JP5814048B2 - Method for producing black-plated steel sheet and method for producing molded body of black-plated steel sheet - Google Patents

Description

  The present invention relates to a method for producing a black-plated steel sheet and a method for producing a molded body of a black-plated steel sheet.

  In the fields of building roofing materials, exterior materials, home appliances, automobiles, and the like, there is an increasing need for steel plates having a black appearance from the viewpoint of design and the like. As a method for blackening the surface of a steel plate, there is a method of forming a black coating film by applying a black paint to the surface of the steel plate. However, in the above fields, plated steel sheets plated with hot dip Zn plating, hot dip Al-containing Zn plating, hot Al, Mg-containing Zn plating, etc. are often used from the viewpoint of corrosion resistance. Has a silvery white color with metallic luster. Therefore, in order to obtain a black appearance with high designability by applying a black paint, the coating film must be thickened to conceal the base color, resulting in high coating costs. Further, when the coating film is thick in this way, there is a problem that resistance welding such as spot welding cannot be performed.

  As a method of shielding the metallic luster and silver-white color tone of the plated steel sheet without forming a black coating film, a method of blackening the plating layer itself has been proposed (see, for example, Patent Document 1). Patent Document 1 discloses a method in which a molten Al-containing Zn-plated steel sheet is steam-treated in a high-temperature and high-humidity atmosphere to form a thin black film on the surface of the plating layer.

Japanese Unexamined Patent Publication No. 64-56881

  However, the black-plated steel sheet described in Patent Document 1 has a problem that it has poor black appearance retention. That is, in the black-plated steel sheet described in Patent Document 1, since the black film is formed only on the surface layer of the plating layer, the lower silver-white plating layer is exposed just by slightly removing the black film, It was not practical.

  In the technique described in Patent Document 1, in order to improve the retention of the black appearance, it is conceivable to blacken the entire plating layer. However, in the technique described in Patent Document 1, if the entire plating layer is blackened, the plating layer becomes brittle, so that the adhesion of the plating layer is reduced and the corrosion resistance of the plated steel sheet is also reduced ( Patent Document 1, page 471, upper left column, 8th to 11th line, upper right column, 14th to 19th line).

  As described above, the conventional black-plated steel sheet cannot achieve both black appearance retention and workability (plated layer adhesion).

  This invention is made | formed in view of this point, and it aims at providing the black plating steel plate which is excellent in both the retainability and workability of a black external appearance.

The present inventor uses a molten Al- and Mg-containing Zn-plated steel sheet having a plating layer containing a ternary eutectic structure of Al / Zn / Zn ₂ Mg as an original sheet, and treats the plated steel sheet with steam at 105 ° C or higher. As a result, it was found that the above problems could be solved, and further studies were made to complete the present invention.

That is, the 1st of this invention is related with the manufacturing method of the following black plated steel plates.
[1] Step of preparing molten Al containing Mg: 1.0 to 22.0 mass%, Mg: 1.5 to 10.0 mass%, molten Al having an Mg-containing Zn plating layer, and Mg-containing Zn-plated steel sheet And a step of bringing the molten Al, Mg-containing Zn-plated steel sheet into contact with water vapor at 105 ° C. or higher; the number of moles of Zn oxide [Zn (O ₀ ) on the surface of the plating layer before being brought into contact with water vapor The ratio [Zn (O / O ₀ )] of the number of moles of Zn oxide [Zn (O)] in the surface layer of the plating layer after contacting with water vapor is in the range of 60 to 2700; The number of moles of Al oxide on the surface of the plating layer after contact with water vapor [Al (O) relative to the number of moles of Al oxide on the surface of the plating layer before contact with water vapor [Al (O ₀ )] )] ratio [Al _{(O /} O 0 of) is 50 In the range of 00; the number of moles of the plating layer surface of the oxide of Mg prior to contacting the water vapor [Mg (O _0)] for the oxides of the plated layer surface of the Mg after contacting the water vapor The ratio [Mg (O / O ₀ )] of the number of moles of [Mg (O)] is in the range of 40 to 240; the number of moles of Zn hydroxide on the surface of the plating layer before contacting with water vapor [Zn _(OH 0)] for the ratio of the number of moles of the hydroxide of the plating layer surface of the Zn after contacting water vapor [Zn (OH)] [Zn (OH / OH 0)] is 7 270; Al water of the plating layer surface layer after contact with water vapor, relative to the number of moles of Al hydroxide [Al (OH ₀ )] of the plating layer surface layer before contact with water vapor Oxide mole number [Al (OH)] ratio [Al (OH / OH ₀ )] is in the range of 8 to 20; the number of moles of Mg hydroxide in the surface layer of the plating layer before contacting with water vapor [Mg (OH ₀ )] The ratio [Mg (OH / OH ₀ )] of the number of moles of Mg hydroxide [Mg (OH)] in the surface layer of the plating layer is in the range of 10 to 90.
[2] The method for producing a black-plated steel sheet according to [1], wherein the molten Al and Mg-containing Zn plating layer includes a ternary eutectic structure of Al / Zn / Zn ₂ Mg.
[3] The method for producing a black-plated steel sheet according to [1] or [2], further comprising a step of forming an inorganic coating on the surface of the molten Al, Mg-containing Zn-plated steel sheet.
[4] The inorganic coating is one kind selected from the group consisting of valve metal oxide, valve metal oxyacid salt, valve metal hydroxide, valve metal phosphate and valve metal fluoride. The manufacturing method of the black plating steel plate as described in [3] containing 2 or more types of compounds.
[5] The valve metal according to [4], wherein the valve metal is one or more metals selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Mo, W, Si, and Al. Manufacturing method of black plated steel sheet.
[6] The method for producing a black-plated steel sheet according to [1] or [2], further comprising a step of forming an organic resin film on a surface of the molten Al, Mg-containing Zn-plated steel sheet.
[7] The organic resin contained in the organic resin film is a urethane resin obtained by reacting a polyol composed of an ether polyol and an ester polyol with a polyisocyanate; a ratio of the ether polyol in the polyol Is 5-30 mass%, The manufacturing method of the black plating steel plate as described in [6].
[8] The method for producing a black-plated steel sheet according to [7], wherein the organic resin film further contains a polyhydric phenol.
[9] The method for producing a black-plated steel sheet according to any one of [6] to [8], wherein the organic resin film includes a lubricant.
[10] The organic resin film is selected from the group consisting of valve metal oxide, valve metal oxyacid salt, valve metal hydroxide, valve metal phosphate, and valve metal fluoride. Or the manufacturing method of the black plating steel plate as described in any one of [6]-[9] containing 2 or more types of compounds.
[11] The valve metal according to [10], wherein the valve metal is one or more metals selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Mo, W, Si, and Al. Manufacturing method of black plated steel sheet.
[12] The method for producing a black-plated steel sheet according to any one of [6] to [11], wherein the organic resin film is a laminate layer or a coating layer.
[13] The method for producing a black-plated steel sheet according to any one of [6] to [12], wherein the organic resin film is a clear coating film.

Moreover, the 2nd of this invention is related with the manufacturing method of the molded object of the following black plating steel plates.
[14] Step of preparing molten Al containing Mg: 1.0 to 22.0 mass%, Mg: 1.5 to 10.0 mass%, molten Al having an Mg-containing Zn plating layer, and Mg-containing Zn-plated steel sheet A step of contacting the molten Al, Mg-containing Zn-plated steel sheet with water vapor of 105 ° C. or higher; and a step of forming the molten Al, Mg-containing Zn-plated steel sheet before or after contacting with the water vapor The moles of Zn oxide on the surface of the plating layer after contact with water vapor relative to the number of moles of Zn oxide on the surface of the plating layer before contact with water vapor [Zn (O ₀ )] The ratio [Zn (O / O ₀ )] of the number [Zn (O)] is in the range of 60 to 2700; the number of moles of Al oxide on the surface of the plating layer before contacting with water vapor [Al ( Water for O ₀ )] The ratio [Al (O / O ₀ )] of the number of moles of Al oxide [Al (O)] in the surface layer of the plating layer after contact with steam is in the range of 50 to 200; The number of moles of Mg oxide [Mg (O)] on the surface of the plating layer after contacting with water vapor relative to the number of moles [Mg (O ₀ )] of Mg oxide on the surface of the plating layer before The ratio [Mg (O / O ₀ )] is in the range of 40 to 240; water vapor relative to the number of moles of Zn hydroxide [Zn (OH ₀ )] on the plating layer surface layer before contact with water vapor The ratio [Zn (OH / OH ₀ )] of the number of moles of Zn hydroxide [Zn (OH)] in the surface layer of the plating layer after being in contact with the metal is in the range of 7 to 270; number of moles of the hydroxide of the plating layer surface of the Al prior to the [Al _(OH 0)] To, the ratio of the number of moles of the hydroxide of the plating layer surface of Al after contacting water vapor [Al (OH)] [Al (OH / OH 0)] is in the range of 8 to 20; The number of moles of Mg hydroxide on the surface of the plating layer after contacting with water vapor [Mg (OH ₀ )] with respect to the number of moles of Mg hydroxide on the surface of the plating layer before contacting with water vapor [Mg (OH ₀ )] The ratio [Mg (OH / OH ₀ )] of (OH)] is in the range of 10 to 90.

  ADVANTAGE OF THE INVENTION According to this invention, it can manufacture the black plating steel plate which has the black external appearance excellent in the designability, and is excellent in the retainability of black external appearance, workability, and corrosion resistance, and its molded object. The black-plated steel sheet produced by the present invention is excellent in design, black appearance retention, workability, and corrosion resistance, so that it is used for, for example, building roofing materials and exterior materials, home appliances, automobiles, etc. Useful as a steel sheet.

Electron micrograph showing the cross section of the plated layer of molten Al, Mg-containing Zn-plated steel sheet before contact with water vapor Electron micrograph showing the cross section of the plated layer of molten Al, Mg-containing Zn-plated steel sheet after contact with water vapor

1. Method for Producing Black Plated Steel Sheet The method for producing the black plated steel sheet of the present invention includes 1) a first step of preparing molten Al, Mg-containing Zn plated steel sheet (hereinafter also referred to as “plated steel sheet”), and 2) molten Al, And a second step of bringing the Mg-containing Zn-plated steel sheet into contact with water vapor. Furthermore, as an optional step, it may have a step of 3) forming an inorganic film or an organic resin film on the surface of the molten Al, Mg-containing Zn-plated steel sheet before or after the second step.

[First step]
In the first step, a molten Al, Mg-containing Zn-plated steel sheet is prepared.

The molten Al, Mg-containing Zn-plated steel sheet has a plating layer containing a ternary eutectic structure of Al / Zn / Zn ₂ Mg. Each phase (Al phase, Zn phase, and Zn ₂ Mg phase) forming the ternary eutectic structure of Al / Zn / Zn ₂ Mg has an irregular size and shape, and is intricate with each other. (See FIG. 1). The Al phase in the ternary eutectic structure is derived from the Al "phase at high temperature in the Al-Zn-Mg ternary equilibrium diagram (Al solid solution that dissolves Zn and contains a small amount of Mg). The Al "phase at high temperature usually appears separated into a fine Al phase and a fine Zn phase at room temperature. The Zn phase in the ternary eutectic structure is a Zn solid solution in which a small amount of Al is dissolved, and in some cases, Mg is further dissolved. The Zn ₂ Mg phase in the ternary eutectic structure is an intermetallic compound phase in the vicinity of a point where Zn is about 84% by mass in the Zn—Mg binary equilibrium diagram.

The molten Al- and Mg-containing Zn-plated steel sheet having a plating layer containing a ternary eutectic structure, for example, Al is 1.0 to 22.0 mass%, Mg is 1.5 to 10.0 mass%, and the balance is substantially Further, it can be manufactured by a hot dipping method using a Zn alloy plating bath. By doing in this way, the plating layer which consists of Al: 1.0-22.0 mass%, Mg: 1.5-10.0 mass%, remainder: Zn and an unavoidable impurity, and contains a ternary eutectic structure. Can be formed. Moreover, in order to improve the adhesiveness of a base-material steel plate and a plating layer, Si which can suppress the growth of the Al-Fe alloy layer in the interface of a base-material steel plate and a plating layer is 0.005-2.0 mass%. A range may be added to the plating bath. Furthermore, Ti, B, Ti—B alloy, Ti-containing compound or B-containing compound may be added to the plating bath in order to suppress the formation and growth of Zn ₁₁ Mg ₂ phase that adversely affect the appearance and corrosion resistance. The amount of these compounds added is preferably set so that B is in the range of 0.001 to 0.045% by mass such that Ti is in the range of 0.001 to 0.1% by mass. . If an excessive amount of Ti or B is added, there is a possibility that precipitates grow on the plating layer.

The molten Al- and Mg-containing Zn-plated steel sheet having a plating layer having the above composition is superior in corrosion resistance to the molten Al-containing Zn-plated steel sheet. In the plating layer having the above composition, Zn, Al, and Mg are present as a ternary eutectic structure of Al / Zn / Zn ₂ Mg.

  The Al content of the plating layer is preferably in the range of 1.0 to 22.0 mass%, and the Mg content is preferably in the range of 1.5 to 10.0 mass%. When the Al content and the Mg content are out of the above ranges, the adhesion of the plating layer after being brought into contact with water vapor is lowered.

  Although the thickness of a plating layer is not specifically limited, The inside of the range of 1-100 micrometers is preferable. When the thickness of the plating layer is less than 1 μm, scratches that reach the base steel sheet during handling are likely to enter, so that the black appearance retention and corrosion resistance may be lowered. On the other hand, when the thickness of the plating layer exceeds 100 μm, since the ductility of the plating layer and the base steel plate when subjected to compression is different, the plating layer and the base steel plate may be peeled off at the processed portion.

  The kind of the base steel plate of the molten Al, Mg-containing Zn plated steel plate is not particularly limited. For example, as the base steel plate, a steel plate made of low carbon steel, medium carbon steel, high carbon steel, alloy steel, or the like can be used. When good press formability is required, a steel sheet for deep drawing made of low carbon Ti-added steel, low carbon Nb-added steel, or the like is preferable as the base steel sheet.

[Second step]
In the second step, the plated steel sheet prepared in the first step is brought into contact with water vapor to blacken the plating layer. By this step, the lightness (L value) of the plating layer surface can be reduced to 60 or less. The lightness (L value) of the plating layer surface is measured using a spectroscopic color difference meter.

  The temperature of water vapor when the plated steel sheet is brought into contact with water vapor is preferably 105 ° C. or higher, and more preferably in the range of 105 to 350 ° C. When the temperature of the water vapor is less than 105 ° C., only the surface layer portion of the plating layer is blackened, and the black appearance retention cannot be sufficiently improved. On the other hand, when the temperature of water vapor exceeds 350 ° C., the composition of the plating layer may change, and the corrosion resistance and adhesion of the plated steel sheet may be reduced.

  The relative humidity of water vapor when the plated steel sheet is brought into contact with water vapor is preferably in the range of 30% to 100%. That is, the steam at 105 ° C. or higher that is brought into contact with the plated steel sheet may be heated steam having a relative humidity of less than 100% or saturated steam having a relative humidity of 100%. When the relative humidity of water vapor is less than 30%, in order to sufficiently blacken, it is necessary to lengthen the time for contact with water vapor, and productivity is lowered.

  The atmospheric pressure of water vapor when bringing the plated steel sheet into contact with water vapor is not particularly limited, and may be normal pressure (atmospheric pressure) or may be pressurized. Under normal pressure (atmospheric pressure), when water vapor adjusted to the specified temperature and relative humidity is sprayed onto the plated steel sheet, the temperature and relative humidity of the water vapor change depending on the distance between the outlet and the plated steel sheet and the ambient temperature. There is a risk of it. In order to avoid such a problem, it is preferable to bring the plated steel sheet into contact with water vapor in a closed container adjusted to a predetermined temperature and relative humidity.

  What is necessary is just to set suitably the time which makes a plated steel plate contact with water vapor | steam according to the temperature of water vapor | steam, relative humidity, a composition of a plating layer, etc. FIG. For example, the plating layer can be blackened in a shorter time as the content of Mg in the plating layer is larger. Usually, the brightness (L value) of the surface of the plating layer can be reduced to 60 or less by bringing steam having a temperature of 105 to 350 ° C. and a relative humidity of 30 to 100% into contact with the plated steel sheet for about 0.017 to 120 hours. .

In the second step, when the plated steel sheet is brought into contact with water vapor (oxidation treatment), oxides and hydroxides of Zn, Al, and Mg are generated in the plating layer. In the second step, the mechanism of blackening of the plating layer is unknown, but it is assumed that the formation of oxides and / or hydroxides of Zn, Al, Mg in the plating layer is involved. The One hypothesis is that Zn, Al, Mg oxide or hydroxide (eg, ZnO _1-x ) having an oxygen-deficient defect structure is formed in the plating layer by bringing the plated steel sheet into contact with water vapor. It is considered that the plating layer is blackened (Yukio Uchida et al., “Blackening film of Zn-Al alloy hot-dip plated steel sheet”, Iron and Steel (Journal of the Iron and Steel Institute of Japan), No. 72, No. 72, 1013-1020; see Mitsuru Koda, et al., “The mechanism of black change in Zn-4% Al-based hot-dip galvanized steel sheet and its suppression method”, Nisshin Steel Technical Report, 63, pages 77-88).

  As described above, when the plated steel sheet is brought into contact with water vapor, oxides and hydroxides of Zn, Al, Mg, which are thought to contribute to the blackening of the plating layer, are generated in the plating layer. If the oxides and hydroxides of Zn, Al, and Mg are excessively produced, the corrosion resistance of the plated steel sheet may be reduced. On the other hand, when the production amount of Zn, Al, Mg oxide and hydroxide in the plating layer is too small, the plating layer cannot be sufficiently blackened.

Therefore, the ratio of the number of moles of oxide or hydroxide of the plating layer surface layer after contacting with water vapor to the number of moles of oxide or hydroxide of the plating layer surface layer before contacting with water vapor is in the following range. It is preferable to adjust the temperature, relative humidity, atmospheric pressure, treatment time, etc. of the superheated steam so as to be inside. By setting the ratio of the oxide or hydroxide within the following range, the plating layer can be sufficiently blackened while maintaining the corrosion resistance.
Zn (O / O ₀ ): 60-2700
Al (O / O ₀ ): 50 to 200
Mg (O / O ₀ ): 40-240
Zn (OH / OH ₀ ): 7 to 270
Al (OH / OH ₀ ): 8-20
Mg (OH / OH ₀ ): 10 to 90

Here, [Zn (O / O ₀ )] is the plating layer surface layer after contact with water vapor with respect to the number of moles of Zn oxide [Zn (O ₀ )] in the plating layer surface layer before contact with water vapor It means the ratio of the number of moles of Zn oxide [Zn (O)]. [Zn (OH / OH ₀ )] is the plating layer surface layer after contact with water vapor with respect to the number of moles of Zn hydroxide [Zn (OH ₀ )] in the plating layer surface layer before contact with water vapor. The number of moles of Zn hydroxide [Zn (OH)]. The same applies to Al and Mg. The “plating layer surface layer” means a portion of 0.05 to 0.10 μm from the surface of the plating layer.

  The ratio of the number of moles of oxide or hydroxide on the surface of the plating layer before and after contact with water vapor is measured from the surface of the plating layer toward the steel plate using a time-of-flight secondary ion mass spectrometer (TOF-SIMS). The Ga ions are irradiated in the depth direction, and the average number of secondary ions of oxides and hydroxides contained in the plating layer having a depth of 0.05 to 0.10 μm is measured.

  When the plated steel sheet is brought into contact with water vapor, Zn, Al, Mg oxides and hydroxides are initially generated in the surface layer of the plating layer, and Zn, Al, Mg oxides are also formed inside the plating layer over time. And hydroxide is produced. When the time for which the plated steel sheet is brought into contact with water vapor is short, oxides and hydroxides of Zn, Al, Mg are generated only in the surface layer of the plating layer, and only the surface layer of the plating layer is blackened. As described above, the blackened plated steel sheet in which only the surface layer of the plating layer is blackened, the silvery white portion located under the blackened surface layer portion is exposed even if the blackened surface layer portion is slightly shaved, and the black appearance is retained. Inferior to

  Therefore, in order to sufficiently secure the black appearance, plating is performed until Zn, Al, Mg oxides and hydroxides are sufficiently generated in at least 20% of the surface side of the plating layer. It is preferable to bring the steel sheet into contact with water vapor. Here, the “20% portion on the surface side of the plating layer” means a portion having a thickness of 2 μm on the surface side when the thickness of the plating layer is 10 μm, for example.

More specifically, in the 20% portion on the surface side of the plating layer, the Zn phase contains 1% by mass or more of oxygen at any point, and the Al phase contains 10% by mass of oxygen at any point. The Zn ₂ Mg phase is preferably contained at least 5% by mass of oxygen at any point. When the oxygen content in each phase is less than the above lower limit, the black appearance may not be sufficiently retained. The oxygen content in each part of the plating layer can be measured using an energy dispersive X-ray spectrometer (EDX).

[Third step]
In the third step optionally performed before or after the second step, an inorganic coating or an organic resin coating is formed on the surface of the molten Al, Mg-containing Zn-plated steel sheet. The inorganic coating and the organic resin coating improve the corrosion resistance and galling resistance (retainability of black appearance) of the black-plated steel sheet.

(Inorganic coating)
The inorganic coating is one or more kinds selected from the group consisting of valve metal oxides, valve metal oxyacid salts, valve metal hydroxides, valve metal phosphates and valve metal fluorides. Those containing a compound (hereinafter also referred to as “valve metal compound”) are preferred. By including the valve metal compound, it is possible to provide an excellent barrier action while reducing the environmental load. Valve metal refers to a metal whose oxide exhibits high insulation resistance. Examples of the valve metal include one or more metals selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Mo, W, Si, and Al. Known valve metal compounds may be used.

Moreover, a self-repairing action can be imparted by including a soluble fluoride of valve metal in the inorganic coating. The valve metal fluoride dissolves in the moisture in the atmosphere and then re-precipitates as a sparingly soluble oxide or hydroxide on the surface of the plated steel plate exposed from the film defect. fill in. In order to include the soluble fluoride of valve metal in the inorganic coating, the soluble fluoride of valve metal may be added to the inorganic coating, or soluble fluoride such as (NH ₄ ) F separately from the valve metal compound May be added.

  The inorganic film may further contain a soluble or hardly soluble metal phosphate or composite phosphate. Soluble phosphate elutes from the inorganic film to the film defect and reacts with the metal of the plated steel sheet to become insoluble phosphate, thereby complementing the self-repairing action of the valve metal with soluble fluoride. In addition, the hardly soluble phosphate is dispersed in the inorganic film to improve the film strength. Examples of the metal contained in the soluble metal phosphate or composite phosphate include alkali metals, alkaline earth metals, and Mn. Examples of the metal contained in the hardly soluble metal phosphate or the composite phosphate include Al, Ti, Zr, Hf, and Zn.

  The inorganic film can be formed by a known method. For example, an inorganic paint containing a valve metal compound or the like may be applied to the surface of the molten Al or Mg-containing Zn-plated steel sheet before or after contact with water vapor and dried without being washed with water. Examples of the coating method include a roll coating method, a spin coating method, and a spray method. When a valve metal compound is added to the inorganic paint, an organic acid having a chelating action may be added to the inorganic paint so that the valve metal compound can be stably present in the inorganic paint. Examples of organic acids include tannic acid, tartaric acid, citric acid, oxalic acid, malonic acid, lactic acid and acetic acid.

(Organic resin film)
The organic resin constituting the organic resin film is urethane resin, epoxy resin, olefin resin, styrene resin, polyester resin, acrylic resin, fluorine resin, or a combination of these resins, or these resins. Or a modified product thereof. By using these flexible organic resins, generation of cracks can be suppressed when forming a black-plated steel sheet, and corrosion resistance can be improved. Further, when the valve resin compound is included in the organic resin film, the valve metal compound can be dispersed in the organic resin film (organic resin matrix) (described later).

  The organic resin film preferably contains a lubricant. By including the lubricant, galling resistance can be improved. The type of the lubricant is not particularly limited and may be selected from known ones. Examples of the lubricant include organic waxes such as fluorine, polyethylene, and styrene, and inorganic lubricants such as molybdenum disulfide and talc.

  The organic resin film preferably contains the aforementioned valve metal compound, similarly to the inorganic film. By including the valve metal compound, it is possible to provide an excellent barrier action while reducing the environmental load.

  Further, the organic resin film may further contain a soluble or hardly soluble metal phosphate or composite phosphate, similarly to the inorganic film. Soluble phosphate is eluted from the organic resin film to the film defect portion and reacts with the metal of the plated steel sheet to become insoluble phosphate, thereby complementing the self-repairing action of the valve metal with soluble fluoride. Further, the hardly soluble phosphate is dispersed in the organic resin film to improve the film strength.

  When the organic resin film contains a valve metal compound or a phosphate, an interface reaction layer is usually formed between the plated steel sheet and the organic resin film. Interfacial reaction layer consists of zinc fluoride, zinc phosphate, valve metal fluoride, phosphoric acid, which is a reaction product of fluoride or phosphate contained in organic paint and metal or valve metal contained in plated steel sheet It is a dense layer made of salt. The interface reaction layer has an excellent environmental shielding ability and prevents corrosive components in the atmosphere from reaching the plated steel sheet. On the other hand, in the organic resin film, particles of valve metal oxide, valve metal hydroxide, valve metal fluoride, phosphate, and the like are dispersed in the organic resin matrix. Since particles such as valve metal oxide are three-dimensionally dispersed in the organic resin matrix, corrosive components such as moisture that have permeated the organic resin matrix can be captured. As a result, the organic resin film can greatly reduce the corrosive components reaching the interface reaction layer. An excellent anticorrosive effect is exhibited by the organic resin film and the interface reaction layer.

  For example, the organic resin film is a urethane resin film containing a urethane resin having excellent flexibility. The urethane-based resin constituting the urethane-based resin film is obtained by reacting a polyol and a polyisocyanate, but after forming the urethane-based resin film, when performing steam treatment to give a black color tone, the polyol is It is preferable to use an ether polyol (polyol containing an ether bond) and an ester polyol (polyol containing an ester bond) in combination at a predetermined ratio.

  When a urethane-based resin film is formed using only an ester-based polyol as a polyol, the ester bond in the urethane-based resin is hydrolyzed by water vapor, so that the corrosion resistance cannot be sufficiently improved. On the other hand, when a urethane-based resin film is formed using only an ether-based polyol as the polyol, the adhesion with the plated steel sheet is not sufficient, and the corrosion resistance cannot be sufficiently improved. In contrast, the present inventors use ether polyols and ester polyols in combination at a predetermined ratio, taking advantage of both and making up for the disadvantages, thereby significantly improving the corrosion resistance of the plated steel sheet. I found out that I could make it. According to this, even if it performs a water vapor | steam process in order to provide a black color tone after forming a urethane type resin film, the corrosion-resistant improvement effect by a urethane type resin film can be maintained. That is, a black-plated steel sheet having a black color tone and excellent corrosion resistance can be produced.

  The kind of ether polyol is not particularly limited, and may be appropriately selected from known ones. Examples of the ether polyol include polyethylene glycol, polypropylene glycol, linear polyalkylene polyol such as ethylene oxide or propylene oxide adduct of glycerin, and the like.

  The kind of ester polyol is not particularly limited, and may be appropriately selected from known ones. For example, as the ester polyol, a linear polyester having a hydroxy group in the molecular chain obtained by reacting a dibasic acid and a low molecular polyol can be used. Examples of dibasic acids include adipic acid, azelaic acid, dodecanedioic acid, dimer acid, isophthalic acid, hexahydrophthalic anhydride, terephthalic acid, dimethyl terephthalate, itaconic acid, fumaric acid, maleic anhydride, Esters are included.

  The ratio of the ether-based polyol in the polyol composed of the ether-based polyol and the ester-based polyol is preferably in the range of 5 to 30% by mass. When the ratio of the ether-based polyol is less than 5% by mass, the ratio of the ester-based polyol is excessively increased, so that the urethane-based resin film is easily hydrolyzed, and the corrosion resistance may not be sufficiently improved. On the other hand, when the ratio of the ether-based polyol is more than 30% by mass, the ratio of the ether-based polyol is excessively increased, so that the adhesion with the plated steel sheet is lowered and the corrosion resistance may not be sufficiently improved. .

  The kind of polyisocyanate is not particularly limited, and may be appropriately selected from known ones. For example, a polyisocyanate compound having an aromatic ring can be used as the polyisocyanate. Examples of polyisocyanate compounds having an aromatic ring include hexamethylene diisocyanate, o-, m- or p-phenylene diisocyanate, 2,4- or 2,6-tolylene diisocyanate, 2 hydrogenated aromatic rings. , 4- or 2,6-tolylene diisocyanate, diphenylmethane-4,4′-diisocyanate, 3,3′-dimethyl-4,4′-biphenylene diisocyanate, ω, ω′-diisocyanate-1,4-dimethylbenzene, ω , Ω′-diisocyanate-1,3-dimethylbenzene and the like. These may be used alone or in combination of two or more.

  The urethane resin film preferably further contains a polyhydric phenol. When the urethane-based resin film contains a polyhydric phenol, a concentrated layer of polyhydric phenol is formed at the interface between the plated steel plate and the polyhydric phenol to firmly adhere them. Therefore, the corrosion resistance of the urethane resin film can be further improved by blending polyhydric phenol into the urethane resin film.

  The kind of polyhydric phenol is not particularly limited, and may be appropriately selected from known ones. Examples of the polyhydric phenol include tannic acid, gallic acid, hydroquinone, catechol, and phloroglucinol. Moreover, the compounding quantity of the polyhydric phenol in a urethane type resin film has the preferable inside of the range of 0.2-30 mass%. When the blending amount of the polyhydric phenol is less than 0.2% by mass, the effect of the polyhydric phenol cannot be exhibited sufficiently. On the other hand, when the blending amount of the polyhydric phenol is more than 30% by mass, the stability of the paint may be lowered.

  The organic resin film may be a coating layer or a laminate layer. Moreover, it is preferable that an organic type resin film is a clear coating film from a viewpoint of utilizing the black external appearance of a black plating steel plate.

  The organic resin film can be formed by a known method. For example, when the organic resin film is a coating layer, an organic paint containing an organic resin or a valve metal compound is applied to the surface of the molten Al, Mg-containing Zn-plated steel sheet before or after contacting with water vapor. What is necessary is just to apply | coat and to dry without washing with water. Examples of the coating method include a roll coating method, a spin coating method, and a spray method. When a valve metal compound is added to the organic paint, an organic acid having a chelating action may be added to the organic paint so that the valve metal compound can be stably present in the organic paint. When an organic paint containing an organic resin, valve metal compound, fluoride, phosphate, etc. is applied to the surface of the plated steel sheet, inorganic anions such as fluorine ions and phosphate ions and metal or valve metal contained in the plated steel sheet A film (interfacial reaction layer) consisting of a reaction product with the above is formed preferentially and densely on the surface of the plated steel plate, on which a valve metal oxide, a valve metal hydroxide, a valve metal fluoride, An organic resin film in which particles such as phosphate are dispersed is formed. On the other hand, when the organic resin film is a laminate layer, an organic resin film containing a valve metal compound or the like may be laminated on the surface of the plated steel sheet.

  By the above procedure, the plating layer can be blackened to produce a black-plated steel sheet having excellent black appearance and workability.

  Since the manufacturing method of the present invention is blackened using water vapor, a black-plated steel sheet can be manufactured without imposing a load on the environment.

  Further, in the black plated steel sheet obtained by the production method of the present invention, the component (Zn, Al, Mg oxide and / or hydroxide) considered to impart a black color tone is not only the surface of the plating layer. It also exists inside. Therefore, the black-plated steel sheet obtained by the production method of the present invention can maintain a black appearance even if the surface of the plating layer is scraped, and has excellent black appearance retention.

  In addition, in the black-plated steel sheet obtained by the production method of the present invention, a component (Zn, Al, Mg oxide and / or hydroxide) considered to impart a black color tone forms one film. And dispersed in the plating layer. Therefore, the black-plated steel sheet obtained by the production method of the present invention is excellent in workability without lowering the adhesion of the plating layer. Of course, the black-plated steel sheet obtained by the production method of the present invention also has excellent corrosion resistance similar to that of ordinary molten Al and Mg-containing Zn-plated steel sheets.

  Moreover, since the black plating steel plate obtained by the manufacturing method of this invention has not formed the coating film, it is also possible to perform spot welding similarly to a normal molten Al and Mg containing Zn plating steel plate.

2. Method for Producing Black Plated Steel Sheet Molded Body The method for producing the black plated steel sheet according to the present invention includes 1) a first step of preparing a molten Al, Mg-containing Zn-plated steel sheet, and 2) a molten Al, Mg-containing Zn. A second step of bringing the plated steel sheet into contact with water vapor; and 3) a third step of forming the molten Al, Mg-containing Zn-plated steel sheet before or after the second step.

[First step and second step]
The first step and the second step are the same steps as the first step and the second step of the above-described black-plated steel sheet manufacturing method.

[Third step]
In a third step performed before or after the second step, a molten Al, Mg-containing Zn-plated steel sheet is formed. Specifically, when the third step is performed after the second step, the black-plated steel sheet brought into contact with water vapor is formed to obtain a molded body of the black-plated steel sheet. On the other hand, when performing a 2nd step after a 3rd step, the plated steel plate before making it contact with water vapor | steam is shape | molded. In this case, in the second step performed after the third step, the formed body of the plated steel sheet is brought into contact with water vapor to blacken the formed body of the plated steel sheet.

  The method for forming the molten Al, Mg-containing Zn-plated steel sheet is not particularly limited, and can be appropriately selected from known methods such as pressing, handling, and drawing.

  By the above procedure, a molded body of a black-plated steel sheet having excellent black appearance retention and workability can be produced.

  Since the manufacturing method of this invention is blackened using water vapor | steam, it can manufacture the molded object of a black plating steel plate, without applying a load to an environment.

  In addition, in the molded body of the black-plated steel sheet obtained by the production method of the present invention, the component (Zn, Al, Mg oxide and / or hydroxide) considered to give a black color tone is the surface of the plating layer. As well as inside. Therefore, the molded body of the black-plated steel sheet obtained by the production method of the present invention can maintain a black appearance even if the surface of the plating layer is scraped, and has excellent black appearance retention.

  Moreover, since the molded body of the black-plated steel sheet obtained by the production method of the present invention does not form a coating film, spot welding may be performed in the same manner as the molded body of normal molten Al, Mg-containing Zn-plated steel sheet. Is possible.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail with reference to an Example, this invention is not limited by these Examples.

[Example 1]
Using SPCC having a plate thickness of 0.8 mm as a base material, a molten Al / Mg-containing Zn-plated steel plate having a plating layer thickness of 0.8 to 100 μm was produced. At this time, the composition of the plating bath (concentration of Zn, Al and Mg) was changed to produce 22 types of plated steel sheets having different compositions of the plating layers. Table 1 shows the composition of the plating bath and the thickness of the plating layer of the 22 types of plated steel sheets produced. The composition of the plating bath and the composition of the plating layer are the same.

1 is an electron micrograph showing a cross section of a plated layer of a No. 8 plated steel sheet (a plated steel sheet of Comparative Example 8 described later). In the plated steel sheets other than No. 2, as shown in FIG. 1, a ternary eutectic structure of Al / Zn / Zn ₂ Mg and a primary Al phase were formed in the plating layer.

The produced plated steel sheet was placed in a high-temperature and high-pressure moist heat treatment apparatus (Hisaka Manufacturing Co., Ltd.), and the plating layer was brought into contact with water vapor under the conditions shown in Table 2. Table 2 shows the results of measuring the lightness (L value) of the surface of the obtained plated steel sheet using a spectroscopic color difference meter (TC-1800; Tokyo Denshoku Co., Ltd.). In the comparative example 9 of Table 2, instead of making it contact with water vapor | steam, the black coating material was apply | coated to the surface of a plated steel plate (urethane resin base, carbon black 20 mass%, film thickness 2 micrometers).

Using TOF-SIMS (TRIFT II; ULVAC-PHI Co., Ltd.), the ratio of the number of moles of Zn, Al and Mg oxides and hydroxides on the surface of the plating layer before and after the steam treatment was measured. Specifically, using TOF-SIMS, Ga ions are irradiated in the depth direction from the surface of the plating layer toward the inside of the steel sheet, and secondary ions released from the sample surface are separated by mass in time of flight. The average number of secondary ions of oxides and hydroxides of plating components having an analysis depth of 0.05 to 0.10 μm was measured (primary ion species: Ga ⁺ , detected ion species: secondary ions, primary acceleration voltage: 15 kV, raster area: 20 × 20 μm, analysis interval: 0.0012 μm). Table 3 shows the measurement results for each plated steel sheet.

FIG. 2 is an electron micrograph showing a cross section of the plated layer of the plated steel sheet of Example 11 after the steam treatment. In FIG. 2, “A” indicates a location corresponding to the Zn phase, “B” indicates a location corresponding to the Al phase, and “C” indicates a location corresponding to the Zn ₂ Mg phase.

Three points (Zn phase, Al phase, Zn ₂ Mg phase, respectively) in the portion of the plating layer 20% from the surface of the plating layer (when the thickness of the plating layer is 10 μm, the portion of 2 μm from the surface of the plating layer) Correspondence; see A, B, and C in FIG. 2) was analyzed using an energy dispersive X-ray spectrometer (EDX) attached to a scanning electron microscope (S-4000; Hitachi, Ltd.). Table 4 shows the results of analysis by EDX.

From Table 4, in the blackened plated steel sheet (Examples 1 to 22 and Comparative Examples 2 to 6) having an L value of 60 or less, the Zn phase contained oxygen in an amount of 1% by mass or more at least in the surface side 20% part of the plating layer. It is understood that the Al phase contains 10% by mass or more of oxygen, and the Zn ₂ Mg phase contains 5% by mass or more of oxygen.

  About each plated steel plate (Examples 1-22, Comparative Examples 1-9) after a water vapor process, the color tone change test, the corrosion resistance test, and the adhesiveness test were done. The results of each test are shown in Table 5.

  In the color change test, a SKD11 mold whose surface was polished with sandpaper (# 1000) was brought into contact with both sides of a test piece (width 30 mm × length 300 mm) cut out from each plated steel sheet, and 50 kgf was passed through the mold. The test piece was withdrawn at a rate of 100 mm / min while applying the load, and the change in lightness (L value) on the surface of the plated layer before and after drawing was measured. When the brightness change before and after the drawing was 5% or less, “◯” was evaluated, and when it was more than 5% and 10% or less, “Δ” was evaluated, and when it was more than 10%, “X” was evaluated.

  In the corrosion resistance test, a test piece (width 70 mm × length 150 mm) cut from each plated steel plate is sealed, and then a 35 ° C. NaCl aqueous solution is sprayed on the test piece for 8 hours in accordance with JIS Z2371. went. When the white rust generation area ratio after spraying was 5% or less, it was evaluated as “◯”, when it exceeded 5% and 10% or less, “Δ”, and when it exceeded 10%, it was evaluated as “x”.

The adhesion test was performed by closely bending (4t) a test piece cut out from each plated steel sheet and performing a cellophane tape peeling test on the bent portion. When the peeled area ratio of the plating layer after peeling the cellophane tape is 0% (no peeling), “◎”, when it exceeds 0% and less than 5%, “◯”, when it is 5% or more and less than 10%, [Delta] "When 10% or more," x "was evaluated.

  As shown in Table 5, since the plated steel sheet of Comparative Example 1 does not contain Mg in the plating layer, it cannot be sufficiently blackened, and the adhesion of the plating layer has decreased. .

  Moreover, since the content of Al or Mg in the plating layer of the plated steel sheets of Comparative Examples 2 to 5 was outside the proper range, the adhesion of the plating layer was lowered.

  In the plated steel sheet of Comparative Example 6, the temperature of water vapor was high, and oxides and hydroxides were excessively formed in the plating layer, so that the corrosion resistance and the adhesion of the plating layer were lowered.

  In the plated steel sheet of Comparative Example 7, the relative humidity of water vapor was low, and oxides and hydroxides could not be sufficiently formed in the plating layer.

  The plated steel sheet of Comparative Example 8 was not blackened at all because it was not in contact with water vapor.

  Since the plated steel sheet of Comparative Example 9 was blackened by the black coating film, the black appearance could not be maintained when brought into contact with the mold.

  On the other hand, the plated steel plates of Examples 1 to 22 were sufficiently blackened, and were good results in all of black color retention, corrosion resistance, and plating layer adhesion.

  In addition, the evaluation of the color tone change test of the plated steel plate of Example 2 is “△” because the thickness of the plating layer is as thin as 0.8 μm and scratches reaching the base steel plate by processing have entered. Conceivable.

  From the above, it can be seen that the method for producing a black-plated steel sheet according to the present invention can produce a black-plated steel sheet having excellent black appearance, workability, and corrosion resistance.

[Example 2]
Apply the inorganic chemical conversion treatment liquid shown in Table 6 to the No. 15 plated steel sheet in Table 1, put in an electric oven without washing with water, and heat-dry under conditions where the ultimate plate temperature is 120 ° C. An inorganic coating was formed on the surface of the steel plate.

The plated steel sheet on which the inorganic film was formed was placed in a high-temperature and high-pressure wet heat treatment apparatus, and the plating layer was brought into contact with water vapor under the conditions shown in Table 7. Table 7 shows the results of measuring the lightness (L value) of the surface of the obtained plated steel sheet using a spectroscopic color difference meter.

Using TOF-SIMS, the ratio of the number of moles of oxides and hydroxides of Zn, Al and Mg in the surface layer of the plating layer before and after the steam treatment was measured. Table 8 shows the measurement results of each plated steel sheet.

Three points (Zn phase, Al phase, Zn ₂ Mg phase) at a site where the thickness of the plating layer is 20% from the surface of the plating layer (when the thickness of the plating layer is 10 μm, a site of 2 μm from the surface of the plating layer) The composition was analyzed using an energy dispersive X-ray spectrometer (EDX) attached to the scanning electron microscope. Table 9 shows the results of analysis by EDX.

About each plated steel plate (Examples 23-41, Comparative Examples 10-12) after a water vapor process, the color tone change test, the corrosion resistance test, and the adhesiveness test were done. The color tone change test and the adhesion test were performed according to the procedure described above. The corrosion resistance test was performed by spraying a 35 ° C. NaCl aqueous solution onto the test piece for 24 hours in accordance with JIS Z2371. The results of each test are shown in Table 10.

  From Table 10, it can be seen that by forming the inorganic coating, the corrosion resistance of the black-plated steel sheet and the adhesion of the plating layer can be further improved.

[Example 3]
Electric oven without applying the organic chemical conversion treatment liquid shown in Table 11 to the black-plated steel plate (L value: 30) of Example 11 in Table 2 and the plated steel plate (L value: 93) of Comparative Example 8 without washing with water And heated and dried under the condition that the ultimate plate temperature is 160 ° C. to form an organic resin film on the surface of the plated steel plate.

The corrosion resistance test was done about each plated steel plate (Examples 42-60, Comparative Examples 13-15) which formed the organic type resin film. The corrosion resistance test was performed by spraying a 35 ° C. NaCl aqueous solution onto the test piece for 24 hours in accordance with JIS Z2371. The results of each test are shown in Table 12.

  From Table 12, it turns out that the corrosion resistance of a black plating steel plate can be improved more by forming an organic resin film.

[Example 4]
Polyethylene wax (average particle size: 1.0 μm) was added to No. 3, 4 and 6 organic chemical conversion treatment solutions shown in Table 11 at 10 g / L to prepare a wax-containing organic chemical conversion treatment solution.

  An electric oven without applying the prepared wax-containing organic chemical conversion treatment liquid to the black-plated steel sheet of Example 11 (L value: 30) in Table 2 and the plated steel sheet of Comparative Example 8 (L value: 93) and washing with water. And heated and dried under the condition that the ultimate plate temperature is 160 ° C. to form an organic resin film on the surface of the plated steel plate.

  About each plated steel plate (Examples 61-71, Comparative Examples 16-18) which formed the organic type resin film, the color tone change test and the corrosion resistance test were done. The results of each test are shown in Table 13.

  In the color tone change test, a SKD11 mold whose surface was polished with sandpaper (# 500) was brought into contact with both surfaces of a test piece (width 30 mm × length 300 mm) cut out from each plated steel sheet, and 50 kgf was passed through the mold. The test piece was withdrawn at a rate of 100 mm / min while applying the load, and the change in lightness (L value) on the surface of the plated layer before and after drawing was measured. When the brightness change before and after the drawing was 5% or less, “◯” was evaluated, and when it was more than 5% and 10% or less, “Δ” was evaluated, and when it was more than 10%, “X” was evaluated.

The corrosion resistance test was performed by spraying a 35 ° C. NaCl aqueous solution onto the test piece for 24 hours in accordance with JIS Z2371. When the white rust generation area ratio after spraying was 5% or less, it was evaluated as “◯”, when it exceeded 5% and 10% or less, “Δ”, and when it exceeded 10%, it was evaluated as “x”.

  From Table 13, it is possible to suppress the color tone change of the black plated steel sheet by forming the organic resin film, and it is possible to further suppress the color tone change of the black plated steel sheet by adding wax to the organic resin film. I understand that.

[Example 5]
Polyethylene wax (average particle size: 1.0 μm) was added to No. 3 organic chemical conversion treatment solution No. 3 shown in Table 11 to prepare a wax-containing organic chemical conversion treatment solution.

  Apply the inorganic chemical conversion solution of No. 1 shown in Table 6 or the wax-containing organic chemical conversion solution shown in Table 6 to the No. 8 plated steel sheet of Table 1, and place it in an electric oven without washing with water. Was heated and dried at 160 ° C. to form a chemical conversion film (inorganic film or organic resin film) on the surface of the plated steel sheet.

  Either subjecting the plated steel sheet subjected to chemical conversion treatment or the No. 8 plated steel sheet not subjected to chemical conversion treatment to contact with water vapor and then subjected to cylindrical drawing (Examples 72 to 74), or after performing cylindrical drawing processing, contact with water vapor (Examples 75-77). The steam treatment was performed for 5 hours under the conditions of a temperature of 170 ° C. and a relative humidity of 80%. The conditions of cylindrical drawing are as follows: punch diameter: 50 mm, punch shoulder R: 15 mm, die diameter: 54 mm, die shoulder R: 8 mm, punching diameter: 100 mm, drawing height: 25 mm, plated steel sheet on which no chemical conversion treatment film is formed Oil was applied only to the plated steel sheet on which the inorganic film was formed.

Table 14 shows the results of measuring the lightness (L value) of the surface of the sliding portion of the formed plated steel sheet using a spectroscopic color difference meter. In addition, about the oiled molded object, the brightness was measured after carrying out alkali degreasing (pH10, liquid temperature 60 degreeC, immersion time 1 minute).

  From Table 14, it can be seen that even if the steam treatment is performed after the plated steel sheet is formed, a molded body having a black appearance can be produced in the same manner as in the case where the steam treatment is performed.

[Example 6]
No. in Table 1 15 coated with the organic chemical conversion treatment liquid shown in Table 15 and Table 16, put in an electric oven without washing with water, and dried by heating under the condition that the ultimate plate temperature is 160 ℃, An organic resin film (urethane resin film) was formed on the surface.

The plated steel sheet on which the organic resin film was formed was placed in a high-temperature and high-pressure wet heat treatment apparatus, and the plating layer was brought into contact with water vapor under the conditions shown in Table 17. Table 17 shows the results of measuring the brightness (L value) of the surface of the obtained plated steel sheet using a spectroscopic color difference meter.

Using TOF-SIMS, the ratio of the number of moles of oxides and hydroxides of Zn, Al and Mg in the surface layer of the plating layer before and after the steam treatment was measured. Table 18 shows the measurement results of the respective plated steel sheets.

Three points (Zn phase, Al phase, Zn ₂ Mg phase) at a site where the thickness of the plating layer is 20% from the surface of the plating layer (when the thickness of the plating layer is 10 μm, a site of 2 μm from the surface of the plating layer) The composition was analyzed using an energy dispersive X-ray spectrometer (EDX) attached to the scanning electron microscope. Table 19 shows the results of analysis by EDX.

About each plated steel plate (Examples 78-104) after a water vapor process, the color tone change test, the corrosion resistance test, and the adhesiveness test were done. The color tone change test and the adhesion test were performed according to the procedure described above. The corrosion resistance test was performed by spraying a 35 ° C. NaCl aqueous solution on a test piece for 36 hours in accordance with JIS Z2371. When the area ratio of white rust after spraying is 0%, “◎” is 1% or more and 5% or less, “◯”, when it is over 5% and 10% or less, “△”, when it is over 10% Was evaluated as “×”. The results of each test are shown in Table 20.

  In this example, after an organic resin film was formed on a molten Al, Mg-containing Zn-plated steel sheet, the plated steel sheet on which the organic resin film was formed was brought into contact with water vapor and blackened. In this case, even if an organic resin film is formed, the corrosion resistance may not be sufficiently improved (see Table 20; Examples 91 to 100). On the other hand, the black plated steel sheets of Examples 78 to 90 in which the urethane-based resin film was formed by combining the ether-based polyol and the ester-based polyol at a predetermined ratio had sufficiently improved corrosion resistance.

  From Table 20, it can be seen that the corrosion resistance is improved by adding a urethane resin to the valve metal compound (see Examples 82, 83, 93, 94, and 101 to 103). Moreover, it turns out that corrosion resistance can be improved more by adding at least one of a valve metal compound and a phosphate to a urethane type resin film (see Examples 79, 82, 83, 86 and 90). Moreover, it turns out that corrosion resistance can be further improved by adding a polyhydric phenol to a urethane-type resin film rather than the case where a valve metal compound or a phosphate is added (Examples 80, 81, 84 and 87-). 89).

  The black-plated steel sheet of the present invention is useful as a plated steel sheet used in, for example, building roofing materials, exterior materials, home appliances, automobiles, etc., because it is excellent in designability, black appearance retention and workability. .

Claims (12)

Al: 1.0 to 22.0 mass%, Mg: molten Al containing 1.5 to 10.0 mass%, a molten Al having a Mg-containing Zn plating layer, a step of preparing a Mg-containing Zn-plated steel sheet;
Contacting the molten Al, Mg-containing Zn-plated steel sheet with water vapor at 105 ° C or higher,
The number of moles of Zn oxide [Zn (O ₀ ) on the surface of the plating layer after contacting with water vapor to the number of moles of Zn oxide [Zn (O ₀ )] on the surface of the plating layer before contacting with water vapor )] Ratio [Zn (O / O ₀ )] is in the range of 60-2700,
The number of moles of Al oxide on the surface of the plating layer after contact with water vapor [Al (O) relative to the number of moles of Al oxide on the surface of the plating layer before contact with water vapor [Al (O ₀ )] )] Ratio [Al (O / O ₀ )] is in the range of 50-200,
The number of moles of Mg oxide on the surface of the plating layer after contacting with water vapor [Mg (O) relative to the number of moles of Mg oxide on the surface of the plating layer before contacting with water vapor [Mg (O ₀ )] )] Ratio [Mg (O / O ₀ )] is in the range of 40-240,
The number of moles of Zn hydroxide [Zn (OH ₀ )] on the surface of the plating layer before contacting with water vapor [Zn hydroxide on the surface of the plating layer after contacting with water vapor [Zn] (OH)] ratio [Zn (OH / OH ₀ )] is in the range of 7 to 270,
The number of moles of Al hydroxide on the surface of the plating layer after contacting with water vapor [Al (OH ₀ )] relative to the number of moles of Al hydroxide on the surface of the plating layer before contacting with water vapor [Al (OH)] ratio [Al (OH / OH ₀ )] is in the range of 8-20,
The number of moles of Mg hydroxide on the surface of the plating layer after contacting with water vapor [Mg (OH ₀ )] with respect to the number of moles of Mg hydroxide on the surface of the plating layer before contacting with water vapor [Mg (OH ₀ )] (OH)] ratio [Mg (OH / OH ₀ )] is in the range of 10-90,
Manufacturing method of black plated steel sheet. _{2. The} method for producing a black-plated steel sheet according to claim 1, wherein the molten Al and Mg-containing Zn plating layer includes a ternary eutectic structure of Al / Zn / Zn ₂ Mg.   The manufacturing method of the black plating steel plate of Claim 1 which further has a step which forms an inorganic type film | membrane on the surface of the said fusion | melting Al and Mg containing Zn plating steel plate. The inorganic coating is one or more selected from the group consisting of valve metal oxides, valve metal oxyacid salts, valve metal hydroxides, valve metal phosphates and valve metal fluorides. only containing the compound,
The valve metal is one or more metals selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Mo, W, Si and Al.
The manufacturing method of the black plating steel plate of Claim 3.   The method for producing a black-plated steel sheet according to claim 1, further comprising a step of forming an organic resin film on a surface of the molten Al, Mg-containing Zn-plated steel sheet. The organic resin contained in the organic resin film is a urethane resin obtained by reacting a polyol composed of an ether polyol and an ester polyol with polyisocyanate,
The ratio of the ether polyol in the polyol is 5 to 30% by mass.
The manufacturing method of the black plating steel plate of Claim 5 . The said organic resin film is a manufacturing method of the black plating steel plate of Claim 6 which further contains polyhydric phenol. The said organic resin film is a manufacturing method of the black plating steel plate of Claim 5 containing a lubricant. The organic resin film is one or two kinds selected from the group consisting of valve metal oxide, valve metal oxyacid salt, valve metal hydroxide, valve metal phosphate and valve metal fluoride. only contains the above compounds,
The valve metal is one or more metals selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Mo, W, Si and Al.
The manufacturing method of the black plating steel plate of Claim 5 . The method for producing a black-plated steel sheet according to claim 5 , wherein the organic resin film is a laminate layer or a coating layer. The said organic resin film is a manufacturing method of the black plated steel plate of Claim 5 which is a clear coating film. Al: 1.0 to 22.0 mass%, Mg: molten Al containing 1.5 to 10.0 mass%, a molten Al having a Mg-containing Zn plating layer, a step of preparing a Mg-containing Zn-plated steel sheet;
Contacting the molten Al, Mg-containing Zn-plated steel sheet with water vapor at 105 ° C or higher;
Forming the molten Al, Mg-containing Zn-plated steel sheet before or after contacting with the water vapor, and
The number of moles of Zn oxide [Zn (O ₀ ) on the surface of the plating layer after contacting with water vapor to the number of moles of Zn oxide [Zn (O ₀ )] on the surface of the plating layer before contacting with water vapor )] Ratio [Zn (O / O ₀ )] is in the range of 60-2700,
The number of moles of Al oxide on the surface of the plating layer after contact with water vapor [Al (O) relative to the number of moles of Al oxide on the surface of the plating layer before contact with water vapor [Al (O ₀ )] )] Ratio [Al (O / O ₀ )] is in the range of 50-200,
The number of moles of Mg oxide on the surface of the plating layer after contacting with water vapor [Mg (O) relative to the number of moles of Mg oxide on the surface of the plating layer before contacting with water vapor [Mg (O ₀ )] )] Ratio [Mg (O / O ₀ )] is in the range of 40-240,
The number of moles of Zn hydroxide [Zn (OH ₀ )] on the surface of the plating layer before contacting with water vapor [Zn hydroxide on the surface of the plating layer after contacting with water vapor [Zn] (OH)] ratio [Zn (OH / OH ₀ )] is in the range of 7 to 270,
The number of moles of Al hydroxide on the surface of the plating layer after contacting with water vapor [Al (OH ₀ )] relative to the number of moles of Al hydroxide on the surface of the plating layer before contacting with water vapor [Al (OH)] ratio [Al (OH / OH ₀ )] is in the range of 8-20,
The number of moles of Mg hydroxide on the surface of the plating layer after contacting with water vapor [Mg (OH ₀ )] with respect to the number of moles of Mg hydroxide on the surface of the plating layer before contacting with water vapor [Mg (OH ₀ )] (OH)] ratio [Mg (OH / OH ₀ )] is in the range of 10-90,
A method for producing a molded body of a black-plated steel sheet.