JP6796100B2 - Coated galvanized steel sheet - Google Patents

Description

The present invention relates to a coated plated steel sheet, and more particularly to a coated plated steel sheet in which a protective layer is provided on a plated steel sheet having a plating layer containing Al, Zn, and Mg.

Plated steel sheets having a plating layer containing Zn and Al (hereinafter referred to as Zn-Al-based plated steel sheets) are widely used for applications such as building materials, materials for automobiles, and materials for home appliances. Among them, Zn—Al-based plated steel sheets having a high aluminum content (for example, 25 to 75% by mass) represented by Galvalume steel sheet (registered trademark) have excellent corrosion resistance and are in great demand.

In recent years, in order to meet the demand for further improvement of corrosion resistance, a Zn-Al-based plated steel sheet in which Mg is added to the plating layer (hereinafter referred to as Mg-containing Zn-Al-based plated steel sheet) has been proposed (patented). Reference 1).

International Publication No. 2011/102434

In an Mg-containing Zn-Al-based plated steel sheet provided with a plating layer containing not only Zn and Al but also Mg, non-uniform brightness tends to occur on the surface of the plating layer. It is considered that this is because, for example, when the hot-dip galvanized metal containing Al, Zn, and Mg is adhered to the steel sheet for production, the adhered amount of the hot-dip galvanized metal becomes non-uniform. For example, a portion where the amount of hot-dip galvanized metal adhered during manufacturing may appear darker than other portions.

Even if the brightness of the surface of the plating layer is non-uniform, it does not affect the excellent corrosion resistance of the Mg-containing Zn—Al-based plated steel sheet. However, since the surface appearance of the Mg-containing Zn-Al-based plated steel sheet becomes non-uniform, for example, when the Mg-containing Zn-Al-based plated steel sheet is used without painting, there is a problem that the appearance is poor. ..

An object of the present invention is to provide a coated plated steel sheet provided with a plating layer containing Al, Zn, and Mg, and in which deterioration of appearance is suppressed even if the surface brightness of the plating layer is non-uniform. ..

The coated plated steel sheet according to the embodiment of the present invention includes a steel sheet, a plating layer, and a protective layer laminated in this order, and the plating layer contains Al, Zn, and Mg, and the protective layer is provided. Contains a resin and inorganic particles having a refractive index of 1.5 or more.

According to the present invention, it is possible to obtain a coated plated steel sheet provided with a plating layer containing Al, Zn, and Mg and in which deterioration of appearance is suppressed even if the surface brightness of the plating layer is non-uniform.

FIG. 1 is a schematic cross-sectional view showing a coated plated steel sheet according to the present embodiment.

Hereinafter, modes for carrying out the present invention will be described.

As shown in FIG. 1, the coated plated steel sheet 1 according to the present embodiment includes a steel sheet 10, a plating layer 20, and a protective layer 30 laminated in this order. The plating layer 20 contains Al, Zn, and Mg. The protective layer 30 contains a resin and inorganic particles 31 having a refractive index of 1.5 or more. Since the plating layer 20 contains Al, Zn, and Mg, the coated plated steel sheet 1 can have high corrosion resistance. Further, since the protective layer 30 contains the inorganic particles 31 having a refractive index of 1.5 or more, deterioration of the appearance of the coated plated steel sheet 1 is suppressed even if the surface brightness of the plating layer 20 is non-uniform. Will be done. When the coated plated steel sheet 1 is manufactured, as will be described later, the hot-dip galvanized metal is attached to the steel sheet 10, and then the hot-dip galvanized metal is adjusted by a gas wiping method. May be non-uniform. In particular, since the hot-dip galvanized metal contains Mg, the amount of the hot-dip galvanized metal adhered tends to be non-uniform. The reason why Mg affects the uniformity of the adhesion amount of the hot-dip galvanized metal and the mechanism by which the non-uniformity of the adhesion amount of the hot-dip galvanized metal affects the brightness of the surface of the plating layer 20 have not been completely elucidated. .. However, for example, it is presumed that the Al concentration on the surface layer of the plating layer 20 tends to decrease in a portion where the amount of hot-dip galvanized metal adhered is small during manufacturing, which is one of the reasons why the surface brightness of the plating layer 20 becomes non-uniform. Will be done. Therefore, it is considered that the brightness of the surface of the plating layer 20 becomes non-uniform, and the portion where the amount of the hot-dip galvanized metal adhered at the time of manufacture is small looks darker than the other portions. However, in the present embodiment, the inorganic particles 31 contained in the protective layer 30 diffusely reflect light, so that the non-uniformity of the surface of the plating layer 20 can be made less noticeable. In particular, when the refractive index of the inorganic particles 31 is 1.5 or more, light is more easily diffusely reflected. Therefore, even if the surface brightness of the plating layer 20 is non-uniform, light is diffusely reflected by the protective layer 30, making it difficult to visually recognize the non-uniform brightness of the plating layer 20, and deterioration of the surface appearance is suppressed. To.

Each layer and material constituting the coated plated steel sheet 1 will be described in detail.

Examples of the steel plate 10 include various members such as thin steel plates and thick steel plates.

[Plating layer 20]
The plating layer 20 is formed by a known means such as immersing the steel plate 10 in a hot-dip galvanizing bath.

The plating layer 20 contains Al, Zn, and Mg. When the plating layer 20 contains aluminum (Al) and zinc (Zn), the surface of the plating layer 20 is covered with a thin aluminum oxide film. The protective action of this oxide film particularly improves the corrosion resistance of the surface of the plating layer 20. Further, the sacrificial anticorrosion action of zinc suppresses edge creep at the cut end face of the coated plated steel sheet 1. Therefore, high corrosion resistance is imparted to the coated plated steel sheet 1. Further, when the plating layer 20 contains magnesium (Mg), which is a metal lower than Zn, the sacrificial anticorrosion action of the plating layer 20 is strengthened, and the corrosion resistance of the coated plated steel sheet 1 is further improved.

The Al content of the plating layer 20 is preferably 1% by mass or more and 75% by mass or less. When the Al content is 1% by mass or more, the corrosion resistance on the surface of the plating layer 20 is ensured, so that the coated plated steel sheet 1 can have high corrosion resistance. When the Al content is 75% by mass or less, the sacrificial anticorrosion effect of Zn is sufficiently exhibited, the hardening of the plating layer 20 is suppressed, and the bending workability of the coated plated steel sheet 1 can be improved. The Al content is more preferably 45% by mass or more, more preferably 65% by mass or less, and further preferably 45% by mass or more and 65% by mass or less.

The Mg content of the plating layer 20 is preferably more than 0% by mass and 6.0% by mass or less. When the Mg content is 0.1% by mass or more, the effect of adding Mg clearly appears. When the Mg content is 0.5% by mass or more, the effect of improving corrosion resistance can be stably obtained, which is more preferable. The Mg content is more preferably 5.0% by mass or less, and even more preferably 3.0% by mass or less. The Mg content is particularly preferably 1.0% by mass or more and 3.0% by mass or less.

The plating layer 20 may contain one or more elements selected from Si, Ni, Ce, Cr, Fe, Ca, Sr and rare earths. When the plating layer 20 contains one or more elements selected from the group consisting of alkaline earth elements such as Ni and Cr; Ca and Sr; and rare earth elements such as Y, La and Ce, the aluminum of the plating layer 20 The corrosion resistance of the coated plated steel sheet 1 is further improved by strengthening both the protective action caused by the above and the sacrificial anticorrosion action caused by zinc.

In particular, the plating layer 20 preferably contains at least one of Ni and Cr. When the plating layer 20 contains Ni, the Ni content of the plating layer 20 is preferably more than 0% by mass and 1% by mass or less. The Ni content is more preferably 0.01% by mass or more and 0.5% by mass or less. When the plating layer 20 contains Cr, the Cr content in the plating layer 20 is preferably more than 0% by mass and 1% by mass or less. This content is more preferably 0.01% by mass or more and 0.5% by mass or less. In these cases, the corrosion resistance of the coated plated steel sheet 1 is improved. In order to improve the corrosion resistance, for example, Ni and Cr are present near the interface between the steel sheet 10 and the plating layer 20, or the concentration of Ni and Cr in the plating layer 20 is higher as the concentration distribution is closer to the steel sheet 10. It is preferable to have such a bias.

The plating layer 20 may contain Si. When the plating layer 20 contains Si, the mechanical workability of the coated plated steel sheet 1 can be improved. The Si content of the plating layer 20 is preferably 0.5% by mass or more and 10% by mass or less with respect to the Al content. When the content of Si with respect to Al is 0.5% by mass or more, excessive alloying of Al and the steel sheet 10 in the plating layer 20 is sufficiently suppressed. If the content of Si with respect to Al is more than 10% by mass, not only the action of Si is saturated, but also dross is likely to occur in the hot-dip galvanizing bath during the production of the plating layer 20. The content of Si with respect to Al is particularly preferably 1.0% by mass or more. Further, the content of Si with respect to Al is particularly preferably 5.0% by mass or less. It is particularly preferable that the Si content is 1.0% by mass or more and 5.0% by mass or less.

When the plating layer 20 contains Si, the mass ratio of Si: Mg in the plating layer 20 is preferably in the range of 100:50 to 100: 300. In this case, the formation of the Si—Mg layer in the plating layer 20 is particularly promoted, and the generation of wrinkles in the plating layer 20 is further suppressed. The mass ratio of Si: Mg is preferably 100: 70 to 100: 250, and more preferably in the range of 100: 100 to 100: 200.

When the plating layer 20 contains Si, the plating layer 20 preferably contains a Si—Mg phase of 0.2% by volume or more and 15% by volume or less. The Si-Mg phase is a layer composed of an intermetallic compound of Si and Mg, and can be dispersed and present in the plating layer 20. The volume ratio of the Si-Mg phase in the plating layer 20 is equal to the area ratio of the Si-Mg phase on the cut surface when the plating layer 20 is cut in the thickness direction thereof. The Si-Mg phase on the cut surface of the plating layer 20 can be clearly confirmed by electron microscope observation. Therefore, by measuring the area ratio of the Si-Mg phase on the cut surface, the volume ratio of the Si-Mg phase in the plating layer 20 can be indirectly measured. The higher the volume ratio of the Si—Mg phase in the plating layer 20, the more the generation of wrinkles in the plating layer 20 is suppressed. This is because in the process of forming the plating layer 20 by solidifying the hot-dip plating metal by cooling during the production of the plating layer 20, the Si—Mg phase is formed by the hot-dip plating metal before the hot-dip plating metal is completely solidified. It is considered that this Si-Mg phase is precipitated inside and suppresses the flow of the hot-dip plated metal. The volume ratio of the Si—Mg phase is more preferably 0.2% by volume or more and 10% by volume or less, and further preferably 0.4% by volume or more and 5% by volume or less.

The plating layer 20 may contain one or more of Ca, Sr, Y, La and Ce. When the plating layer 20 contains Ca, the Ca content of the plating layer 20 is preferably more than 0% by mass and 0.5% by mass or less. The Ca content is more preferably 0.001% by mass or more and 0.1% by mass or less. When the plating layer 20 contains Sr, the Sr content of the plating layer 20 is preferably more than 0% by mass and 0.5% by mass or less. The Sr content is more preferably 0.001% by mass or more and 0.1% by mass or less. When the plating layer 20 contains Y, the Y content of the plating layer 20 is preferably more than 0% by mass and 0.5% by mass or less. The Y content is more preferably 0.001% by mass or more and 0.1% by mass or less. When the plating layer 20 contains La, the La content of the plating layer 20 is preferably more than 0% by mass and 0.5% by mass or less. The La content is more preferably 0.001% by mass or more and 0.1% by mass or less. When the plating layer 20 contains Ce, the Ce content of the plating layer 20 is preferably more than 0% by mass and 0.5% by mass or less. The Ce content is more preferably 0.001% by mass or more and 0.1% by mass or less. In these cases, the corrosion resistance of the coated plated steel sheet 1 is improved, and the effect of suppressing defects on the surface of the plated layer 20 is expected.

Alkaline earth elements (Be, Ca, Ba, Ra), Sc, Y, and lanthanoid elements (La, Ce, Pr, Nd, Pm, Sm, Eu, etc.) exert the same effects as Sr. The total content of these components in the plating layer 20 is preferably 1.0% by mass or less in terms of mass ratio.

Zn occupies the balance of all the constituent elements of the plating layer 20 excluding the constituent elements other than Zn.

The plating layer 20 may contain elements other than Al, Zn, Mg, Si, Ni, Ce, Cr, Fe, Ca, Sr and rare earth elements. For example, the plating layer 20 may contain one or more elements selected from the group consisting of Pb, Sn, Co, B, Mn and Cu. Elements other than Al, Zn, Mg, Si, Ni, Ce, Cr, Fe, Ca, Sr and rare earth elements may be contained in the plating layer 20 as constituent elements thereof, and may be eluted from the steel sheet 10 or plated. It may be mixed as an impurity in the raw material of the bath. The ratio of the total amount of elements other than Al, Zn, Mg, Si, Ni, Ce, Cr, Fe, Ca, Sr and rare earths in the plating layer 20 is preferably 0.1% by mass or less.

However, needless to say, the plating layer 20 may contain unavoidable impurities such as Pb, Cd, Cu, and Mn. The content of the unavoidable impurities is preferably as small as possible, and it is particularly preferable that the total content of the unavoidable impurities is 1% by mass or less in terms of mass ratio with respect to the plating layer 20.

An alloy layer containing, for example, Al and Cr may be interposed between the steel sheet 10 and the plating layer 20.

[Protective layer 30]
The protective layer 30 is also generally called a chemical conversion treatment layer, and is a layer formed to prevent corrosion of the plating layer 30. The protective layer 30 is formed by, for example, forming a plating layer 20 on a steel plate 10, applying a chemical conversion treatment agent to the plating layer 20, and drying the plating layer 20.

The protective layer 30 contains a resin. That is, the protective layer 30 is formed by a chemical conversion treatment agent containing a resin. The chemical conversion treatment agent is, for example, a chromium-containing treatment agent such as a chromate treatment agent or a trivalent chromium acid treatment agent; a phosphoric acid-based treatment agent such as a zinc phosphate treatment agent or an iron phosphate treatment agent; cobalt, nickel, tungsten. , Oxide treatment agent containing metal oxide such as zirconium alone or in combination; Treatment agent containing inhibitor component to prevent corrosion; Binder component (organic, inorganic, organic-inorganic composite, etc.) and inhibitor component Combined treatment agent; Treatment agent in which an inhibitor component and a metal oxide are combined; Treatment agent in which a binder component and a sol such as silica, titania, or zirconia are combined; or Treatment in which the components of the treatment agent exemplified above are further combined. It is an agent.

The resin includes, for example, at least one selected from the group consisting of urethane resin, acrylic resin, polyester resin, alkyd resin, epoxy resin, and amino resin.

The resin preferably contains a urethane resin. That is, the protective layer 30 preferably contains a urethane resin. In this case, the corrosion resistance of the protective layer 30 can be enhanced.

More preferable examples of the chemical conversion treatment agent containing a resin include an oxide treatment agent containing zirconium and a treatment agent containing chromium.

The zirconium-containing oxide treatment agent contains, for example, a water- and water-dispersible polyester urethane resin, a water-dispersible acrylic resin, a zirconium compound such as sodium zirconium carbonate, and hindered amines. The water-dispersible polyester-based urethane resin is synthesized, for example, by reacting a polyester polyol with a hydrogenated isocyanate and self-emulsifying by copolymerizing a dimethylolalkyl acid. Such a water-dispersible polyester-based urethane resin can impart high water resistance to the protective layer 30 without using an emulsifier, and can improve the corrosion resistance and alkali resistance of the coated galvanized steel sheet 1.

The chromium-containing treatment agent contains, for example, water and a water-dispersible acrylic resin, a silane coupling agent having an amino group, and a source of chromium ions such as ammonium chromate and ammonium dichromate. The water-dispersible acrylic resin can be obtained by copolymerizing, for example, a carboxyl group-containing monomer such as acrylic acid and a glycidyl group-containing monomer such as glycidyl acrylate. The protective layer 30 formed from this chemical conversion treatment agent has high water resistance, corrosion resistance, and alkali resistance. Further, the protective layer 30 formed from this chemical conversion treatment agent can suppress the generation of white rust and black rust on the hot-dip galvanized steel sheet 1, and can improve the corrosion resistance of the hot-dip galvanized steel sheet 1.

The protective layer 30 contains inorganic particles 31. The refractive index of the inorganic particles 31 is 1.5 or more. Since the protective layer 30 contains inorganic particles 31 having a refractive index of 1.5 or more, light is diffusely reflected by the protective layer 30, and even when the surface brightness of the plating layer 20 is non-uniform, the coated plated steel sheet 1 Deterioration of appearance is suppressed.

The type of the inorganic particles 31 is not particularly limited as long as it has a refractive index of 1.5 or more. Examples of the inorganic particles 31 having a refractive index of 1.5 or more include titanium oxide, calcium carbonate, zinc oxide, iron black, barium sulfate, and carbon black. One of these may be used alone, or two or more thereof may be used in combination.

The upper limit of the refractive index of the inorganic particles 31 is not particularly limited, but is, for example, 4.0 or less. Further, the refractive index of the inorganic particles 31 is more preferably 2.0 or more. In this case, deterioration of the surface appearance of the coated plated steel sheet 1 is further suppressed.

The difference in refractive index between the inorganic particles 31 and the resin contained in the protective layer 30 is preferably 0.3 or more in absolute value. In this case, the light is more diffusely reflected by the protective layer 30, so that the non-uniformity of the brightness of the plating layer 20 becomes less noticeable. The difference in refractive index between the inorganic particles 31 and the resin is more preferably 0.5 or more in absolute value. The upper limit of the difference in refractive index between the inorganic particles 31 and the resin is not particularly limited, but may be, for example, an absolute value of 3.0 or less.

The average particle size of the inorganic particles 31 is preferably 0.1 μm or more and 1.0 μm or less. When the average particle size of the inorganic particles 31 is 0.1 μm or more, the protective layer 30 can make the non-uniformity of the brightness of the surface of the plating layer 20 more inconspicuous. Further, since the average particle size of the inorganic particles 31 is 1.0 μm or less, it is possible to prevent the inorganic particles 31 from protruding from the protective layer 30 and reducing the smoothness of the surface of the protective layer 30, so that the corrosion resistance of the protective layer 30 is reduced. Can be suppressed from decreasing. The average particle size of the inorganic particles 31 is more preferably 0.2 μm or more and 0.5 μm or less. In this case, the protective layer 30 can make the non-uniformity of the brightness of the surface of the plating layer 20 more inconspicuous. The average particle size of the inorganic particles 31 is a volume-based median diameter calculated from the measured value of the particle size distribution by the laser diffraction / scattering method, and can be obtained by using a commercially available laser analysis / scattering type particle size distribution measuring device.

The inorganic particles 31 are preferably contained in the protective layer 30 in an amount of 0.1% by mass or more and 5.0% by mass or less. When the inorganic particles 31 are contained in the protective layer 30 in an amount of 0.1% by mass or more, light is sufficiently diffusely reflected by the protective layer 30, and the non-uniformity of the brightness of the surface of the plating layer 20 becomes less noticeable. Further, when the inorganic particles 31 are contained in the protective layer 30 in an amount of 5.0% by mass or less, it is possible to prevent the metallic luster of the coated plated steel sheet 1 from being lowered. Therefore, even in the unpainted state, the coated plated steel sheet 1 can have a good surface appearance because the non-uniformity of the brightness of the surface of the plating layer 20 is inconspicuous and has a sufficient metallic luster. .. It is more preferable that the inorganic particles 31 are contained in the protective layer 30 in an amount of 0.3% by mass or more and 3.0% by mass or less.

The inorganic particles 31 preferably contain a white pigment. That is, the protective layer 30 preferably contains a white pigment. When the protective layer 30 contains a white pigment, light is more easily diffusely reflected by the protective layer 30, so that the non-uniformity of the brightness of the surface of the plating layer 20 becomes less noticeable. Examples of white pigments include titanium oxide, zinc oxide, barium sulphate, aluminum oxide, magnesium oxide, and calcium carbonate. One of these may be used alone, or two or more thereof may be used in combination.

It is particularly preferable that the white pigment contains titanium oxide. That is, the protective layer 30 preferably contains titanium oxide. When the protective layer 30 contains titanium oxide, light is particularly easily diffusely reflected in the protective layer 30, so that the non-uniformity of the brightness of the surface of the plating layer 20 becomes particularly inconspicuous.

The white pigment is preferably contained in the protective layer 30 in an amount of 0.1% by mass or more and 5.0% by mass or less. When the white pigment is contained in the protective layer 30 in an amount of 0.1% by mass or more, light is sufficiently diffusely reflected by the protective layer 30, and the non-uniformity of the brightness of the surface of the plating layer 20 becomes less noticeable. Further, when the white pigment is contained in the protective layer 30 in an amount of 5.0% by mass or less, it is possible to prevent the metallic luster of the coated plated steel sheet 1 from being lowered. Therefore, even in the unpainted state, the coated plated steel sheet 1 can have a good surface appearance because the non-uniformity of the brightness of the surface of the plating layer 20 is inconspicuous and has a sufficient metallic luster. .. It is more preferable that the white pigment is contained in the protective layer 30 in an amount of 1.0% by mass or more and 3.0% by mass or less.

The protective layer 30 preferably further contains a dark pigment. When the protective layer 30 contains a dark pigment, the non-uniformity of the lightness of the surface of the plating layer 20 is more likely to be concealed. Examples of dark pigments include carbon black, iron black, chromium oxide, iron oxide, and cobalt aluminate. One of these may be used alone, or two or more thereof may be used in combination.

The dark pigment is preferably contained in the protective layer 30 in an amount of 0.1% by mass or more and 3.0% by mass or less. When the dark pigment is contained in the protective layer 30 in an amount of 0.3% by mass or more, the non-uniformity of the lightness of the surface of the plating layer 20 is more easily concealed. Further, when the dark pigment is contained in the protective layer 30 in an amount of 3.0% by mass or less, it is possible to prevent the metallic luster of the coated plated steel sheet 1 from being lowered. Therefore, even in the unpainted state, the coated plated steel sheet 1 can have a good surface appearance because the non-uniformity of the brightness of the surface of the plating layer 20 is inconspicuous and has a sufficient metallic luster. .. It is more preferable that the dark pigment is contained in the protective layer 30 in an amount of 0.3% by mass or more and 1.5% by mass or less.

The protective layer 30 may further contain additives other than the inorganic particles 31 and the dark pigment. The protective layer 30 may contain, for example, inorganic particles having a refractive index of less than 1.5, organic particles, a cross-linking agent, an adhesion-imparting agent, a rust preventive, and the like.

The amount of adhesion of the protective layer 30 is preferably 0.3 g / m ² or more and 5.0 g / m ² or less. When the amount of adhesion of the protective layer 30 is within this range, the protective layer 30 has good corrosion resistance, and the non-uniformity of the brightness of the surface of the plating layer 20 can be sufficiently concealed. The amount of adhesion of the protective layer 30 is more preferably 0.5 g / m ² or more and 3.0 g / m ² or less.

A chemical conversion treatment layer other than the protective layer 30 may be formed between the plating layer 20 and the protective layer 30. Further, the plating layer 20 may be subjected to a plating treatment such as a nickel plating treatment or a cobalt plating treatment.

Further, a coating film may be formed by applying a paint on the protective layer 30. For example, a coating film can be formed by applying a coating material containing a resin and a pigment on the protective layer 30 and baking the coating film. Further, the clear paint may be applied on the protective layer 30 and formed into a film to form the clear layer. However, in the present embodiment, since the coated plated steel sheet 1 includes the protective layer 30 containing the inorganic particles 31, the appearance is deteriorated due to the non-uniformity of the surface brightness of the plated layer 20 even if it is unpainted. Is suppressed.

The plating layer 20 and the protective layer 30 may be provided on only one side of the steel sheet 10, or may be provided on both sides of the steel sheet 10.

The L ^* value of the coated plated steel sheet 1 at a watermark angle of 110 ° is preferably 15 or more and 30 or less. The L ^* value can be measured using a commercially available variable angle color difference meter. The L ^* value at a watermark angle of 110 ° means the average value of the results of measuring the L ^* value at a watermark angle of 110 ° at at least five positions arranged at intervals of 100 mm in one direction on the protective layer 30. To do. Further, the watermark angle means an angle deviating from the specular reflection direction of the light incident on the coated plated steel sheet at 45 °. That is, the L ^* value at a watermark angle of 110 ° is measured as follows. First, using the CIE standard light source D65, light is incident on the steel sheet at an angle of 45 ° from the light source. The L ^* value of the reflected light reflected in the direction of 110 ° with respect to the specularly reflected light of the incident light is measured. When the L ^* value at a watermark angle of 110 ° is 15 or more, the non-uniformity of the brightness of the surface of the plating layer 20 in the coated plated steel sheet 1 becomes less noticeable. Further, when the L ^* value at the watermark angle of 110 ° is 30 or less, it is possible to prevent the metallic luster of the coated plated steel sheet 1 from being lowered. The L ^* value of the coated plated steel sheet 1 at a watermark angle of 110 ° is more preferably 21 or more and 27 or less.

[Manufacturing method of coated plated steel sheet]
The coated plated steel sheet 1 according to the present embodiment is manufactured by forming a plating layer 20 by subjecting the steel sheet 10 to a plating treatment, and further forming a protective layer 30 on the plating layer 20.

Examples of the method for plating the steel sheet 10 include a method in which the steel sheet 10 is preheated in a non-oxidizing furnace, then reduced and annealed in a reduction furnace, and then immersed in a hot-dip plating bath and then pulled up. Further, as another method for plating the steel sheet 10, for example, a method using a total reduction furnace can be mentioned. In either method, the hot-dip galvanized metal is attached to the steel sheet 10, the amount of the hot-dip galvanized metal adhered is adjusted by a gas wiping method, and then the steel sheet 10 is cooled to form the plating layer 20 on the steel sheet 10. it can. These steps can be performed continuously.

Before forming the protective layer 30 on the plating layer 20, as a base treatment for the surface of the plating layer 20, cleaning with pure water or various organic solvent solutions, an aqueous solution containing an acid, an alkali or various etching agents and various organics are performed. Cleaning with a solvent solution or the like may be performed. When the surface of the plating layer 20 is washed in this way, a small amount of Mg-based oxide film may be present on the surface layer of the plating layer 20, or inorganic and organic stains may be attached to the surface of the plating layer 20. However, these Mg-based oxide films, stains, and the like are removed from the plating layer 20, which can improve the adhesion between the plating layer 20 and the protective layer 30.

The protective layer 30 can be formed by a known method such as a roll coating method, a spray method, a dipping method, an electrolytic treatment method, or an air knife method using the above-mentioned chemical conversion treatment agent. After the application of the chemical conversion treatment agent, if necessary, steps such as leaving at room temperature and drying or baking with a heating device such as a hot air furnace, an electric furnace, or an induction heating furnace may be added. A curing method using energy rays such as infrared rays, ultraviolet rays, and electron beams may be applied. The temperature and drying time at the time of drying are appropriately determined according to the type of chemical conversion treatment agent used, the required productivity, and the like. The protective layer 30 formed in this way becomes a continuous or discontinuous film on the plating layer 20. The thickness of the protective layer 30 is appropriately determined according to the type of treatment, the required performance, and the like.

Hereinafter, the present invention will be specifically described with reference to Examples. However, the present invention is not limited to the following examples.

(1) Preparation of Coated Plated Steel Sheet First, a long steel sheet having a plating layer (Al content 55% by mass, Mg content 2% by mass, Zn content 43% by mass), a thickness of 0.5 mm and a width of 900 mm. (SGL steel sheet manufactured by Nittetsu Sumikin Steel Sheet Co., Ltd.) was prepared. In all of the plated steel sheets used, the brightness of the plated layer is as non-uniform.

A chemical conversion treatment agent having the composition shown in the “Composition” column of Table 1 is applied onto the above plating layer by a bar coater, and then dried at a maximum temperature of 90 ° C. for 5 seconds to form a protective layer. Formed. The maximum temperature reached means the maximum temperature of the steel sheet reached during drying. The amount of adhesion of the protective layer is as shown in the column of "amount of adhesion" in Table 1.

As a result, coated plated steel sheets of Examples 1 to 12 and Comparative Example 1 were obtained.

The details of each component described in the "Composition" column of Table 1 are as follows.
-Resin: Water-based urethane resin, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., product name Superflex 210
-Titanium oxide: manufactured by Ishihara Sangyo Co., Ltd., product name Typek CR-90, refractive index 2.72, average particle size 0.25 μm
-Zinc oxide A: manufactured by Sakai Chemical Industry Co., Ltd., product name XZ-300F-LP, refractive index 2.00, average particle size 0.10
-Zinc oxide B: manufactured by Sakai Chemical Industry Co., Ltd., product name XZ-3000F-LP, refractive index 2.00, average particle size 3.00
-Silica: manufactured by Nissan Chemical Industries, Ltd., product name Snowtex MP-4540M, refractive index 1.47, average particle size 0.45 μm
-Cr / Fe fired pigment: Tokan Material Technology Co., Ltd., product name 42-707 A
Carbon black: Mitsubishi Chemical Co., Ltd., product name MA10 0
-Epoxy compound: manufactured by Nagase ChemteX Corporation, product name Denacol EX-614B
-Surfactant: Made by Big Chemie Japan Co., Ltd., Product name BYK-348

(2) Evaluation of coated plated steel sheet (2-1) Visual evaluation The non-uniformity of the brightness of the plated layer in the coated plated steel sheet of Examples 1 to 12 and Comparative Example 1 was visually observed and evaluated according to the following criteria. .. The results are shown in the "Visual" column of Table 1.
A: The brightness of the surface of the plating layer was uniform B: The brightness of the surface of the plating layer was slightly non-uniform C: The brightness of the surface of the plating layer was non-uniform.

(2-2) Measurement of L ^* value Using a variable angle color difference meter (manufactured by X-Rite Co., Ltd., product number MA-68II), the watermark angle was set to 110 °, and Examples 1 to 12 and Comparative Example 1 were used. The L ^* value on the protective layer of the coated plated steel sheet was measured at five positions at 100 mm intervals in the length direction. The average value of this L ^* value is shown in the “L ^* value” column of Table 1.

(2-3) Measurement of ΔL Using a variable angle color difference meter (manufactured by X-Rite Co., Ltd., product number MA-68II), the watermark angle was set to 110 °, and the coating plating of Examples 1 to 12 and Comparative Example 1 was performed. The L ^* value on the protective layer of the steel sheet was measured at five positions at 100 mm intervals in the length direction. The difference between the maximum value and the minimum value of this L ^* value is shown in the "ΔL" column as an absolute value.

(2-4) Metallic luster The metallic luster on the surface of the plated layer in the coated plated steel sheets of Examples 1 to 12 and Comparative Example 1 was visually observed and evaluated according to the following criteria. The results are shown in the "Metallic luster" column of Table 1.
A: The metallic luster on the surface of the plating layer was good. B: There were some spots on the surface of the plating layer where the metallic luster was not good.

(2-5) Heat-shielding property Using an ultraviolet-visible near-infrared spectrophotometer (manufactured by Shimadzu Corporation, product number UV-3600Plus), the coated plated steel sheets of Examples 11 and 12 at 780 to 2500 nm specified by JISK5602. The solar reflectance of was measured. The results are evaluated according to the following criteria and are shown in the "heat shield" column of Table 1.
A: The solar reflectance of the coated galvanized steel sheet was 60% or more. B: The solar reflectance of the coated plated steel sheet was less than 60%.

1 Coated plated steel sheet 10 Steel sheet 20 Plating layer 30 Protective layer 31 Inorganic particles

Claims (9)

A steel plate, a plating layer, and a protective layer are laminated in this order and provided.
The plating layer contains Al, Zn, and Mg and contains
The protective layer, a resin and a refractive index of 1.5 or more, and contains the inorganic particles having an average particle diameter of 0.1μm or more 1.0μm or less, and a dark pigment,
The solar reflectance at 780 to 2500 nm defined by JIS K 5602 is 60% or more.
Unpainted,
Coated galvanized steel sheet. The inorganic particles are contained in the protective layer in an amount of 0.1% by mass or more and 5.0% by mass or less.
The coated plated steel sheet according to claim 1. The inorganic particles contain a white pigment.
The coated plated steel sheet according to claim 1 or 2. The white pigment is contained in the protective layer in an amount of 0.1% by mass or more and 5.0% by mass or less.
The coated plated steel sheet according to claim 3. The white pigment contains titanium oxide,
The coated plated steel sheet according to claim 3 or 4. The dark pigment is contained in the protective layer in an amount of 0.1% by mass or more and 3.0% by mass or less.
The coated plated steel sheet according to any one of claims 1 to 5 . The amount of adhesion of the protective layer is 0.3 g / m ² or more and 5.0 g / m ² or less.
The coated plated steel sheet according to any one of claims 1 to 6 . The Al content of the plating layer is 1% by mass or more and 75% by mass or less, and the Mg content is 6.0% by mass or less.
The coated plated steel sheet according to any one of claims 1 to 7 . The L ^* value at a watermark angle of 110 ° is 15 or more and 30 or less.
The coated plated steel sheet according to any one of claims 1 to 8 .

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