Plated steel sheet and method for manufacturing the same

Abstract

This invention provides a coated steel sheet that has low brightness immediately after manufacturing and whose coating layer peeling is suppressed. The coated steel sheet of this invention has a coating layer consisting of 1.0 to 22.0% by mass of aluminum, 1.5 to 10.0% by mass of magnesium, with the remainder being zinc and trace additives that can be added arbitrarily. The surface brightness (L*) of the aforementioned coated steel sheet is 50 or less, and the X-ray diffraction spectrum obtained by X-ray diffraction completely satisfies (1) to (3). (1) A / B series: 0.001 or higher, 0.015 or lower (2) A / C series 1.2 and above (3) Display the half-width d of the peak of A as above 0.30 degrees (deg) and below 1.00 degrees. Additionally, for the A series: displaying the peak intensity of the 100-plane peaks of zinc oxide appearing between 31.27 degrees and 32.27 degrees at 2θ. B series: Displays the peak intensity of the zinc 101 surface peaks occurring between 42.73 degrees and 43.73 degrees with a 2θ value of 42.73 degrees. The strength of the C-series when 2θ is 30.00 degrees.

Description

Technical Field

[0001] The present invention relates to a plated steel sheet and a method for manufacturing the same. Prior Art

[0002] For steel sheets used in building roofing materials or exterior finishing materials, household appliances, automobiles, etc., steel sheets with low apparent brightness (for example, blackening) are required to enhance the designability. For example, the black plated steel sheets described in Patent Document 1 and Patent Document 2 form black oxides by subjecting a zinc plating layer containing molten aluminum and magnesium formed on the surface of the steel sheet to steam treatment, and thus exhibit a black appearance.

[0003] In addition, as described in Patent Document 3, the molten zinc plated steel sheet that has been skin-rolled after plating turns black during storage or transportation. [Prior Art Documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-241665 [Patent Document 2] International Publication No. 2016 / 157665 [Patent Document 3] Japanese Patent Application Laid-Open No. 11-335866 Summary of the Invention Problems to be Solved by the Invention

[0005] Plated steel sheets with low surface brightness as described in Patent Document 1 or Patent Document 2 have been explored for various applications due to their high designability. In addition, as described in Patent Document 3, although the molten zinc plated steel sheet that has been skin-rolled turns black over time, the method of suppressing blackening is explored in this document, and blackening is not desired. In addition, for applications that require designability, it is preferable that the brightness is low from the time when the plated steel sheet is just manufactured.

[0006] Incidentally, it is considered that the brightness of the plated steel sheets described in Patent Document 1 or Patent Document 2 is lowered due to oxides such as zinc oxide formed by steam treatment (refer to Patent Document 2). In addition, since black oxides are also formed inside the plating of the plated steel sheet described in Patent Document 1, a black appearance can be maintained even in the processed parts. On the other hand, in recent years, it has also been required that the plated steel sheet be processed under more severe conditions, and it is required that the oxides formed on the surface are difficult to peel off even under severe processing conditions.

[0007] The present invention is completed in view of this point, and its purpose is to provide a plated steel plate and a method for manufacturing the plated steel plate, wherein the brightness of the plated steel plate is low right after it is manufactured, and the peeling of the coating layer can be suppressed more than before. The means to solve the problem

[0008] One aspect of the present invention for solving the above-mentioned problems relates to the following plated steel sheets [1] to [4]. [1] A plated steel sheet comprising a steel sheet and a plated layer, The coating layer is composed of an aluminum content of 1.0 mass % to 22.0 mass %, a magnesium content of 1.5 mass % to 10.0 mass %, and the remainder is zinc and any trace additives added. The surface brightness (L*) is less than 50, and The X-ray diffraction spectrum obtained by X-ray diffraction of the above-mentioned coating layer using a copper tube at a voltage of 50 kV and a current of 300 mA fully satisfies the following (1) to (3), (1) A / B: 0.001 or more and 0.015 or less (2) A / C ratio 1.2 or above (3) The half width d of the peak of A is greater than 0.30 degrees and less than 1.00 degrees. also, Series A: The peak intensity of the peak of the 100 surface of zinc oxide that appears between 2θ of 31.27 degrees and 32.27 degrees, B series: shows the peak intensity of the peak of zinc 101 surface appearing between 2θ of 42.73 degrees and 43.73 degrees, The intensity at 2θ of C system is 30.00 degrees. [2] The plated steel sheet as described in [1], wherein the plated layer comprises an amorphous phase containing magnesium, zinc and oxygen, and a phase containing a zinc oxide phase. [3] A plated steel sheet as described in [1] or [2], wherein when any 10 cross sections with a length of 15 μm are observed in a direction parallel to the surface of the plated steel sheet, in any cross section, a zinc metal phase or an aluminum metal phase is contained within a range of 1 μm in depth from the surface on the opposite side of the steel sheet. [4] The plated steel sheet as described in any one of [1] to [3], wherein a chemical conversion treatment film is provided on the side of the plated layer opposite to the steel sheet.

[0009] One aspect of the present invention for solving the above problems relates to a method for manufacturing a plated steel sheet described in [5] below. [5] A method for manufacturing a plated steel sheet, comprising the following steps: A step of preparing a material plated steel sheet having a steel sheet and a plating layer, the plating layer being composed of 1.0 mass% or more and 22.0 mass% or less of aluminum, 1.5 mass% or more and 10.0 mass% or less of magnesium, and the remainder being zinc and optionally added trace additives; A step of imparting strain to the aforementioned plating layer, using a skin pass roll having an arithmetic mean surface roughness Ra of 2.1 μm or more and 2.8 μm or less, and performing skin pass rolling under conditions such that the elongation rate of the material plated steel sheet becomes 0.8% or more and 1.3% or less, and the rolling load (tons) becomes 4.0 times or more and 7.0 times or less the product of the plate thickness (mm) and the plate width (m), and A step of subjecting the material plated steel sheet having the plating layer with the aforementioned imparted strain to steam treatment. Effect of the Invention

[0010] According to the present invention, it is possible to provide a plated steel sheet having a low brightness immediately after production and capable of suppressing peeling of the plating layer, and a method for manufacturing the plated steel sheet. Brief Explanation of the Drawings

[0011] FIG. 1A is a cross-sectional STEM bright-field image of an image obtained by photographing a cross-section of a plated steel sheet according to an embodiment of the present invention with a scanning transmission electron microscope (STEM), and FIG. 1B is a schematic diagram showing the zinc metal phase and the aluminum metal phase in FIG. 1A. Embodiment

[0012] 1. Plated Steel Sheet One embodiment of the present invention relates to a plated steel sheet having a steel sheet and a plating layer.

[0013] 1-1. Steel Sheet The type of the steel sheet is not particularly limited, and hot-rolled soft steel sheets and steel strips described in JIS G 3131 (2018), hot-rolled steel sheets and steel strips for automobiles described in JIS G 3131 (2018), cold-rolled steel sheets and steel strips described in JIS G 3134 (2017), and various stainless steel sheets (including Austenite-based, Martensite-based, Ferrite-based, and Ferrite-Martensite two-phase systems) and other various steel sheets can be used.

[0014] 1-2. Plating layer The coating layer is composed of an aluminum content of 1.0 mass % to 22.0 mass %, a magnesium content of 1.5 mass % to 10.0 mass %, and the remainder is zinc and any trace additives added, so-called a zinc-based coating layer containing aluminum and magnesium. In addition, these contents are the ratios of the contents of these elements to the total mass of the coating layer.

[0015] The plated layer may contain any trace additives or unavoidable impurities. Trace additives are elements added to improve the corrosion resistance of the plated layer. Trace additives include tin, bismuth, indium, calcium, yttrium, lanthanum, cerium, silicon, chromium, titanium, nickel, cobalt, vanadium, niobium, copper, manganese, iron, strontium, antimony, lead, boron, lithium, zirconium, molybdenum, tungsten, silver, phosphorus and other elements. The content of these trace additives can be made above the detection limit and below 1% by mass.

[0016] The aluminum in the coating layer is passivated to improve the corrosion resistance of the coated steel sheet and suppress the generation of scum during manufacturing. In addition, when aluminum is present in the coating layer in moderation, it is easy to reduce the brightness of the coating layer by water vapor treatment. When the aluminum content is made to be 1.0 mass % or more, the corrosion resistance of the coated steel sheet can be fully improved, and the generation of scum can be fully suppressed, and the brightness of the coating layer can be easily reduced. When the aluminum content is made to be 22.0 mass % or less, the adhesion of the coating layer can be fully improved, and the sacrificial corrosion protection effect of zinc can be fully exerted, and the brightness of the coating layer can be easily reduced.

[0017] The magnesium in the plating layer can produce dense corrosion products uniformly on the surface of the plating layer in a corrosive environment, prevent corrosion factors from eroding and improve the corrosion resistance of the plated steel sheet. In addition, when magnesium is moderately present in the plating layer, the brightness of the plating layer can be easily reduced by water vapor treatment. When the magnesium content is made to be 1.5% by weight or more, the above-mentioned dense and uniform corrosion products can be fully generated, and the corrosion resistance of the plated steel sheet can be fully improved, and the brightness of the plating layer can be easily reduced. When the magnesium content is made to be 10.0% by weight or less, the sacrificial corrosion protection effect of zinc can be fully exerted, and it is also easy to suppress the generation of scum.

[0018] When the plated steel sheet having the above composition is subjected to a water vapor treatment, oxides such as zinc oxide (ZnO) are formed on the surface and inside of the plated layer, thereby reducing the surface brightness of the plated steel sheet. However, if excessive zinc oxide is formed, the plated layer may peel off due to the peeling of zinc oxide during processing under more severe conditions (for example, 2T bending or processing under more severe conditions). Therefore, based on the following findings, the present inventors have developed a plated steel sheet that is less likely to peel off the plated layer when processed under more severe conditions and that also sufficiently reduces the brightness.

[0019] Generally, zinc oxide is a semiconductor that can transmit visible light because its band gap energy is greater than that of visible light. Therefore, it is a transparent substance, and light diffusely reflects and appears white when observed in powder. In other words, the formation of zinc oxide alone cannot sufficiently reduce the brightness of the plated steel sheet. When the inventors of the present invention studied this point, they found that the degree of blackening of zinc oxide in the plated steel sheet whose brightness was reduced by water vapor treatment can be evaluated by the half width of the peak (near 2θ=31.77 degrees) showing zinc oxide in the X-ray diffraction spectrum. A large half width of the X-ray diffraction spectrum usually indicates that there are many lattice defects in the crystal or the crystal size is small. It can be seen from this that in the plated steel sheet whose brightness is reduced by water vapor treatment, there is zinc oxide with many lattice defects or small crystal size, or both. It can also be considered that due to the effect of the lattice defects or the size of the crystal, an energy level is formed between the band gaps of zinc oxide, and visible light is absorbed by this energy level, thereby reducing the brightness of the plated steel sheet treated with water vapor.

[0020] Based on this knowledge, the inventors of the present invention believe that as long as zinc oxide with more lattice defects or smaller crystal sizes than before is formed, even if the amount of zinc oxide is reduced during processing, the plating layer will not be easily peeled off and the brightness of the plated steel sheet will be sufficiently reduced.

[0021] Specifically, the surface brightness (L*) of the plated steel sheet in this embodiment is 50 or less. By subjecting the plated steel sheet having the above composition to a water vapor treatment, oxides such as zinc oxide (ZnO) can be formed inside the plated layer, and the surface brightness of the plated steel sheet can be reduced. The surface brightness (L*) of the plated steel sheet is preferably 45 or less, and more preferably 40 or less.

[0022] The surface brightness (L* value) of the coating layer was measured using a colorimeter (CR-400 manufactured by Konica Minolta Co., Ltd.) in accordance with the diffuse illumination vertical light receiving method including front reflected light in accordance with JIS Z8722:2009. The illumination diameter during the measurement was set to 11 mmΦ and the measurement diameter was set to 8 mmΦ.

[0023] In addition, the X-ray diffraction spectrum obtained by X-ray diffraction of the coating layer of the plated steel sheet in this embodiment using a copper tube at a voltage of 50 kV and a current of 300 mA fully satisfies the following (1) to (3), (1) A / B: 0.001 or more and 0.015 or less (2) A / C ratio 1.2 or above (3) The half width d of the peak of A is greater than 0.30 degrees and less than 1.00 degrees. also, Series A: The peak intensity of the peak of the 100 face of zinc oxide that appears between 2θ of 31.27 degrees and 32.27 degrees. B series: shows the peak intensity of the peak of zinc 101 surface appearing between 2θ of 42.73 degrees and 43.73 degrees, The intensity at 2θ of C system is 30.00 degrees.

[0024] A series: indicates the peak intensity (unit: cps) at 2θ of 31.77 degrees on the 100 plane of zinc oxide. In addition, B series: indicates the peak intensity (unit: cps) at 2θ of 43.23 degrees on the 101 plane of zinc.

[0025] Regarding condition (1), when A / B is 0.001 or more, it can be said that zinc is oxidized to form a sufficient amount of zinc oxide. In addition, when A / B is 0.015 or less, since excessive zinc oxide is not formed, it is difficult for the plating layer to be peeled off during processing due to the peeling of zinc oxide. From the viewpoint of such a balance, A / B is preferably 0.001 or more and 0.012 or less, more preferably 0.001 or more and 0.011 or less, and even more preferably 0.001 or more and 0.008 or less.

[0026] Regarding condition (2), when A / C is 1.2 or more, it can be said that a sufficient amount of zinc oxide has been formed. From the viewpoint of preventing the plating layer from peeling off during processing due to the peeling off of zinc oxide, the upper limit of A / C is preferably 3.5 or less. From the viewpoint of achieving such a balance, A / C is preferably 1.5 or more and 3.0 or less, and more preferably 1.5 or more and 2.7 or less.

[0027] Regarding condition (3), when the half width d of the peak showing A (100° of zinc oxide) is 0.30°, it can be said that a large number of lattice defects have been generated or fine zinc oxide has been formed. When the half width d is 1.00° or less, it can be said that a peak that is too wide has not been formed and a sufficient amount of zinc oxide has been formed. From the viewpoint of achieving such a balance, the half width d is preferably 0.40 to 0.90, and more preferably 0.50 to 0.80.

[0028] Thus, in this embodiment, since an appropriate amount of zinc oxide is formed and the lattice defects of the zinc oxide are increased or the crystal size of the zinc oxide is reduced (i.e., the half width d is increased), even a small amount of zinc oxide can sufficiently reduce the brightness of the plating layer. Therefore, by appropriately controlling the amount of zinc oxide, it is also possible to suppress the peeling of the plating layer during processing due to the peeling of zinc oxide.

[0029] The coating layer preferably has an amorphous phase containing magnesium, zinc and oxygen and a zinc oxide phase. The amorphous phase is a phase formed by the MgZn2 phase existing in the coating layer before the water vapor treatment and is modified by the water vapor treatment. The MgZn2 phase is oxidized (blackened) earlier. Therefore, when the plated steel sheet containing the MgZn2 phase is subjected to the water vapor treatment, a low-brightness plated steel sheet can be produced in a short time. In addition, the MgZn2 phase is relatively uniformly distributed in the entire coating layer. Therefore, when the plated steel sheet containing the MgZn2 phase is subjected to the water vapor treatment, a plated steel sheet with less uneven brightness can be obtained.

[0030] FIG. 1A is a cross-sectional STEM image of the plated steel sheet of the present embodiment taken by a scanning transmission electron microscope (STEM), and FIG. 1B is a schematic diagram showing the zinc metal phase and the aluminum metal phase in FIG. 1A (In addition, in the cross-sectional STEM bright field image, since objects with large atomic weight appear dark, the actual cross-sectional color tone of the cross section cannot be reflected in FIG. 1A ). The plated steel sheet of the present embodiment can sufficiently reduce the brightness of the plated layer even if the water vapor treatment time is shortened. Therefore, as shown in FIG. 1A and FIG. 1B , the plated layer can contain an unoxidized zinc metal phase or an aluminum metal phase. In the present embodiment, since the efficiency of reducing the brightness is increased by increasing the lattice defects of zinc oxide or reducing the crystal size of zinc oxide, the brightness (L*) of the surface of the plated layer becomes extremely low even if an unoxidized zinc metal phase or an aluminum metal phase exists near the plated surface layer. In addition, when the plated layer contains a predetermined amount of zinc metal phase or aluminum metal phase, since these phases are softer than zinc oxide, it is difficult to peel off the plated layer during processing.

[0031] At this time, from the viewpoint of ensuring the peeling resistance of the plated layer in the processed portion, it is preferred that the zinc metal phase and the aluminum metal phase are uniformly distributed on the surface of the plated layer. Specifically, when a cross section with a length of 15 μm is observed at any 10 locations in a direction parallel to the surface of the plated steel sheet, the plated layer contains a zinc metal phase or an aluminum metal phase within a depth of 1 μm from the surface on the opposite side of the steel sheet in any cross section.

[0032] The zinc metal phase or aluminum metal phase contained in the plating layer is measured by the Cryo FIB-μ sampling method from the average point on the surface of the plated steel sheet using a focused ion beam device. In the obtained cross section, an observation range with a width of 15μm is set along the surface of the plated steel sheet, and this observation range is observed by a transmission electron microscope (TEM), and the phase of the plated surface layer is identified by elemental analysis and electron diffraction analysis using energy dispersive X-ray spectroscopy (EDS). Then, a judgment range with a depth of 1μm is set along the surface of the plated layer to determine whether the zinc metal phase or aluminum metal phase is contained in this judgment range. In addition, the surface of the plated layer is usually not linear, but has an irregular concave-convex shape. Therefore, a judgment range with a depth of 1μm is determined along this concave-convex shape. 10 average points on the surface of the plated steel sheet are arbitrarily set, and the cross section is observed to determine whether the zinc metal phase or aluminum metal phase exists.

[0033] The average film thickness of the coating layer is preferably 3 μm or more and 100 μm or less. The larger the average film thickness of the coating layer, the less likely it is that scratches generated during processing will reach the steel sheet, thereby improving the appearance retention and corrosion resistance. The smaller the average film thickness of the coating layer, the more it can suppress the peeling of the coating layer during processing due to the difference in ductility between the steel sheet and the coating layer.

[0034] 1-3. Chemical conversion treatment membrane The plated steel sheet may also have a chemical conversion film on the outer side (the opposite side of the steel sheet). The chemical conversion film can improve the adhesion between the zinc-based plated layer and the primer film and the corrosion resistance of the steel sheet. The type of chemical conversion film is not particularly limited, and it can be made into a layer formed by a known chemical conversion treatment such as chromate treatment, chromate-free treatment and phosphate treatment. Among these layers, a chromate-free chemical conversion film formed by a chromate-free treatment is preferred.

[0035] The chromate-free chemical conversion film can be made into a layer containing, for example, an adhesive resin, a silane coupling agent, a zirconium compound, silicon dioxide, phosphoric acid or its salt, a fluoride, a valve metal compound, and an organic acid. The chemical conversion film containing these materials can easily improve the adhesion with the zinc-based plating layer and has a relatively high barrier property (density) to corrosion factors such as moisture or corrosive ions, so it is easy to improve the corrosion resistance of the plated steel sheet.

[0036] The type of binder resin is not particularly limited, and known organic resins such as polyester resin, polyurethane resin, epoxy resin, phenol resin, acrylic resin and polyolefin resin can be used. From the viewpoint of improving the adhesion with the zinc-based plating layer, it is preferred to use polyester resin, polyurethane resin, epoxy resin and acrylic resin having a polar part or polar functional group in the molecular chain. These resins can be used alone or in combination of two or more.

[0037] The content of the binder resin relative to the total mass of the chemical conversion treatment film is preferably 1 mass % to 85 mass %, more preferably 1 mass % to 60 mass %, and even more preferably 1 mass % to 40 mass %.

[0038] The valve metal compound is a compound containing one or more compounds selected from the group consisting of vanadium, niobium, tantalum and tungsten. Among them, vanadium and niobium are preferred. The valve metal compound helps to improve the corrosion resistance of the chemical conversion treated steel sheet or suppress excessive gloss in the chemical conversion treated steel sheet. Examples of the valve metal compound may include oxides, hydroxides and fluorides of the above valve metals.

[0039] The content of the valve metal compound in the chemical conversion treatment film is preferably 0.005 to 2.0 mass % when converted to valve metal from the viewpoint of improving corrosion resistance.

[0040] Examples of phosphoric acid or its salt include phosphoric acids such as orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, triphosphoric acid and tetraphosphoric acid or their salts (e.g., ammonium salts such as triammonium phosphate and diammonium hydrogen phosphate), phosphonic acids such as aminotris(methylenephosphonic acid), 1-hydroxyethylidene-1,1-diphosphonic acid, ethylenediaminetetra(methylenephosphonic acid) and diethylenetriaminepenta(methylenephosphonic acid) or their salts, and organic phosphoric acids such as phytic acid or their salts. In addition to ammonium salts, metal salts of sodium, magnesium, aluminum, potassium, calcium, manganese, nickel, zinc and iron may be used as the salt. These phosphoric acids or their salts may be used alone or in combination of two or more.

[0041] The content of phosphoric acid or its salt is preferably 1% by mass or more and 20% by mass or less, and more preferably 1% by mass or more and 10% by mass or less, relative to the total mass of the chemical conversion film. By making the above range, the adhesion between the chemical conversion film and the zinc-based plating layer can be further improved, and the corrosion resistance of the plated steel sheet can be further improved.

[0042] Examples of organic acids include tartaric acid, tannic acid, citric acid, oxalic acid, malonic acid, lactic acid, acetic acid, and ascorbic acid.

[0043] In the chemical conversion solution for forming the chemical conversion treatment film, the amount of organic acid added can be set to be 2 g / L or more and 80 g / L or less. By setting it within the above range, the adhesion between the chemical conversion film and the zinc-based plating layer can be further improved, and the corrosion resistance of the plated steel sheet can be further improved.

[0044] Silane coupling agents and zirconium compounds form cross-linked structures in the chemical conversion film, which can improve the adhesion between the chemical conversion film and the zinc-based plating layer, improve the barrier properties, and further improve the corrosion resistance of the plated steel sheet. In addition, silicon dioxide, phosphoric acid or its salt, fluoride, and vanadium compounds act as inhibitors to form a precipitation film or a passivation film, which can further improve the corrosion resistance of the plated steel sheet.

[0045] Examples of silane coupling agents include γ-(2-aminoethyl)aminopropyl trimethoxysilane, γ-(2-aminoethyl)aminopropyl methyl dimethoxysilane, γ-(2-aminoethyl)aminopropyl triethoxysilane, γ-(2-aminoethyl)aminopropyl methyl diethoxysilane, γ-(2-aminoethyl)aminopropyl methyl dimethoxysilane, γ-methacryloxypropyl trimethoxysilane, γ-methacryloxypropyl methyl dimethoxysilane, γ-methacryloxypropyl triethoxysilane, γ-methacryloxypropyl methyl diethoxysilane, N-β-(N-ethylene) N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(N-vinylbenzylaminoethyl)-γ-aminopropylmethyldimethoxysilane, N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltriethoxysilane, N-β-(N-vinylbenzylaminoethyl)-γ-aminopropylmethyldiethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-thiolpropyltrimethoxysilane, γ-thio Alkylpropyl methyl dimethoxysilane, γ-mercaptopropyl triethoxysilane, γ-mercaptopropyl methyl diethoxysilane, methyl trimethoxysilane, dimethyl dimethoxysilane, methyl triethoxysilane, dimethyl diethoxysilane, vinyl triethoxysilane, γ-chloropropyl trimethoxysilane, γ-chloropropyl methyl dimethoxysilane, γ-chloropropyl triethoxysilane, γ-chloropropyl methyl diethoxysilane, hexamethyldisilazane, γ-anilinopropyl trimethoxysilane, γ-anilinopropyl methyl dimethoxysilane, γ-anilinopropyl triethoxysilane, γ-anilinopropyl methyl diethoxy Silane coupling agents include vinyl trimethoxysilane, vinyl methyl dimethoxysilane, vinyl triethoxysilane, vinyl methyl diethoxysilane, octadecyl dimethyl [3-(trimethoxysilyl) propyl] ammonium chloride, octadecyl dimethyl [3-(methyl dimethoxysilyl) propyl] ammonium chloride, octadecyl dimethyl [3-(triethoxysilyl) propyl] ammonium chloride, octadecyl dimethyl [3-(methyl diethoxysilyl) propyl] ammonium chloride, γ-chloropropyl methyl dimethoxysilane, γ-mercaptopropyl methyl dimethoxysilane, methyl trichlorosilane, dimethyl dichlorosilane and trimethyl chlorosilane. These silane coupling agents may be used alone or in combination of two or more.

[0046] In the chemical conversion treatment liquid for forming the chemical conversion treatment film, the amount of the silane coupling agent added can be set to be 2 g / L or more and 80 g / L or less. When it is set to the above range, the adhesion between the chemical conversion treatment film and the zinc-based plating layer can be further improved, and the corrosion resistance of the plated steel sheet can be further improved.

[0047] Examples of zirconium compounds include zirconium propionate, zirconium butyrate, zirconium tetraacetylacetonate, zirconium monoacetylacetonate, zirconium diacetylacetonate, zirconium monoethylacetylacetonate, zirconium acetylacetonate diethylacetylacetate, zirconium acetate, zirconium monostearate, zirconium carbonate, ammonium zirconium carbonate, potassium zirconium carbonate, and sodium zirconium carbonate. These zirconium compounds may be used alone or in combination of two or more.

[0048] In the chemical conversion treatment liquid for forming the chemical conversion treatment film, the amount of zirconium compound added can be set to be 2 g / L or more and 80 g / L or less. When it is set to the above range, the adhesion between the chemical conversion treatment film and the zinc-based plating layer can be further improved, and the corrosion resistance of the plated steel sheet can be further improved.

[0049] As the silicon dioxide, commercially available silicon dioxide and powdered silicon dioxide can be widely used.

[0050] In the chemical conversion treatment liquid for forming the chemical conversion treatment film, the amount of silicon dioxide added can be set to be 1 g / L or more and 40 g / L or less. When it is set to be within the above range, the corrosion resistance of the plated steel sheet can be further improved.

[0051] Examples of fluorides include ammonium hexafluorozirconate, ammonium silicofluoride, ammonium titanate, sodium fluoride, potassium fluoride, calcium fluoride, lithium fluoride, hydrofluoric titanate, and hydrofluoric zirconate. These fluorides may be used alone or in combination of two or more.

[0052] The content of fluoride is preferably 1% by mass to 20% by mass, and more preferably 1% by mass to 10% by mass, relative to the total mass of the chemical conversion film. When the content is within the above range, the adhesion between the chemical conversion film and the zinc-based plating layer can be further improved, and the corrosion resistance of the plated steel sheet can be further improved.

[0053] Examples of vanadium compounds include vanadium pentoxide, metavanadic acid, ammonium metavanadate, sodium metavanadate, and vanadium trichloride, which are reduced to divalent to tetravalent vanadium compounds by a reducing agent, and vanadium trioxide, vanadium dioxide, vanadium sulfate, vanadium oxalate, vanadium acetylacetonate, vanadium acetylacetonate, vanadium trichloride, phosphovanadomolybdic acid, vanadium sulfate, vanadium dichloride, vanadium oxide, and the like. These vanadium compounds may be used alone or in combination of two or more.

[0054] The content of the vanadium compound relative to the total mass of the chemical conversion film is preferably 1 mass % to 20 mass %, and more preferably 1 mass % to 10 mass %. When the above range is made, the adhesion between the chemical conversion film and the zinc-based plating layer can be further improved, and the corrosion resistance of the plated steel sheet can be further improved.

[0055] The adhesion amount of the chemical conversion treatment film is preferably 10 mg / m2 to 1,000 mg / m2, more preferably 20 mg / m2 to 800 mg / m2, and even more preferably 50 mg / m2 to 600 mg / m2. In addition, the adhesion amount of the inorganic chemical conversion treatment film without adhesive resin, when converted into the adhesion amount of valve metal, is preferably 20 mg / m2 to 100 mg / m2, and more preferably 40 mg / m2 to 80 mg / m2. In addition, the adhesion amount of the organic chemical conversion treatment film containing adhesive resin is preferably 0.3 μm to 2.5 μm in thickness, and more preferably 0.8 μm to 1.5 μm.

[0056] The chemical conversion treatment film is formed by applying a chemical conversion treatment solution containing the above-mentioned components on the surface of the zinc-based plated layer and drying it. In addition, the chemical conversion treatment solution may contain an acid and an alkali for adjusting the pH.

[0057] 2. Method for manufacturing plated steel sheet An example of a method for producing the above-mentioned plated steel sheet is the following method: preparing a material plated steel sheet having a steel sheet, and a coating layer having an aluminum content of not less than 1.0 mass % and not more than 22.0 mass %, a magnesium content of not less than 1.5 mass % and not more than 10.0 mass %, and the remainder being zinc and any trace additives added (hereinafter, the prepared plated steel sheet before steam treatment will be referred to as "material plated steel sheet"), imparting strain to the coating layer of the material plated steel sheet, and performing steam treatment on the material plated steel sheet having the strained coating layer.

[0058] 2-1. Preparation of materials: Plated steel sheet First, a raw plated steel sheet is prepared. The raw plated steel sheet may be prepared by forming a plated layer having the above composition on a steel sheet, or by purchasing a raw plated steel sheet having the above plated layer on the surface of the steel sheet.

[0059] The method for forming the coating layer is not limited, and for example, the coating layer can be formed by a hot-dip coating method in which the steel sheet is immersed in a coating bath composed of an aluminum content of 1.0 mass % to 22.0 mass %, a magnesium content of 1.5 mass % to 10.0 mass %, and the remainder is zinc and any trace additives added, and then drawn out and cooled. At this time, the average film thickness of the coating layer can be adjusted by changing the immersion time or the gas volume and pressure blown in during cooling.

[0060] Before the steel sheet is immersed in the plating bath, it may be subjected to pre-treatment such as cleaning and degreasing as required.

[0061] 2-2. Apply strain Strain can be imparted to the material by rolling the plated steel sheet, etc.

[0062] The rolling method is not particularly limited, and for example, a method of applying pressure to the material plated steel sheet by passing the material plated steel sheet between relatively rotating skin pass rolls can be used.

[0063] In this embodiment, the surface roughness of the skin-pass roller is preferably greater than 2.1 μm and less than 2.8 μm, and more preferably greater than 2.3 μm and less than 2.6 μm. When the surface roughness Ra of the skin-pass roller is greater than 2.1 μm, sufficient strain can be formed to generate zinc oxide with more lattice defects or smaller crystal size. When the surface arithmetic mean roughness Ra of the skin-pass roller is less than 2.8 μm, the reduction in the design of the plated steel sheet due to excessive unevenness of the plated surface can be suppressed.

[0064] In addition, the elongation of the plated steel sheet after the skin-pass rolling is preferably 0.8% to 1.3%, and more preferably 0.8% to 1.1%. When the elongation of the plated steel sheet after the skin-pass rolling is 0.8% or more, sufficient strain can be formed to generate zinc oxide with more lattice defects or smaller crystal size. When the elongation of the plated steel sheet after the skin-pass rolling is 1.3% or less, the decrease in the adhesion of the coating layer due to the generation of excessive zinc oxide can be suppressed.

[0065] Furthermore, the rolling load (ton) during skin-pass rolling is preferably 4 times or more and 7 times or less of the product of the plate thickness (mm) and the plate width (m). The load during skin-pass rolling is greater as the thickness of the rolled plate increases. When the pressure applied during skin-pass rolling is 4 times or more of the product of the plate thickness (mm) and the plate width (m), appropriate stress is imparted to the plated steel plate, and zinc oxide with more lattice defects or smaller crystal sizes can be generated. When the rolling load (ton) during skin-pass rolling is 7 times or less of the product of the plate thickness (mm) and the plate width (m), the plating layer is less likely to crack (break). Moreover, the strain release caused by cracking can be suppressed, making it easier to simultaneously reduce brightness and suppress peeling of the plating layer during processing.

[0066] 2-3. Steam treatment The steam treatment can be carried out by placing the plated steel sheet in a high temperature and high humidity environment and allowing the water vapor to contact the plated layer. The steam treatment is preferably carried out in a closed container.

[0067] By steam treatment, the phase containing any one of zinc, aluminum and magnesium in the coating layer can be oxidized and the volume of these phases can be expanded. Therefore, a plurality of fine protrusions can be formed on the surface of the coating layer to reduce the gloss of the coated steel sheet, and the brightness of the coated steel sheet can be reduced by the phase that becomes black due to oxidation.

[0068] The temperature of the steam treatment is preferably 105°C to 210°C, more preferably 105°C to 150°C. Since the higher the temperature, the faster the oxidation of the coating layer, the faster the zinc oxide is formed, so the brightness of the coated steel sheet can be reduced in a shorter time. Furthermore, the lower the temperature, the more cracking caused by rapid oxidation can be suppressed.

[0069] The relative humidity of the environment during the water vapor treatment is preferably 60% to 100%, and more preferably 85% to less than 100%. The higher the relative humidity, the shorter the time in which the gloss and brightness of the plated steel sheet can be reduced. On the other hand, when the relative humidity is less than 100%, the adhesion of condensed water to the surface of the plated steel sheet can be suppressed, and the gloss and brightness of the plated steel sheet can be reduced more evenly.

[0070] The oxygen concentration of the environment during the water vapor treatment is preferably below 13% by volume. When the oxygen concentration is high, white zinc oxide is easily formed, and it is difficult to obtain a black appearance. The oxygen concentration can be reduced by increasing the concentration of water vapor (relative humidity), introducing an inert gas into the environment (replacing the air in the sealed container with an inert gas), or removing the air in the sealed container with a vacuum pump. The above-mentioned inert gas can be argon, nitrogen, helium, etc.

[0071] The treatment time (soaking time) of the water vapor treatment is preferably 1 hour to 35 hours, more preferably 5 hours to 25 hours. The longer the treatment time, the lower the gloss and brightness of the plated steel sheet. The shorter the treatment time, the more it can suppress the generation of cracks in the plated layer due to volume expansion during the water vapor treatment, or the peeling of the plated layer during processing.

[0072] At this time, the conditions such as the temperature and treatment time of the water vapor treatment can be adjusted according to the composition of the plated steel sheet (the ratio of each phase), so as to adjust the gloss and brightness of the produced plated steel sheet to the desired level.

[0073] On the plated steel sheet thus produced, a chemical conversion treatment film or the like may be formed by a known method.

[0074] The plated steel sheet described above has low surface brightness, excellent design, and is not prone to plating peeling due to processing. Therefore, it is suitable as a plated steel sheet used in building roof materials, exterior materials, home appliances, automotive components, etc. [Example]

[0075] Hereinafter, the present invention will be described in detail with reference to embodiments, but the present invention is not limited to the scope of these embodiments.

[0076] [Test 1] 1. Production of plated steel sheets A cold rolled steel sheet described in JIS G3141:2021 with a thickness of 0.6 to 1.2 mm and a width of 1.05 m was used as a substrate to produce several zinc-coated steel sheets containing molten aluminum and magnesium (material plated steel sheets) with different compositions and thicknesses of the coating layers. In addition, a skin-pass rolling process was performed using a skin-pass rolling mill arranged at the rear section (downstream side of the plate passing direction) of the plating device. At this time, the surface roughness of the skin-pass rolling mill, the elongation of the material plated steel sheet, and the rolling load can be changed to give strain to the material plated steel sheet under different conditions.

[0077] Then, the material plated steel sheet is placed in an ultra-accelerated life test apparatus (manufactured by Hirayama Seisakusho Co., Ltd., PC-304R8) to allow water vapor to contact the plated layer, thereby obtaining a plated steel sheet with a low-brightness plated layer. At this time, the temperature, relative humidity and soaking time of the water vapor treatment can be changed, and the material plated steel sheet can be subjected to water vapor treatment under different conditions.

[0078] The produced plated steel sheet was subjected to X-ray diffraction measurement. The X-ray diffraction analysis device was RINT-TTR III (manufactured by Rigaku Co., Ltd.), and the obtained X-ray diffraction pattern was analyzed by the analysis software PDXL2 (manufactured by Rigaku Co., Ltd.). The analysis confirmed whether there was a diffraction peak caused by the MgZn2 phase, and when the MgZn2 phase was confirmed, it was determined that the plated steel sheet contained the MgZn2 phase.

[0079] Tables 1 and 2 show the plating compositions, film thicknesses of the plating layers, skin pass rolling conditions, and steam treatment conditions of the plated steel sheets 1 to 26 thus obtained.

[0080] [Table 1]

[0081] [Table 2]

[0082] 2. Measurement and evaluation 2-1. X-ray diffraction (XRD) measurement The X-ray diffraction patterns of the coating layers of the plated steel sheets 1 to 26 were analyzed by using an X-ray diffraction analysis device RINT-TTR III (manufactured by Rigaku Co., Ltd.) and analysis software PDXL2 (manufactured by Rigaku Co., Ltd.). The measurement conditions were: a copper tube, a voltage of 50 kV, a current of 300 mA, a divergence slit of 1 / 2°, a divergence vertical limiting slit of 5 mm, an open scattering slit and a light receiving slit, a monochromatic light receiving slit, and a horizontal goniometer with an angle measuring radius of 280 mm. The detector was a D / teX Ultra Full, and the X-ray diffraction measurement was performed at a scanning speed of 2 degrees / minute, a step size of 0.01 degrees, a scanning axis of 2θ / θ, and a scanning range of 5 to 100 degrees to obtain the X-ray diffraction patterns. From the obtained X-ray diffraction spectrum, the peak intensity (A) of the peak showing the 100 face of zinc oxide appearing between 2θ of 31.27 degrees and 32.27 degrees, the peak intensity (B) of the peak showing the 101 face of zinc appearing between 2θ of 42.73 degrees and 43.73 degrees, and the intensity (C) when 2θ is 30.00 degrees were obtained. The values of A / B and A / C were also obtained. In addition, the obtained X-ray diffraction spectrum was background processed by the fitting method, smoothed by the B smoothing curve (spline), and Kα2 was removed by the Rachinger method (the intensity ratio of Kα1 to Kα2 is 0.4970). After this processing, the peak shape was fitted with the segmented pseudo-Voigt function, and the half width d of the peak showing A was obtained by the analysis software. For zinc oxide series, use the data of PDF card number 00-036-1451, and for zinc series, use the data of PDF card number 00-004-0831.

[0083] 2-2. STEM measurement The cross section processed by the Cryo FIB-μ sampling method from the average position of the surface of the plated steel sheet was subjected to STEM measurement using a focused ion beam device. The focused ion beam device was prepared by using NB5000 manufactured by Hitachi High-Tech. Specifically, in the obtained cross section, an observation range with a width of 15 μm was set along the surface of the plated steel sheet, and this observation range was observed by a transmission electron microscope (TEM), and the phase of the plated surface layer was identified by elemental analysis and electron diffraction analysis using energy dispersive X-ray spectroscopy (EDS). The electron microscope used was a 200 kV-field emission transmission electron microscope JEM-2100 manufactured by JEOL, and the EDS analysis device used was a JED-2300T manufactured by JEOL. Then, a judgment range with a depth of 1 μm was set along the surface of the plated layer, and it was determined whether the zinc metal phase or the aluminum metal phase was contained in this judgment range. In addition, the judgment range with a depth of 1 μm was a range of 1 μm from each surface along the concave and convex shape of the surface of the plated layer. 10 average points on the surface of the plated steel sheet are randomly selected for observation and identification to confirm whether there is a zinc metal phase or an aluminum metal phase in all cross sections. If there is a cross section of a zinc metal phase or an aluminum metal phase in one or more of the 10 selected points, it is evaluated as "yes", and if there is less than one point, it is evaluated as "no".

[0084] 2-3. Evaluation of brightness The surface brightness (L* value) of the coating layer was measured using a colorimeter (CR-400 manufactured by Konica Minolta Co., Ltd.) in accordance with JIS Z8722:2009, using diffuse illumination and vertical illumination including specular reflection light. The illumination diameter during measurement was set at 11 mm Φ and the measurement diameter was set at 8 mm Φ. The peeling of the coating layer was evaluated according to the following criteria, using the obtained brightness (L* value) as a reference. ◎: L* value is below 40 ○: L* value is greater than 40 and below 50 ×: L* value is greater than 50

[0085] 2-4. Evaluation of peeling of coating A 50 mm x 50 mm test piece with a thickness of 0.8 mm obtained from each plated steel sheet was subjected to 2T bending. Then, a tape (made by Nichiban Co., Ltd., cellophane tape) was attached to the top of the bent portion and peeled off, and the peeled tape was observed with a magnifying glass. The peeling of the plating layer was evaluated according to the following criteria, based on the maximum size of the plating peeling piece attached to the tape (the maximum distance between the tops of the peeling piece). ◎: The maximum size of the peeled plated sheet is less than 0.2mm ○: The maximum size of the peeled plated sheet is greater than 0.2 mm and less than 0.5 mm △: The maximum size of the peeled plated sheet is greater than 0.5 mm and less than 1 mm ×: The maximum size of the peeled plated sheet is more than 1 mm

[0086] The measurement and evaluation results are shown in Table 3.

[0087] [Table 3]

[0088] As shown in Tables 1 to 3, by subjecting a plated steel sheet having an aluminum content of not less than 1.0 mass % and not more than 22.0 mass %, a magnesium content of not less than 1.5 mass % and not more than 10.0 mass %, and the remainder being zinc and any trace additives added, to a water vapor treatment, a low-brightness plated steel sheet (plated steel sheet 1 to plated steel sheet 18) can be obtained.

[0089] At this time, when appropriate strain is given to the material plated steel sheet before the water vapor treatment, the brightness of the coating layer can be sufficiently reduced, and even in a 2T bending test that is more severe than before, a plated steel sheet (plated steel sheet 1 to plated steel sheet 18) in which the coating layer is not easily peeled off can be obtained.

[0090] On the other hand, the plated steel sheet 19 containing a small amount of aluminum in the plated layer, the plated steel sheet 20 containing a small amount of magnesium in the plated layer, and the plated steel sheet 22 containing an excessive amount of aluminum cannot be fully blackened even by steam treatment.

[0091] Furthermore, the plated steel sheet 21, which had an excessively large elongation during the skin-pass rolling treatment, produced a large amount of zinc oxide during the water vapor treatment, and the plated layer peeled off in a large amount during the 2T bending test. In addition, since the roller roughness during the skin-pass rolling test was small, the elongation was small, or the load was small, in order to make the plated steel sheet 23 and the plated steel sheet 24, which were given a small strain, have more lattice defects, or zinc oxide with a small crystal size could not be fully generated and fully blackened, a large amount of zinc oxide must be generated, so that the plated layer peeled off in a large amount during the 2T bending test. In addition, similarly, for the plated steel sheet 25, which had a small elongation or a small load during the skin-pass rolling test and a small strain, the plated layer did not fully blacken during the water vapor treatment in which the plated layer did not peel off much during the 2T bending test. In addition, for the plated steel sheet 26 with an excessively large load during the skin rolling test, the strain is released due to the generation of cracks, and zinc oxide with more lattice defects or smaller crystal size cannot be fully generated. Therefore, when the water vapor treatment with little peeling of the coating is performed in the 2T bending test, the coating does not fully turn black.

[0092] In addition, cross sections of the plated steel sheets 1 to 18 were processed by the Cryo FIB-μ sampling method from an average position on the surface using a focused ion beam device, and STEM measurement was performed. In addition, for the plated steel sheets 1 to 18, STEM measurements were performed on the cross sections processed by the Cryo FIB-μ sampling method from the average position of the surface using a focused ion beam device. The observation range was observed by a transmission electron microscope (TEM), and the phase of the plated surface layer was identified by elemental analysis and electron diffraction analysis using energy dispersive X-ray spectroscopy (EDS). The results confirmed that the MgZn2 phase in any of the plated steel sheets was changed into an amorphous phase containing magnesium, zinc and oxygen and a phase containing zinc oxide.

[0093] In addition, the surface of the plated steel sheet 26 with increased rolling load during skin-pass rolling was observed with a scanning electron microscope, and cracks were found on the plated layer. Moreover, the plated layer could not be fully blackened, probably because of the strain released by the cracks.

[0094] [Experiment 2] 1. Production of plated steel sheets The same operation as in Experiment 1 was performed to form a coating layer, perform skin-pass rolling and steam treatment to obtain coated steel sheets A and B. The coating composition, coating layer thickness, skin-pass rolling conditions and steam treatment conditions of the coated steel sheets A and B are shown in Table 4.

[0095] [Table 4]

[0096] The materials shown in Table 5 were added to water in the amounts shown in the table and mixed to prepare treatment liquids 1 to 18 for chemical conversion treatment.

[0097] [Table 5]

[0098] The respective treatment liquids were attached to the surface of the plated steel sheet A or the plated steel sheet B, and heated and dried at a plate temperature of 120°C to form a chemical conversion treatment film. The amounts of the treatment liquids attached were: treatment liquids 1 to 9 belonging to the inorganic treatment liquids, which were respectively prepared so that the amount of valve metal in the chemical conversion treatment film became the amount shown in Table 5, and treatment liquids 10 to 18 belonging to the organic treatment liquids, which were respectively prepared so that the film thickness of the chemical conversion treatment film became the amount shown in Table 6.

[0099] 2. Measurement and evaluation 2-1. X-ray diffraction (XRD) measurement The same operation as in Experiment 1 was performed to perform X-ray diffraction measurement and obtain an X-ray diffraction spectrum. The values of A / B and A / C were determined from the obtained X-ray diffraction spectrum. In addition, the half width d of the peak showing A was determined.

[0100] 2-2. STEM measurement STEM measurement was performed in the same manner as in Experiment 1. Then, it was determined whether a zinc metal phase or an aluminum metal phase was contained within a determination range of 1 μm in depth along the surface of the plating layer.

[0101] 2-3. Evaluation of brightness The brightness (L* value) of the coating surface was measured by the same operation as in Experiment 1.

[0102] 2-4. Evaluation of peeling of coating The peeling evaluation of the plating layer was carried out in the same manner as in Experiment 1.

[0103] 2-5. Evaluation of corrosion resistance After sealing the end faces of the test pieces of 50 mm × 100 mm with a plate thickness of 0.8 mm obtained from the respective plated steel sheets, a salt spray test was performed by spraying a 35°C NaCl aqueous solution for 12 hours in accordance with JIS Z2371:2015. After 12 hours of spraying, the area ratio of white rust on the test piece was measured, and the area ratio of the area of white rust to the total area of the test was obtained (white rust generation area / total area of the test piece: white rust generation ratio), and the food resistance was evaluated according to the following criteria. ◎: White rust generation rate is 0% ○: White rust generation rate is greater than 0% and less than 5% △: White rust generation rate is more than 5%

[0104] The measurement and evaluation results are shown in Tables 6 and 7.

[0105] [Table 6]

[0106] [Table 7]

[0107] As shown in Tables 3 to 7, even with the chemical conversion treated plated steel sheets, the brightness of the plated layer can be sufficiently reduced, and even with the more stringent 2T bending test than the conventional one, a plated steel sheet with a plated layer that is not easily peeled off can be obtained.

[0108] This application claims the priority of Japanese Patent Application No. 2023-211053 filed on December 14, 2023. The contents described in the original application specification, scope of patent application and drawings of the application are incorporated into this application by reference. [Industrial Applicability]

[0109] The plated steel sheet of the present invention has excellent design properties with low surface brightness and is not prone to peeling of the plated layer due to processing. Therefore, the plated steel sheet can be applied to various fields requiring good design.

Claims

1. A coated steel sheet having a steel sheet and a coating layer, wherein the coating layer is composed of an aluminum content of 1.0% to 22.0% by mass, a magnesium content of 1.5% to 10.0% by mass, and the remainder being zinc and any trace additives, the surface brightness (L*) being 50 or less, and the X-ray diffraction spectrum obtained by X-ray diffraction of the aforementioned coating layer using a copper tube at a voltage of 50 kV and a current of 300 mA completely satisfies the following (1) to (3), (1) A / B series 0.001 to 0.015 (2) A / C series 1.2 to 3.5 (3) Display the half-width of the peak of A series d series 0.30 degrees to 1.00 degrees; In addition, A series: display the peak intensity of the peak of the 100 surface of zinc oxide that appears between 31.27 degrees and 32.27 degrees, B series: display the peak intensity of the peak of the 101 surface of zinc that appears between 42.73 degrees and 43.73 degrees, C series intensity when 2θ is 30.00 degrees.

2. The plated steel sheet as described in claim 1, wherein, The aforementioned coating system has: an amorphous phase containing magnesium, zinc and oxygen, and a phase containing zinc oxide.

3. The plated steel sheet as described in claim 1 or 2, wherein, When observing any 10 cross sections with a length of 15 μm in a direction parallel to the surface of the aforementioned coated steel plate, a zinc or aluminum metal phase is found within any cross section at a depth of 1 μm from the surface opposite to the aforementioned steel plate.

4. The plated steel sheet as described in claim 1 or 2, wherein, A chemical conversion treatment film is present on the opposite side of the aforementioned coating layer from the aforementioned steel plate.

5. A method for manufacturing a coated steel sheet as described in any one of claims 1 to 4, comprising the following steps: preparing a material coated steel sheet having a steel sheet and a coating layer, the coating layer being composed of an aluminum content of 1.0% to 22.0% by mass, a magnesium content of 1.5% to 10.0% by mass, and the remainder being zinc and any added trace additives; and applying strain to the aforementioned coating layer by using a surface-smoothing roll with an arithmetic mean surface roughness Ra of 2.1 μm to 2.8 μm, wherein the elongation of the material coated steel sheet is such that... The surface is light-rolled under the condition that the coating thickness (mm) is 4.0 times to 7.0 times the product of the plate thickness (mm) and the plate width (m); and the plated steel sheet having the aforementioned strain-imposed coating is subjected to steam treatment; the plated steel sheet obtained after the aforementioned steam treatment fully satisfies the following conditions (1) to (3): (1) A / B ratio is 0.001 to 0.015; (2) A / C ratio is 1.2 to 3.5; (3) the half-width d of the peak of A is 0.30 degrees to 1.00 degrees; wherein, Series A: Displays the peak intensity of the 100 plane of zinc oxide when 2θ is between 31.27 degrees and 32.27 degrees; Series B: Displays the peak intensity of the 101 plane of zinc oxide when 2θ is between 42.73 degrees and 43.73 degrees; Series C: Displays the intensity when 2θ is 30.00 degrees.

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