KR20150080012A - Coated plated steel material - Google Patents

Abstract

The coated plated steel material comprises a steel material and a coating on the surface of the steel material, the coating comprising, in order from the steel material, a plating layer, an uncoated layer on the surface of the plated layer, Wherein the plating layer contains Al, Zn, Si, and Mg as constituent elements, the Al content is 25 to 75 mass%, the Mg content is 0.1 to 10 mass%, and the plating layer is 0.2 to 15 Wherein the mass ratio of Mg in the Si-Mg phase to the total amount of Mg in the plating layer is not less than 3% and not more than 100%, and the undercoating treatment layer contains an organic resin and an organic Wherein the organic silicon compound is contained in an amount of 2 to 1,500 parts by mass based on 100 parts by mass of the organic resin, and the thickness of the organic coating layer is 0.2 to 100 占 퐉.

Description

{COATED PLATED STEEL MATERIAL}

The present invention relates to a coated plated steel material.

The present application is based on Japanese Patent Application No. 2011-182890 filed on August 24, 2011, Japan, and Japanese Patent Application No. 2011-182830 filed on August 24, 2011, , And the contents are used here.

BACKGROUND ART Conventionally, molten Zn-Al-based plated steel has been widely used for applications such as building materials, automobile materials, and materials for home appliances. Among them, the high aluminum (25 to 75 mass%) · zinc alloy plated steel sheet typified by 55% aluminum-zinc alloy plated steel plate (galvanic steel plate (registered trademark)) is superior in corrosion resistance to ordinary hot dip galvanized steel sheet , Demand continues to expand. In recent years, particularly in construction materials, improvement of corrosion resistance and workability has been demanded, and improvement of corrosion resistance and the like of molten Zn-Al based plated steel material by addition of Mg or the like to the plating layer has been attempted (see Patent Documents 1 to 3) 4).

However, in a high-aluminum-zinc alloy plated steel sheet containing Mg, wrinkles are easily generated on the surface of the plating layer, which causes a problem of deterioration of the surface appearance. In addition, when the plating layer is chemically treated to form the chemical conversion treatment layer or to the coating layer by coating or the like because the surface of the plating layer is roughly raised by the wrinkles, the chemical conversion treatment layer and the coating layer The thickness of the film is liable to become uneven. As a result, there is a problem in that the improvement of the corrosion resistance of the coated steel sheet due to painting or the like is not sufficiently exhibited.

For example, Patent Document 1 discloses a method for producing a copper alloy having a surface with a hot-dip coating layer containing 3 to 13% by mass of Si, 2 to 8% by mass of Mg and 2 to 10% by mass of Zn and a remaining amount of Al and inevitable impurities Al-Si-Mg-Zn based molten Al-base coated steel sheet. In Patent Document 1, the molten plated layer also contains 0.002 to 0.08% of Be and 0 to 0.1% of Sr, or 3 to 13% of Si, 2 to 8% of Mg, 2 to 10% of Zn, and 0.003 , 0.05 to 0.05% of Sr and 0 to 0.1% of Sr, or 3 to 13% of Si, 2 to 8% of Mg, 2 to 10% of Zn, 0 to 0.003% of Be and 0.07 to 1.7% of Sr , Or 3 to 13% of Si, 2 to 8% of Mg, 2 to 10% of Zn, 0 to 0.003% of Be and 0.1 to 1.0% of Sr, or 3 to 13% Or more of Zn, 2 to 10% of Zn, 0.003 to 0.08% of Be and 0.1 to 1.7% of Sr, or 3 to 13% of Si, 2 to 8% of Mg, 2 to 10% of Zn, , 0.003 to 0.05%, and Sr in an amount of 0.1 to 1.0%.

In the technique disclosed in Patent Document 1, the corrosion resistance of the hot-dip coated steel material is improved by adding Mg to the plated layer, but wrinkles are likely to occur in the plated layer due to the addition of Mg. Patent Document 1 also discloses that oxidation of Mg is suppressed by adding Sr or Be to the plating layer, and as a result, wrinkles are suppressed. However, suppression of wrinkles is not sufficient.

It is difficult to sufficiently remove the wrinkles formed on the plated layer by the temper rolling treatment and the like, and this has been a cause of deterioration of the appearance of the hot-dip galvanized steel.

In addition, the conventional high aluminum (25 to 75 mass%) -Zinc alloy coated steel sheet can be manufactured by a method in which the durability (corrosion rate of the plating layer) and the internal lubrication property (the property of suppressing red rust generated from the steel sheet) However, the corrosion resistance of the machined portion where the scratch-generating portion of the coating surface and the steel material of the base are deformed (the performance of suppressing deterioration of the appearance due to corrosion of the plating layer due to the occurrence of white rust And the ability to inhibit the coating film from swelling due to the corrosion reaction). Particularly, attention has not been paid to the point of view of improvement of the internal whiteness in the case of receiving the heating in the use and the irradiation of the ultraviolet ray in the use of the organ.

Japanese Patent Laid-Open No. 11-279735 Japanese Patent No. 3718479 International Publication No. 2008/025066 pamphlet Japanese Patent Application Laid-Open No. 2007-284718

The present invention has been made in view of the above-mentioned reasons. It is an object of the present invention to provide a method of manufacturing a steel plate which is excellent in corrosion resistance of a machined portion with a coated surface and a deformed steel material of a base and is subjected to heating, Which is exposed to ultraviolet rays, is excellent in weatherability, and is free from appearance defects due to the plating layer, and has a good appearance.

The inventors of the present invention investigated the problem of deterioration of the appearance of the surface of the plated steel material as described above. Since Mg is an element that is easily oxidized as compared with other elements constituting the plating layer during the hot dip treatment using the hot dip galvanizing bath containing Mg, Mg reacts with oxygen in the atmosphere in the surface layer of the hot- Based oxide is generated. As a result, Mg is concentrated in the surface layer of the molten plated metal, and the formation of the Mg-based oxide film (the film composed of the oxide of the metal including Mg) is accelerated in the surface layer of the molten plated metal. In the process of cooling and solidifying the molten plated metal, since the Mg-based oxide film is formed before solidification in the molten plated metal is completed, a difference in fluidity occurs between the surface layer and the interior of the molten plated metal. As a result, even if the inside of the molten plated metal flows, the Mg-based oxide film on the surface layer does not follow up, and as a result, when the wrinkles or sagging that can be generated can not be entirely concealed by the coating on the upper layer, . ≪ / RTI >

Accordingly, the inventors of the present invention have found a means for suppressing the deterioration of appearance such as wrinkles and sagging, in order to suppress the difference in flowability in the molten plated metal during the above-mentioned hot-dip plating treatment.

On the other hand, in addition to the coating undercoating treatment of the hot-dip coating material capable of suppressing the deterioration of the whitening resistance in the machined portion after coating due to the deterioration of the processability of the plating layer caused thereby, The occurrence of white rust, which is liable to occur in a portion subjected to processing, is suppressed. In addition, in the case of heating, and in use of an organ, the undercoating layer and the plating layer are exposed in the cut end face, The present invention has been accomplished based on the results of intensive investigation of a coating treatment of a hot-dip coating material which can maintain a beautiful appearance over a long period of time by suppressing white rust,

That is, the gist of the present invention will be described together with the preferred embodiments as follows.

(1) The coated plated steel material according to the first aspect of the present invention is a coated plated steel material comprising a steel material and a coating on the surface of the steel material, wherein the coating comprises, in order from the steel material, a plating layer, Wherein the plating layer contains Al, Zn, Si and Mg as constituent elements and further contains Cr, and the Al content is 25 to 75% by mass, Wherein the Mg content in the Si-Mg phase is 0.1 to 10 mass%, the Cr content is 0.02 to 1.0 mass%, the plating layer contains 0.2 to 15 volume% of Si-Mg phase, Wherein the organic undercoating layer comprises an organic resin and an organic silicon compound, wherein the organic silicon compound has an alkylene group, a siloxane bond, and -SiR ¹ R ² > R < ³ > , Two of R ¹ , R ² and R ³ are each an alkoxy group or a hydroxy group, and the remaining one of R ¹ , R ² and R ³ is an alkoxy group, a hydroxy group, or a methyl group , The organic silicon compound is 2 to 1,500 parts by mass based on 100 parts by mass of the organic resin, and the thickness of the organic coating layer is 0.2 to 100 占 퐉.

(2) The coated plated steel material according to (1), wherein the Mg content is 0 mass% or more and 60 mass% or less in any region where the diameter is 4 mm and the depth is 50 nm in the outermost layer at a depth of 50 nm from the surface of the plating layer %.

(3) In the coated plated steel material according to (1), the ratio of the Si-Mg phase on the surface of the plating layer may be 0% or more and 30% or less in area ratio.

(4) In the coated plated steel material according to (2), the ratio of the Si-Mg phase on the surface of the plating layer may be 0% or more and 30% or less in area ratio.

(5) In the coated plated steel material according to any one of (1) to (4), the uncoated layer may contain at least one selected from a zirconium compound and a titanium compound.

(6) The coated plated steel material according to any one of (1) to (4), wherein, in the uncoated treated layer, one or two or more of the following (1) to (5) are included in 100 parts by mass of the organic resin do.

(1) 50 to 3333 parts by mass of at least one selected from a zirconium compound and a titanium compound, or 1 to 50 parts by mass of at least one selected from the zirconium compound and the titanium compound

(2) 0.5 to 100 parts by mass of silica

(3) Phosphoric acid compound 0.5 to 40 parts by mass

(4) 1 to 50 parts by mass of tannin, tannic acid, or tannic acid

(5) Ethylenic fluoride 0.5 to 10 parts by mass

(7) In the coated plated steel material according to any one of (1) to (5), the organic coating layer may include two layers of a lower layer containing a rust preventive pigment and a colored upper layer.

(8) In the coated plated steel material according to any one of (1) to (5), the adhesion amount of the undercoated layer may be 10 to 2000 mg / m ² .

(9) In the coated plated steel material according to (6), the organic coating layer may include two layers of a lower layer containing a rust preventive pigment and a colored upper layer.

(10) In the coated plated steel material according to (6), the deposition amount of the undercoated layer may be 10 to 2000 mg / m ² .

(11) In the coated plated steel material according to (7), the adhesion amount of the undercoated layer may be 10 to 2000 mg / m ² .

According to the embodiments described in the above items (1) to (13), it is possible to provide a corrosion-resistant portion of the coated surface with a corrosion- Coated steel sheet is excellent in whitening resistance in the case of the above-mentioned steel sheet, and the occurrence of wrinkles and sagging of the surface is suppressed, and the appearance is good.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic view showing an example of a hot-dip plating apparatus in an embodiment of the present invention. FIG.
Fig. 2 is a schematic view of a part showing another example of the above-mentioned hot-dip coating processing apparatus.
Fig. 3A is a schematic view showing an example of a heating apparatus used in overexposure treatment in the embodiment of the present invention. Fig.
Fig. 3B is a schematic view showing an example of a warming container used in the overflow treatment in the embodiment of the present invention. Fig.
Fig. 4A is an image obtained by photographing the cut surface of the hot-dip coated steel sheet obtained at the level M5 of the embodiment by an electron microscope. Fig.
4B is a graph showing the elemental analysis results of the Si-Mg phase at the level M5 of the embodiment.
5A is a graph showing the results of depth direction analysis of the plating layer by the glow discharge emission spectroscopic analyzer with respect to the level M5 of the embodiment.
5B is a graph showing the results of the depth direction analysis of the plating layer by the glow discharge emission spectroscopic analyzer with respect to the level M50 of the embodiment.
Fig. 6 is an image obtained by photographing the surface of the plated layer in the molten plated steel sheet obtained at the level M5 of the embodiment by an electron microscope. Fig.
7A shows a photograph of the appearance of the plating layer with respect to the level M5 of the embodiment.
7B shows a photograph of the appearance of the plating layer with respect to the level M10 of the reference example.
8A shows an optical microscope photograph of the appearance of the plating layer with respect to the level M62 of the embodiment.
8B shows an optical microscope photograph of the appearance of the plating layer with respect to the level M5 of the embodiment.
Fig. 9 shows a photograph of the appearance of the plating layer with respect to the level M50 of the embodiment. Fig.
Fig. 10 is a graph showing the result of evaluation of the overfitting treatment on the level M5 of the embodiment of the molten plated steel sheet. Fig.
11A is an example of a schematic view showing the layer structure of a coated plated steel material in the embodiment of the present invention.
Fig. 11B is an example of a schematic diagram showing the layer structure of the coated plated steel material in the embodiment of the present invention. Fig.
Fig. 11C is an example of a schematic view showing the layer structure of the coated plated steel material in the embodiment of the present invention. Fig.
Fig. 11D is an example of a schematic diagram showing the layer structure of the coated plated steel material in the embodiment of the present invention. Fig.
Fig. 11E is an example of a schematic view showing the layer structure of the coated plated steel material in the embodiment of the present invention. Fig.
Fig. 11F is an example of a schematic view showing the layer structure of the coated plated steel material in the embodiment of the present invention. Fig.
Fig. 11G is an example of a schematic view showing the layer structure of a coated plated steel material in the embodiment of the present invention. Fig.
11H is an example of a schematic view showing the layer structure of the coated plated steel material in the embodiment of the present invention.

Hereinafter, the present invention will be described in detail.

[Painted plated steel]

The coated plated steel material according to the present embodiment has a steel material 1 and a coating 29 on the surface of the steel material 1, as shown in Figs. 11A to 11H. The coating 29 is provided with an aluminum-zinc alloy plating layer 23 (hereinafter referred to as a "plating layer 23") and an uncoated layer (not shown) on the surface of the plating layer 23 24 and an organic coating layer 25 on the surface of the coating undercoat layer 24. That is, a plating layer 23 is plated on the surface of the steel material 1, and an upper coating layer 24 and an organic coating layer 25 are successively coated on the upper surface thereof. As the steel material 1, various members such as a thin steel plate, a thick steel plate, a section steel, a steel pipe, and a steel wire can be cited. That is, the shape of the steel material 1 is not particularly limited. The plating layer 23 is formed by a hot-dip plating process.

[Plating layer (23)]

The plating layer 23 includes Al, Zn, Si, and Mg as constituent elements. The Al content in the plating layer 23 is 25 to 75 mass%. The Mg content is 0.1 to 10 mass%. As a result, Al particularly improves the corrosion resistance of the surface of the plating layer 23, and the edge creep at the cut end face of the molten plated steel, in particular, is suppressed by the action of the sacrifice by Zn, Corrosion resistance is imparted. Further, excessive alloying of Al in the plated layer 23 and the steel 1 is suppressed by Si, and the alloy layer 26 (described later) interposed between the plated layer 23 and the steel 1 melts The workability of the plated steel material is inhibited from being impaired. Further, the plating layer 23 contains Mg, which is a base metal rather than Zn, so that the sacrificial action of the plating layer 23 is strengthened, and the corrosion resistance of the molten plated steel is further improved.

The plating layer 23 contains 0.2 to 15% by volume of the Si-Mg phase. The Si-Mg phase is an image composed of an intermetallic compound of Si and Mg, and is dispersed and present in the plating layer 23.

The volume ratio of the Si-Mg phase in the plating layer 23 is equal to the area ratio of the Si-Mg phase in the cut surface when the plating layer 23 is cut in its thickness direction. The Si-Mg phase at the cut surface of the plating layer 23 can be clearly identified by an electron microscope observation. Therefore, the volume ratio of the Si-Mg phase in the plating layer 23 can be indirectly measured by measuring the area ratio of the Si-Mg phase on the cut surface.

The higher the volume ratio of the Si-Mg phase in the plating layer 23, the more the generation of wrinkles in the plating layer 23 is suppressed. This is because in the process in which the plated layer 23 is formed by solidification by cooling the molten plated metal during the manufacture of the molten plated steel, the Si-Mg phase is precipitated in the molten plated metal before the molten plated metal is completely solidified, -Mg phase suppresses the flow of the molten plated metal. The volume ratio of the Si-Mg phase is more preferably 0.2 to 10%, and still more preferably 0.4 to 5%.

The plating layer 23 is composed of a Si-Mg phase and other phases containing Zn and Al. The phase containing Zn and Al is mainly composed of an α-Al phase (dendrite structure) and a Zn-Al-Mg phase (interdendrite structure). The phase containing Zn and Al may be an image formed of Mg-Zn ₂ (Mg-Zn ₂ phase), an image made of Si (Si phase), or an Fe-Al intermetallic compound depending on the composition of the plating layer 23 (Fe-Al phase), and the like. The phase containing Zn and Al occupies a portion of the plating layer 23 excluding the Si-Mg phase. Therefore, the volume ratio of the phase containing Zn and Al in the plating layer 23 is preferably in the range of 99.8 to 85%, more preferably in the range of 99.8 to 90%, further preferably in the range of 99.6 to 95%.

The mass ratio of Mg in the Si-Mg phase to the total amount of Mg in the plating layer 23 is 3 mass% or more and 100 mass% or less. Mg not contained in the Si-Mg phase is contained in the phase containing Zn and Al. In the phase containing Zn and Al, Mg or the like it is contained in the Mg-containing oxide film formed on the plating surface of the of the α-phase of the Al, Zn-Al-Mg-phase process, the Mg-Zn _2. When Mg is contained in the? -Al phase, Mg is dissolved in the? -Al phase.

The mass ratio of Mg in the Si-Mg phase to the total amount of Mg in the plating layer 23 can be calculated in a state in which the Si-Mg phase is regarded as having a stoichiometric composition of Mg ₂ Si. Actually, the Si-Mg phase may contain a small amount of elements other than Si and Mg such as Al, Zn, Cr, and Fe, and the composition ratio of Si and Mg in the Si-Mg phase may be slightly varied in the stoichiometric composition It is very difficult to strictly determine the amount of Mg in the Si-Mg phase. Accordingly, in the present invention, when the mass ratio of Mg in the Si-Mg phase to the total amount of Mg in the plating layer 23 is determined, it is considered that the Si-Mg phase has a stoichiometric composition of Mg ₂ Si as described above.

The mass ratio R of Mg in the Si-Mg phase to the total amount of Mg in the plating layer 23 is calculated by the following equation (1).

R = 100 x AMg / (M x CMG / 100) ... (One)

R is the mass ratio (mass%) of Mg in the Si-Mg phase to the total amount of Mg in the plating layer 23 and AMg is the Si-Mg phase in the plating layer 23 per unit area as viewed from the plane of the plating layer 23 the Mg content (g / m ²⁾ contained in, m is the total Mg in the mass (g / m ^2), the plating layer 23 of the coating when viewed unit in the plane of the plate layer 23, CMG is a plating layer (23) (% By mass), respectively. The mass M of the plating layer 23 per unit area in the plane of the plating layer 23 refers to the mass of the plating layer 23 attached to the surface of the steel sheet per unit area on the surface of the steel sheet .

AMg is calculated from the following equation (2).

AMg = V ₂ x? ₂ x? (2)

V ₂ represents the volume (m ³ / m ² ) of the Si-Mg phase in the plating layer 23 per unit area as viewed from the plane of the plating layer 23. ρ ₂ represents the density of the Si-Mg phase, and its value is 1.94 × 10 ⁶ (g / m ³ ). ? represents the mass ratio of Mg contained in the Si-Mg phase, and the value is 0.63.

V ₂ can be calculated from the following equation (3).

_{V 2 = V 1 × R 2} /100 ... (3)

V ₁ is the total volume (m ³ / m ² ) of the plating layer 23 per unit area as viewed from the plane of the plating layer 23 and R ₂ is the volume ratio (volume%) of the Si-Mg layer in the plating layer 23 Respectively.

V ₁ can be calculated from the following equation (4).

V ₁ = M / ρ ₁ ... (4)

ρ ₁ represents the density (g / m ³ ) of the entire plating layer 23. The value of rho ₁ is calculated by weighted averaging the density of the constituent elements of the plating layer 23 at room temperature based on the composition of the plating layer 23.

In the present embodiment, Mg in the plating layer 23 is included in the Si-Mg phase at a high ratio as described above. As a result, the amount of Mg present in the surface layer of the plating layer 23 is reduced, whereby formation of the Mg-based oxide film in the surface layer of the plating layer 23 is suppressed. Therefore, wrinkles of the plating layer 23 caused by the Mg-based oxide film are suppressed. The larger the ratio of Mg in the Si-Mg phase to the total amount of Mg, the more wrinkles are suppressed. This ratio is more preferably 5 mass% or more, more preferably 20 mass% or more, and particularly preferably 50 mass% or more. The upper limit of the ratio of Mg in the Si-Mg phase to the total amount of Mg is not particularly limited and may be 100% by mass.

It is preferable that the Mg content is 0 mass% or more and less than 60 mass% in any region where the size is 4 mm in diameter (measuring portion diameter) and 50 nm in depth in the outermost layer at a depth of 50 nm from the surface of the plating layer 23. The Mg content in the outermost layer of the plating layer 23 is measured by Glow Discharge-Optical Emission Spectroscopy (GD-OES). That is, as a more specific measuring method, each glow discharge intensity derived from each detected element is converted into a mass ratio of the element by conversion with a coefficient obtained from a measurement value of a known standard sample or a known coefficient or composition, , The glow emission time corresponding to the depth of 50 nm was determined by a standard sample and the mass ratio in terms of the glow discharge intensity ratio of Mg was 0 mass% or more and less than 60 mass% at any point up to the emission time obtained by the standard sample .

The smaller the Mg content in the outermost layer of the plating layer 23, the wrinkles caused by the Mg-based oxide film are suppressed. This Mg content is more preferably less than 40 mass%, more preferably less than 20 mass%, and more preferably less than 10 mass%, in any region where the size of the outermost layer of the plating layer 23 is 4 mm in diameter and 50 nm in depth Particularly preferred.

It is preferable that the area ratio of the Si-Mg phase on the surface of the plating layer 23 is 30% or less. If the Si-Mg phase is present in the plating layer 23, the Si-Mg phase is thin on the surface of the plating layer 23 and is easily formed into a mesh shape. If the area ratio of this Si-Mg phase is large, the appearance of the plating layer 23 changes . When the state of distribution of the surface of the plating surface on the Si-Mg is not uniform, unevenness of gloss is observed on the outer surface of the plating layer 23 by visual observation. This unevenness of gloss is an appearance defect called sagging. When the area ratio of the Si-Mg phase on the surface of the plating layer 23 is 30% or less, sagging is suppressed and the appearance of the plating layer 23 is improved. The presence of the Si-Mg phase on the surface of the plating layer 23 is also effective for maintaining the corrosion resistance of the plating layer 23 for a long period of time. When the deposition of the Si-Mg phase on the surface of the plating layer 23 is suppressed, the deposition amount of the Si-Mg phase into the plating layer 23 relatively increases. As a result, the amount of Mg in the plating layer 23 is increased, whereby the action of sacrificing Mg in the plating layer 23 is exerted for a long period of time, whereby the high corrosion resistance of the plating layer 23 is maintained for a long period of time do. In order to improve the appearance of the plating layer 23 and maintain the corrosion resistance of the plating layer 23, the area ratio of the Si-Mg phase on the surface of the plating layer 23 is more preferably 20% or less, more preferably 10% , And particularly preferably 5% or less.

The content of Mg in the plating layer 23 is in the range of 0.1 to 10 mass% as described above. If the Mg content is less than 0.1 mass%, the corrosion resistance of the plating layer 23 is not sufficiently secured. When the content is more than 10% by mass, not only the action of improving the corrosion resistance is saturated but also dross is likely to occur in the hot-dip galvanizing bath 2 at the time of producing the hot-dip galvanized steel. The content of Mg is also preferably 0.5% by mass or more, more preferably 1.0% by mass or more. The Mg content is preferably 5.0 mass% or less, more preferably 3.0 mass% or less. It is particularly preferable that the content of Mg is in the range of 1.0 to 3.0 mass%.

The content of Al in the plating layer 23 is in the range of 25 to 75 mass%. When the content is 25 mass% or more, the Zn content in the plating layer 23 is not excessive, and the corrosion resistance on the surface of the plating layer 23 is sufficiently secured. When the content is 75 mass% or less, the effect of the sacrificial system by Zn is sufficiently exhibited, and the hardening of the plating layer 23 is suppressed, so that the workability of the hot-dip galvanized steel is improved. Also, from the viewpoint that the flowability of the molten plated metal is not excessively lowered during the production of the hot-dip galvanized steel, the content of Al is 75 mass% or less even from the viewpoint of further suppressing the wrinkling of the plated layer 23. The content of Al is particularly preferably 45 mass% or more. The content of Al is particularly preferably 65 mass% or less. It is particularly preferable that the content of Al is in the range of 45 to 65 mass%.

The content of Si in the plating layer 23 is preferably in the range of 0.5 to 10 mass% with respect to the content of Al. If the content of Si to Al is 0.5 mass% or more, excessive alloying of Al and the steel material 1 in the plating layer 23 is sufficiently suppressed. When the content is more than 10 mass%, the action of Si is saturated, and dross is easily generated in the hot-dip galvanizing bath 2 during production of the hot-dip galvanized steel. The Si content is particularly preferably at least 1.0% by mass. The Si content is particularly preferably 5.0 mass% or less. It is particularly preferable that the content of Si is in the range of 1.0 to 5.0 mass%.

Further, it is preferable that the mass ratio of Si: Mg in the plating layer 23 is in the range of 100: 50 to 100: 300. In this case, the formation of the Si-Mg layer in the plating layer 23 is particularly promoted, and the generation of wrinkles in the plating layer 23 is further suppressed. The mass ratio of Si: Mg is also preferably 100: 70 to 100: 250, more preferably 100: 100 to 100: 200.

The plating layer 23 also contains Cr as a constituent element. The growth of the Si-Mg phase in the plating layer 23 is promoted by Cr to increase the volume ratio of the Si-Mg phase in the plating layer 23 and the ratio of Mg in the Si-Mg phase to the total amount of Mg in the plating layer 23 . As a result, the wrinkles of the plating layer 23 are further suppressed. The content of Cr in the plating layer 23 is in the range of 0.02 to 1.0 mass%. If the content of Cr in the plating layer 23 is more than 1.0% by mass, the above-mentioned action is saturated and dross is easily generated in the hot-dip galvanizing bath 2 during the production of the hot-dip galvanized steel. The content of Cr is particularly preferably 0.05 mass% or more. The content of Cr is particularly preferably 0.5 mass% or less. The content of Cr is preferably in the range of 0.07 to 0.2 mass%.

It is preferable that the content of Cr in the outermost layer at a depth of 50 nm from the surface of the plating layer 23 is 100 to 500 mass ppm. In this case, the corrosion resistance of the plating layer 23 is further improved. This is considered to be because a passive film is formed on the plating layer 23 when Cr is present in the outermost layer, and the anode dissolution of the plating layer 23 is suppressed. The content of Cr is preferably 150 to 450 mass ppm, more preferably 200 to 400 mass ppm.

It is preferable that an alloy layer 26 containing Al and Cr is interposed between the plating layer 23 and the steel material 1. [ In the embodiment of the present invention, the alloy layer 26 is regarded as a layer different from the plating layer 23. The alloy layer 26 may contain various metal elements such as Mn, Fe, Co, Ni, Cu, Zn, and Sn in addition to Al and Cr as constituent elements. When such an alloy layer 26 is present, the growth of the Si-Mg phase in the plating layer 23 is promoted by Cr in the alloy layer 26 to increase the volume ratio of the Si-Mg phase in the plating layer 23, The ratio of Mg in the Si-Mg phase to the total amount of Mg in the Mg-free layer 23 becomes high. As a result, wrinkling or sagging of the plating layer 23 is further suppressed. Particularly, the ratio of the content of Cr in the alloy layer 26 to the content of Cr in the plating layer 23 is preferably 2 to 50. In this case, since the growth of the Si-Mg phase is promoted near the alloy layer 26 in the plating layer 23, the area ratio of the Si-Mg phase on the surface of the plating layer 23 is lowered, The corrosion resistance of the metal plate 23 is maintained over a longer period of time. The ratio of the content of Cr in the alloy layer 26 to the content of Cr in the plating layer 23 is preferably 3 to 40 and more preferably 4 to 25. The amount of Cr in the alloy layer 26 can be derived by measuring the cross section of the plating layer 23 using an energy dispersive X-ray analyzer (EDS).

The thickness of the alloy layer 26 is preferably in the range of 0.05 to 5 mu m. When the thickness is 0.05 탆 or more, the above-mentioned action by the alloy layer 26 is effectively exhibited. If the thickness is 5 占 퐉 or less, the alloy layer 26 makes it difficult to impair the workability of the hot-dip galvanized steel.

When the plating layer 23 contains Cr, the corrosion resistance after the processing of the plating layer 23 is also improved. The reason is thought to be as follows. When the plating layer 23 is subjected to severe processing, cracks may be generated in the plating layer 23. At this time, water or oxygen enters the plating layer 23 through the cracks, and the alloy in the plating layer 23 is directly exposed to the corrosive factors. However, the Cr present in the surface layer of the plating layer 23 and the Cr present in the alloy layer 26 suppress the corrosion reaction of the plating layer 23, thereby suppressing the expansion of corrosion starting from the crack. In order to particularly improve the corrosion resistance after processing of the plating layer 23, the content of Cr in the outermost layer at a depth of 50 nm from the surface of the plating layer 23 is preferably 300 mass ppm or more, more preferably 200 to 400 mass ppm . The ratio of the content of Cr in the alloy layer 26 to the content of Cr in the plating layer 23 is preferably 20 or more, more preferably 20 to 30, in order to particularly improve the corrosion resistance after processing of the plating layer 23 .

The plating layer 23 preferably contains Sr as a constituent element. In this case, the formation of the Si-Mg layer in the plating layer 23 is particularly promoted by Sr. The formation of the Mg-based oxide film in the surface layer of the plating layer 23 is suppressed by Sr. This is presumably because the formation of the Mg-based oxide film is inhibited because the Sr oxide film is more easily formed than the Mg-based oxide film. As a result, the generation of wrinkles in the plating layer 23 is further suppressed. The content of Sr in the plating layer 23 is preferably in the range of 1 to 1000 mass ppm. If the content of Sr is less than 1 mass ppm, the above-mentioned action will not be exerted. If the content is more than 1000 mass ppm, the action of Sr will be saturated. In addition, Dross is liable to occur. The content of Sr is particularly preferably 5 mass ppm or more. The content of Sr is particularly preferably 500 mass ppm or less, more preferably 300 mass ppm or less. The content of Sr is preferably in the range of 20 to 50 mass ppm.

The plating layer 23 preferably contains Fe as a constituent element. In this case, the formation of the Si-Mg layer in the plating layer 23 is particularly promoted by Fe. Further, Fe contributes to miniaturization of the microstructure and the sequin structure of the plating layer 23, whereby the appearance and workability of the plating layer 23 are improved. The content of Fe in the plating layer 23 is preferably in the range of 0.1 to 0.6 mass%. If the content of Fe is less than 0.1 mass%, the microstructure and the sequin structure of the plating layer 23 become coarse, and the appearance of the plating layer 23 deteriorates and the workability deteriorates. When the content is more than 0.6 mass%, the sequins of the plating layer 23 become very fine or disappear, so that appearance improvement due to the sequins can not be achieved. In the production of the hot-dip galvanized steel, Dross is liable to be generated, and the appearance of the plating layer 23 becomes worse. The content of Fe is particularly preferably 0.2 mass% or more. The Fe content is particularly preferably 0.5 mass% or less. It is particularly preferable that the content of Fe is in the range of 0.2 to 0.5% by mass. After plating, the floral pattern appearing on the surface of the steel plate 1 is called a sequin.

The plating layer 23 may contain an element selected from alkaline earth elements, Sc, Y, lanthanoid elements, Ti and B as constituent elements.

The alkaline earth elements (Be, Ca, Ba, and Ra), Sc, Y, and lanthanoid elements (La, Ce, Pr, Nd, Pm, Sm, Eu and the like) exert the same effect as Sr. The total amount of these components in the plating layer 23 is preferably 1.0 mass% or less by mass.

If the plating layer 23 contains at least one of Ti and B, the α-Al phase (dendritic structure) of the plating layer 23 becomes finer and the sequins become finer. As a result, the appearance of the plating layer 23 . Further, generation of wrinkles in the plating layer 23 is further suppressed by at least one of Ti and B. This is because the Si-Mg phase is finely smoothened by the action of Ti and B and the finely divided Si-Mg phase effectively suppresses the flow of the molten plated metal in the process of solidifying the molten plated metal to form the plated layer 23 . Such miniaturization of the plating structure also relaxes the concentration of stress in the plating layer 23 at the time of bending, suppressing generation of large cracks, and further improving the bending workability of the plating layer 23. In order for this action to be exhibited, it is preferable that the total content of Ti and B in the hot-dip galvanizing bath 2 is in the range of 0.0005 to 0.1 mass% in mass ratio. The total content of Ti and B is particularly preferably 0.001% by mass or more. The total content of Ti and B is particularly preferably 0.05% by mass or less. It is particularly preferable that the total content of Ti and B is in the range of 0.001 to 0.05 mass%.

Zn occupies the remainder portion excluding the constituent elements other than Zn out of the constituent elements of the plating layer 23.

It is preferable that the plating layer 23 does not contain any other element as the constituent element. In particular, the plating layer 23 may be formed of a material containing only Al, Zn, Si, Mg, Cr, Sr, and Fe as constituent elements or a material containing Al, Zn, Si, Mg, Cr, Sr, and Fe, Sc, Y, a lanthanoid element, Ti and B as constituent elements.

However, needless to say, the plating layer 23 may contain inevitable impurities such as Pb, Cd, Cu, and Mn. The content of the inevitable impurities is preferably as small as possible, and it is particularly preferable that the total content of the inevitable impurities is 1% by mass or less with respect to the plating layer 23 in mass ratio.

[Uncoated layer (24)]

The undercoating layer 24 covered with the upper layer of the plating layer 23 contains an organic resin and an organic silicon compound having an alkylene group, a siloxane bond and a crosslinkable functional group represented by the following formula (X) as essential components .

-SiR ¹ R ² R ³ ... ... (X)

R ¹ , R ² and R ³ in the formula represent, independently of each other, an alkoxy group or a hydroxy group. Any one of R ¹ , R ² and R ³ may be substituted with a methyl group. That is, two of R ¹ , R ² , and R ³ are each an alkoxy group or a hydroxy group, and the remaining one of R ¹ , R ² , and R ³ is an alkoxy group or a hydroxy group or a methyl group .

The organic resin which is an essential component of the uncoated layer 24 is excellent in barrier properties of corrosive factors such as water and oxygen and has an Mg-based oxide film formed on the surface layer of the above- Is also excellent in the retention of the initial corrosion products of Zn and Mg generated by the action of the sacrificial system of Zn and Mg. In addition to improving the adhesion between the uncoated layer 24 and the plated layer 23, the organic resin may also impart flexibility to the uncoated layer 24, To be able to follow the deformation of the boss. Thus, the coating-untreated layer 24 containing the organic resin prevents the peeling of the organic coating layer 25 and the lowering of the adhesiveness even in the portion where the coated plated steel is processed and deformed, ), It is superior in corrosion resistance, particularly in weathering resistance, and has an effect of delaying the generation of red rust.

The plating layer 23 of the present invention contains 25 to 75 mass% of Al and 0.2 to 15 volume% of the Si-Mg phase. As the volume ratio of the Si-Mg phase in the plating layer 23 is higher, the generation of wrinkles in the plating layer 23 is suppressed, while the Si-Mg phase is weak and weak, so that the plating layer 23 ), Cracks tend to occur at the time of processing. Even if cracks are formed, Zn and Mg in the plating layer 23 are exerted in a sacrificial manner, so that the inner rust resistance is not impaired, but white rust, which is a corrosion product of Zn and Mg, is likely to be generated in the processed region. Further, cracks are formed to lower the adhesiveness of the upper layer with the organic film, and even when the organic film of the processed part falls off, corrosion promoting substances such as water, oxygen, and salt are likely to come into contact with the plating layer 23, It is an easy factor. The organic resin, which is an essential component of the coating under-treatment layer 24, also has a feature of imparting flexibility to the undercoating layer 24 and excellent adhesion with the coating layer 23 and the organic film in the upper layer. That is, the coated plated steel material having the undercoating treatment layer 24 has excellent followability against the deformation (elongation and compression) of the steel material generated at the time of processing, and therefore, And scratches. If cracks occur in the organic coating, the organic coating at that position is hard to fall off from the surface of the plating, so that appearance and corrosion resistance (particularly, whitening resistance) can be maintained.

On the other hand, the organosilicon compound which is another essential component of the undercoating treatment layer 24 is not only excellent in the barrier properties of the corrosion factor (water, oxygen, etc.) The Mg-based oxide film and the initial corrosion products of Zn and Mg generated by the action of the sacrificial system of Zn and Mg in the plating layer 23 are also excellent. As a result, the undercoated layer 24 containing the organosilicon compound is superior in corrosion resistance, particularly in whitening resistance, to the hot-rolled steel material without such an effect, and has the effect of delaying the generation of red rust.

The organosilicon compound also has an excellent balance of flexibility and hardness. That is, the undercoating treatment layer 24 containing the organosilicon compound has excellent followability against the deformation (elongation and compression) of the steel material generated when the plated steel material is processed, The undercoating layer 24 is uniformly coated with no damage such as cracks or scratches and thus can maintain excellent corrosion resistance and stain resistance and has an appropriate hardness so that the organic coating layer 25 of the upper layer has scratches An effect of preventing the scratches from advancing to the plating layer 23 can also be expected.

The organic resin and the organosilicon compound form a more dense coating film by crosslinking with each other so that the barrier properties of the corrosion factor (water or oxygen) and the Mg-based oxide film or the plating layer formed on the surface layer of the plating layer 23 It is expected that the retention of the initial corrosion products of Zn and Mg generated by the action of the sacrificial system of Zn and Mg is increased.

Hereinafter, the structure of the coating under treatment layer 24 will be described.

≪ About organic resin &

The organic resin is not limited to a specific kind, and examples thereof include a polyester resin, a polyurethane resin, an epoxy resin, an acrylic resin, a polyolefin resin, or a modified product of these resins. As such organic resin, one or more organic resins (unmodified ones) may be mixed and used. Alternatively, an organic resin obtained by modifying at least one other organic resin in the presence of at least one organic resin May be used alone or in combination of two or more.

The polyester resin is not particularly limited and, for example, those obtained by condensation polymerization of a polyester raw material containing a polycarboxylic acid component and a polyol component can be used. The polyester resin thus obtained may be water-soluble by dissolving or dispersing it in water.

Examples of the polycarboxylic acid component include phthalic acid, phthalic anhydride, tetrahydrophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, methyltetrahydrophthalic acid, methyltetrahydrophthalic anhydride, The present invention further relates to a method for producing a lactic acid-containing polymeric acid, which comprises reacting at least one monomer selected from the group consisting of lactic acid, maleic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, adipic acid, azelaic acid, sebacic acid, , Dodecenylsuccinic acid, dodecenylsuccinic acid, cyclohexane-1,4-dicarboxylic acid, and anhydrous endo acid. As the polycarboxylic acid component, one of the above components may be used, or a plurality of the above components may be used.

Examples of the polyol component include ethylene glycol, diethylene glycol, 1,3-propanediol, 1,2-propanediol, triethylene glycol, 2-methyl-1,3-propanediol, 2,2- Propanediol, 2-methyl-1, 4-butanediol, 2-methyl-3-methyl-1,4 Butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, 1,3- Cyclohexanedimethanol, hydrogenated bisphenol-A, dimer diol, trimethylol ethane, trimethylol propane, glycerin, pentaerythritol and the like. As the polyol component, one of the above components may be used, or a plurality of the above components may be used.

The polyurethane resin is not particularly limited and, for example, a resin obtained by reacting a polyol compound with a polyisocyanate compound, and then chain-stretching the resin by a chain extender. The polyol compound is not particularly limited as long as it is a compound containing two or more hydroxyl groups per molecule, and examples thereof include ethylene glycol, propylene glycol, diethylene glycol, 1,6-hexanediol, neopentyl glycol, triethylene glycol, A polyether polyol such as glycerin, trimethylol ethane, trimethylol propane, polycarbonate polyol, polyester polyol and bisphenol hydroxypropyl ether, polyester amide polyol, acryl polyol, polyurethane polyol, or a mixture thereof have. The polyisocyanate compound is not particularly limited as long as it is a compound containing two or more isocyanate groups per molecule, and examples thereof include aliphatic isocyanates such as hexamethylene diisocyanate (HDI) and alicyclic diisocyanates such as isophorone diisocyanate (IPDI) Aromatic diisocyanates such as isocyanate and tolylene diisocyanate (TDI), aromatic aliphatic diisocyanates such as diphenylmethane diisocyanate (MDI), and mixtures thereof. The chain extender is not particularly limited as long as it is a compound containing at least one active hydrogen in the molecule, and examples thereof include ethylenediamine, propylenediamine, hexamethylenediamine, diethylenetriamine, dipropylenetriamine, , And tetraethylene pentamine; aromatic polyamines such as tolylene diamine, xylylenediamine and diaminodiphenyl methane; aromatic polyamines such as diaminocyclohexylmethane, piperazine, 2,5-dimethylpiperazine, isophorone Aliphatic amines such as hydrazine such as hydrazine, succinic dihydrazide, adipic acid dihydrazide and phthalic acid dihydrazide, and hydrazines such as hydroxyethyldiethylenetriamine, 2 - [(2-aminoethyl) amino] ethanol , 3-aminopropanediol, and other alkanolamines. These compounds may be used alone or in combination of two or more.

Examples of the epoxy resin include, but not limited to, bisphenol A epoxy resin, bisphenol F epoxy resin, hydrogenated bisphenol A epoxy resin, hydrogenated bisphenol F epoxy resin, resorcinol epoxy resin, novolak type epoxy resin, An epoxy resin such as an epoxy resin can be used. The epoxy resin may be one obtained by forcibly emulsifying the epoxy resin with a surfactant to form a water-based resin. The epoxy resin may be neutralized with an organic acid or an inorganic acid by reacting the epoxy resin with an amine compound such as diethanolamine or N-methylethanolamine Or a resin obtained by radical polymerization of a high acid value acrylic resin in the presence of these epoxy resins and neutralization with ammonia or an amine compound or the like.

The acrylic resin is not particularly limited and includes, for example, alkyl (meth) acrylates such as ethyl (meth) acrylate, 2-ethylhexyl (meth) acrylate and n-butyl (meth) Hydroxyalkyl (meth) acrylates such as hydroxyethyl (meth) acrylate, and (meth) acrylic esters such as alkoxysilane (meth) acrylate are reacted with (meth) acrylic acid in water, And those obtained by polymerization. The polymerization initiator is not particularly limited and azo compounds such as persulfates such as potassium persulfate and ammonium persulfate, azobiscyano valeric acid and azobisisobutyronitrile can be used. Here, "(meth) acrylate" means acrylate and methacrylate, and "(meth) acrylic acid" means acrylic acid and methacrylic acid.

The polyolefin resin is not particularly limited and, for example, unsaturated carboxylic acids such as ethylene and methacrylic acid, acrylic acid, maleic acid, fumaric acid, itaconic acid and crotonic acid are subjected to radical polymerization under high temperature and high pressure, , Basic metal compounds such as KOH, NaOH, and LiOH, or ammonia or amine compounds containing the metal compounds, and the like.

The organic resin preferably contains a resin containing at least one functional group selected from an ester group, a urethane group and urea groups in the structure in order to improve corrosion resistance and scratch resistance as a coated plated steel material. In order to improve the corrosion resistance as a coated plated steel material, it is necessary that the uncoated layer 24 is coated uniformly on the plated steel material as the base material without damages such as cracks (excellent workability) It is important to suppress the permeability. In addition, it is important that the adhesion strength between the coating under-treatment layer 24 and the plating surface is high. In order to realize such an undercoating treatment layer 24, it is preferable to use an organic resin containing a specific resin structure as a film forming component. Specifically, it is preferable to use an organic resin having a specific cohesive energy as described above in the resin structure of the organic resin By introducing a functional group, both the elongation and the strength of the coating film can be increased higher, and the adhesion and the corrosion resistance can be enhanced.

The resin containing the ester group, the urethane group, and the urea group in the resin structure includes, but not limited to, a polyester resin containing an ester group, a polyurethane resin containing a urethane group , Polyurethane resins containing both urethane groups and urea groups, and the like. These may be used alone or in combination of two or more. For example, even when an ester group, a urethane group, and a urea group, which are obtained by mixing a polyester resin containing an ester group and a polyurethane resin containing both urethane groups and urea groups, as an organic resin do.

≪ About the organosilicon compound >

The organosilicon compound may be an alkylene group, a siloxane bond,

-SiR ¹ R ² R ³ ... ... (X)

(Wherein in R ^1, R ² and R ³ are, independently of each other, represents an alkoxy group or a hydroxyl group. Further, it is even any one of R ^1, R ² and R ³ dogs are substituted with methyl group, that is, R ^1, Wherein ^{two of} R ² and R ³ are each an alkoxy group or a hydroxy group and the remaining one of R ¹ , R ² and R ³ is an alkoxy group or a hydroxy group or a methyl group) The organic silicon compound containing a functional group enhances the adhesion between the coating under-treatment treatment layer 24 and the plating surface and the adhesion between the coating under-treatment treatment layer 24 and the organic coating film in the upper layer. Further, the organic resin or the organic resin and the silica particles to be described later are crosslinked to increase the strength of the coating undercoat layer 24 and the permeation inhibition of the corrosion promoting substances such as water, oxygen, and salts.

The organosilicon compound is not particularly limited as long as it contains an alkylene group, a siloxane bond and a crosslinkable functional group represented by the above formula (X), and examples thereof include an alkylene group, a siloxane bond and a crosslinkable functional group , And can be stably present in an aqueous medium containing water as a main component. The organosilicon compound preferably contains at least one crosslinkable functional group selected from the group consisting of an amino group, an epoxy group and a hydroxyl group (apart from those contained in the above-described formula (X)), And is preferable for enhancing the corrosion resistance of the coated plated steel material. In addition, since these crosslinkable functional groups exhibit hydrophilicity, when the coating composition for forming the undercoating layer 24 is an aqueous coating material, it is preferable that at least one kind of crosslinkable functional group selected from an amino group, an epoxy group and a hydroxyl group is It is also advantageous to increase the stability of the organosilicon compound in an aqueous solvent. In the present specification, the stability in an aqueous solvent means that it is difficult to generate agglomerates or sediments in an aqueous solvent over time, but the phenomenon of thickening or gelation is unlikely to occur.

As such an organosilicon compound, a hydrolysis-condensation product of a silane coupling agent and the like can be mentioned. Specific examples of the silane coupling agent include vinyltrimethoxysilane, vinyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxy Silane, 3-glycidoxypropylmethyldiethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxy Silane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxy Silane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- (aminoethyl) Propylmethyldimethoxysilane, bis (trimethoxysilylpropyl) amine, 3-triethoxysilyl-N- (1,3-di 3-aminopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-isocyanatopropyltriethoxysilane, and bis (trimethoxysilyl) hexane. The silane coupling agent may be used singly or in combination of two or more kinds.

It is particularly preferable that the organosilicon compound is obtained by a reaction between a silane coupling agent containing an amino group and a silane coupling agent containing an epoxy group. It is possible to form a dense coating film having a high crosslinking density by the reaction between the amino group and the epoxy group and the reaction between the alkoxysilyl groups or the partial hydrolysis products thereof contained in each of the silane coupling agent and the silane coupling agent The corrosion resistance, scratch resistance and stain resistance of the coated hot-dip coated steel can be further improved. Examples of the silane coupling agent containing an amino group include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N- Aminoethyl) -3-aminopropyltriethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane and bis (trimethoxysilylpropyl) amine. Examples of the silane coupling agent (BE) include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxy Silane.

The molar ratio (BA / BE) when the silane coupling agent containing an amino group is referred to as BA and the silane coupling agent containing an epoxy group as BE is preferably 0.5 or more and 2.5 or less, more preferably 0.7 or more and 1.6 or less . When the molar ratio (BA / BE) is less than 0.5, the film-formability is lowered and the corrosion resistance improving effect becomes insufficient. On the other hand, when it is more than 2.5, the water resistance is lowered and the corrosion resistance improving effect becomes insufficient.

The number average molecular weight of the organosilicon compound is preferably from 1,000 to 10,000, more preferably from 2,000 to 100,000. Here, the method of measuring the molecular weight is not particularly limited, but any of the direct measurement by the TOF-MS method and the conversion measurement by the chromatography method may be used. When the number average molecular weight is less than 1000, the water resistance of the formed film is lowered, and alkali resistance and corrosion resistance are lowered in some cases. On the other hand, if the number average molecular weight is more than 10,000, it is difficult to stably dissolve or disperse the organosilicon compound in an aqueous medium containing water as a main component, and the storage stability of the coating composition for forming a coating under treatment layer may be lowered . The number-average molecular weight of the organosilicon compound is preferably 2000 or more and 5000 or less.

[Uncoated layer (24)]

The undercoating layer 24 coated on the upper layer of the plating layer 23 may contain at least one selected from a zirconium compound and a titanium compound as a film forming component in addition to the organic resin and the organic silicon compound.

At least one selected from zirconium compounds and titanium compounds that are components of the untreated treatment layer 24 is not only excellent in barrier property (corrosion resistance) of corrosion factor (water or oxygen) And it is excellent in heat resistance and durability against energy rays such as ultraviolet rays. Adhesion between the Al oxide and Mg oxide on the surface of the plating layer 23 is also good. That is, the hot-dip galvanized steel sheet coated with the undercoating layer 24 comprising at least one selected from the zirconium compound and the titanium compound as the film forming component is excellent in whiteness, especially when heated, It is possible to maintain the whitening resistance for a long period of time by keeping the coating under treatment layer 24 and the organic coating layer 25 in the upper layer for a long period of time have.

Hereinafter, the structure of the coating under treatment layer 24 will be described.

≪ About zirconium compound and titanium compound >

As the zirconium compound and the titanium compound to be contained in the treatment agent for forming the untreated treatment layer 24, the zirconium compound is not particularly limited. Examples of the zirconium compound include zirconyl nitrate, zirconyl acetate, zirconyl sulfate, zirconium ammonium carbonate , Zirconium carbonate, potassium zirconium carbonate, sodium zirconium carbonate, zirconium acetate, zirconium hydrofluoric acid, and salts thereof. Among these zirconium compounds, zirconium hydrofluoric acid, a salt thereof, and a zirconium compound containing a zirconium carbonate complex ion are preferable from the viewpoint of corrosion resistance. Not be particularly limited as long as the zirconium compound containing zirconium carbonate complex ions, for example, zirconium carbonate complex ions _{[Zr (CO 3) 2 (OH} ) 2 ] _2- or _{[Zr (CO 3) 3 (OH} ) ] ₃ -, ammonium salts, potassium salts, sodium salts and the like.

Examples of the titanium compound include titanium oxalate, titanyl sulfate, titanium chloride, titanium lactate, titanium isopropoxide, titanium isocyanate, titanium ethoxide, titanium 2-ethyl-1-hexano Tetraisopropyl titanate, tetra-n-butyl titanate, titania sol, titanium hydrofluoric acid, and salts thereof. Of these titanium compounds, titania sol, titanium lactate, titanium hydrofluoric acid or its salt and the like are preferable from the viewpoint of corrosion resistance.

The amount of the zirconium compound and the titanium compound is preferably 1 to 3333 parts by mass per 100 parts by mass of the organic resin in order to improve the scratch corrosion resistance. On the other hand, when the blending amount of the zirconium compound and the titanium compound is large, the proportion of the inorganic component in the undercoating component increases, and the coating undercoat layer 24 is backed off, Therefore, when the corrosion resistance of the processed portion is emphasized, a more preferable blending amount may be 1 to 50 parts by mass in 100 parts by mass of the organic resin. When the content of the zirconium compound and the titanium compound is less than 1 part by mass, the barrier property (corrosion resistance) of the corrosion factor is low, so that when the film is scratched or the corrosion endurance of the cut end face of the coated plated steel becomes insufficient, The durability against the energy ray of the light source may be insufficient. If the content is more than 3333 parts by mass, the undercoating layer may be retreated to deteriorate the film adhesion of the film-bending portion, resulting in insufficient corrosion resistance at the bending portion.

The method for producing the organosilicon compound is not particularly limited, and examples thereof include a method of dissolving or dispersing a silane coupling agent in water and stirring at a predetermined temperature for a predetermined time to obtain an aqueous solution of a hydrolysis-condensation product, A method in which an aqueous solution is obtained by dissolving or dispersing an organosilicon compound such as a hydrolysis-condensation product in water, a method in which an organosilicon compound such as a hydrolysis-condensation product of a silane coupling agent is dissolved in an alcohol-based organic solvent such as methanol, ethanol or isopropanol, And a method of obtaining a solution. In order to dissolve or disperse the silane coupling agent or the hydrolyzed condensate thereof in the aqueous medium, an acid, an alkali, an organic solvent, a surfactant and the like may be appropriately added, and in particular, an organic acid is added to adjust the pH to 3 to 6 Is preferable from the viewpoint of storage stability. It is preferable that the solid concentration of the aqueous liquid of the organic silicon compound or the alcohol-based liquid is 25 mass% or less. If the solid content concentration of the organosilicon compound (B) exceeds 25 mass%, the storage stability of the aqueous liquid or the alcohol-based liquid may be lowered.

The content of the organic silicon compound is 2 to 1,500 parts by mass based on 100 parts by mass of the organic resin. If it is less than 2 parts by mass, the effect of improving the corrosion resistance may not be obtained or the storage stability of the coating composition for forming the undercoating layer 24 may be lowered. On the other hand, if it exceeds 1500 parts by mass, sufficient corrosion resistance may not be obtained.

≪ About silica particles >

It is preferable that the undercoating treatment layer 24 further contains silica particles. By containing the silica particles, the corrosion resistance can be further improved.

Here, the content of the silica particles is preferably 0.5 parts by mass or more and 100 parts by mass or less based on 100 parts by mass of the organic resin. When the amount is less than 0.5 part by mass, the effect of improving the corrosion resistance may not be obtained. When the amount is more than 100 parts by mass, the cohesion of the undercoating layer 24 may be lowered. The content of the silica particles is more preferably 5 to 50 parts by mass, particularly preferably 10 to 30 parts by mass with respect to 100 parts by mass of the organic resin.

The type of the silica particles is not particularly limited, and examples thereof include silica particles such as colloidal silica and fumed silica. Examples of commercially available products include commercially available products such as SNOWTEX O, SNOWTEX N, SNOWTEX C, SNOWTEX IPA-ST (manufactured by Nissan Chemical Industries Ltd.), Adelite AT-20N, Adelite AT-20A (manufactured by Asahi Denka Kogyo Co., ), Aerosil 200 (manufactured by Nippon Aerosil Co., Ltd.), functional spherical silica HPS series (manufactured by Toagosei Co., Ltd.), and Nipsil series (manufactured by Tosoh Silica Co., Ltd.).

In addition, it is preferable to contain spherical silica particles having an average particle diameter of 5 nm or more and 20 nm or less as silica particles in order to improve corrosion resistance. When the average particle diameter of the spherical silica particles is less than 5 nm, the coating composition for forming the undercoating treatment layer 24 may cause problems such as gelation. When the average particle diameter exceeds 20 nm, the effect of improving the corrosion resistance May not be obtained sufficiently.

<About phosphoric acid compounds>

It is preferable that the undercoating treatment layer 24 further contains a phosphoric acid compound in order to improve the corrosion resistance. It is more preferable that the phosphate compound is a phosphate ion releasing compound. When the phosphoric acid compound is contained, when the coating composition for forming it comes into contact with the plating layer 23 or after the coating under-treatment layer 24 is formed, , The phosphorus acid ion-containing film reacts with the Mg-based oxide film on the surface of the plating layer 23 to form an insoluble phosphoric acid Mg-based coating film on the surface of the plating layer 23. Thus, the whitening resistance can be greatly improved. When the phosphate compound does not release phosphate ions, that is, it is inexpensive in the environment, the insoluble phosphate compound inhibits the migration of corrosion factors such as water and oxygen, thereby improving the corrosion resistance.

Examples of the phosphoric acid compound include, but are not limited to, phosphoric acids such as orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, triphosphoric acid and tetraphosphoric acid and their salts, aminotri (methylenephosphonic acid), 1- Phosphinic acid and salts thereof such as ethylenediamine tetra (methylene phosphonic acid) and diethylenetriamine penta (methylene phosphonic acid), and organic phosphoric acids such as phytic acid, and salts thereof And the like. The cation species of the salt is not particularly limited and examples thereof include Cu, Co, Fe, Mn, Sn, V, Mg, Ba, Al, Ca, Sr, Nb, Y, Ni and Zn. These phosphoric acid compounds (D) may be used alone or in combination of two or more.

The content of the phosphoric acid compound is preferably 0.5 to 40 parts by mass, more preferably 2 to 15 parts by mass, per 100 parts by mass of the organic resin in the undercoating layer 24. If the content of the phosphoric acid compound is less than 0.5 parts by mass, the effect of improving the corrosion resistance may not be obtained. If the content is more than 40 parts by mass, the corrosion resistance and the coating film adhesion of the processed portion may deteriorate and the coating stability to form a coating film may deteriorate , Problems such as gelation and precipitation of agglomerates may occur).

For tannins, tannic acid, or tannates,

It is preferable that the untreated treatment layer 24 further contains tannin, tannic acid, or tannic acid salt.

Tannin, tannic acid or tannic acid salt is a generic term for aromatic compounds having a complex structure having a large number of phenolic hydroxyl groups distributed widely in plants. The tannin, tannic acid, or tannic acid salt used in the untreated layer 24 may be a hydrolyzable tannic acid or a condensed tannic acid. Examples of the tannins include, but are not limited to, hammamititanin, persimmon tannin, tea tannin, dumbbell tannin, myrrh tannin, mirovalan tannin, dibidibitannin, alvarovilla tannin, valonitannin, catechin tannin, etc. have. Examples of the tannic acid or tannic acid salt include commercially available ones such as tannic acid extract A, B tannic acid, N tannic acid, industrial tannic acid, refined tannic acid, Hi tannic acid, F tannic acid, "National tannic acid" (all manufactured by Dainippon Pharmaceutical Co., Ltd.), "Tannic acid: AL" (manufactured by Fuji Chemical Industry Co., Ltd.), and the like may also be used. Such tannin, tannic acid or tannic acid salt may be used singly or in combination of two or more kinds.

The tannin, the tannic acid, or the tannic acid salt is firmly adhered to the plating layer 23 and is also in close contact with the resin, particularly the water-based resin. Therefore, the surface of the coating under treatment layer 24 itself and the upper surface of the organic coating layer 25 Thereby improving the adhesion to the substrate. Even when the underlying plated steel material is deformed, the adhesion of the coating layer 24 prevents itself from peeling off the organic undercoat layer 25 on the under-treatment treatment layer 24, and as a result, the corrosion resistance of the processed portion is also improved. The content of tannin, tannic acid or tannic acid salt is preferably 1 to 50 parts by mass with respect to 100 parts by mass of the organic resin. When the amount is less than 1 part by mass, the effect of addition is small. When the amount is more than 50 parts by mass, the corrosion resistance of the processed portion is lowered and the stability of the treatment solution is lowered. A more preferable content is 4 to 20 parts by mass with respect to 100 parts by mass of the organic resin.

&Lt; About etchant fluoride >

When the etchant fluoride is further added to the undercoating treatment layer 24, adhesion with the plating surface is improved. As a result, the corrosion resistance of the processed portion may be improved. As the etchant fluoride, zinc fluoride tetrahydrate, zinc hexafluorosilicate hexahydrate, and the like can be used. The content of the etchant fluoride is preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the organic resin. If the amount is less than 0.5 part by mass, the effect of addition is small, and if it exceeds 10 parts by mass, the etching effect is saturated and the adhesion is not improved.

&Lt; Adherence amount of coating-untreated layer 24 >

Adhesion amount of the treatment layer 24 is not coated is not particularly limited, from 10 to 2000mg / m ² is preferable, more preferably 20 to 1000mg / m ^2, more preferably 20 to 300mg / m ^2, particularly preferably Gt; mg / m &lt; ^{2 &} gt ;. If the coating amount of the coating under-treatment layer 24 is less than 10 mg / m ² , sufficient corrosion resistance and coating film adhesion may not be obtained. On the other hand, if the deposition amount of the undercoating treatment layer 24 exceeds 2000 mg / m ² , it is economically disadvantageous. In addition, when the undercoating treatment layer 24 is formed from an aqueous coating material, Coating film defects may occur and the appearance and performance of the coated plated steel product as an industrial product may not be stably obtained. In addition, the cohesion of the undercoating treatment layer 24 is insufficient, and the adhesion and corrosion resistance may be deteriorated.

The adhesion amount of the undercoating treatment layer 24 can be determined by calculating the difference in mass of the plated steel before and after the coating and calculating the difference in mass of the plated steel before and after peeling the uncoated undercoat layer 24 after coating, The coating film is subjected to fluorescence X-ray analysis to measure the amount of the element which is known in advance in the coating film and the amount of the element is known.

[Organic Coating Layer (25)]

The coated plated steel according to each embodiment of the present invention is one in which one or more organic coating layers 25 are coated on one side or both sides of the plated steel with the undercoating treatment layer 24 interposed therebetween. Alternatively, in areas where high corrosion resistance and organic film adhesion are not a problem, the uncoated layer 24 and the organic coating layer 25 may be partially omitted.

Examples of the binder resin that is the main component of the coating film of the organic coating layer 25 include a polyester resin, an epoxy resin, a urethane resin, an acrylic resin, a melamine resin, a fluororesin, and the like. A thermosetting resin is more preferable. Examples of the thermosetting resin include polyester resins such as epoxy polyester resins, polyester resins, melamine polyester resins and urethane polyester resins, and acrylic resins. These resins have better processability than other resins, Cracks do not easily occur in the coating layer even after processing.

The polyester resin as a main component of the organic coating layer 25 is not particularly limited, but generally known ester compounds of polybasic acids and polyhydric alcohols, and those synthesized by a generally known esterification reaction can be used.

Examples of the polybasic acid include, but are not limited to, phthalic acid, isophthalic acid, terephthalic acid, phthalic anhydride, trimellitic acid anhydride, maleic acid, adipic acid and fumaric acid. These polybasic acids may be used either singly or in combination.

Examples of the polyhydric alcohol include, but are not limited to, ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, neopentylene glycol, 1,4-butanediol, Diol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, polytetramethylene ether glycol, glycerin, trimethylol ethane, trimethylol propane, trimethylolbutane, hexanetriol, pentaerythritol, dipentaerythritol And the like. These polyhydric alcohols may be used alone or in combination of two or more.

When the above polyester resin is used, it is preferable to blend a curing agent because the hardness of the coating layer is increased and the scratch resistance is improved. The curing agent is not particularly limited, but any one or both of commonly known amino resins and polyisocyanate compounds can be used.

The amino resin is not particularly limited. For example, resins obtained by reaction of urea, benzoguanamine, melamine and the like with formaldehyde, and alkyl ethers of these resins with alcohol can be used. Specifically, methylated urea resin, n-butylated benzoguanamine resin, methylated melamine resin, n-butylated melamine resin, iso-butylated melamine resin and the like can be given.

Resins widely used in the field of coated hot-dip coated steels are polyester / melamine-based resins having a polyester resin as a main resin and a melamine resin as a curing agent. The melamine resin referred to herein means at least one or more of methylated melamine, n-butylated melamine and isobutylated melamine.

The polyisocyanate compound is not particularly limited and is preferably an isocyanate compound blocked with a block agent such as phenol, cresol, aromatic secondary amine, tertiary alcohol, lactam, oxime and the like. Examples of the polyisocyanate compound that is more preferable include HDI (hexamethylene diisocyanate) and derivatives thereof, TDI (tolylene diisocyanate) and derivatives thereof, MDI (diphenylmethane diisocyanate) and derivatives thereof, XDI (xylene diisocyanate) Hydrogenated TDI and derivatives thereof, hydrogenated MDI and derivatives thereof, hydrogenated XDI and derivatives thereof, and the like can be given as examples of the hydrogenated TDI and IPDI (isophorone diisocyanate) and its derivatives, TMDI (trimethylhexamethylene diisocyanate) and derivatives thereof.

&Lt; Composition of Coating Film of Organic Coating Layer 25 >

In the present invention, the constitution of the coating layer of the organic coating layer 25 is not particularly limited, and it may have only one coating film, or may have two or more coating films. Further, As shown in FIG. However, as described below, in order to secure excellent designability and corrosion resistance, it is preferable that the coating layer is a coating layer containing two or more coating layers.

When the organic coating layer 25 is two or more layers, it is preferable that at least one layer is a layer containing a rust preventive pigment in order to enhance the corrosion resistance of the coated hot-dip coated steel. It is more preferable that the layer containing the anticorrosive pigment is arranged on the plated steel material side than the other layers in order to enhance the corrosion resistance. Examples of the anticorrosive pigments include, but are not limited to, phosphoric acid-based anticorrosive pigments such as zinc phosphate, iron phosphate, aluminum phosphate, zinc phosphate and aluminum tripolyphosphate, and molybdate-based pigments such as calcium molybdate, aluminum molybdate and barium molybdate Silane-based anticorrosive pigments such as calcium silicate, silica-based anticorrosive pigments such as water-dispersed silica, fumed silica and calcium ion-exchanged silica, and iron-based anticorrosive pigments such as silicon iron Chromate-free anticorrosive pigments such as pigments, or generally known chrome-based anticorrosive pigments such as strontium chromate, potassium chromate, barium chromate, and calcium chromate. However, from the viewpoint of recent environmental preservation, it is more preferable to use a chromate-free anticorrosive pigment as the anticorrosive pigment in the present invention. These rust-preventive pigments may be used singly or in combination.

The amount of the anticorrosive pigment to be added is preferably 1% by mass or more and 40% by mass or less based on the solid content of the layer containing the anticorrosive pigment in the organic coating layer (25). If the addition amount of the anticorrosive pigment is less than 1% by mass, the improvement of the corrosion resistance is not sufficient. If it exceeds 40% by mass, the workability is lowered, and the coating layer may fall off during processing and the corrosion resistance tends to deteriorate.

When the organic coating layer 25 is two or more layers, it is preferable that at least one layer is a colored coating layer containing a coloring pigment in order to enhance the designability of the coated plated steel material. The outermost layer may be a colored coating layer containing a coloring pigment. The outermost layer may include a high-permeability coating layer, and a colored coating layer may be disposed thereunder.

The coloring pigment is not particularly limited, and examples thereof include pigments such as titanium oxide, zinc oxide, iron oxide, zirconium oxide, calcium carbonate, barium sulfate, carbon black, phthalocyanine blue, naphthol red, disazo yellow, disazo pyrazolone orange Can be used. It may be an inorganic pigment or an organic pigment. As the coloring pigment, generally known metallic pigments such as aluminum pigments and nickel pigments may be used, and either granular or flake-like forms may be used. These colored pigments may be used alone or in combination of plural kinds.

The amount of the colored pigment to be added is preferably 5% by mass or more and 70% by mass or less based on the solids content of the layer containing the color pigment in the organic coating layer (25). When the addition amount of the color pigment is less than 5 mass%, the intended decorative effect (coloring effect) may be lowered. When the addition amount exceeds 70 mass%, the corrosion resistance of the coating layer and the porosity may be deteriorated.

The thickness of the organic coating layer 25 is preferably 0.2 to 100 mu m. When the thickness is less than 0.2 mu m, the effects such as coloration by the organic coating layer 25, designation, blocking of the corrosion factor for rusting of the coated steel sheet are insufficient, and when the thickness exceeds 100 mu m, the effect of the coating layer is saturated, There is a problem that it is difficult to obtain a uniform appearance because the surface of the coating layer is likely to be uneven and that the organic coating film is likely to be cracked in the processed portion of the coated steel sheet. The thickness of the organic coating layer 25 is preferably 3 to 40 占 퐉, more preferably 15 to 40 占 퐉.

The thickness of the organic coating layer 25 can be measured by observing the cross section of the organic coating layer 25 or using an electronic film thickness measuring instrument or the like. Alternatively, the mass of the organic coating layer 25 attached per unit area of the plated steel may be calculated by dividing the specific gravity of the organic coating layer 25 or the specific gravity after drying of the coating solution. The adhesion mass of the organic coating layer 25 can be determined by calculating the difference in mass of the plated steel before and after coating, calculating the mass difference between the plated steel before and after peeling the coated organic coating layer 25, And X-ray analysis to measure the abundance of an element that is known in advance in the coating film. The specific gravity of the organic coating layer 25 or the specific gravity of the coating after drying may be determined by measuring the volume and mass of the organic coating layer 25 that has been isolated, measuring the volume and mass after taking a suitable amount of the coating in the container, , The amount of the constituent components of the organic coating layer 25 and the specific gravity of each component, and the like.

[Pretreatment layer 28]

The pretreatment layer 28 is provided between the undercoating layer 24 and the metal plate so that the undercoating treatment layer 24 is in contact with the plating steel material The corrosion resistance of the coated plated steel can be further improved. The composition of the pretreatment layer 28 is not particularly limited, but it is preferable to use a silane coupling agent, a crosslinkable zirconium compound, a crosslinkable titanium compound, or the like. These may be used alone or in combination of two or more.

Examples of the silane coupling agent include, but are not limited to, vinyltrimethoxysilane sold by Shin Etsu Chemical Co., Ltd., Toray, Dow Corning, Chisso Corporation, Momentive Performance Materials Japan, Aminopropyltrimethoxysilane, gamma -aminopropylethoxysilane, N- [2- (vinylbenzylamino) ethyl] -3-aminopropyltrimethoxysilane, gamma -aminopropyltrimethoxysilane, Methacryloxypropylmethyldimethoxysilane,? -Methacryloxypropyltrimethoxysilane,? -Methacryloxypropylmethyldiethoxysilane,? -Methacryloxypropyltriethoxysilane,? -Glycidoxypropyltriethoxysilane,? -Methacryloxypropyltrimethoxysilane, Glycidoxypropyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, N -? - (aminoethyl) silane, -aminopropyltrimethoxysilane, N -? - (aminoethyl) -? - Aminopropyltrimethoxysilane, N -? - (aminoethyl) -? - aminopropylmethyldimethoxysilane, N-phenyl-? -Aminopropyltrimethoxysilane,? -Mercaptopropyltrimethoxysilane, . These silane coupling agents may be used alone or in combination of two or more.

The crosslinkable zirconium compound is not particularly limited, and examples thereof include zirconyl nitrate, zirconyl acetate, zirconyl sulfate, ammonium zirconium carbonate, zirconium potassium carbonate, sodium zirconium carbonate, and zirconium acetate. Of these compounds, zirconium compounds containing zirconium complex ions are preferable. As the zirconium compound containing zirconium carbonate complex ions, but not be limited particularly, zirconium carbonate complex ions _{[Zr (CO 3) 2 (OH} ) 2 ] _2- of - or _{[Zr (CO 3) 3 (OH} ) ] ₃ Ammonium salts, potassium salts, and sodium salts. These crosslinkable zirconium compounds may be used alone or in combination of two or more.

The crosslinkable titanium compound is not particularly limited and includes, for example, dipropoxy bis (triethanolaminato) titanium, dipropoxy bis (diethanolaminato) titanium, propoxytris (diethanolaminato) (Triethanolamine) titanium, dibutoxybis (diethanolaminato) titanium, dipropoxy bis (acetylacetonate) titanium, dibutoxybis (acetylacetonate) titanium, dihydroxybis Propyl dioxy titanium bis (ethyl acetoacetate), oxotitan bis (monoammonium oxalate), isopropyl tri (N-amidoethyl aminoethyl) titanate, and the like can be used. . These crosslinkable titanium compounds may be used alone or in combination of two or more.

[Manufacturing method of painted plated steel material]

The coated plated steel according to the present embodiment is produced by plating an aluminum-zinc alloy on the surface of a steel material 1 and forming an uncoated layer 24 and an organic coating layer 25 on the upper layer.

[Process for producing hot-dip galvanized steel]

In the preferred embodiment, a hot-dip coating bath 2 having a composition that matches the composition of the constituent elements of the plating layer 23 is prepared at the time of manufacturing the hot-dip galvanized steel. The alloy layer 26 is formed between the steel material 1 and the plating layer 23 by the hot-dip plating treatment, and the fluctuation of the composition due to the alloy layer 26 is negligibly small.

In this embodiment, for example, an alloy containing 25 to 75 mass% of Al, 0.5 to 10 mass% of Mg, 0.02 to 1.0 mass% of Cr, 0.5 to 10 mass% of Si relative to Al, 1 to 1000 mass ppm of Sr , 0.1 to 1.0 mass% of Fe, and Zn is prepared. Zn occupies the remaining portion excluding the components other than Zn in the entire components in the hot dip coating bath (2). The mass ratio of Si: Mg in the hot dip coating bath 2 is preferably in the range of 100: 50 to 100: 300.

The hot dip coating bath 2 may further contain a component selected from an alkaline earth element, Sc, Y, lanthanoid element, Ti, and B. These components are contained in the hot-dip coating bath 2 as required. The total amount of the alkaline earth elements (Be, Ca, Ba, Ra), Sc, Y and lanthanoid elements (La, Ce, Pr, Nd, Pm, Sm, Eu and the like) in the hot- , And preferably not more than 1.0% by mass. When the hot dip coating bath 2 contains a component containing at least one of Ti and B, the total content of Ti and B in the hot dip coating bath 2 is preferably in the range of 0.0005 to 0.1% by mass Do.

It is preferable that the hot-dip coating bath 2 does not contain any components other than those described above. In particular, the hot dip coating bath 2 preferably contains only Al, Zn, Si, Mg, Cr, Sr, and Fe. It is also preferable that the hot dip coating bath 2 contains only elements selected from Al, Zn, Si, Mg, Cr, Sr and Fe and alkaline earth elements, Sc, Y, lanthanoid elements, Ti and B.

For example, in preparing the hot-dip coating bath 2, the hot-dip coating bath 2 preferably contains 25 to 75% of Al, 0.02 to 1.0% of Cr, 0.5 to 1% of Si, Or more of an element selected from the group consisting of an alkaline earth element, a lanthanoid element, Ti, and B, and the balance amount is 0.1 to 10%, Mg is 0.1 to 0.5%, Fe is 0.1 to 0.6%, Sr is contained in a range of 1 to 500 ppm, It is preferable that the portion is Zn.

However, needless to say, the hot dip coating bath 2 may contain inevitable impurities such as Pb, Cd, Cu, and Mn. The content of the inevitable impurities is preferably as small as possible, and it is particularly preferable that the total content of the inevitable impurities is 1 mass% or less in mass ratio with respect to the molten bath 2.

When the hot dip galvanizing treatment is applied to the steel material 1 using the hot dip galvanizing bath 2 having such a composition, the corrosion resistance of the surface of the galvanized layer 23 is improved particularly by Al, Particularly, the edge creep at the cut end face of the hot-dip coated steel is suppressed, so that the hot-dip galvanized steel is provided with high corrosion resistance.

Further, since the plating layer 23 contains Mg which is a nonmetal than Zn, the sacrificial action of the plating layer 23 is further enhanced, and the corrosion resistance of the hot-dip coated steel is further improved.

Further, wrinkles are less likely to be generated in the plating layer 23 formed by the hot-dip plating treatment. Conventionally, when molten metal (molten plated metal) containing Mg is attached to the steel material 1 by the hot-dip plating treatment, Mg is easily concentrated in the surface layer of the molten plated metal, , And the plating layer 23 was liable to wrinkle due to the Mg-based oxide film. However, when the plating layer 23 is formed by using the hot-dip galvanizing bath 2 having the above composition, the concentration of Mg in the surface layer of the hot-dip metal attached to the steel 1 is suppressed, Wrinkles are less likely to occur on the surface of the substrate 23. Further, the flowability of the inside of the molten plated metal is reduced, and the flow of the molten plated metal itself is suppressed, so that the wrinkles are less likely to occur.

It is considered that the Mg concentration and the inhibition of the flow of the molten metal as described above are caused by the following mechanism.

In the course of cooling and solidifying the molten plated metal adhered on the surface of the steel material 1, the? -Al phase first precipitates as initial crystals and grows into a dendritic shape. As the solidification of the Al-rich Al-Al phase progresses, the Mg and Si concentrations in the molten plated metal in the remaining portion (that is, in the solidified components of the molten plated metal) are gradually increased. Next, when the steel material 1 is cooled and its temperature is further lowered, the Si-containing phase (Si-Mg phase) containing Si is coagulated and precipitated in the molten plated metal in the remaining portion. This Si-Mg phase is an alloy composed of Mg and Si as described above. This precipitation / growth of the Si-Mg phase is promoted by Cr, Fe and Sr. By introducing Mg in the molten plated metal onto the Si-Mg, migration of Mg to the surface layer of the molten plated metal is inhibited, and Mg concentration in the surface layer of the molten plated metal is suppressed.

Also, Sr in the molten plated metal contributes to suppression of Mg concentration. This is considered to be because Sr is an easily oxidizable element like molybdenum metal in the molten plated metal, and therefore Sr forms an oxide film on the surface of the plating in competition with Mg and consequently suppresses the formation of the Mg-based oxide film.

Further, as described above, the Si-Mg phase coagulates and grows in the molten plated metal in the remaining portion other than the alpha -Al phase as the initial crystal, so that the molten plated metal is in a solid-liquid phase state, As a result, occurrence of wrinkles on the surface of the plating layer is suppressed.

Fe is important in controlling the microstructure and sequins of the plating layer 23. The reason why Fe affects the structure of the plating layer 23 is not clear at this point, but Fe is alloyed with Si in the hot-dip galvanized metal, and this alloy becomes a solidifying nucleus at the time of solidification of the hot- I think.

Since Sr is a non-element like Mg, the sacrificial action of the plating layer 23 is further enhanced by Sr, and the corrosion resistance of the hot-dip galvanized steel is further improved. Sr also acts to inhibit the formation of the Si-phase and the Si-Mg phase in the form of precipitates, and consequently, the Si phase and the Si-Mg phase are spheroidized, and the occurrence of cracks in the plating layer 23 is suppressed.

During the hot dip treatment, an alloy layer 26 containing a part of Al in the molten plated metal is also formed between the plating layer 23 and the steel material 1. For example, in the case where the steel material 1 is not subjected to the pre-plating described later, an Fe-Al alloy layer 26 mainly composed of Al in the hot-dip galvanizing bath 2 and Fe in the steel material 1 . In the case where the steel material 1 is pre-plated as described below, it is preferable that the steel material 1 contains a part or all of the constituent elements of Al and pre-plating in the hot-dip galvanizing bath 2, A layer 26 is formed.

When the hot dip coating bath 2 contains Cr, the alloy layer 26 contains Cr as well as Al as a constituent element. The alloy layer 26 may contain Si, Mn, Fe, Co, Ni, Cu, Zn, or the like in addition to Al and Cr as constituent elements depending on the composition of the molten bath 2, Sn, and the like.

In the alloy layer 26, a part of Cr in the molten plated metal is contained at a higher concentration than in the plating layer 23. When the alloy layer 26 is formed, the growth of the Si-Mg phase in the plating layer 23 is promoted by Cr in the alloy layer 26 to increase the volume ratio of the Si-Mg phase in the plating layer 23, The ratio of Mg in the Si-Mg phase to the total amount of Mg in the Mg-free layer 23 becomes high. As a result, the wrinkles of the plating layer 23 are further suppressed. Further, since the alloy layer 26 is formed, the corrosion resistance of the hot-dip galvanized steel is further improved. That is, the growth of the Si-Mg phase is promoted in the vicinity of the alloy layer 26 in the plating layer 23, so that the area ratio of the Si-Mg phase on the surface of the plating layer 23 is lowered, And the corrosion resistance of the plating layer 23 is maintained for a longer period of time. Particularly, the ratio of the content of Cr in the alloy layer 26 to the content of Cr in the plating layer 23 is preferably 2 to 50. The ratio of the content of Cr in the alloy layer 26 to the content of Cr in the plating layer 23 is preferably 3 to 40 and more preferably 4 to 25. The amount of Cr in the alloy layer 26 can be derived by measuring the cross section of the plating layer 23 using an energy dispersive X-ray analyzer (EDS).

If the thickness of the alloy layer 26 is excessive, the workability of the hot-dip coated steel is lowered. However, excessive growth of the alloy layer 26 is suppressed by the action of Si in the hot dip coating bath 2, Of the present invention. The thickness of the alloy layer 26 is preferably in the range of 0.05 to 5 mu m. When the thickness of the alloy layer 26 is in the above range, the corrosion resistance of the hot-dip galvanized steel is sufficiently improved and the workability is sufficiently improved.

Further, in the plating layer 23, the concentration of Cr is maintained in a certain range in the vicinity of the surface thereof, and the corrosion resistance of the plating layer 23 is further improved. The reason for this is not clear, but it is presumed that the complex oxide film is formed near the surface of the plating layer 23 by the combination of Cr with oxygen. In order to improve the corrosion resistance of the plating layer 23, it is preferable that the content of Cr in the outermost layer at a depth of 50 nm in the plating layer is 100 to 500 mass ppm.

When the hot dip coating bath 2 contains Cr, the corrosion resistance of the plating layer 23 after bending and deformation is also improved. The reason is thought to be as follows. Cracks may be generated in the coating film on the plating layer 23 and the coating layer 23 in some cases. At this time, water or oxygen enters the plating layer 23 through the cracks, and the alloy in the plating layer 23 is directly exposed to the corrosive factors. However, the Cr present in the surface layer of the plating layer 23 and the Cr present in the alloy layer 26 suppress the corrosion reaction of the plating layer 23, thereby suppressing the expansion of corrosion starting from the crack.

The molten plated metal handled in the above preferred embodiment is a multi-element molten metal containing seven or more elements and its coagulation process is very complicated, so it is difficult to predict theoretically. However, Leading to the acquisition of this important knowledge.

By adjusting the composition of the hot-dip coating bath 2 as described above, it is possible to suppress the wrinkling and sagging in the coating layer 23 as described above, and to secure the corrosion resistance and workability of the hot-dip galvanized steel.

If the content of Al in the hot-dip coating bath 2 is less than 25%, the Zn content in the plating layer 23 becomes excessive, the corrosion resistance on the surface of the plating layer 23 becomes insufficient, The effect of the sacrificial system by Zn is reduced and the plating layer 23 is hardened and the bending workability of the hot-dip coated steel material is lowered. If the content is more than 75%, the flowability of the molten plated metal becomes large, and there is a fear that the plated layer 23 may be wrinkled. The content of Al is particularly preferably 45% or more. The content of Al is particularly preferably 65% or less. The content of Al is preferably in the range of 45 to 65%.

If the content of Cr in the hot-dip coating bath 2 is less than 0.02%, the corrosion resistance of the plating layer 23 is not sufficiently ensured and the wrinkling or sagging of the plating layer 23 is difficult to be sufficiently suppressed. The effect of improving the corrosion resistance is not only saturated but also the dross is easily generated in the hot dip coating bath 2. The content of Cr is particularly preferably 0.05% or more. The content of Cr is particularly preferably 0.5% or less. The content of Cr is preferably in the range of 0.07 to 0.2%.

If the content of Si in the hot-dip galvanizing bath 2 is less than 0.5%, the above-mentioned effect will not be exerted. If the content is more than 10%, the action due to Si will be saturated and the hot- Dross is liable to occur. The content of Si is particularly preferably 1.0% or more. The content of Si is particularly preferably 5.0% or less. The content of Si is preferably in the range of 1.0 to 5.0%.

If the content of Mg in the hot dip coating bath 2 is less than 0.1%, the corrosion resistance of the plating layer 23 is not ensured sufficiently. If the content of Mg exceeds 10%, the function of improving the corrosion resistance is saturated, The dross is likely to occur in the substrate 2. The Mg content is preferably 0.5% or more, more preferably 1.0% or more. The Mg content is preferably 5.0% or less, more preferably 3.0% or less. In particular, the content of Mg is preferably in the range of 1.0 to 3.0%.

If the content of Fe in the hot-dip coating bath 2 is less than 0.1%, the microstructure and the sequin structure of the plating layer 23 become coarse, and the appearance of the plating layer 23 may deteriorate and the workability may deteriorate. If the content is more than 0.6%, the sequins of the plating layer 23 become very fine or disappear, so that appearance improvement due to the sequins can not be achieved, and dross is easily generated in the hot dip coating bath 2 Throw away. The content of Fe is particularly preferably 0.2% or more. The content of Fe is particularly preferably 0.5% or less. In particular, the content of Fe is preferably in the range of 0.2 to 0.5%.

If the content of Sr in the hot-dip coating bath 2 is less than 1 ppm, the above-mentioned effect will not be exerted. If the content exceeds 500 ppm, the action of Sr will be saturated, It becomes easy to occur. The content of Sr is particularly preferably 5 ppm or more. The content of Sr is particularly preferably 300 ppm or less. The content of Sr is also preferably in the range of 20 to 50 ppm.

(La, Ce, Pr), Sc, Y, and lanthanoid elements (La, Ce, Ba, and Ba), when the hot dip coating bath (2) contains a component selected from alkaline earth elements and lanthanoid elements , Nd, Pm, Sm, Eu, etc.) exert the same effect as Sr. The total amount of these components in the hot-dip coating bath 2 is preferably not more than 1.0% by mass as described above.

When the hot dip coating bath 2 contains Ca in particular, the generation of dross in the hot dip coating bath 2 is remarkably suppressed. In the case where the molten bath 2 contains Mg, it is difficult to avoid the generation of a certain degree of dross even if the Mg content is 10% by mass or less. In order to secure a good appearance of the molten plated steel, The occurrence of dross due to Mg is remarkably suppressed when the hot dip coating bath 2 further contains Ca. This further suppresses deterioration of the appearance of the hot-dip galvanized steel by the dross and reduces the labor required for removing the dross from the hot dip galvanizing bath 2. The content of Ca in the hot-dip coating bath 2 is preferably in the range of 100 to 5000 mass ppm. With this content being 100 mass ppm or more, the occurrence of dross in the hot dip coating bath 2 is effectively suppressed. If the content of Ca is excessive, dross due to Ca may occur. If the content of Ca is 5000 mass ppm or less, dross due to Ca is suppressed. This content is also preferably in the range of 200 to 1000 mass ppm.

When the at least one of Ti and B is contained in the hot dip coating bath 2, the α-Al phase (dendritic structure) of the plating layer 23 is made finer to make the sequins of the plating layer 23 finer, The appearance of the plating layer 23 is improved. Further, generation of wrinkles in the plating layer 23 is further suppressed. This is because effectively suppressing the flow of the molten plated metal in the process in which the Si-Mg phase is refined by the action of Ti and B and the finely divided Si-Mg phase coagulates the molten plated metal to form the plated layer 23 . Further, by miniaturization of the plating structure, concentration of stress in the plating layer 23 at the time of bending is relaxed, generation of large cracks and the like are suppressed, and bending workability is further improved. In order for this action to take place, the total content of Ti and B in the hot-dip galvanizing bath 2 is preferably in the range of 0.0005 to 0.1% by mass. The total content of Ti and B is particularly preferably 0.001% or more. The total content of Ti and B is particularly preferably 0.05% or less. In particular, it is preferable that the total content of Ti and B is in the range of 0.001 to 0.05%.

The plating layer 23 is formed by a hot-dip coating process using such a hot-dip coating bath 2. In the plating layer 23, Mg concentration in the surface layer is suppressed as described above. Thus, as described above, it is preferable that the Mg content is less than 60% by mass in any region where the size is 4 mm in diameter and 50 nm in depth in the outermost layer at a depth of 50 nm from the surface of the plating layer 23. In this case, the amount of the Mg-based oxide film in the outermost layer of the plating layer 23 becomes particularly small, and wrinkles caused by the Mg-based oxide film are further suppressed. The smaller the Mg content in the outermost layer, the wrinkles caused by the Mg-based oxide film are suppressed. This Mg content is more preferably less than 40 mass%, more preferably less than 20 mass%, and particularly preferably less than 10 mass%. Particularly, it is preferable that there is no portion where the Mg content is 60 mass% or more in the outermost layer of the thickness of 50 nm of the plating layer 23, and it is preferable that there is no portion where the Mg content is 40 mass% or more , And it is more preferable that the portion where the Mg content is 20 mass% or more is not present.

The physical meaning of the Mg content will be described. The Mg content of the stoichiometric MgO oxide is about 60 mass%. That is, when the Mg content is less than 60% by mass, MgO (MgO-only oxide film) of the stoichiometric composition is not present in the outermost layer of the plating layer 23, or formation of MgO of this stoichiometric composition is remarkably suppressed . In the present embodiment, excessive oxidation of Mg in the outermost layer of the plating layer 23 is suppressed, so that formation of an oxide film by MgO alone is suppressed. A composite oxide containing a small amount or a large amount of oxides of elements other than Mg such as Al, Zn, and Sr is formed in the outermost layer of the plating layer 23, so that the Mg content in the surface layer of the plating layer 23 is relatively small .

The Mg content in the outermost layer of the plating layer 23 can be analyzed using a glow discharge emission spectrometer. When it is difficult to obtain a highly accurate quantitative concentration analysis value, by comparing the concentration curves of a plurality of elements contained in the plating layer 23, it is confirmed that the oxide film of MgO alone can not be recognized in the outermost layer of the plating layer 23 do.

The volume ratio of the Si-Mg phase in the plating layer 23 is preferably in the range of 0.2 to 15% by volume. The volume ratio of the Si-Mg phase is more preferably 0.2 to 10%, further preferably 0.3 to 8%, and particularly preferably 0.4 to 5%. When the Si-Mg phase is thus present in the plating layer 23, Mg at the time of forming the plating layer is sufficiently introduced on the Si-Mg, and the flow of the molten plated metal is sufficiently inhibited by the Si-Mg phase, ) Is further suppressed.

In the hot-dip galvanized steel, as described above, the wrinkles on the surface of the plating layer 23 are suppressed, and in particular, the surface of the plating layer 23 has a height of more than 200 mu m and no ridge having a steepness greater than 1.0 desirable. The steepness is a value defined by (the height of the ridge (mu m)) / (the width of the bottom of the ridge (mu m)). The bottom of the ridge is the intersection of the ridge with a virtual plane containing the flat surface around the ridge. The height of the ridge is the height from the bottom of the ridge to the tip of the ridge. When the sharpness is low, the appearance of the plating layer 23 is further improved. It is also possible to prevent the ridges from piercing the coating under-treatment treatment layer 24 when the coating under-treatment treatment layer 24 is formed on the plating layer 23 as described later, Can be easily made uniform. As a result, the appearance of the hot-dip coated steel material is improved, and the coated hot-dip coated steel material can exhibit more excellent corrosion resistance and the like by the layer of the undercoating treated layer (24).

The adjustment of the degree of Mg concentration, the state of the Si-Mg phase, the thickness of the alloy layer 26 and the steepness of the ridges of the surface of the plating layer 23 is carried out in such a manner that the molten bath 2, And then performing a hot-dip coating process.

In the hot-dip plating treatment, a steel sheet 1 on which a pre-plating layer 27 containing at least one component selected from Cr, Mn, Fe, Co, Ni, Cu, A hot-dip coating process may be performed. The pre-plating process is performed on the steel material 1 before the above-mentioned hot-dip plating process, so that the pre-plated layer 27 is formed on the surface of the steel material 1. This pre-plated layer 27 improves the wettability of the steel material 1 and the molten plated metal at the time of the hot-dip plating treatment, and improves the adhesion between the steel material 1 and the plated layer 23.

The pre-plated layer 27 depends on the kind of the metal constituting the pre-plated layer 27, but contributes to further improving the surface appearance and corrosion resistance of the plated layer 23. [ For example, when the pre-plating layer 27 containing Cr is formed, the formation of the alloy layer 26 containing Cr is promoted between the steel 1 and the plating layer 23, and the corrosion resistance of the molten- And further improved. For example, when the pre-plating layer 27 containing Fe or Ni is formed, the wettability of the steel material 1 and the molten plated metal is improved, and the adhesion of the plating layer 23 is greatly improved. Further, And the surface appearance of the plating layer 23 is further improved. It is considered that the promotion of precipitation of the Si-Mg phase is caused by the reaction of the pre-plating layer 27 and the molten plated metal.

The amount of deposition of the pre-plated layer 27 is not particularly limited, but it is preferable that the amount of deposition on one side of the steel material 1 is in the range of 0.1 to 3 g / m ² . When the deposition amount is less than 0.1 g / m ^2, it is difficult to coat the surface of the steel material with the pre-plating layer 27, and the improvement effect by pre-plating is not sufficiently exhibited. When the adhesion amount exceeds 3 g / m ² , not only the improvement effect is saturated but also the manufacturing cost is increased.

Hereinafter, the outline of the hot-dip plating apparatus for performing the hot-dip plating treatment on the steel material 1 and the suitable processing conditions for the hot-dip plating treatment will be described.

The steel material 1 to be treated is a member formed of steel such as carbon steel, alloy steel, stainless steel, nickel chrome steel, nickel chrome molybdenum steel, chromium steel, chromium molybdenum steel, and manganese steel. As the steel material 1, various members such as a thin steel plate, a thick steel plate, a section steel, a steel pipe, and a steel wire can be cited. That is, the shape of the steel material 1 is not particularly limited.

The steel material 1 may be subjected to flux treatment before the hot-dip coating process. By this flux treatment, the wettability and adhesiveness of the steel material 1 to the molten bath 2 can be improved. The steel material 1 may be subjected to a heating annealing and reduction treatment before being dipped in the hot dip coating bath 2, and this treatment may be omitted. As described above, the steel material 1 may be pre-plated before the hot-dip coating process.

Hereinafter, the manufacturing process of the molten plated steel material (molten plated steel sheet) when the plate material (steel plate 1a) is employed as the steel material 1, that is, when the molten plated steel sheet is produced, will be described.

The hot dip treatment apparatus shown in Fig. 1 is provided with a conveying device for continuously conveying the steel sheet 1a. This conveying apparatus is constituted by a feeder 3, a winder 12, and a plurality of conveying rolls 15. In this conveying apparatus, the feeder 3 holds the coil 13 (first coil 13) of the long steel plate 1a. The first coil 13 is unloaded by the feeder 3 and the steel plate 1a is conveyed to the winder 12 while being supported by the conveying roll 15. [ The steel plate 1a is wound by the winder 12 and the winder 12 holds the coil 14 (second coil 14) of the steel plate 1a.

In this hot-dip coating apparatus, the heating furnace 4, the annealing and cooling section 5, the snort 6, the port 7, and the heat exchanger 7 are arranged in this order from the upstream side of the conveying path of the steel sheet 1a by the above- An injection nozzle 9, a cooling device 10, and a rough rolling / shape correcting device 11 are sequentially installed. The heating furnace 4 heats the steel sheet 1a. This heating furnace 4 is constituted by a non-oxidizing furnace or the like. The annealing and cooling section 5 heats and anneals the steel sheet 1a, followed by cooling. The annealing / cooling section 5 is connected to the heating furnace 4, and has an annealing furnace on the upstream side and a cooling stand (cooler) on the downstream side. The inside of the annealing / cooling section 5 is maintained in a reducing atmosphere. The snout 6 is a tubular member in which the steel sheet 1a is conveyed and one end thereof is connected to the annealing and cooling section 5 and the other end is connected to the hot- 2. The inside of the Snart 6 is maintained in a reducing atmosphere as in the annealing / cooling part 5. The port 7 is a container for storing the hot-dip coating bath 2, and a sink roll 8 is disposed therein. The injection nozzle 9 injects gas toward the steel plate 1a. The injection nozzle 9 is disposed above the port 7. The injection nozzle 9 is disposed at a position where the gas can be injected toward both surfaces of the steel plate 1a lifted from the port 7. The cooling device (10) cools the molten plated metal attached to the steel plate. As the cooling device 10, a cooling device, a mist cooling device, and the like are provided, and the cooling device 10 cools the steel plate 1a. The rough rolling and shape correcting apparatus 11 performs temper rolling and shape correction of the steel sheet 1a on which the plating layer 23 is formed. The rough rolling and shape correcting apparatus 11 is provided with a skin pass mill or the like for performing rough rolling on the steel sheet 1a or a tension leveler for performing shape correction on the steel sheet 1a after rough rolling do.

In the hot dip treatment using the hot dip galvanizing apparatus, the steel sheet 1a is first loosened from the feeder 3 and continuously fed. After the steel sheet 1a is heated in the heating furnace 4, the steel sheet 1a is conveyed to the annealing and cooling section 5 in a reducing atmosphere and annealed in the annealing furnace, and at the same time, After the surface is cleaned, such as removing or reducing oxide film, cooling is performed in the cooling zone. The steel sheet 1a then passes through the Snart 6 and further enters the port 7 and is immersed in the hot-dip plating bath 2 in the port 7. The steel sheet 1a is supported on the sink roll 8 in the port 7 so that its conveying direction is switched upward and taken out from the hot- As a result, the molten metal is attached to the steel sheet 1a.

Subsequently, gas is injected from the injection nozzle 9 on both surfaces of the steel sheet 1a, thereby adjusting the amount of the molten plated metal adhered to the steel sheet 1a. The method of adjusting the deposition amount by the gas injection is referred to as the gas wiping method. It is preferable that the adhesion amount of the molten plated metal is adjusted to be in the range of 40 to 200 g / m ² together on both sides of the steel sheet 1a.

Examples of the gas (wiping gas) to be sprayed on the steel sheet 1a in the gas wiping method include air, nitrogen, argon, helium, water vapor and the like. These wiping gases may be sprayed on the steel plate 1a after being preheated. In the present embodiment, the surface oxidation of Mg (the oxidation of Mg in the surface layer of the molten plated metal and the increase of the Mg concentration) in the molten plated metal is essentially suppressed by using the molten bath 2 of a specific composition. Thus, even when oxygen is contained in the wiping gas or oxygen is contained in the airflow accompanying the spraying of the wiping gas, the amount of plating adhered (the amount of plating adhered on the steel plate 1a The amount of metal) can be adjusted.

The method of adjusting the plating amount is not limited to the gas wiping method described above, and various deposition amount control methods can be applied. Examples of the deposition amount control method other than the gas wiping method include a roll thrusting method in which the steel sheet 1a is passed between a pair of rolls disposed immediately above the bath surface of the hot dip galvanizing bath 2, A method of disposing shielding plates close to the steel plate 1a to remove the molten plated metal with the shielding plate, a method of applying electromagnetic force to the molten plated metal attached to the steel plate 1a, , And a method of adjusting the amount of plating adhesion using a natural gravity drop without exerting an external force. Two or more types of plating adhesion amount adjusting methods may be combined.

Next, the steel sheet 1a is transported further upward than the position of the injection nozzle 9, and then transported to the bottom by being supported by the two transport rolls 15. That is, the steel plate 1a is transported in the reverse U-shaped path. In this inverted U-shaped path, the steel sheet 1a is cooled in the cooling device 10 by air cooling, mist cooling, or the like. As a result, the molten plated metal adhered on the surface of the steel sheet 1a solidifies to form the plated layer 23.

The surface temperature of the molten plated metal (or the plated layer 23) is set to 300 deg. C or lower by the cooling device 10 so that the solidification of the molten plated metal is completely completed by cooling by the cooling device 10. [ Lt; / RTI &gt; The surface temperature of the molten plated metal is measured, for example, by a radiation thermometer or the like. In order to form the plating layer 23 in this manner, the cooling rate during the period from the time when the steel sheet 1a is taken out of the hot-dip coating bath 2 until the surface of the hot-dip coated metal on the steel sheet 1a is cooled to 300 deg. 5 to 100 DEG C / sec. In order to control the cooling rate of the steel sheet 1a, it is preferable that the cooling device 10 has a temperature control function for adjusting the temperature of the steel sheet 1a along the conveying direction and the plate width direction. The cooling device 10 may be divided into a plurality of parts along the conveying direction of the steel sheet 1a. 1 shows a primary cooling device 101 for cooling the steel plate 1a in a path which is transported further upward than an arrangement position of the injection nozzle 9 and a primary cooling device 101 for cooling the steel plate 1a A secondary cooling device 102 for cooling the secondary cooling device 1a is provided. The primary cooling apparatus 101 and the secondary cooling apparatus 102 may also be divided into a plurality of units. In this case, for example, in the primary cooling apparatus 101, the steel sheet 1a is cooled until the surface of the molten-plated metal reaches a temperature of 300 占 폚 or lower, 1a can be cooled so that the temperature at the time of introduction into the rough rolling and shape correcting apparatus 11 becomes 100 DEG C or less.

In the process of cooling the steel sheet 1a, it is preferable that the cooling rate of the surface of the molten plated metal is 50 DEG C / sec or less while the surface temperature of the molten plated metal on the steel sheet 1a is 500 DEG C or more. In this case, precipitation of the Si-Mg phase on the surface of the plating layer 23 is particularly suppressed, thereby suppressing occurrence of sagging. The reason why the cooling rate in this temperature range affects the precipitation behavior of the Si-Mg phase is not necessarily clear at this point, but if the cooling rate in this temperature range is fast, the temperature gradient in the thickness direction of the molten plated metal becomes large , So that precipitation of the Mg-Si layer is preferentially promoted on the surface of the molten plated metal having a lower temperature, and as a result, the deposition amount of the Si-Mg phase on the outermost surface of the plating is increased. The cooling rate in this temperature range is more preferably 40 DEG C / sec or less, and particularly preferably 35 DEG C / sec or less.

After cooling, the steel sheet 1a is subjected to temper rolling by the temper rolling and shape correcting device 11, and shape correction is carried out. The rolling reduction by temper rolling is preferably in the range of 0.3 to 3%. It is preferable that the elongation percentage of the steel sheet 1a by shape correction is 3% or less.

Subsequently, the steel plate 1a is wound by a winding machine 12, and the coil 14 of the steel plate 1a is held by the winding machine 12.

The temperature of the hot dip coating bath 2 in the port 7 is set to a temperature higher than the solidification starting temperature of the hot dip coating bath 2 and 40 ° C higher than the solidification starting temperature . It is more preferable that the temperature of the hot dip coating bath 2 in the port 7 is higher than the solidification starting temperature of the hot dip coating bath 2 and lower than or equal to the temperature 25 占 폚 higher than the solidification starting temperature. When the upper limit of the temperature of the hot dip galvanizing bath 2 is thus limited, the steel sheet 1a is taken out of the hot dip galvanizing bath 2 and is heated until the molten metal adhered to the steel sheet 1a coagulates Time is shortened. As a result, the time during which the molten plated metal adhered to the steel sheet 1a is in a flowable state is shortened, thereby making it more difficult for the plating layer 23 to be wrinkled. When the temperature of the hot dip coating bath 2 is 20 캜 or higher than the solidification starting temperature of the hot dip coating bath 2, the generation of the wrinkles in the coating layer 23 is remarkably suppressed.

When the steel sheet 1a is taken out from the hot dip galvanizing bath 2, it may be taken out into a non-oxidizing atmosphere or a low oxidizing atmosphere, and the steel sheet 1a may be melted by the gas wiping method The adjustment amount of the plating metal may be adjusted. In order to do this, for example, as shown in Fig. 2, the temperature of the molten bath 1 is raised from the molten bath 2 upstream of the molten bath 2, Is preferably surrounded by the hollow member 22 and the inside of the hollow member 22 is filled with a non-oxidizing gas such as nitrogen gas or a low oxidizing gas. Non-oxidizing gas or low oxidizing gas means a gas having a lower oxygen concentration than the atmosphere. It is preferable that the oxygen concentration of the non-oxidizing gas or the low oxidizing gas is 1000 ppm or less. The atmosphere filled with the non-oxidizing gas or the low oxidizing gas is a non-oxidizing atmosphere or a low oxidizing atmosphere. The oxidation reaction is suppressed in this atmosphere. The injection nozzle 9 is disposed inside the hollow member 22. The hollow member 22 is provided so as to surround the conveying path of the steel material 1 from the upper side of the hot-dip galvanizing bath 2 (the upper side of the hot-dip galvanizing bath 2) to the upper side of the hot- have. It is also preferable that the gas injected from the injection nozzle 9 is a non-oxidizing gas such as nitrogen gas or a low oxidizing gas. In this case, since the steel sheet 1a taken out from the hot-dip galvanizing bath 2 is exposed to a non-oxidizing atmosphere or a low-oxidizing atmosphere, the oxidation of the hot-dip metal attached to the steel sheet 1a is suppressed, The Mg-based oxide film is hardly formed on the surface layer of the substrate. As a result, generation of wrinkles in the plating layer 23 is further suppressed. Instead of using the hollow member 22, a part of the hot dip galvanizing apparatus including the conveying path of the steel sheet 1a or the entire hot-dip galvanizing apparatus may be arranged in a non-oxidizing atmosphere or a low oxidizing atmosphere.

It is also preferable that the steel plate 1a after the hot-dip coating treatment is further subjected to an over-treatment treatment. In this case, the workability of the hot-dip coated steel material is further improved. The overheating treatment is carried out by maintaining the steel sheet 1a within a predetermined temperature range for a predetermined time.

Fig. 3A and Fig. 3B show an apparatus used for overexposure treatment, wherein Fig. 3A shows a heating apparatus. 3 (b) shows the warming container 20. The heating device has a conveying device in which the steel sheet 1a after hot-dip treatment is continuously conveyed. This conveying device is constituted by a feeder 16, a winder 17, and a plurality of conveying rolls 21 as in the conveying device in the hot-dip treatment apparatus. A heating furnace 18 such as an induction heating furnace is provided on the conveying path of the steel plate 1a by this conveying device. The thermal insulation container 20 is not particularly limited as long as the coil 19 of the steel sheet 1a can be held therein and the thermal insulation container 20 has a heat insulating property. The thermal insulation container 20 may be a large-sized container (thermal insulation room).

The coil 14 of the steel plate 1a after the hot dip treatment is first carried from the winder 12 of the hot dip galvanizing apparatus to a crane or a truck or the like, And is maintained in the feeder 16 of the feeder. In the heating apparatus, the steel plate 1a is loosened from the feeder 16 and fed continuously. The steel plate 1a is heated to a temperature suitable for overexposure treatment in the heating furnace 18 and then wound by a winder 17. The coil 19 of the steel plate 1a is wound by the winder 17 maintain.

Subsequently, the coil 19 of the steel plate 1a is conveyed from the winder 17 to a crane, a truck or the like, and is held in the warming container 20. The coil 19 of the steel plate 1a is held in the warming container 20 for a certain period of time so that the steel plate 1a is subjected to an overexposure treatment.

The plating layer 23 formed on the surface of the steel sheet 1a according to the present embodiment contains Mg and a slight amount of Mg oxide on the surface of the plating layer 23, Even if the plating layers 23 are overlapped with each other in the coils of the plating layers 23a and 23a, As a result, even if the keeping time at the time of the overflow treatment is long or the holding temperature is high, it is difficult to cause seizure, so that the steel sheet 1a can be subjected to sufficient overaging treatment. As a result, the workability of the hot-dip coated steel sheet is greatly improved, and the efficiency of the overflow treatment is improved.

In the overflow treatment, particularly, the temperature of the steel sheet 1a after heating by the heating apparatus is in the range of 180 to 220 ° C, that is, when the temperature of the steel sheet 1a is within the above range, Lt; / RTI &gt; It is preferable that the holding time (y (hr)) of the steel sheet 1a in the thermal insulation container satisfies the following formula (5).

5.0 x 10 ²² x t ^-10.0? Y? 7.0 x 10 ²⁴ x t ^{-10. 0} ... (5)

(150? T? 250)

T (占 폚) in the formula (5) is the temperature (holding temperature) of the steel sheet 1a in the holding time y (hr) and is the lowest temperature when the temperature fluctuation occurs in the steel sheet 1a .

Further, in the present embodiment, the hot dip galvanizing apparatus and the heating apparatus are separate apparatuses, but the hot dip galvanizing apparatus may also serve as the heating apparatus by providing the heating furnace 18. In such an apparatus, various elements may be added, removed, or replaced as necessary, so that the design may be appropriately changed. The apparatus and apparatus for hot dip galvanizing according to the present embodiment are suitable for the case where the steel material 1 is the steel sheet 1a. The configuration of the hot-dip galvanizing apparatus, the heating apparatus, Design changes are possible. When the preliminary plating treatment is applied to the steel material 1, this preliminary plating treatment can also be variously changed depending on the kind, shape, and the like of the steel material 1. [

[Method of producing coated hot-dip galvanized steel]

The coated plated steel according to each embodiment of the present invention is produced by forming the above-described coating-untreated layer 24 and the organic coating layer 25 on the upper side of the steel material subjected to the above-mentioned hot-dip plating treatment. When the pretreatment layer 28 is provided, the pretreatment layer 28 is formed on the steel material subjected to the above-mentioned hot-dip coating treatment, and the surface of the pretreatment layer 28 is coated with an undercoating layer 24, . Here, when forming the undercoating treatment layer 24 and the pretreatment layer 28, a coating agent for forming the pretreatment layer 28 is coated on the plated steel material, followed by drying and baking to form the pretreatment layer 28, The coating composition for forming the coating under-treatment layer 24 may be coated on the pretreatment layer 28 and dried and baked. The coating composition for forming the undercoating treatment layer 24 and the coating agent for forming the pretreatment layer 28 may be applied to the base plated steel material by wet-on-wet or multilayer simultaneous coating, and then the entire coating composition may be simultaneously baked and dried .

The plating layer 23 may be subjected to nickel plating treatment or cobalt plating treatment before the pretreatment layer 28 or the undercoating treatment layer 24 is formed. An aqueous solution optionally containing an acid, an alkali or various etching agents, or cleaning with various organic solvent liquids may be performed. If the surface of the plating layer 23 is cleaned in this way, even if a small amount of the Mg-based oxide film is present on the surface layer of the plating layer 23 or if the surface of the plating layer 23 is stained with inorganic or organic stains, The adhesion between the plating layer 23 and the pretreatment layer 28 or the undercoating treatment layer 24 can be improved. Details of the method of forming the undercoating layer 24, the pretreatment layer 28, and the organic coating layer 25 will be described below.

&Lt; Method of forming the uncoated layer 24 >

The method of forming the undercoating treatment layer 24 is not particularly limited. For example, the method of forming the undercoating treatment layer 24 may include a method of forming an undercoating treatment layer 24 by using an organic solvent, a silane coupling agent, a zirconium compound, and a titanium compound in an aqueous solvent or an organic solvent- Applying the coating composition on a plated steel and heating and drying it. (Hereinafter abbreviated as "water-based treatment agent") using an aqueous solvent is used for coating for use of a treatment agent using an organic solvent-based solvent (hereinafter abbreviated as "organic solvent-based treatment agent" Since there is no need to spare the line, it is possible to greatly reduce the manufacturing cost, and there is also an advantage in terms of environment such that the discharge of the volatile organic compound (VOC) can be greatly suppressed. Therefore, It is preferable to use an agent. Here, the aqueous solvent used in the aqueous treatment agent means a solvent in which water is the main component of the solvent. The amount of water in the solvent is preferably 50% by mass or more. The solvent other than water may be an organic solvent, but it may be an organic solvent solvent. However, the amount of organic solvent contained in the organic solvent additive defined in the Ordinance on Prevention of Organic Solvent Poisoning under the Industrial Safety and Health Law (5% by weight of the organic solvent listed in Attachment 6-2 of the Enforcement Decree of the Industrial Safety and Health Act) And more preferably not exceeding the above range). Further, the organic solvent-based solvent means a solvent in which the organic solvent is the main component of the solvent.

The treatment agent for forming the undercoating treatment layer 24 is not limited to a specific method and can be obtained by an arbitrary method. As an example, a preferable treatment agent is taken as an example. The components of the coating layer 24 are added to an aqueous solvent or an organic solvent, which is a dispersion medium, and the mixture is stirred by a disperser to dissolve or disperse the dispersion . When the dispersion medium is an aqueous solvent, a known hydrophilic solvent such as ethanol, isopropyl alcohol, t-butyl alcohol, and alcohols such as propylene glycol, and the like may be added as necessary in order to improve the solubility or dispersibility of each component Esters such as ethyl acetate and butyl acetate, and ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone may be added to the reaction mixture.

The method of applying the treatment agent to the plated steel material is not particularly limited and any known method may be used. For example, as a coating method, roll coating, curtain coating, spray coating, bar coating, dipping, electrostatic coating and the like are available.

The method of heating and drying at the time of forming the coating-untreated layer 24 from the treatment agent is not particularly limited and may be carried out by any method. For example, it is possible to heat the plated steel material before coating the treatment agent, or to heat the plated steel material after application, or to perform drying by combining them. There is no particular limitation on the heating method, and hot air, induction heating, near-infrared rays, direct heating, etc. may be used alone or in combination to dry the treating agent to be baked. The drying baking temperature is preferably 60 占 폚 to 250 占 폚 at the reaching plate temperature, and most preferably 80 占 폚 to 150 占 폚. If the reaching plate temperature is less than 60 캜, the coating film and the solvent component desorption are insufficient, and the corrosion resistance and adhesion between the plating layer 23 and the organic coating layer 25 may be insufficient. On the other hand, Or the coating under-treatment layer 24 is oxidized unnecessarily, whereby the corrosion resistance and the adhesion with the plating layer 23 or the organic coating layer 25 may become insufficient. The drying baking time (heating time) is preferably 1 second to 60 seconds, more preferably 3 seconds to 20 seconds. If the drying baking time is less than 1 second, the coats of the coating film and the desorption of the solvent components are insufficient and the corrosion resistance and the adhesion with the coating layer 23 or the organic coating layer 25 may be insufficient. If the drying baking time is more than 60 seconds, .

&Lt; Method of forming organic coating layer 25 >

The method for forming the organic coating layer 25 is not particularly limited, and for example, a coating material containing a binder resin or a precursor thereof, a coloring pigment, and a rust-preventive pigment is applied on a plated steel material in an aqueous solvent or an organic solvent- Heating, irradiation of energy such as ultraviolet rays, volatilization of a solvent, or a combination of two or more of the above-mentioned means. When a paint using an aqueous solvent (hereinafter abbreviated as "water-based paint") is used, an exclusive paint line for using a paint using an organic solvent-based solvent (hereinafter abbreviated as "organic solvent-based paint" There is a possibility that there is no need to pass through, and in that case, since it is possible not only to greatly reduce the manufacturing cost but also to greatly reduce the emission of volatile organic compounds (VOC), there is also an environmental advantage. Is preferably used. Here, the aqueous solvent used in the water-based paint means a solvent in which water is the main component of the solvent. The amount of water in the solvent is preferably 50% by mass or more. Solvents other than water may be organic solvent solvents. However, organic solvents contained in the Organic Solvent Poisoning Prevention Regulations of the Occupational Safety and Health Act (5% by weight of the organic solvents listed in Article 6-2 of the Attached Table of the Enforcement Decree of the Industrial Safety and Health Act) And more preferably not exceeding the above range). Further, the organic solvent-based solvent means a solvent in which the organic solvent is the main component of the solvent.

The coating material for forming the organic coating layer 25 is not limited to a specific method and can be obtained by an arbitrary method. As an example, a preferable coating material is taken as an example, and the components of the organic coating layer 25 are added to an aqueous solvent or an organic solvent, which is a dispersion medium, and stirred by a disperser to dissolve or disperse the dispersion. When the dispersion medium is an aqueous solvent, a known hydrophilic solvent such as ethanol, isopropyl alcohol, t-butyl alcohol, and alcohols such as propylene glycol, and the like may be added as necessary in order to improve the solubility or dispersibility of each component Esters such as ethyl acetate and butyl acetate, and ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone may be added to the reaction mixture.

The coating method of the paint is not particularly limited and any known method may be used. For example, as a coating method, roll coating, curtain coating, spray coating, bar coating, dipping, electrostatic coating and the like are available. When the coating material is a powder coating material, powder coating, electrostatic powder coating, fluidized painting, or the like can be used.

The curing / film forming method for forming the organic coating layer 25 from the coating material is not particularly limited and may be carried out by any method. For example, before coating the coating composition, it is preferable to heat the plated steel material in advance, heat the plated steel material after coating, combine these materials, and further irradiate energy such as ultraviolet rays, volatilization of the solvent, The curing and film forming can be performed by a combination of two or more of the means. There is no particular limitation on the heating method, and hot air, induction heating, near-infrared rays, direct burning, etc. may be used alone or in combination to dry the paint to be baked. In the case of performing curing and film formation by heating, the drying baking temperature is preferably 100 占 폚 to 250 占 폚, more preferably 120 占 폚 to 230 占 폚, and most preferably 130 占 폚 to 220 占 폚 . If the reaching plate temperature is less than 100 占 폚, the coating film may be insufficiently formed and the corrosion resistance, scratch resistance and stain resistance may be deteriorated. When the temperature exceeds 250 占 폚, baking hardening may be excessive and corrosion resistance may be deteriorated. The drying baking time (heating time) is preferably 1 second to 60 seconds, more preferably 3 seconds to 20 seconds. If the drying baking time is less than 1 second, the coats of the coating film are insufficient and the corrosion resistance, scratch resistance and stain resistance may be lowered.

&Lt; Method of forming pre-treatment layer 28 >

The pretreatment layer 28 is formed by applying a coating agent for forming the pretreatment layer 28 to at least one side of the plated steel and heating and drying it. There is no particular limitation on the coating method of the coating agent, but known roll coating, spray coating, bar coating, dipping, electrostatic coating and the like can be suitably used. The baking drying method is not particularly limited, and the plated steel material may be heated beforehand, the plated steel material may be heated after the application, or the combination may be combined and dried. The heating method is not particularly limited, and hot air, induction heating, near infrared rays, direct heating, etc. may be used alone or in combination. As for the baking drying temperature, it is preferable that the baking temperature is 60 캜 to 150 캜. If the temperature is reached to less than 60 캜, drying may be insufficient and the adhesion of the coated film to the base plated steel and the corrosion resistance of the coated plated steel may be lowered. If the temperature is higher than 150 캜, the adhesion of the coated film to the base plated steel may be deteriorated . The more preferred temperature is 70 캜 to 130 캜.

The coated plated steel material produced by the present embodiment has the unevenness of the plating surface caused by the wrinkling and sagging of the plated layer 23 being suppressed. Therefore, compared with conventional high-Al-containing and Mg-containing plated steel materials, Do. In addition, due to the effect of the coating under-treatment treatment layer 24, corrosion resistance of a machined portion deformed by a scratch-generating portion and a base material of a coating surface, which is not considered in conventional high-Al-content and Mg- . In addition, it is also excellent in the whitening resistance in the case of being subjected to heating and in the case of being irradiated with ultraviolet rays in the use of organs.

The coated plated steel material can be employed for construction materials, automobile materials, materials for household appliances, and various other applications, and can be suitably used particularly for applications requiring corrosion resistance at the processing site.

11A to 11H show the layered structure of the coated plated steel in the embodiment of the present invention. 11A shows a layer structure formed of the steel material 1, the plating layer 23, the uncoated layer 24, and the organic coating layer 25. Fig. 11B shows a layer structure formed of the steel material 1, the alloy layer 26, the plated layer 23, the uncoated layer 24, and the organic coating layer 25. Fig. 11C shows a layer structure formed of the steel material 1, the pre-plated layer 27, the plated layer 23, the uncoated layer 24, and the organic coating layer 25. Fig. 11D shows a layer structure formed of the steel material 1, the plating layer 23, the pretreatment layer 28, the uncoated layer 24, and the organic coating layer 25. Fig. 11E shows a layer structure formed of the steel material 1, the pre-plated layer 27, the alloy layer 26, the plated layer 23, the uncoated layer 24, and the organic coating layer 25. 11F shows a layer structure formed of the steel material 1, the alloy layer 26, the plated layer 23, the pretreatment layer 28, the uncoated layer 24, and the organic coating layer 25. 11G shows a layer structure formed of the steel material 1, the pre-plated layer 27, the plated layer 23, the pretreatment layer 28, the uncoated layer 24, and the organic coating layer 25. 11H shows a layer structure formed of a steel material 1, a pre-plated layer 27, an alloy layer 26, a plated layer 23, a pretreatment layer 28, an undercoated layer 24, and an organic coating layer 25 .

Example

The present invention will be further described with reference to Examples using a hot-dip coated steel sheet. However, the present invention is not limited to the following examples.

(1) Hot-dip coated steel sheet (Hot-dip galvanized steel sheet)

First, a method of manufacturing a hot-dip coated steel sheet, an evaluation test method and a test result of the hot-dip coated steel sheet obtained thereby will be described.

[1.1. Production method of hot-dip coated steel sheet]

As the steel material 1, a long steel sheet 1a (low carbon aluminum killed steel material) having a thickness of 0.80 mm and a width of 1000 mm was used. This steel sheet 1a was subjected to a hot-dip coating treatment using the hot-dip coating apparatus shown in Fig. The treatment conditions are shown in Tables 1 to 3. The coagulation initiation temperatures shown in Tables 1 to 3 are values derived from the liquid curve of the state diagram of the bath of Zn-Al binary system and correspond to the contents of Al in each of the molten bath bath compositions shown in Tables 1 to 3 Value. In addition, the level of M68, the M69, before the hot dip coating process the steel plate (1a), the by carrying out Ni pre-plating, the level of the amount of deposition M68 (single-sided) 0.5g / m ^2, coating weight levels of M69 (single-sided) 2.0g / m &lt; ^{2 &} gt ;. At the level M70, a pre-plating layer 27 of 1.0 g / m ² in adhesion amount (single side) was formed by performing Zn-10% Cr pre-plating treatment. In other Examples and Comparative Examples, pre-plating treatment was not performed.

The temperature at which the steel sheet 1a penetrated into the hot-dip galvanizing bath 2 was 580 캜. When the steel sheet 1a was taken out from the hot dip coating bath 2, it was taken out into an air atmosphere, and gas wiping was also performed in an air atmosphere. However, for the level M71, the conveyance path of the steel sheet 1a on the upstream side of the hot-dip coating bath 2 is surrounded by the seal box (hollow member 22), and the spray nozzle 9 were arranged so that the inside of the seal box was made nitrogen atmosphere and the inside of the hollow member 22 was subjected to gas wiping by nitrogen gas.

In the cooling device 10, the steel sheet 1a was cooled until the surface temperature of the molten plated metal (the plated layer 23) became 300 캜. The cooling rate at the time of cooling was 45 占 폚 / sec. However, for the levels M76 and M77, the cooling rate in the temperature range where the surface temperature of the plated metal is 500 DEG C or higher is changed, and the cooling rate at the level M76 is 38 DEG C / sec in this process, The speed was set at 28 DEG C / sec.

The reduction rate at the time of temper rolling was 1%, and the elongation rate of the steel sheet 1a at the time of shape correction was 1%.

[1.2. Evaluation test of hot-dip coated steel sheet]

The following evaluation tests were conducted on the hot-dip coated steel sheet obtained in the production of the hot-dip coated steel sheet.

(1.2.1 Evaluation of volume ratio of Si-Mg phase)

The hot-dip coated steel sheet was cut in the thickness direction to obtain a sample. This sample was embedded in a resin so that the cut surface was exposed, and then the cut surface was polished into a mirror-like shape. The cut surface was observed by an electron microscope. As a result, it was clear that a Si-Mg phase was distributed in the plating layer 23 on this cut surface.

An image obtained by photographing the cut surface of the hot-dip coated steel sheet obtained at the level M5 by an electron microscope is shown in Fig. The elemental analysis was performed using an energy dispersive X-ray analyzer (EDS) on the portion where the precipitation of the Si-Mg phase was recognized. The results are shown in FIG. 4B. According to these results, it can be seen that only the two elements of Mg and Si are strongly detected. O (oxygen) was also detected because the oxygen adsorbed on the sample was detected in the sample preparation stage.

The area ratio (%) of the Si-Mg phase on the cut surface is measured by performing image analysis based on the sensed image on the cut surface of the plating layer 23 in the range of 20 mm in the direction perpendicular to the thickness direction Respectively. Since the Si-Mg phase exhibits a dark gray shade and is clearly distinguished from the other phases, it is possible to easily discriminate by image analysis.

The area ratio (%) thus obtained was regarded as coinciding with the volume ratio of Si-Mg phase, and the volume ratio of Si-Mg phase was evaluated. The results are shown in Tables 4 to 6.

(1.2.2. Evaluation of Mass Ratio of Mg Content in Si-Mg Phase to Total Mg Content)

The mass ratio of the amount of Mg in the Si-Mg phase to the total amount of Mg in the plating layer 23 (mass ratio of Mg amount in Tables 4 to 6) was calculated by the above-mentioned equations (1) to (4). The results are shown in Tables 4 to 6.

(1.2.3. Evaluation of surface Mg content)

Elemental analysis of the components contained in the plating layer 23 in the hot-dip coated steel sheet in the depth direction (the thickness direction of the plating layer 23) was performed by Glow Discharge-Optical Emission Spectroscopy (GD-OES) . In the measurement, the diameter of the measurement area was 4 mm, the output was 35 W, the measurement atmosphere was Ar gas, the measurement pressure was 600 Pa, the discharge mode was normal sputtering, the duty cycle was 0.1, the analysis time was 80 seconds and the sampling time was 0.02 sec / The light emission intensity of the element contained in the plating layer 23 was measured. In order to convert the obtained light emission intensity value into a quantitative concentration value (mass% concentration), elemental analysis of a standard sample such as a 7000-series Al alloy or a steel material having a known component concentration was also performed separately. Since the GD-OES data is in the form of a change with respect to the sputter time of the light emission intensity, the sputter depth is measured by cross-sectional observation of the sample after completion of the measurement and the sputter depth is divided by the total sputter time, To specify the depth position of the plating layer 23 in the GD-OES depth direction profile.

As for the level M5 and the level M50, the analysis results are shown in Figs. 5A and 5B, respectively. According to this, it can be confirmed that the Mg concentration in the surface layer of the plating layer 23 rises sharply at the level M50.

Based on this result, the content of Mg in a region having a size of 4 mm in diameter and a depth of 50 nm in the outermost layer at a depth of 50 nm in the plating layer 23 was derived. The results are shown in Tables 4 to 6.

(1.2.4. Evaluation of surface Cr content)

The integrated value of the Cr emission intensity in a region having a diameter of 4 mm and a depth of 50 nm from the outermost surface of the plating layer 23 was measured by GD-OES in the same manner as in the case of the evaluation of the surface layer Mg amount. Similarly, the integral value of the Cr emission intensity of the entire plating layer 23 was also measured, and the ratio of the integral value of the Cr emission intensity in this region to this value was obtained. Based on the ratio of the integral value of the Cr emission intensity and the chemical analysis value of the total amount of Cr in the plated layer 23 by ICP, the ratio of the Cr value in the region of 4 mm in diameter and 50 nm in depth from the outermost surface of the plated layer 23 And the content of Cr was calculated. The results are shown in Tables 4 to 6.

(1.2.5 Evaluation of area ratio of Si-Mg phase on the surface of plating layer)

The surface of the plating layer 23 was observed by an electron microscope. A photograph of the surface M5 of the surface of the plating layer 23 taken by an electron microscope is shown in Fig. According to this observation result, it can be confirmed that the Si-Mg phase is distributed on the surface of the plating layer 23. Based on this result, the area of the Si-Mg phase on the surface of the plating layer 23 was measured, and based on this, the area ratio of the Si-Mg phase on the surface of the plating layer 23 was calculated. The results are shown in Tables 4 to 6.

(1.2.6 Evaluation of alloy layer 26)

The hot-dip coated steel sheet was cut in the thickness direction to obtain a sample. This sample was embedded in a resin so that the cut surface was exposed, and then the cut surface was polished into a mirror-like shape. On this cut surface, an alloy layer 26 interposed between the plating layer 23 and the steel sheet 1a was formed. The thickness of the alloy layer 26 was measured. Further, a 10 占 퐉 20 占 퐉 portion of the polished surface was sampled from the polished surface by a converged ion beam apparatus to prepare a micro sample processed to a thickness of 50 nm or less. This microsample was quantitatively analyzed by using an energy dispersive X-ray analyzer (EDS) under the conditions of an acceleration voltage of 200 kV and a probe diameter of 1 nm.

Based on these results, the ratio of the mass ratio of Cr in the alloy layer 26 to the mass ratio of Cr in the plating layer 23 was calculated (Cr content ratio in Tables 4 to 6). The results are shown in Tables 4 to 6.

(1.2.7. Appearance evaluation)

The appearance of the surface of the plated layer 23 in the hot-dip coated steel sheet was visually observed by an optical microscope. 7A shows a photograph of the surface of the plating layer 23 at the level M5. 7B shows a photograph of the surface of the plating layer 23 at the level M10. 8A shows an optical microscope photograph of the surface of the plating layer 23 at the level M62. 8B shows an optical microscope photograph of the surface of the plating layer 23 at the level M5. Fig. 9 shows a photograph of the appearance of the plating layer 23 at the level M50.

Based on the observation result, the degree of wrinkling on the surface of the plating layer 23 was evaluated by the following criteria. The results are shown in Tables 4 to 6. The degree of unevenness due to the wrinkles, sagging, dross adhesion and the size of the sequins on the surface of the coating layer 23 recognized in this observation result is also reflected on the surface of the coated plated steel material, State as a state.

5: Wrinkles are not recognized.

4: Wrinkles are slight (wrinkles of the degree shown in Fig. 7A).

3: Less wrinkles (when the degree of wrinkles is between 4 and 2).

2: Wrinkle degree (better than that shown in Fig. 7B).

1: The wrinkles are remarkable (wrinkles of the degree shown in Fig. 7B).

Based on the observation result, the degree of sagging of the surface of the plating layer 23 was evaluated by the following criteria. The results are shown in Tables 4 to 6.

2: Sagging is not allowed.

1: Sagging is recognized (sagging to the extent shown in FIG. 9).

In addition, based on the observation result, the degree of the dross adhering to the plating layer 23 was evaluated by the following criteria. The results are shown in Tables 4 to 6.

2: There is no adhesion of dross accompanied by unevenness on the surface of the plated layer 23, or adhesion of dross accompanying unevenness is recognized to be less than 5 sites per 1 m ² .

1: At least five drosses per 1 m ² are allowed to adhere to the surface of the plated layer 23 accompanied by unevenness.

Further, by observing the appearance characteristics of the plating layer 23 except for wrinkles, sagging, and dross, a leveling of the sequins was recognized at level M78 (see other columns in Table 6).

(1.2.8 Evaluation of over-treatment)

The overheating treatment was carried out by varying the keeping temperature (t (C)) and the keeping time (y (hr)) for the coil of the molten steel sheet at the level M5. The results were evaluated as follows.

3: Cohesion did not occur between the plating layers in the coil, and the workability was improved.

2: No adhesion occurred in the plating layer between the coils, but the workability was not improved.

1: Cohesion occurred in the plating layer between coils.

The results are shown in the graph of Fig. The abscissa in the graph represents the test temperature (t (占 폚)) and the ordinate represents the test time (y (hr)). The results of the evaluation in the insulated temperature and the insulated time are shown at positions corresponding to the insulated temperature (t (占 폚)) and the insulated time (y (hr)) in the graph in the test. The area sandwiched between the dashed lines in the graph is the area where the keeping temperature (t (占 폚)) and the keeping time (y (hr)) satisfy the following formula (5).

5.0 x 10 ²² x t ^-10.0? Y? 7.0 x 10 ²⁴ x t ^{-10. 0} ... (5)

(150? T? 250)

(2) Painted plated steel

Next, a description will be given of a method of producing a coated plated steel material, an evaluation test method and a test result of the coated plated steel material obtained thereby. The coated plated steel, [1.1. Coated steel sheet produced in the method of producing a hot-dip galvanized steel sheet by forming an uncoated layer 24 and one or more organic coat layers 25 as an upper layer thereon.

[2.1. Manufacture of painted plated steel]

(2.1.1. Formation of Uncoloured Treatment Layer 24)

The coating composition for forming the undercoating treatment layer 24 was prepared by mixing the organic resin shown in Table 7, the organic silicon compound shown in Table 8, the silica particles shown in Table 9, the phosphoric acid compound (D) shown in Table 10, , The tannin or tannic acid salt shown in Table 11, the etchant fluoride shown in Table 12 and the pretreatment layer 28, and the zirconium compound and the titanium compound shown in Table 13 were mixed in the amounts shown in Tables 19 to 28 (parts by mass of solids) , And the mixture was stirred using a paint dispersing machine. The coating composition was coated on the surface of the hot-dip coated steel sheet prepared in [1.1] above with a roll coater so as to have a predetermined adhesion amount and heated and dried so as to have a predetermined arrival plate temperature so that the coating film . The coating composition of the undercoating treatment layer 24, the coating amount of the coating, and the PMT (arrival plate temperature) of the coating undercoating layer 24 are also shown in Tables 19-28. In some examples, the pretreatment layer 28 shown in Table 12 was formed. Among the organosilicon compounds shown in Table 8, B4 to B19 were produced by reacting the amino group-containing silane coupling agent with BA and the epoxy group-containing silane coupling agent with BE at the BA / BE molar ratio shown in Table 8 Organosilicon compounds, and their molecular weights describe the molecular weights of the organosilicon compounds produced by the reaction.

(2.1.2. Coating Composition for Organic Coating Layer (25)) [

The paint composition for forming the organic coating layer 25 was prepared by blending the binder resin shown in Table 14, the coloring pigment shown in Table 15, and the rust preventing pigment shown in Table 16 in the compounding amount (mass part of solid content) shown in Table 17 , And stirring was carried out using a paint dispersing machine. If necessary, cyclohexanone and Solvesso 150 were diluted with a mixed solvent having a mass ratio of 1: 1 and adjusted to a viscosity capable of being applied. Hereinafter, when the organic film layer 25 includes two or more layers, these organic film layers 25 are referred to as a lower layer film, an upper layer film, and an uppermost layer film in this order in the order close to the untreated layer 24, Is referred to as a lower layer paint, an upper layer paint and an uppermost layer paint, respectively.

Of the binder resins shown in Table 14, pellets, flakes and sheets were dissolved in an organic solvent (Sorbesso 150, a product of Esso Oil Co., Ltd., mixed with cyclohexanone in a ratio of 1: 1 by mass). 30% (mass% based on resin solid content) of methylated melamine (Cymel 303 manufactured by Mitsui Cytec) was added to the polyester resins H1 and H2 shown in Table 14 as a melamine resin as a curing agent, 1.0% (mass% based on the total resin solid content) of Catalyst 602 manufactured by Saitec Corporation was added.

(2.1.3. Painted plated steel)

The lower layer paint of (2.1.2) was coated on the upper layer of the undercoating treatment layer 24 formed in (2.1.1) with a roll coater so as to have a predetermined film thickness, To form a lower layer coating film. Subsequently, the upper layer of the lower layer coating was coated with a roller curtain coater so as to have a predetermined film thickness, and the layer was heated and dried under the condition that the plate reaching temperature of the plate reached 230 캜 to form a coating layer including two layers To obtain a plated steel material. When the organic film includes one layer, the procedure for forming the lower layer film is omitted. The coating composition of the coated plated steel material thus obtained and the film thickness of the coating film are shown in Table 18.

In the case of coated plated steel with an organic coating film including three layers, two kinds of upper layer coating materials are laminated on the upper layer of the lower coating film of the above (2.1.3) with a slide hopper type curtain coater, Followed by heating and drying at a temperature of 230 占 폚 to form an organic coating film including three layers to obtain a coated plated steel material. In this case, the film disposed on the uppermost layer among the three organic films is referred to as an uppermost layer film, and the film disposed between the uppermost layer film and the lower layer film is referred to as an upper layer film. The coating composition of the coated plated steel and the film thickness of the coating are shown in Table 18.

(2.1.4 Evaluation test)

Test specimens having a size of 70 mm x 150 mm were cut out from the coated plated steel material obtained in the above (2.1.3), and subjected to the appearance evaluation, the corrosion resistance evaluation of the processed portion by the exposure test, and the surface scratch corrosion resistance (Organic film adhesion property in Tables 29 to 37) and organic film adhesion property (water resistance in Tables 29 to 37) of the bent portion after hot water immersion were evaluated by the following evaluation methods and evaluation criteria Respectively. The evaluation results are shown in Tables 29 to 37. (Appearance corrosion resistance in Table 38), adhesion of the organic film in the bent portion (adhesion of the organic film in Table 38), bending strength of the bent portion after hot water immersion (The SST processing in Table 38) and the organic film adhesion (the bending adhesion in Table 38) of the bent portion were evaluated by the results of evaluation of corrosion resistance of the organic film (waterproof adhesion in Table 38), evaluation of end face corrosion resistance by exposure test, Were evaluated by the following evaluation methods and evaluation criteria. The evaluation results are shown in Table 38.

[Appearance evaluation]

The appearance of the surface of the coated plated steel sheet was observed by naked eyes and an optical microscope as in the case of the plating surface.

Based on the observation result, the degree of wrinkling on the coating surface was evaluated by the following criteria. The results are shown in Tables 29 to 37 and Table 38. In addition, the degree of irregularity due to the wrinkles, sagging, dross adhesion, and the size of the spangle on the surface of the coating recognized in this observation reflects the plating surface of the base, and the result of this observation was equivalent to that of the plating surface.

The ratings in Tables 29 to 37 and Table 38 are as follows. The embodiment of the present invention is rated 2 or more.

1: If a wrinkle of 1 equivalent is recognized in the following points.

2: A sagging or dross of 1 equivalent is recognized in the following grades.

3: When neither 1 nor 2 above occurs.

The wrinkles on the coating surface (the surface of the organic coating layer 25) were evaluated according to the following criteria.

5: Wrinkles are not recognized.

4: Wrinkles are slight (wrinkles of the degree shown in Fig. 7A).

3: Less wrinkles (when the degree of wrinkles is between 4 and 2).

2: Degree of wrinkles (better than that shown in Fig. 7B).

1: The wrinkles are remarkable (wrinkles of the degree shown in Fig. 7B).

Sagging of the coating surface (surface of the organic coating layer 25) was evaluated according to the following criteria.

2: Sagging is not allowed.

1: Sagging is recognized (sagging to the extent shown in FIG. 9).

The dross on the coating surface (the surface of the organic coating layer 25) shows the degree of the dross adhered to the plating layer 23 that can be observed on the surface of the organic coating layer 25, based on the observation result, Respectively.

2: There is no adhesion of dross accompanied by unevenness on the surface of the plated layer 23, or adhesion of dross accompanying unevenness is recognized to be less than 5 sites per 1 m ² .

1: At least five drosses per 1 m ² are allowed to adhere to the surface of the plated layer 23 accompanied by unevenness.

[Corrosion resistance of processed part by exposure test]

The test piece was subjected to 5 mm extrusion processing using an Erickson tester (conforming to the A dimension of JIS Z 2247) at the center of the test piece, and the end surface was tape-sealed. Under the conditions equivalent to C4 under the ISO9223 standard and under JIS D 0205, The road was installed on the south side, and the occurrence of rust after 3 years was checked and rated as follows.

5: Less than 1% area of white rust.

4: White rust occurrence area is 1% or more, less than 5%.

3: The area of white rust occurrence is 5% or more and less than 10%.

2: The area of white rust is 10% or more and less than 30%.

1: White rust occurrence area is 30% or more, or red rust occurrence is recognized.

[Corrosion resistance of plane scratches by exposure test]

An X-shaped scratch was applied to the center of the test piece by an NT cutter and the end surface was tape-sealed. The end surface of the test piece was installed in a condition equivalent to JIS D 0205 in accordance with ISO9223 And the occurrence of rust after 3 years has been checked, and the evaluation is given as follows.

5: Expansion width of 1/4 or less with respect to rating 1.

4: Expansion width of 1/3 or less with respect to rating 1.

3: Expansion width less than 1/2 with respect to rating 1.

2: Expansion width of 2/3 or less with respect to rating 1.

1: most significant expansion width, or the generation of red rust which can be clearly observed from the front side.

[Adhesion of the organic film to the bent portion]

A bending test was carried out with two plates having a thickness of 0.8 mm so as to be outside the organic coating film in accordance with JIS G 3322 at the inner spacing of the bending and to attach a cellotape (registered trademark) to the cracks and bent portions generated in the coating film The state of the organic film which was removed when peeled off was observed and evaluated according to the following evaluation criteria.

4: Clear cracks are not recognized.

3: Fine cracks are recognized.

2: Clear cracks, or a small amount of film fell off.

1: Clear film detachment.

[Adhesion of the organic film to the bent portion after hot water immersion]

The end faces of the test pieces were tape-sealed and immersed in ion-exchanged water at 80 ° C for 40 hours. Thereafter, according to JIS G 3322, four plates having a thickness of 0.8 mm were bend Tests were carried out to observe the state of the organic film which was removed when the film was peeled after the cellotape (registered trademark) was attached to the cracks and bent portions formed on the film, and evaluated by the following evaluation criteria.

4: Clear cracks are not recognized.

3: Fine cracks are recognized.

2: Clear cracks, or a small amount of film fell off.

1: Clear film detachment.

As shown in Tables 29 to 37, the examples of the present invention show excellent appearance at a rating of 2 points or more in any evaluation test, corrosion resistance in the processed portion by the exposure test, the surface flaw corrosion resistance in the exposure test, And the organic film adhesion of the bent portion after hot water immersion. On the other hand, in Comparative Examples 1 to 4 in which the contents of the molten plated layer were out of the range of the present invention, corrosion resistance was poor, and Comparative Examples 5 to 10 were inferior in appearance. In Comparative Example 16 and Comparative Example 17, since the amount of Mg contained in the molten plated layer is less than 0.1% by mass, the corrosion resistance of the processed portion and the scratch portion is inferior. In Comparative Example 11 in which the undercoat film was not provided, the corrosion resistance of the processed portion and the water resistance of the organic film were inferior. In Comparative Example 12 in which the proportion of the organic silicon compound to the organic resin was too small, the scratch corrosion resistance was poor. In Comparative Example 13 in which the ratio of the organic silicon compound to the organic resin was excessive, the corrosion resistance of the processed portion and the water resistance of the water-resistance were inferior. In Comparative Example 14 in which the thickness of the organic coating film was too thin, the corrosion resistance at the processed portion and the corrosion resistance at the scratch portion were poor. In Comparative Example 15 in which the thickness of the organic coating film was too thick, cracks easily formed in the organic coating film in the bending process, and the adhesion of the organic coating film was deteriorated.

[End face corrosion resistance by exposure test]

The long side of the test specimen was subjected to shear cutting so that the burr would be downward, and the circumference of the test specimen mounting hole was sealed around the circumference of the test piece mounting hole. Under the conditions equivalent to C4 according to ISO9223, the condition according to JIS D 0205, And the expansion width of rust and the occurrence of red rust from the end face after the lapse of 3 years were checked, and the evaluation was given as follows.

5: Expansion width of 1/4 or less with respect to rating 1.

4: Expansion width of 1/3 or less with respect to rating 1.

3: Expansion width less than 1/2 with respect to rating 1.

2: Expansion width of 2/3 or less with respect to rating 1.

1: most significant expansion width, or the generation of red rust which can be clearly observed from the front side.

[Corrosion resistance of processed part by salt spray test]

The test piece was subjected to 6 mm extrusion processing with an Erickson tester (in accordance with the A dimension of JIS Z 2247) at the center of the test piece, tape sealing the end surface, and a salt spray test according to JIS Z 2371 for 240 hours and 1000 And the rust occurrence status at each test time of the portion subjected to Erichen processing was observed and evaluated according to the following evaluation criteria.

5: Less than 1% area of white rust.

4: White rust occurrence area is 1% or more, less than 5%.

3: The area of white rust occurrence is 5% or more and less than 10%.

2: The area of white rust is 10% or more and less than 30%.

1: White rust occurrence area is over 30%.

[Adhesion of the organic film to the bent portion]

According to JIS G 3322, a bending test was carried out with four plates having a thickness of 0.8 mm so as to be outside of the organic film to the outside of the bending, and a cellotape (registered trademark) was attached to the cracks and bent portions generated in the film The state of the organic film which was removed when peeled off was observed and evaluated according to the following evaluation criteria.

4: Clear cracks are not recognized.

3: Fine cracks are recognized.

2: Clear cracks, or a small amount of film fell off.

1: Clear film detachment.

As shown in Table 38, the examples of the present invention exhibited excellent appearance, end face corrosion resistance, processed portion corrosion resistance, and organic film adhesion property at two or more points in any evaluation test.

While the preferred embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to these examples. Those skilled in the art will recognize that various changes and modifications may be made without departing from the spirit and scope of the invention as defined by the appended claims.

Industrial Applicability According to the present invention, the corrosion resistance of the flaw-formed portion of the coated surface and the processed portion deformed by the steel material of the base is good, and when the fired portion is heated and the organ is irradiated with ultraviolet rays, In addition, the occurrence of wrinkles and sagging of the surface is suppressed to provide a coated plated steel having good appearance.

1: steel material 1a: steel sheet
2: hot dip galvanizing bath 3:
4: heating furnace 5: annealing and cooling section
6: Snout 7: Port
8: sink roll 9: injection nozzle
10: cooling device 11: rough rolling and shape correcting device
12: Winder 13: Coil (first coil)
14: coil (second coil) 15: conveying roll
16: Feeder 17: Winder
18: heating furnace 19: coil
20: thermal insulation container 21: conveying roll
22: hollow member
23: Aluminum-zinc alloy plating layer (plating layer)
24: non-coating treatment layer 25: organic coating layer
26: alloy layer 27: pre-plated layer
28: Pretreatment layer 29: Coating
101: primary cooling device 102: secondary cooling device

Claims (11)

Steel,
The coating on the surface of this steel,
And,
Wherein the coating has a plating layer, an uncoated layer on the surface of the coating layer, and an organic coating layer on the surface of the uncoated layer,
Wherein the plating layer contains Al, Zn, Si, Mg and Cr as constituent elements, and further contains Al at 25 to 75 mass%, Mg at 0.1 to 10 mass%, Cr at 0.02 to 1.0 mass% 0.5 to 10% by mass with respect to the Al content, the balance being Zn and inevitable impurities,
Wherein the plating layer contains 0.2 to 15% by volume Si-Mg phase,
The mass ratio of Mg in the Si-Mg phase to the total amount of Mg in the plating layer is 3% or more and 100% or less,
A bump having a height greater than 200 占 퐉 and a feed rate greater than 1.0 is not present on the surface of the plating layer,
Wherein the coating under treatment layer comprises an organic resin and an organic silicon compound,
The organosilicon compound has an alkylene group, a siloxane bond, and a crosslinkable functional group represented by -SiR ¹ R ² R ³ ,
^{Two of} R ¹ , R ² , and R ³ are each an alkoxy group or a hydroxy group,
The remaining one of R ¹ , R ² , and R ³ is an alkoxy group, a hydroxy group, or a methyl group,
The organosilicon compound is contained in an amount of 2 to 1,500 parts by mass based on 100 parts by mass of the organic resin,
Wherein the thickness of the organic coating layer is 0.2 to 100 mu m
Wherein the coated steel sheet is a coated steel sheet. The method according to claim 1,
In any region where the size is 4 mm in diameter and the depth is 50 nm in the outermost layer at a depth of 50 nm on the surface of the plating layer, the Mg content is 0 mass% to less than 60 mass%
Wherein the coated steel sheet is a coated steel sheet. The method according to claim 1,
Wherein the ratio of the Si-Mg phase on the surface of the plating layer is 0% or more and 30% or less
Wherein the coated steel sheet is a coated steel sheet. 3. The method of claim 2,
Wherein the ratio of the Si-Mg phase on the surface of the plating layer is 0% or more and 30% or less
Wherein the coated steel sheet is a coated steel sheet. 5. The method according to any one of claims 1 to 4,
Wherein the coating under treatment layer contains at least one selected from a zirconium compound and a titanium compound
Wherein the coated steel sheet is a coated steel sheet. 5. The method according to any one of claims 1 to 4,
The coated plated steel material according to any one of claims 1 to 5, wherein 100 parts by mass of the organic resin is contained in the untreated layer.
(1) 50 to 3333 parts by mass of at least one selected from a zirconium compound and a titanium compound, or 1 to 50 parts by mass of at least one selected from the zirconium compound and the titanium compound
(2) 0.5 to 100 parts by mass of silica
(3) Phosphoric acid compound 0.5 to 40 parts by mass
(4) 1 to 50 parts by mass of tannin, tannic acid, or tannic acid
(5) 0.5-10 mass parts of etchant fluoride 5. The method according to any one of claims 1 to 4,
Wherein the organic coating layer comprises a lower layer comprising a rust preventive pigment and two layers of a colored upper layer
Wherein the coated steel sheet is a coated steel sheet. 5. The method according to any one of claims 1 to 4,
Wherein the coating amount of the undercoating treatment layer is 10 to 2000 mg / m ²
Wherein the coated steel sheet is a coated steel sheet. The method according to claim 6,
Wherein the organic coating layer comprises a lower layer comprising a rust preventive pigment and two layers of a colored upper layer
Wherein the coated steel sheet is a coated steel sheet. The method according to claim 6,
Wherein the coating amount of the undercoating treatment layer is 10 to 2000 mg / m ²
Wherein the coated steel sheet is a coated steel sheet. 8. The method of claim 7,
Wherein the coating amount of the undercoating treatment layer is 10 to 2000 mg / m ²
Wherein the coated steel sheet is a coated steel sheet.

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