mean height of the scale-limited surface Sq, one or more of an arithmetic mean height of the scale-limited surface Sa being 0.10 to 10.0 nm, a maximum height Sz being 1.0 to 1000 nm and a quadratic mean height r of the scale-limited surface Sq being 0.10 to 100 nm are satisfied.
2. 2. Metal sheet with surface treatment (1) according to claim 1, characterized in that, when the surface roughness in a rectangular area with a side of 5 μm on the surface of the conversion coating (13) is represented by an arithmetic mean height of the surface limited on scale Sa, a maximum height of the surface limited on scale Sz and a quadratic mean height of the surface limited on scale Sq, one or more of an arithmetic mean height of the surface limited on scale Sa being 0.10 to 10.0 nm, a maximum height of the surface limited on scale Sz being 1.0 to 1000 nm and a quadratic mean height of the surface limited on scale Sq being 0.10 to 100 nm are satisfied.
3. 3. Metal sheet with surface treatment (1) according to claim 1 or 2, characterized in that a rectangular area with a side of 1 μm on the surface of the conversion coating (13) contains 1 or more and 100 or less particles of granular organosilicon compound with a major axis of 10 nm or more and 300 nm or less.
4. 4. Metal sheet with surface treatment (1) according to any one of claims 1 to 3, characterized in that the coating layer (12) has an average chemical composition containing, in % by mass, Al: more than 4.0% and less than 25.0%, Mg: more than 1.0% and less than 12.5%, Sn: 0% to 20%, Bi: 0% and less than 5.0%, In: 0% and less than 2.0%, Ca: 0% to 3.0%, Y: 0% to 0.5%, La: 0% and less than 0.5%, Ce: 0% and less than 0.5%, Si: 0% and less than 2.5%, Cr: 0% and less than 0.25%, Ti: 0% and less than 0.25%, Ni: 0% and less than 0.25%, Co: 0% and less than 0.25%, V: 0% and less than 0.25%, Nb: 0% and less than 0.25%, Cu: 0% and less than 0.25%, Mn: 0% and less than 0.25%, Fe: 0% to 5.0%, Sr: 0% and less than 0.5%, Sb: 0% and less than 0.5%, Pb: 0% and less than 0.5%, and B: 0% and less than 0.5%, with the remainder being Zn and impurities.

Description

[Technical Field] [001] The present invention relates to a metal sheet with surface treatment. [002] Priority is claimed in Japanese patent application No. 2020-189316, filed on November 13, 2020, the contents of which are incorporated herein by reference. [Fundamentals of the Technique] [003] Conventionally, the treatment of steel sheets with a coating layer containing zinc with a chromate, such as a hexavalent chromate, in order to prevent rust has been widely carried out, and in order to impart greater resistance to corrosion, resistance to fingerprints, resistance to scratches, lubricity and the like as needed, it is then coated with an organic resin and, in addition, extra coating with various paints is carried out. [004] In recent years, in the context of increasing environmental problems, there has been a movement to avoid chromate treatments. Since the chromate treatment layer itself has advanced corrosion resistance and paint adhesion, these performance aspects are expected to be significantly reduced if this chromate treatment is not carried out. Therefore, it has become necessary to form a rust-preventive layer with favorable corrosion resistance and paint adhesion simply by one-step treatment with an organic resin without performing a base treatment based on a chromate treatment. [005] Patent Document 1 describes a metal surface treatment material with a composite coating containing the respective components obtained by applying a metal surface treatment agent composed of an organosilicon compound, at least one fluorine compound selected from fluorotitanic acid and fluorozironic acid, phosphoric acid, and a vanadium compound to a metal material surface and drying. [006] Patent Document 2 describes a common metal surface treatment material composite coating containing an organosilicon compound, at least one fluorine compound selected from fluorotitanic acid and fluorozironic acid, phosphoric acid, a vanadium compound, and a lubricant that is at least one selected from the group consisting of an aqueous dispersion of polyethylene wax, polypropylene wax and polytetrafluoroethylene, and has an average particle size of 0.01 μm to 1.0 μm and a softening temperature of 100°C or higher on a metal surface. [007] Patent Document 3 describes a chromate-free surface-treated metal material with a conversion coating formed by applying an aqueous treatment agent containing an organosilicon compound and an organofluorine compound with a perfluoroalkyl group to the surface of a metal material, and drying or baking. [008] Patent Document 4 describes a metal material with a surface treatment with a composite coating containing an organosilicon compound as a film-forming component, at least one metal compound selected from the group consisting of titanium compounds and zirconium compounds, a phosphate compound and a fluorine compound as inhibitor components, and wherein an abundance ratio of cyclic siloxane bonds and chain siloxane bonds in the organosilicon compound is 1.0 to 2.0 as a W1/W2 ratio of absorbance W1 at 1090 to 1100 cm-1 indicating a cyclic siloxane bond and absorbance W2 at 1030 to 1040 cm-1 indicating a chain siloxane bond according to an FT-IR reflection method on the surface of a metal material. [Citation List] [Patent Document] [Patent Document 1] [009] Japanese patent no. 4776458 [Patent Document 2] [0010] Japanese patent no. 5335434 [Patent Document 3] [0011] Japanese patent no. 4709942 [Patent Document 4] [0012] Japanese patent no. 5336002 [Summary of the Invention] [Problems to be solved by the invention] [0013] Incidentally, the lubricity performance of a galvanized steel sheet on which a conversion coating is formed by a chemical conversion treatment is determined by the conversion coating on the outermost surface. Lubricity is evaluated by factors such as a dynamic coefficient of friction on the surface of the conversion coating. When a conventional chromate coating is replaced by a non-chromate coating, a non-chromate replacement coating is required to have a lubricity level equivalent to that of the chromate coating. If the lubricity of the non-chromate coating is reduced, when a plurality of coated steel sheets are stacked flat, load collapse is more likely to occur, which was not a problem with the chromate coating. Furthermore, if the lubricity of the non-chromate coating differs from the lubricity of the chromate coating, for example, when rolling is performed on the coated steel sheet, it is necessary to readjust the processing adjustment conditions. However, so far there have been no attempts to approximate the lubricity of a non-chromate coating to the lubricity of a chromate coating. [0014] The present invention was made in view of the above circumstances and an objective of the present invention is to provide a metal sheet with a surface treatment with a conversion coating that has a level of lubricity equivalent to that of a conventional chromate coating and has excellent corro