JP2017172014A - Black plated steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a black plated steel sheet having a small amount of Mg included in a galvanized layer.SOLUTION: The content of Al is 0.1-10.0 mass% or less, and the content of Mg is 0.1 mass% or less. The surface of a molten Al-containing Zn plated layer having black Zn oxide distributed in the plated layer has a brightness of 60 or less in an Lvalue.SELECTED DRAWING: None

Description

  The present invention relates to 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 standpoint of design. 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-mentioned fields, plated steel sheets plated with hot-dip Zn plating, hot Al-containing Zn plating, hot Al or Mg-containing Zn plating are often used, and the surface of these plated steel sheets has a metallic luster. It has a certain silver-white color tone. 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 of forming a thin black film on the surface of a plating layer by spraying high-temperature water vapor on a molten Al, Mg-containing Zn-plated steel sheet for 24 hours or more. In the black plated steel sheet described in Patent Document 1, Mg, Cu, Bi, or the like is included in the plating layer as a blackening promoting element. However, it is described that when the content of the blackening promoting element exceeds 1%, the oxidation of Zn is suppressed, and thus the blackening promoting effect is decreased.

Furthermore, in order to form a thick black film to enhance the retention of the black appearance after processing, and to produce it by a short blackening treatment, Al: 1.0 to 22.0 mass%, Mg: 1.3 to A molten Al / Mg-containing Zn-plated steel sheet containing 10.0% by mass and having a Zn ₂ Mg phase distributed in the plating layer is used as a raw sheet, and the plated steel sheet is contacted with water vapor in a sealed container. A method of blackening the plating layer has been proposed (see Patent Document 2).

Japanese Unexamined Patent Publication No. 64-56881 JP2013-241665A

In the black-plated steel sheet described in Patent Document 2, Mg contained in the Zn ₂ Mg phase takes oxygen from Zn to form an oxygen-deficient oxide, so that the black oxide is distributed to the deep part of the plated steel sheet. Therefore, the black-plated steel sheet described in Patent Document 2 is excellent in retention of the black appearance after processing, and can be manufactured by a short-time blackening treatment. However, in the method described in Patent Document 2, it is considered that the plating layer is not sufficiently blackened if a certain amount of Mg is not present in the plating layer.

  On the other hand, with the increase in demand for black-plated steel sheets, there is a demand for blackening a plating layer having a wider composition.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a black-plated steel sheet having a blackened plating layer although the amount of Mg contained in the plating layer is small.

  The present inventor made a plated steel sheet having a molten Al-containing Zn plating layer having an Al content of 0.1% by mass or more and 10.0% by mass or less and an Mg content of 0.1% by mass or less. And the present invention was completed by finding that the above-mentioned problems can be solved by bringing the plated steel sheet into contact with water vapor in a sealed container.

That is, this invention relates to the following black plating steel plates.
[1] The base steel sheet, the Al content is 0.1% by mass or more and 10.0% by mass or less, the Mg content is 0.1% by mass or less, and the Zn black oxide is A black-plated steel sheet having a molten Al-containing Zn plating layer distributed in the plating layer, wherein the surface brightness of the molten Al-containing Zn plating layer is 60 or less in terms of L ^* value.
[2] The black plated steel sheet according to [1], further including an inorganic film, wherein the base steel sheet, the molten Al-containing Zn plating layer, and the inorganic film are laminated in this order.
[3] The inorganic coating may be one kind selected from the group consisting of valve metal oxides, valve metal oxyacid salts, valve metal hydroxides, valve metal phosphates, and valve metal fluorides. The valve metal contains two or more kinds of compounds, and the valve metal is one or more kinds of metals selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, W, Si, and Al. [2] A black-plated steel sheet as described in 1.
[4] The black plated steel sheet according to [1], further including an organic resin film, wherein the base steel sheet, the molten Al-containing Zn plating layer, and the organic resin film are laminated in this order.
[5] The black plated steel sheet according to [4], wherein the organic resin film includes a lubricant.
[6] The organic resin film is one type selected from the group consisting of valve metal oxides, valve metal oxyacid salts, valve metal hydroxides, valve metal phosphates and valve metal fluorides. Or two or more compounds, wherein the valve metal is one or more metals selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, W, Si and Al, [4 ] Or the black-plated steel sheet according to [5].
[7] The black plated steel sheet according to any one of [4] to [6], wherein the organic resin film is a laminate layer or a coating layer.
[8] The black plated steel sheet according to any one of [4] to [7], wherein the organic resin film is a clear coating film.
[9] The black-plated steel sheet according to any one of [1] to [8], which is a processed product.

  ADVANTAGE OF THE INVENTION According to this invention, although there is little quantity of Mg contained in a plating layer, the black plating steel plate which has a blackened plating layer can be provided.

FIG. 1 is an optical microscope image showing a cross-section of a plated layer of a molten Al-containing Zn-plated steel sheet after steam treatment.

1. Black-plated steel sheet The black-plated steel sheet of the present invention has a base steel sheet and a molten Al-containing Zn plating layer (hereinafter also referred to as “plating layer”). The black-plated steel sheet of the present invention may further have an inorganic coating or an organic resin coating. The inorganic coating or organic resin coating is formed such that the base steel plate, the molten Al-containing Zn plating layer, and the inorganic coating or organic resin coating are laminated in this order. The black-plated steel sheet of the present invention may have only one of the inorganic coating and the organic resin coating, or may have both of them. When both the inorganic coating and the organic resin coating are provided, the order of stacking these coatings is not limited, and the inorganic coating is laminated so as to be closer to the molten Al-containing Zn plating layer. Alternatively, the organic resin film may be laminated so as to be closer to the molten Al-containing Zn plating layer.

  The black-plated steel sheet of the present invention can be made not only perfect black but also black gray with higher brightness by adjusting the blackening treatment conditions such as the degree of steam treatment. In the present invention, black plating and black gray plating are collectively referred to as “black plating”, and a steel plate having such black plating is referred to as “black plated steel plate”.

In the black-plated steel sheet of the present invention, 1) the black oxide of Zn is distributed in the plating layer, and 2) the brightness of the plating layer surface is L ^* value of 60 or less (preferably 40 or less, more preferably 35 or less) is one feature. The lightness (L ^* value) of the plating layer surface is measured by a spectral reflection measurement method based on JIS K 5600 using a spectral color difference meter.

  The black-plated steel plate of the present invention may be a plate-like steel plate blackened, or a processed product obtained by blackening a processed steel plate or a blackened plate-like steel plate. The obtained processed product may be used.

[Base steel sheet]
The kind of base 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. Moreover, you may use the high strength steel plate containing P, Si, Mn, etc.

[Fused Al-containing Zn plating layer]
The plating layer is a molten Al-containing Zn plating layer containing 0.1% by mass or more and 10.0% by mass or less of Al. Al is an element that suppresses the growth of the alloy layer of the Zn-based plated steel sheet and improves the plating adhesion during processing. In the present invention, Al is an essential element for blackening as described later. By increasing the Al content beyond the lower limit of the above range, a sufficient alloy layer growth suppressing effect can be imparted. On the other hand, by reducing the amount of Al below the upper limit of the above range, the amount of oxide (dross) generated on the plating bath surface during the production of the plated steel sheet can be reduced, and a beautiful plated steel sheet can be easily obtained. . In addition, since Al itself is difficult to blacken, if the amount of Al exceeds the upper limit of the above range, the amount of Al on the plating surface increases and the portion that does not blacken increases, so that it is difficult to obtain a black-plated steel sheet.

  The molten Al-containing Zn plating layer having the above composition may contain Mg. When the molten Al-containing Zn plating layer contains Mg, the Mg content is 0.0 mass% or more and 0.1 mass% or less. The molten Al-containing Zn plating layer having the above composition is sufficiently blackened by water vapor treatment even if the Mg content is 0.1% by mass or less. The Mg content is preferably 0.01% by mass or less, and more preferably does not contain Mg.

  The black-plated steel sheet of the present invention obtained by blackening a plated steel sheet having a molten Al-containing Zn-plated layer having the above composition is low in the amount of Mg contained in the plated layer, or contains no Mg. It has a softer black plating layer than a black-plated steel sheet containing more. Therefore, even when the plating layer is subjected to tensile stress due to processing of the black plated steel sheet or the like, cracks are hardly generated in the plating layer, so that white rust is hardly generated in the processed portion.

  Further, the black-plated steel sheet of the present invention can be manufactured at a lower cost than a black-plated steel sheet containing more Mg because the plating layer contains a small amount of Mg or contains no Mg at all.

  In addition, in this specification, the value of the content of each component in the plating layer is expressed as a percentage obtained by dividing the mass of each metal component contained in the plating layer by the mass of all metals contained in the plating layer. It is. That is, the mass of oxygen and water contained in the oxide is not included as a component in the plating layer. Therefore, when the elution of the metal component does not occur during the steam treatment, the value of the content of each component in the plating layer does not change before and after the steam treatment.

  The molten Al-containing Zn plating layer has 0.005 mass of Si capable of suppressing the growth of the Al—Fe alloy layer at the interface between the base steel plate and the plating layer in order to improve the adhesion between the base steel plate and the plating layer. You may contain in a plating layer in the range of%-2.0 mass%. If the Si concentration exceeds 2.0 mass%, there is a possibility that a Si-based oxide that inhibits blackening may be generated on the surface of the plating layer. Further, Ti, B, Ti—B alloy, Ti-containing compound or B-containing compound may be contained in the plating layer. The content of these compounds is set so that Ti is in the range of 0.001 mass% to 0.1 mass% and B is in the range of 0.0005 mass% to 0.045 mass%. It is preferable to do. When an excessive amount of Ti or B is contained, there is a possibility that precipitates are grown on the plating layer. In addition, the inclusion of Ti, B, Ti-B alloy, Ti-containing compound or B-containing compound in the plating layer hardly affects the blackening by the water vapor treatment.

  Although the thickness of a plating layer is not specifically limited, The inside of the range of 3-100 micrometers is preferable. When the thickness of the plating layer is less than 3 μm, scratches that reach the base steel sheet during handling are likely to occur, so that the black appearance retention and corrosion resistance may be reduced. 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.

[Black oxide]
The black-plated steel sheet of the present invention contains a black oxide of Zn distributed in the plating layer (see FIG. 1). Here, in the plating layer includes both the surface of the plating layer and the inside of the plating layer. In the present specification, oxides and hydrated oxides are collectively referred to as oxides.

  FIG. 1 is an optical microscope image showing a cross-section of the plated layer of the black-plated steel sheet of the present invention. As shown in FIG. 1, in the black plated steel sheet of the present invention, the black oxide of Zn is distributed in the plating layer. The mechanism of the formation of Zn black oxide is considered as follows.

When the above-mentioned molten Al-containing Zn-plated steel sheet was brought into contact with water vapor in a sealed container, first, the oxide film on the surface of the plating layer reacted with H ₂ O to be changed into a hydrated oxide and passed through this oxide layer. H ₂ O reacts with the metal in the plating layer. At this time, Zn in which Al is dissolved is preferentially oxidized. Over time, Zn oxidation proceeds in the depth direction of the plating layer. Since the oxygen potential is lowered in the water vapor atmosphere, Al having high reactivity with oxygen existing in the vicinity of the Zn oxide takes oxygen from the Zn oxide and becomes Al oxide. For this reason, it is considered that the Zn oxide changes to a non-stoichiometric composition and an oxygen-deficient oxide (for example, ZnO _1-x ). When an oxygen-deficient oxide is generated in this way, light is trapped in the defect level, and the oxide exhibits a black appearance. On the other hand, the Zn contained in the Zn phase has a slow oxidation reaction, and most of it remains as a metal. As a result, the plated layer of the black plated steel sheet obtained by the present invention has a metal structure in which the black oxide of Zn is distributed.

Moreover, Al in the plating layer has an effect of promoting oxidation into the plating layer. Al is more reactive with H ₂ O than Zn and Mg. Therefore, when Al comes into contact with high-temperature steam, it quickly becomes an oxide. After Al is oxidized quickly, oxidation of the Zn phase located inside proceeds in the depth direction of the plating layer. Thus, Al serves as a “pass” for promoting the oxidation of Zn inside the plating layer. As a result, when Al is present in the plating layer, a black oxide of Zn is formed inside the plating layer in a shorter time.

In the black-plated steel sheet described in Patent Document 1, only the surface of the plating layer is blackened by the formation of ZnO _1-x needle-like crystals. On the other hand, in the black plated steel sheet of the present invention, when considering the reaction mechanism described above, a layered black oxide film is formed on the surface of the plated layer, and the black oxide of Zn is distributed inside the plated layer. . Therefore, in the black-plated steel sheet of the present invention, the black appearance is maintained even if the plating layer is scratched by processing. The fact that the oxide inside the plating layer is black indicates that the cross section of the plating layer is observed with an optical microscope (see FIG. 1), or metal Zn and Al in the plating layer (and the plating layer using a saturated HgCl ₂ solution). Mg) when Mg contains Mg can be amalgamated and removed, and only the oxide can be recovered. In addition, the black oxide in a plating layer may be blackened to the inside, and only the surface may be blackened.

[Inorganic film and organic resin film]
The black plated steel sheet of the present invention may be laminated with an inorganic coating or an organic resin coating. The inorganic coating and the organic resin coating improve the corrosion resistance and powdering resistance of the black plated steel sheet. A black-plated steel sheet with a small amount of Mg is unlikely to have sufficient corrosion resistance, and there are cases in which peeling of the plating or powdering occurs in particularly severe processing. However, the black-plated steel sheet of the present invention can achieve practical corrosion resistance and powdering resistance by forming these films even if the corrosion resistance by itself is not sufficiently increased. They found it.

(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, 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 inorganic coating material may contain soluble fluoride of valve metal, or a soluble fluoride such as (NH ₄ ) F separately from the valve metal compound. May be included.

  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.

(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 a lubricant, it is possible to reduce friction between the mold and the surface of the plated steel sheet during press working or the like, and to suppress galling on the surface of the plated steel sheet (improvement of galling resistance). 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 oxyacid salt, valve metal hydroxide, valve metal fluoride, phosphate, etc. 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 a water vapor treatment is performed to give a black color tone after forming the urethane resin film (described later), the effect of improving the corrosion resistance by the urethane 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 sheet and the urethane-based resin film. 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 laminate layer or a coating 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.

  In the black-plated steel sheet of the present invention, the black oxide that imparts a black color tone is present not only on the surface of the plating layer but also on the inside, and is not present in a layered manner on the plating layer. Dispersed in. Therefore, the black-plated steel sheet of the present invention can maintain a black appearance even if the surface of the plating layer is scraped, has excellent black appearance retention, and the adhesion of the plating layer is reduced by blackening. It is excellent in workability.

  Although the manufacturing method of the black plating steel plate of this invention is not specifically limited, The black plating steel plate of this invention can be manufactured by the following method, for example.

2. Black Plated Steel Plate Manufacturing Method The black plated steel plate manufacturing method of the present invention includes 1) a first step of preparing a molten Al-containing Zn plated steel plate, and 2) contacting the molten Al-containing Zn plated steel plate with water vapor in a sealed container. And a second step. 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-containing Zn-plated steel sheet before or after the second step.

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

  In the molten Al-containing Zn-plated steel sheet, for example, the Al content is 0.1 mass% or more and 10.0 mass% or less, the Mg content is 0.1 mass% or less, and the balance is substantially Zn. It can be manufactured by a hot dipping method using an alloy plating bath. By doing in this way, the content of Al is 0.1 mass% or more and 10.0 mass% or less, the content of Mg is 0.1 mass% or less, and the remainder forms a plating layer made of Zn. can do. Moreover, the alloy plating bath may contain Si, Ti, B, a Ti-B alloy, a Ti-containing compound, and a B-containing compound.

[Second step]
In the second step, the plated steel sheet prepared in the first step is brought into contact with water vapor in a sealed container to blacken the plating layer. By this step, the lightness (L ^* value) of the plating layer surface can be reduced to 60 or less (preferably 40 or less, more preferably 35 or less). The brightness (L ^* value) of the plating layer surface is measured using a spectroscopic color difference meter.

  In the second step, if oxygen is present in the atmosphere when performing the water vapor treatment, the plating layer cannot be sufficiently blackened. This is presumed that when steam treatment is performed in an oxygen-rich atmosphere, the formation of gray basic zinc aluminum carbonate in the surface layer is prioritized over the formation of black oxygen-deficient oxide of Zn. Is done. Therefore, in the second step, it is necessary to perform the steam treatment while reducing the oxygen concentration (oxygen partial pressure) in the atmosphere. Specifically, the oxygen concentration during the steam treatment is preferably 13% or less. A method for reducing the oxygen concentration in the atmosphere is not particularly limited. For example, the concentration (relative humidity) of water vapor may be increased, the air in the container may be replaced with an inert gas, or the air in the container may be removed with a vacuum pump or the like. In any case, the steam treatment needs to be performed in a closed container.

  In the manufacturing method of the black plating steel plate of patent document 1, since high temperature steam is sprayed on the surface of a plating steel plate, it is thought that steam processing is performed by the open system which cannot adjust oxygen concentration. However, even if the steam treatment is performed in an open system in which the oxygen concentration cannot be adjusted with respect to the molten Al-containing Zn-plated steel sheet prepared in the first step, the plated layer cannot be sufficiently blackened.

(Processing temperature)
The temperature of the steam treatment is preferably in the range of 50 ° C. or more and 350 ° C. or less. When the temperature of the water vapor treatment is less than 50 ° C., the blackening speed is slow and productivity is lowered. In addition, when water is heated to 100 ° C. or higher in a sealed container, the pressure in the container becomes 1 atm or higher, and the oxygen concentration in the atmosphere can be easily lowered, so the temperature of the steam treatment is 100 ° C. or higher. It is more preferable. On the other hand, when the temperature of the steam treatment is higher than 350 ° C., the blackening speed becomes very fast and it becomes difficult to control. Further, not only the processing apparatus becomes large, but also the total processing time including the time required for temperature increase and decrease becomes longer, which is not practical. Therefore, from the viewpoint of removing oxygen in the atmosphere and controlling the blackening rate, the steam treatment temperature is particularly preferably in the range of 105 ° C. or more and 200 ° C. or less.

When it is desired to lower the temperature of the steam treatment to less than 100 ° C., an inert gas may be placed in the container in order to suppress the mixing of oxygen by setting the pressure in the container to atmospheric pressure or higher. The kind of the inert gas is not particularly limited as long as it is irrelevant to the blackening reaction. Examples of the inert gas include Ar, N ₂ , He, Ne, Kr, and Xe. Among these, Ar, N ₂ and He that can be obtained at low cost are preferable. Further, the steam treatment may be performed after the air in the container is removed by a vacuum pump or the like.

(Relative humidity)
The relative humidity of water vapor during the water vapor treatment is preferably in the range of 30% or more and 100% or less, and more preferably in the range of 30% or more and less than 100%. When the relative humidity of the water vapor is less than 30%, the blackening speed is slow and the productivity is lowered. Moreover, when the relative humidity of water vapor | steam is 100%, there exists a possibility that dew condensation may adhere to the surface of a plated steel plate, and an external appearance defect may arise easily.

  The treatment time for the water vapor treatment can be appropriately set according to the conditions for the water vapor treatment (temperature, relative humidity, pressure, etc.), the amounts of Al and Mg in the plating layer, the required brightness, and the like.

(Pre-heating)
Moreover, you may heat a plated steel plate before performing a water vapor process. The heating temperature of the plated steel sheet at this time is preferably in the range of 150 to 350 ° C. The preheating treatment time may be appropriately set according to the treatment temperature, the amount of Al in the plating layer, and the like. Usually, it may be heated at 250 ° C. for about 2 hours.

  The steam treatment may be performed on any of a plated steel sheet wound in a coil shape, a flat plated steel sheet before forming, or a plated steel sheet after forming or welding.

[Any step]
In an optional 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-containing Zn-plated steel sheet.

  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-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 the inorganic paint contains a valve metal compound, the inorganic paint may contain an organic acid having a chelating action so that the valve metal compound can stably exist in the inorganic paint. Examples of organic acids include tannic acid, tartaric acid, citric acid, oxalic acid, malonic acid, lactic acid and acetic acid.

  The organic resin film can also 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-containing Zn-plated steel sheet before or after contact with water vapor. What is necessary is just 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 the organic coating material contains a valve metal compound, the organic coating material may contain an organic acid having a chelating action so that the valve metal compound can be stably present in the organic coating material. 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.

  When the organic resin film is formed on the surface of the molten Al-containing Zn-plated steel sheet before bringing the molten Al-containing Zn-plated steel sheet into contact with water vapor, the organic resin film is preferably the above-described urethane resin film. As a polyol, a urethane-based resin film using an ether-based polyol and an ester-based polyol in combination at a predetermined ratio can maintain the effect of improving corrosion resistance even when steam treatment is performed. Therefore, even if it performs a 2nd step after an arbitrary step, it can manufacture the black plating steel plate which has a black color tone and was excellent in corrosion resistance.

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

  According to the production method of the present invention, the plating layer can be blackened by forming a black oxide of Zn inside the plating layer in a shorter time.

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

  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 a SPCC having a plate thickness of 1.2 mm as a base material, a molten Al-containing Zn-plated steel plate having a plating layer thickness of 3 to 100 μm was produced. At this time, the composition of the plating bath (concentration of Zn, Al, and Mg) was changed to produce 12 types of plated steel sheets having different plating layer compositions and different plating layer thicknesses. Table 1 shows the composition of the plating bath and the thickness of the plating layer of the 12 types of plated steel sheets produced. The composition of the plating bath and the composition of the plating layer are the same.

  The produced plated steel plate No. 1 to 12 were placed in a high-temperature and high-pressure wet 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 to give Examples 1 to 13.

  In Example 14, the plated steel plate No. 1, a clear urethane resin (manufactured by ADEKA, HUX-522) is coated so that the film thickness becomes 1.5 μm, and then the plated steel sheet is brought into contact with water vapor.

  In Example 15, the plated steel sheet was punched into a circular shape of 100 mmφ, processed oil was applied, and after the cylindrical drawing with a die diameter of 50 mm, a die shoulder R4 mm, and a height of 25 mm, the plated steel sheet was brought into contact with water vapor. It is a thing.

  In addition, Example 16 is a plated steel plate No. 5 subjected to cylindrical drawing similar to that in Example 15. 1, a clear urethane resin was applied in the same manner as in Example 14, and then the plated steel sheet was brought into contact with water vapor.

  In Example 17, plated steel sheet No. 1 coated with a clear urethane resin similar to Example 14 was used. 1, the same cylindrical drawing as in Example 15 was performed, and then the plated steel sheet was brought into contact with water vapor.

  FIG. 1 is an optical microscope image showing a cross section of the plated layer of the plated steel sheet of Example 12 after the steam treatment. It can be seen from this photograph that Zn black oxide is distributed in the plating layer. Also in the plated layers of the plated steel sheets of other examples (Examples 1 to 11 and 13 to 17), it was observed that Zn black oxide was distributed in the plated layer.

For each plated steel sheet (Examples 1 to 17) after the steam treatment, the lightness (L ^* value) of the plating layer surface was measured using a spectroscopic color difference meter (TC-1800, manufactured by Tokyo Denshoku Co., Ltd.), JIS K 5600 Was measured by a spectral reflection measurement method based on the above. The measurement conditions are shown below.
Optical conditions: d / 8 ° method (double beam optical system)
Field of view: 2 degree field of view Measurement method: Reflected light measurement Standard light: C
Color system: CIELAB
Measurement wavelength: 380 to 780 nm
Measurement wavelength interval: 5 nm
Spectrometer: Diffraction grating 1200 / mm
Lighting: Halogen lamp (voltage 12V, power 50W, rated life 2000 hours)
Measurement area: 7.25mmφ
Detection element: Photomultiplier tube (manufactured by Hamamatsu Photonics Co., Ltd., R928)
Reflectance: 0-150%
Measurement temperature: 23 ° C
Standard plate: white

For each plated steel sheet (Examples 1 to 17) after the steam treatment, “L” when the L ^* value is 50 or less, “△” when 50 or more and 60 or less, and “X” when 60 or more. evaluated. Moreover, when the L ^* value was 60 or less, it was evaluated that the plated steel plate was sufficiently blackened.

  Table 2 shows the brightness of the plated layer surface of each plated steel sheet after the steam treatment.

  As Table 2 shows, it turns out that the black plating steel plate of this invention has favorable blackness.

  The black-plated steel sheet of Example 14 that was subjected to water vapor treatment after coating the above-described clear urethane resin was subjected to cylindrical drawing similar to that of Example 15 described above, and the surface of the cylindrical drawn product was wiped with gauze. However, almost no peeling of the black film was observed.

  The surface of the black-plated steel plate of Example 15 that has been subjected to water vapor treatment after the cylindrical drawing process described above is coated with a clear urethane resin similar to that of Example 14 described above, and the coated surface is then gauze. As a result, almost no peeling of the black film was observed.

  In addition, when the surface of the black-plated steel plate of Example 16 that was subjected to water vapor treatment was coated with a clear urethane resin after the above-described cylindrical drawing process was wiped with gauze, almost no peeling of the black film was observed. It was.

  In addition, when the surface of the black-plated steel sheet of Example 17 that was subjected to water vapor treatment after being subjected to cylindrical drawing after coating the above-described clear urethane resin was wiped with gauze, almost no peeling of the black film was observed. It was.

  Moreover, the clear urethane resin similar to Example 14 mentioned above is applied to the surface of the black plated steel plate of Example 1, and then the cylindrical drawing similar to Example 15 described above is performed. When the surface was wiped with gauze, almost no peeling of the black film was observed.

  Further, the black-plated steel sheet of Example 1 was subjected to cylindrical drawing similar to that of Example 15 described above, and then the surface was wiped with gauze after being coated with a clear urethane resin similar to Example 14 described above. The black film was hardly peeled off.

  From the above, it can be seen that peeling of the black coating can be suppressed by providing a clear coating on the surface of the black-plated steel sheet of the present invention.

Since the black plated steel sheet of the present invention is excellent in design and workability, it is useful as a plated steel sheet used in, for example, building roofing materials, exterior materials, home appliances, automobiles, and the like.

Claims (9)

A base steel plate;
The Al content is 0.1% by mass or more and 10.0% by mass or less, the Mg content is 0.1% by mass or less, and the black oxide of Zn is distributed in the plating layer. A molten Al-containing Zn plating layer,
The brightness of the surface of the molten Al-containing Zn plating layer is 60 or less in L ^* value.
Black plated steel sheet. In addition, it has an inorganic film,
The black-plated steel sheet according to claim 1, wherein the base steel sheet, the molten Al-containing Zn plating layer, and the inorganic coating are laminated in this order. 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. A compound of
The valve metal is one or more metals selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, W, Si and Al.
The black plated steel sheet according to claim 2. Furthermore, it has an organic resin film,
The black-plated steel sheet according to claim 1, wherein the base steel sheet, the molten Al-containing Zn plating layer, and the organic resin film are laminated in this order.   The said organic resin film is a black plated steel plate of Claim 4 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. Containing the above compounds,
The valve metal is one or more metals selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, W, Si and Al.
The black-plated steel plate according to claim 4 or 5.   The black-coated steel sheet according to any one of claims 4 to 6, wherein the organic resin film is a laminate layer or a coating layer.   The said organic resin film is a black-plated steel plate as described in any one of Claims 4-7 which is a clear coating film.   The black-plated steel plate according to any one of claims 1 to 8, which is a processed product.