WO2020100286A1 - Precoated steel sheet - Google Patents

Abstract

A precoated steel sheet is provided with: a steel sheet; a zinc alloy plating layer which is arranged on the steel sheet and contains 1 to 25% by mass of Al, 0.1 to 13% by mass of Mg, 0 to 2.0% by mass of Si, and a remainder made up by Zn and impurities; and a colored coating film layer which is arranged on the zinc alloy plating layer and contains at least one of a phosphorus compound and a vanadium compound, a coloring pigment and a binder resin.

Description

Precoated steel sheet

The present invention relates to a precoated steel sheet.

In the case of applying a coating to a product obtained by processing a steel plate, conventionally, the coating is applied after processing the steel plate. A steel plate that is painted after processing is called a post-coated steel plate. Recently, a steel sheet having a colored coating precoated (hereinafter referred to as a precoated steel sheet) has been used instead of the postcoated steel sheet. Precoated steel sheets are used for home appliances, building materials, automobiles and the like.
Precoated steel sheets are required to have various characteristics such as corrosion resistance, workability, and designability according to their applications, and various techniques have been conventionally proposed to realize such characteristics.

Patent Document 1 describes a method for coating a metallic matte precoated steel sheet in which a primer coating, an intermediate coating and a metallic clear coating are coated on a metal plate. According to Patent Document 1, by this method, a metallic tone excellent in film hardness, weather resistance (light resistance, film thickness abrasion resistance), chemical resistance, corrosion resistance, workability, and designability (metallic matte film) It is described that a matte design coated metal plate can be realized.

Patent Document 2 has an undercoat film and an overcoat film on the surface of a metal material that has been subjected to a surface treatment, and the undercoat film contains an anticorrosion pigment having an average particle diameter of 0.01 to 2 μm. A coated metal material having a concentration of 11 to 70% by weight is disclosed. Patent Document 2 describes that excellent corrosion resistance and workability can be realized by using such a coated metal material.

Japanese Unexamined Patent Publication No. 2009-297631 Japanese Patent Laid-Open No. 8-218001

In order to impart various functions, the precoated steel sheet is often formed with a plurality of coatings. This increases the total film thickness of the film formed on the precoated steel sheet.
In addition, a solvent-based paint is often used for forming the colored film on the precoated steel sheet. When a solvent-based paint is used in the production of a precoated steel sheet, an incinerator and a facility against odor are required, and therefore the precoated steel sheet is generally produced in a dedicated painting line. Therefore, not only the manufacturing process of the coated original plate but also the coating process is required, which increases the manufacturing cost of the precoated steel sheet.
On the other hand, there is a demand for a technique that can realize the performance required for a precoated steel sheet such as designability, corrosion resistance, workability, and weather resistance, while being inexpensive.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a precoated steel sheet having excellent designability, corrosion resistance, workability, and weather resistance while achieving a thin colored film.

The present invention adopts the following means in order to solve the above problems and achieve the object.

(1) A precoated steel sheet according to one aspect of the present invention is provided on a steel sheet, the steel sheet, and 1 to 25% by mass of Al, 0.1 to 13% by mass of Mg, and 0 to 2.0% by mass. % Si, the balance being a zinc alloy plating layer consisting of Zn and impurities, and at least one of a phosphate compound and a vanadium compound provided on the zinc alloy plating layer, and containing a color pigment and a binder resin. A colored film layer.
When the colored film layer contains the phosphoric acid compound, the concentration of the phosphoric acid compound is 0.3 to 5.0 mass in terms of P amount with respect to the total solid mass of the colored film layer. %, Which is 2 μm in the thickness direction and 200 μm in the direction parallel to the interface between the color coating layer and the zinc alloy plating layer when the cross section of the color coating layer in the thickness direction is observed by mapping with FE-EPMA. Within this range, 1 to 15 first regions having a phosphorus element concentration of 3% or more are present.
When the colored coating layer contains the vanadium compound, the vanadium compound is a vanadate compound or vanadium oxide, the concentration of the vanadium compound, relative to the total solid mass of the colored coating layer, V amount. Is 0.5 to 8.0% by mass, and when the cross section of the colored film layer in the thickness direction is observed by mapping with FE-EPMA, the thickness direction is increased from the interface toward the surface side. In the range of 1 μm and 200 μm in the direction parallel to the interface, there are 1 to 10 second regions having a vanadium element concentration of 3% or more.
(2) In the precoated steel sheet according to (1), the colored coating layer may include the phosphoric acid compound.
(3) In the precoated steel sheet according to (1) or (2) above, when the cross section of the colored coating layer in the thickness direction is observed by mapping with FE-EPMA, it is 2 μm in the thickness direction and parallel to the interface. Within the range of 40 μm in the direction, 1 to 15 first regions having a phosphorus element concentration of 3% or more may be present.
(4) In the precoated steel sheet according to any one of the above (1) to (3), when the cross section of the colored coating layer in the thickness direction is observed by mapping with FE-EPMA, it is 2 μm in the thickness direction. Further, 1 to 15 first regions having a phosphorus element concentration of 3% or more may be present within a range of 20 μm in the direction parallel to the interface.
(5) In the precoated steel sheet according to any one of the above (1) to (4), the phosphoric acid compound may have an average particle size of 0.10 to 10 μm.
(6) In the precoated steel sheet according to any one of the above (1) to (5), the colored film layer has a layer thickness of more than 8 μm and 15 μm or less, and the thickness direction from the surface of the colored film layer is the thickness direction. In the range of 2 μm in the thickness direction, a center part in the range of 2 μm in the thickness direction centered on the center of the thickness of the colored film layer, and a range of 2 μm in the thickness direction from the interface toward the surface side. The concentration of the elemental phosphorus detected in the range of 2 μm × 200 μm is measured using FE-EPMA for each of the deep areas, and the concentration of the phosphate compound in the surface portion is PA, and the concentration of the phosphate compound in the central portion is Where PA / PB is 0.5 to 2.0 and PA / PC is 0.5 to 2.0, where PB is PB and the concentration of the phosphate compound in the deep portion is PC.
(7) In the precoated steel sheet according to any one of the aspects (1) to (6), the colored film layer has a layer thickness of 8 μm or less, and the colored film layer has a thickness of 2 μm from the surface in the thickness direction. The FE-EPMA is used to map and observe the cross section in the thickness direction with respect to each of the surface part which is the range and the deep part which is the range of 2 μm in the thickness direction from the interface toward the surface side, PA / PC may be 0.5 to 2.0, where PA is the concentration of the phosphoric acid compound in the part and PC is the concentration of the phosphoric acid compound in the deep part.
(8) In the precoated steel sheet according to any one of the aspects (1) to (7), the colored coating layer may include the vanadium compound.
(9) In the precoated steel sheet according to (8), the vanadium compound may have an average particle size of 0.10 to 10 μm.
(10) In the precoated steel sheet according to (8) or (9) above, the layer thickness of the colored film layer is T, and T is 200 μm from the surface of the colored film layer in the thickness direction and in the direction parallel to the interface. The concentration of vanadium element detected using FE-EPMA in the range of PD is PD, T / 2 in the thickness direction from the center of the layer thickness of the colored film layer to the interface, and 200 μm in the interface direction. When the concentration of the vanadium element detected by using FE-EPMA is PE, PE / PD may be 1.0 to 5.0.
(11) In the precoated steel sheet according to any one of the above (8) to (10), the zinc alloy plating layer contains 4 to 22 mass% of Al and 1 to 5 mass% of Mg. You may.
(12) In the precoated steel sheet according to any one of the above (8) to (11), the zinc alloy plating layer may contain 0.01 to 2.0 mass% of Si.
(13) In the precoated steel sheet according to any one of the above (8) to (12), the coloring pigment may be an aluminum pigment.
(14) In the precoated steel sheet according to (13), the color pigment may have an average particle diameter of 7 to 30 μm and an average aspect ratio of 20 or more.
(15) In the pre-coated steel sheet according to (13) or (14), the color pigment is in the range of 0.5 μm from the surface of the colored film layer in the thickness direction, or from the interface to the surface. Therefore, it may not exist in the range of 0.5 μm in the thickness direction.
(16) In the precoated steel sheet according to any one of the above aspects (1) to (15), the binder resin contained in the colored film layer may be a polyester resin and an acrylic resin.
(17) In the precoated steel sheet according to any one of the above (1) to (16), the colored coating layer may further contain melamine.
(18) In the precoated steel sheet according to (17) above, a melamine concentrated layer may be provided on the surface of the colored coating layer.
(19) In the precoated steel sheet according to any one of the above (1) to (18), a chemical conversion treatment coating layer may be further provided between the colored coating layer and the zinc alloy plating layer.
(20) In the precoated steel sheet according to any one of the above (1) to (19), the layer thickness of the colored film layer may be 2 μm or more.

According to each of the above aspects, it is possible to provide a precoated steel sheet having excellent designability, corrosion resistance, workability, and weather resistance while achieving a thin colored film.

It is a schematic diagram which shows the layer structure of the precoat steel plate which concerns on 1st Embodiment of this invention. It is a schematic diagram which shows the layer structure of the precoat steel plate which concerns on 2nd Embodiment of this invention. It is a schematic diagram which shows the layer structure of the precoat steel plate which concerns on 3rd Embodiment of this invention. It is a schematic diagram which shows the presence state of the phosphoric acid compound in the cross section of a colored film in the pre-coated steel sheet which concerns on 1st Embodiment of this invention. It is a schematic diagram which shows the distribution state of the 1st area | region in the coloring film layer which concerns on a prior art. It is a schematic diagram which shows the distribution state of the 1st area | region in the coloring film layer which concerns on a prior art. It is a schematic diagram which shows the distribution state of the 1st area | region in the coloring film layer which concerns on a prior art. In the pre-coated steel sheet which concerns on 2nd Embodiment of this invention, it is a schematic diagram which shows the presence state of the vanadium compound in a colored film layer. FIG. 3 is a schematic diagram showing the existing state of a vanadium compound in a colored film in a precoated steel sheet according to a conventional technique. It is a schematic diagram for demonstrating the surface part, center part, and deep part of a colored film layer in the precoat steel plate which concerns on 1st Embodiment of this invention. It is a schematic diagram for demonstrating the center of layer thickness and layer thickness in the precoat steel plate which concerns on 2nd Embodiment of this invention.

The present inventor, as a result of earnest studies to solve the above problems, with a steel plate used as a pre-coated steel sheet as a specific plated steel sheet, and specified as a rust preventive component for a colored film layer provided on the plated steel sheet. By including the pigment of (1) and further adjusting the distribution of such pigment in the colored coating layer under specific conditions, while achieving thinning of the colored coating, excellent designability, corrosion resistance, processability and weather resistance are achieved together. As a result, the present invention has been completed, and the present invention has been completed.
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and the drawings, constituent elements having substantially the same functional configuration are designated by the same reference numerals, and a duplicate description will be omitted.

[First Embodiment]
(Pre-coated steel sheet 100)
FIG. 1 is a schematic diagram showing a layer structure of a precoated steel sheet 100 according to the first embodiment of the present invention. The precoated steel sheet 100 is provided on the steel sheet 1, contains 1 to 25% by mass of Al, 0.1 to 13% by mass of Mg, and 0 to 2.0% by mass of Si. The zinc alloy plating layer 10 has the balance consisting of Zn and impurities, and the colored film layer 20 provided on the zinc alloy plating layer 10 and containing a phosphoric acid compound, a color pigment, and a binder resin.

(Steel plate 1)
The steel sheet (base steel sheet) 1 used for the precoated steel sheet 100 according to the present embodiment is not particularly limited, and it is possible to use the steel sheet 1 having known characteristics and chemical composition. The chemical composition of the steel sheet 1 is not particularly limited, and is preferably a chemical composition that can realize the mechanical strength required for the precoated steel sheet 100.

(Zinc alloy plating layer 10)
The steel sheet 1 according to the present embodiment contains 1 to 25 mass% Al, 0.1 to 13 mass% Mg, and 0 to 2.0 mass% Si, and the balance Zn and A zinc alloy plating layer 10 made of impurities is provided. That is, the zinc alloy plating layer 10 according to the present embodiment is an alloy plating layer containing a ternary zinc alloy containing Zn, Al and Mg. Since the precoated steel sheet 100 according to the present embodiment has the zinc alloy plating layer 10, the corrosion resistance superior to that of the hot dip galvanized steel sheet can be realized.

If the Al concentration in the zinc alloy plating layer 10 is less than 1% by mass, the corrosion resistance becomes insufficient, which is not preferable. On the other hand, when the Al concentration exceeds 25% by mass, the effect of improving corrosion resistance is saturated.
When the concentration of Mg in the zinc alloy plating layer is less than 0.1% by mass, corrosion resistance becomes insufficient, which is not preferable. On the other hand, when the concentration of Mg exceeds 13 mass%, dross is generated in the plating bath used when forming the zinc alloy plating layer 10, which is not preferable.
The zinc alloy plating layer 10 according to the present embodiment preferably contains 4 to 22 mass% of Al and 1 to 5 mass% of Mg.

In order to further improve the corrosion resistance, the zinc alloy plating layer 10 according to this embodiment preferably further contains Si. The preferable Si concentration in the zinc alloy plating layer 10 is 0.01 to 2.0 mass%. If the Si concentration is less than 0.01% by mass, the effect of improving the corrosion resistance due to the Si content is not sufficient, which is not preferable. When the concentration of Si exceeds 2.0 mass%, dross is likely to occur in the plating bath used when forming the zinc alloy plating layer 10, which is not preferable.

In the present embodiment, as a manufacturing method for forming the zinc alloy plating layer 10, for example, the steel plate 1 is dipped in a plating bath holding a molten Zn—Al—Mg alloy, The method of pulling up the steel plate 1 from such a plating bath is mentioned.
The amount of coating adhered to the steel plate 1 can be controlled by the pulling-up speed of the steel plate 1, the flow rate of the wiping gas ejected from the wiping nozzle provided above the plating bath, the flow rate adjustment, and the like.
In manufacturing the zinc alloy plating layer 10, a cut plate plating method, a continuous method using a coil, or the like may be used.

The amount of the zinc alloy plating layer 10 deposited is preferably in the range of 20 to 100 g / m ² per side of the steel sheet 1. If the amount of the zinc alloy plating layer 10 adhered is less than 20 g / m ² per side, the corrosion resistance of the precoated steel sheet 100 becomes insufficient, which is not preferable. Further, if the amount of the zinc alloy plating layer 10 attached is more than 100 g / m ² per side, the workability of the precoated steel sheet 100 will be reduced, which is not preferable.
The amount of the zinc alloy plating layer 10 deposited is more preferably in the range of 25 to 95 g / m ² per side of the steel sheet 1.

(Colored film layer 20)
A colored coating layer 20 (more specifically, a single colored coating layer 20) is provided on the zinc alloy plating layer 10. The colored film layer 20 contains at least a phosphoric acid compound, a color pigment, and a binder resin.
When the zinc alloy plating layer 10 is provided on both surfaces of the steel sheet 1, the colored film layer 20 may be provided on one zinc alloy plating layer 10 or may be provided on both zinc alloy plating layers 10. Good.

<Phosphate compound>
It is important that the phosphoric acid compound contained in the colored film layer 20 according to the present embodiment is uniformly distributed in the colored film layer 20 in a certain amount, and as long as the phosphoric acid compound is distributed as such, The form in which the phosphoric acid compound is contained is not particularly limited. Hereinafter, the phosphate compound will be described in detail.

Phosphonate compounds release phosphate ions in corrosive environments. The released phosphate ions react with the plating components of the zinc alloy plating layer 10 to form a protective film (not shown) on the surface of the zinc alloy plating layer 10, and the formed protective film improves the corrosion resistance. .. In particular, in order to improve the corrosion resistance after processing, it is important that the phosphoric acid compound can be eluted from the cracked portion (not shown) regardless of which portion of the colored film layer 20 is cracked by the processing.

The colored film layer 20 has a thickness of 2 μm and a range of 200 μm in the direction parallel to the interface 40 between the colored film layer 20 and the zinc alloy plating layer 10 (hereinafter sometimes referred to as the interface direction) (2 μm × 200 μm). Within the range), 1 to 15 first regions 30 having a phosphorus element concentration of 3% or more are present. For example, in the case shown in FIG. 4, the colored film layer 20 includes two first regions 30.

If the number of the first regions 30 is less than 1 in the range of 2 μm × 200 μm, the distribution of the phosphoric acid compound becomes sparse, and a sufficient effect of improving corrosion resistance cannot be obtained, which is not preferable. On the other hand, when the number of the first regions 30 exceeds 15 within the range of 2 μm × 200 μm, the distribution of the phosphoric acid compound becomes too dense, and the barrier property of the colored film layer 20 itself deteriorates, which is preferable. Absent.

The number of the first regions 30 included in the colored film layer 20 is preferably 1 to 15 in the range of 2 μm in the thickness direction and 40 μm in the interface direction (range of 2 μm × 40 μm), and more preferably the thickness. 1 to 15 in the range of 2 μm in the depth direction and 20 μm in the interface direction (range of 2 μm × 20 μm). When the number of the first regions 30 included in the colored film layer 20 is within the above range, more preferable corrosion resistance can be obtained.

FIG. 10 is a schematic diagram for explaining the surface portion 60, the central portion 70, and the deep portion 80 of the colored coating layer 20 in the precoated steel sheet according to the first embodiment of the present invention.
When the layer thickness of the colored film layer 20 is more than 8 μm and 15 μm or less, the surface portion 60 within the range of 2 μm from the surface of the colored film layer 20 and the layer thickness center 90 of the colored film layer 20 are centered. As for the central portion 70 having a range of 2 μm in the thickness direction and the deep portion 80 having a range of 2 μm in the thickness direction from the interface 40 toward the surface side, using FE-EPMA, a range of 2 μm × 200 μm When the concentration of the detected phosphorus element is measured and the concentration of the phosphate compound in the surface portion 60 is PA, the concentration of the phosphate compound in the central portion 70 is PB, and the concentration of the phosphate compound in the deep portion 80 is PC, PA / PB Is preferably 0.5 to 2.0 and PA / PC is preferably 0.5 to 2.0. This is because when PA / PB and PA / PC are 0.5 to 2.0, the phosphoric acid compound is uniformly dispersed in the entire colored film layer 20, and excellent corrosion resistance can be obtained.

When the thickness of the colored film layer 20 is 8 μm or less, the above PA / PC is preferably 0.5 to 2.0. This is because when PA / PC is 0.5 to 2.0, the phosphoric acid compound is uniformly dispersed in the entire colored coating layer 20, and excellent corrosion resistance can be obtained.

The first region 30 is a portion in which the concentration of the phosphorus element is 3% or more, and is a portion in which the phosphoric acid compound mainly exists among the components contained in the colored film layer 20. The first region 30 may include various resin components or the like contained in the colored film layer 20 in addition to the phosphoric acid compound as the main component.
The portion of the colored film layer 20 other than the first region 30 may contain various resin components derived from a binder resin as a main component, and may further contain a coloring pigment or the like.

The colored film layer 20 preferably contains a melamine resin. The type of melamine resin is not particularly limited, but it is preferable to use an imino group type melamine resin. This is because the imino group-type melamine resin is likely to be concentrated on the surface layer of the colored film layer 20, and a melamine resin condensation compound (melamine concentrated layer, not shown) is easily formed. When the concentrated layer of the melamine resin condensation compound is formed on the surface of the colored film layer 20, the colored film layer 20 is provided with a barrier property, and the stain resistance and the corrosion resistance are improved, which is preferable.

Various methods for analyzing the melamine resin in the colored film layer 20 will be described. First, the colored film layer 20 to be analyzed is dyed with osmium oxide. Thereby, the melamine resin in the colored film layer 20 is selectively dyed. Next, using a microtome, a focused ion beam processing device, etc., the colored film layer 20 dyed with osmium oxide is cut along the film thickness direction to prepare a sample whose cross section can be observed. Then, the thin film sample is observed with a transmission electron microscope at a magnification of 100,000 times. In this observation, the triazine site in the thin film sample is observed black in the STEM-BF (bright field) image and white in the STEM-HAADF (dark field) image.
The melamine resin in the colored film layer 20 can be confirmed by the above-described analysis method. The melamine resin in the colored coating layer 20 is analyzed by energy dispersive X-ray spectroscopy or Fourier transform infrared spectroscopy to detect nitrogen and osmium, and to belong to the triazine ring. It can also be confirmed by detecting the vibration peak.

The thickness of the region where the granular melamine resin is concentrated (that is, the thickness of the concentrated portion of the granular melamine resin that is unevenly distributed in layers) is measured by the following method. As described above, the thin film sample is observed with a transmission electron microscope at a magnification of 100,000 to obtain a STEM-BF (bright field) image. The obtained STEM-BF (bright field) image is binarized. Then, in the obtained binarized image, the thickness of a layered region observed black from the surface of the colored film layer 20 was measured at arbitrary 20 points, and the average value thereof was measured for the region where the granular melamine resin was concentrated. Calculate as thickness. When a layered black region is observed from the surface of the colored film layer 20, it is considered that the granular melamine resin is concentrated on the surface layer of the colored film.

5 to 7 are schematic diagrams showing a distribution state of the first regions 30 in the colored film layer 520 according to the conventional technique. In the example shown in FIG. 5, the number of the first regions 30 is small in a part of the colored film layer 520. As described above, when the first region 30 does not exist in the region of 2 μm × 200 μm of the colored film layer, when a crack is generated in a portion where the first region 30 does not exist (that is, a portion where the phosphate compound does not exist). Since a protective film is not formed on the surface of the zinc alloy plating layer 10, sufficient corrosion resistance cannot be ensured.
When a plurality of layers such as a primer layer, a colored film layer, and a clear film layer are formed from the zinc alloy plating layer 10 side using a solvent-based paint like a conventional pre-coated steel sheet (that is, the total film thickness is 20 μm or more). When it is thick, it is possible to improve the corrosion resistance by adding a large amount of a phosphoric acid compound to the primer layer.

FIG. 6 shows a case where the colored film layer 520 includes many first regions 30. As shown in FIG. 6, when the colored film layer contains a large amount of a phosphoric acid compound and the corrosion resistance is improved by only one colored film layer as in the present embodiment, the phosphoric acid compound is used in a corrosive environment. The portion where the is dissolved becomes a passage for the corrosion factor to enter, and the barrier property of the colored film layer itself is deteriorated.
Therefore, the phosphoric acid compound contained in the colored film layer 20 according to the present embodiment is uniformly present in a certain amount in the plane direction of the colored film layer 20 and excessively contained, as shown in FIG. 4, for example. It is necessary not to.

In addition, when a crack is generated in the colored film layer 20, in order to facilitate the reaction with the plating components in a corrosive environment, a certain amount of the first portion near the interface 40 between the colored film layer 20 and the zinc alloy plated layer 10 is used. It is necessary that the region 30 (phosphoric acid compound) is present.
However, as shown in FIG. 7, when the first region 30 (phosphoric acid compound) exists only in the vicinity of the zinc alloy plating layer 10, the following problem occurs. That is, when the depth of the cracks differs depending on the location, the first region 30 (phosphate compound) does not exist near the surface of the colored film layer 20, so that the amount of phosphate ions eluted from the shallow cracks is small. And the corrosion resistance is poor.
Therefore, it is important that the phosphoric acid compound be uniformly distributed not only in the plane direction of the colored film layer 20 but also in the film thickness direction of the colored film layer 20.

When measuring the number of the first regions 30, secondary electron image observation and mapping observation by FE-EPMA (Field Emission Electron Probe Micro Analyzer) are used for the cross section of the colored film layer 20.
The method for measuring the phosphorus element concentration by FE-EPMA mapping observation is as follows. That is, a precoated steel sheet is cut into an appropriate size, and a microtome, focused ion beam processing, resin-embedded polishing, and the like are used to produce a test piece whose cross-section can be observed. Then, FE-EPMA mapping analysis of the colored film layer is performed from the cross-sectional direction at an acceleration voltage of 15 kV (beam diameter of about 30 nm) and a magnification of 5000 times. P is selected as the detection target element, and the existing position and element concentration of the P element are mapped. The P element concentration is obtained from a calibration curve (relational expression between concentration and detection intensity) created using a sample having a known phosphoric acid concentration.

One pixel at the time of mapping is 1.5 × 10 ⁻³ μm ² (diameter: 39 nm). The center of one pixel is irradiated with an electron beam for 50 msec, and the generated X-ray intensity is processed as the intensity detected from one pixel. From the binarized element mapping result, a continuous range of 9 pixels or more is counted as one first region. That is, the range of 8 pixels or less is not counted as one first area. Note that the “continuous 9 or more pixel range” is not particularly limited to continuous in one direction, and may be 9 pixels or more regardless of the direction or shape.

More specifically, in the mapping analysis as described above, first, based on the measurement result of the phosphorus element concentration, the portion where the phosphorus element concentration is 3 mass% or more is located at the position of the first region 30 in the focused visual field. And Next, the number of the first regions 30 was measured for an arbitrary portion having a length of 2 μm in the film thickness direction × 200 μm in the interface direction, and the obtained number was measured along the film thickness direction of the colored film layer. The number of the first regions 30 is within the range of length 2 μm × length 200 μm along the interface direction.
In addition, in the mapping analysis, when the range of 200 μm cannot be observed in one visual field, the mapping analysis is performed in a plurality of visual fields and the analysis results in each visual field are summed to obtain the analysis result in the range of 200 μm.

The distribution state of the first region 30 (phosphoric acid compound) as described above is realized by including the phosphoric acid compound in the coloring film layer 20 at a specific concentration.
That is, since the phosphoric acid compound has a larger specific gravity than the binder resin that functions as the matrix of the colored film layer 20, the treated liquid is usually applied after the treatment liquid for forming the colored film layer 20 is applied. Before being dried and solidified, it is in a state of being likely to settle down (that is, in the direction toward the zinc alloy plating layer 10). However, by using a water-dispersible aqueous resin as the binder resin, the phosphoric acid compounds do not aggregate densely and are easily dispersed. Thereby, the dispersion of the phosphoric acid compound is appropriately realized, and the distribution state of the specific phosphoric acid compound as described above is realized.

Examples of the phosphoric acid compound contained in the colored film layer 20 according to the present embodiment include magnesium phosphate, calcium phosphate, aluminum dihydrogen tripolyphosphate, zinc phosphate, magnesium phosphite, zinc phosphite, phosphomolybdic acid. Examples thereof include zinc, zinc magnesium phosphate, zirconium phosphate, and phosphorus vanadate.
Among these phosphoric acid compounds, a certain phosphoric acid compound may be used alone, or a plurality of phosphoric acid compounds may be used in combination. Among these phosphate compounds, it is particularly preferable to use aluminum dihydrogen tripolyphosphate.

The average particle size of the phosphoric acid compound contained in the colored film layer 20 is preferably 0.10 μm or more.

When the average particle size of the phosphoric acid compound is less than 0.10 μm, the phosphoric acid compound will be distributed in the colored film layer 20 at close intervals, and the above-mentioned distribution state of the phosphoric acid compound will be realized. Can not do it. Further, when the average particle size of the phosphoric acid compound is less than 0.10 μm, the location where the phosphoric acid compound is eluted in the corrosive environment serves as a path for the corrosion factor to enter, and the barrier property of the colored film layer 20 itself deteriorates. It is not preferable because it is also present.

The average particle size of the phosphoric acid compound is preferably 10 μm or less. If the average particle size of the phosphoric acid compound exceeds 10 μm, it may adversely affect the color tone of the precoated steel sheet 100 according to the present embodiment, which is not preferable.
The average particle size of the phosphoric acid compound is more preferably within the range of 1 to 5 μm.

The average particle diameter of the phosphoric acid compound is determined by the following method. The steel sheet is observed from the cross-sectional direction, and phosphorus (P) element is mapped by FE-EPMA. At this time, continuous particles of 9 pixels or more are regarded as one particle, and the area Sp thereof is obtained. The particle size of the phosphoric acid compound is determined by φp = 2 × (Sp / π) ^0.5 . An arbitrary width of 200 μm is measured, and the average of the particle diameter φp of the phosphoric acid compound particles confirmed in that range is obtained.

The concentration of the phosphoric acid compound in the colored film layer 20 is 0.3 to 5.0 mass% in terms of P amount with respect to the total mass of the colored film layer 20.
When the concentration of the phosphoric acid compound exceeds 5.0% by mass, the phosphoric acid compound is distributed in the colored film layer 20 at close intervals, so that the distribution state of the phosphoric acid compound as described above can be realized. Can not. Further, when the concentration of the phosphoric acid compound exceeds 5.0% by mass, the location where the phosphoric acid compound is eluted in the corrosive environment serves as a path for the corrosion factor to enter, and the barrier properties of the colored film layer 20 itself may deteriorate. Therefore, it is not preferable.

If the concentration of the phosphoric acid compound is less than 0.3% by mass, the corrosion resistance of the precoated steel sheet 100 according to this embodiment may be insufficient, which is not preferable.
The concentration of the phosphoric acid compound in the colored film layer 20 is more preferably 1.0 to 3.0 mass% in terms of P content.

Here, the concentration of the phosphoric acid compound in the colored film layer 20 is approximately the same value as the concentration of the phosphoric acid compound contained in the colored coating material used to form the colored film layer 20.
The concentration of the phosphoric acid compound converted into the amount of P in the colored film layer 20 can be measured by analyzing the cross section of the colored film layer 20 by FE-EPMA.

<Color pigment>
As the color pigment contained in the colored film layer 20 according to this embodiment, a color pigment usually used in general coating can be used. Examples of the pigment include color pigments of known colors such as black, white, metallic color, and chromatic color, which are made of known metals or oxides. In addition, in this specification, a coloring pigment represents the pigment which does not contain phosphorus and vanadium.

Here, the type of the color pigment in the colored film layer 20 and the concentration of the color pigment are not particularly limited, and a color pigment type capable of obtaining a desired color tone is appropriately selected to obtain a desired color tone. The concentration may be appropriately selected so that
The concentration of the color pigment contained in the color film layer 20 can be determined by dissolving the color film and quantitatively analyzing the color pigment element with an ICP emission spectral analyzer.

As the metallic color pigment, metal pigments such as aluminum, silver, copper, platinum, gold and brass can be used, but among them, as the metallic pigment, an aluminum pigment (aluminum pigment) is used. Preferably.

Further, it is more preferable that the above-mentioned aluminum pigment has an average particle diameter within a range of 7 to 30 μm and an average aspect ratio (ratio between average particle diameter and thickness) of 20 or more. If the average particle size of the aluminum pigment is less than 7 μm, the metallic appearance may be insufficient, which is not preferable. On the other hand, when the average particle diameter of the aluminum pigment exceeds 30 μm, the appearance becomes nonuniform and the workability is deteriorated, which is not preferable. Further, when the average aspect ratio of the aluminum pigment is less than 20, the appearance may become nonuniform, which is not preferable.
The average particle diameter and average aspect ratio of the color pigment are determined as follows. First, elemental mapping is performed from the surface of the colored film with a field emission-electron probe micro analyzer (FE-EPMA), and the major axis length X1 and the minor axis length X2 of any one pigment are mapped. And the particle size X of the pigment is calculated by (X1 + X2) / 2. Here, the major axis means, within the outline of the image of the pigment specified by elemental mapping, the maximum line segment that traverses the pigment, and the minor axis is a line segment perpendicular to the major axis, Means the largest across the pigments. Next, FE-EPMA is used to perform elemental mapping from the cross-sectional direction, and the thickness Y of any one pigment (the length of the largest line segment that crosses the pigment in the direction perpendicular to the measurement plane of the above-mentioned major axis and minor axis). ) Value is measured. Using the same method, particle diameters and thicknesses of arbitrary 10 or more pigments are obtained, and the averages of the respective pigments are averaged to calculate the average particle diameter [X] and the average thickness [Y] of the pigments. It is calculated by [X] / [Y].

Regarding the color pigments other than the aluminum pigment, the shape thereof is closer to a sphere than the aluminum pigment, and the average particle diameter is often smaller than the aluminum pigment, so that the pigment has a general average particle diameter and an average aspect ratio. It is possible to realize the above-mentioned distribution state of the phosphoric acid compound by appropriately using a material.

The aluminum pigment is in the range of 0.5 μm in the film thickness direction from the interface 40 between the colored film layer 20 and the zinc alloy plating layer 10 toward the surface layer side, or from the outermost surface layer of the colored film layer 20 to the interface 40 side. It does not preferably exist within the range of 0.5 μm in the film thickness direction.
When the aluminum pigment is present near the interface 40 or near the outermost surface layer of the colored film layer 20, the aluminum pigment is liable to be a passageway for a corrosion factor to enter in a corrosive environment, resulting in poor corrosion resistance, which is not preferable. ..
The distance between the interface 40 and the aluminum pigment and the distance between the outermost layer of the colored film layer 20 and the aluminum pigment are cut into an appropriate size of the precoated steel sheet 100 and embedded with resin, the cross section is polished, and the cross section is viewed from an electron microscope. It can be confirmed by observing by observation.

<Binder resin>
The type of resin used as the binder resin is not particularly limited, but for example, a known resin such as a polyester resin, an acrylic resin, a urethane resin, an epoxy resin, a fluororesin, or a modified resin thereof may be used. it can.
Further, these resins may be crosslinked with a known crosslinking agent component such as a melamine resin or an isocyanate resin. Further, as the binder resin, an energy beam curable resin such as an electron beam curable resin or an ultraviolet curable resin may be used.
Among these resins, it is particularly preferable to use at least one of polyester resin and acrylic resin as the binder resin.

<Thickness of colored film layer 20>
The thickness of the colored film layer 20 is preferably in the range of 2 to 15 μm, for example.
When the thickness of the colored film layer 20 is less than 2 μm, the colored film layer 20 is deteriorated when used outdoors, or the surface of the zinc alloy plating layer 10 is discolored to grayish black, and It may be difficult to maintain the color tone of the precoated steel sheet 100 according to the embodiment within a desired range, which is not preferable.
On the other hand, when the thickness of the colored coating layer 20 exceeds 15 μm, the cost for manufacturing the precoated steel sheet 100 increases and the workability tends to decrease, which is not preferable.
The thickness of the colored coating layer 20 is more preferably in the range of 3 to 10 μm.

The thickness of the colored film layer 20 can be measured by observing the cross section of the colored film layer 20 using various microscopes.

(Chemical conversion coating layer)
In the above description, the case where the colored film layer 20 is formed on the surface of the zinc alloy plating layer 10 has been described, but a chemical conversion treatment film layer (not shown) is formed on the surface of the zinc alloy plating layer 10, and the chemical conversion treatment film layer is formed. The color coating layer 20 may be formed on the surface (not shown).
By providing a chemical conversion treatment coating layer (not shown), the adhesion of the colored coating layer 20 can be further improved, and the corrosion resistance can be further improved, which is preferable.

The chemical conversion coating layer (not shown) is formed by a known chemical conversion treatment. Examples of such chemical conversion treatment include zinc phosphate chemical conversion treatment, coating chromate treatment, electrolytic chromic acid treatment, reactive chromate treatment, and chromate-free chemical conversion treatment.

The thickness of the chemical conversion coating layer (not shown) is not particularly limited, and may be, for example, 0.05 to 1 μm. The thickness of the chemical conversion coating layer (not shown) can be measured, for example, by observing a cross section of the chemical conversion coating layer (not shown) with a transmission microscope or the like.

(Method for manufacturing precoated steel sheet 100)
Next, a method for manufacturing the precoated steel sheet 100 according to this embodiment will be described.
The method for manufacturing the precoated steel sheet 100 according to the present embodiment includes a step of applying a colored coating material containing a phosphoric acid compound, a color pigment and a binder resin to the steel sheet 1 on which the zinc alloy plating layer 10 is formed. Here, the above-mentioned colored paint is a colored paint treatment liquid used for forming the colored film layer 20.

The colored paint treatment liquid used for forming the colored film layer 20 has a predetermined dispersion medium (for example, water or an organic solvent) containing a predetermined component to be contained in the colored film layer 20 as described above. It may be contained in a ratio and manufactured by a known method.

The binder resin contained in the colored paint treatment liquid is preferably a water-dispersible aqueous resin. In the process of forming the colored film layer 20, the presence of the water-dispersible resin makes it possible to disperse the phosphoric acid compound so as not to be in a densely aggregated state. Thereby, in the colored film layer 20 according to the present embodiment, it is possible to realize a predetermined distribution state of the phosphoric acid compound. Further, the colored film layer 20 formed of the water-based resin has a better elution property of the phosphoric acid compound than the colored film layer 20 formed of the solvent-based resin, and therefore a smaller amount of the phosphoric acid compound can be used. Corrosion resistance can be improved, which is preferable.

The colored paint treatment liquid preferably contains a melamine resin. This is because the melamine resin not only contributes to the crosslinking reaction of the binder resin but also contributes to the control of the distribution state of the rust preventive pigment. From these viewpoints, it is preferable that the melamine resin contained in the colored coating liquid is an imino group-type melamine resin.

The viscosity of the pigmented coating the processing solution is a 0.8 Pa · s or more when measured under the conditions of a shear rate of 0.01s ^-1 by rheometer, 0.3 Pa · when measured under the conditions of a shear rate of 1000 s ^-1 It is preferably s or less.
Since the phosphoric acid compound has a larger specific gravity than the resin, the phosphoric acid compound is usually in a state where it tends to precipitate downward. On the other hand, by adjusting the viscosity of the coating material within the above range with the viscosity modifier, it is possible to prevent the phosphoric acid compound dispersed in the colored coating from settling due to convection generated when the coating material is heated. In addition, effects such as suppression of sedimentation during storage of paint and uniform appearance by leveling after coating can be obtained.

The type and amount of the viscosity modifier used may be appropriately selected according to the type of binder resin, the type of solvent, and the like. Examples of the viscosity modifier include SN thickener 617 (manufactured by San Nopco Ltd., the main component being an acrylic polymer) which is one of the thickeners. The use of SN thickener 617 is preferable because it imparts thixotropic viscosity to the colored coating liquid.
By adding the SN thickener 617 to the colored paint treatment liquid, the viscosity of the colored paint can be controlled within the above range.

The coating method of the paint treatment liquid is not limited to a specific method, or by immersing the plated steel sheet in the treatment liquid, or by spraying the treatment liquid on the surface of the plated steel sheet, and a predetermined adhesion amount and Examples thereof include a method of controlling the amount of adhesion by using a roll or a gas sprayer, and a method of applying with a roll coater, a curtain coater, or a bar coater.

The method of drying and baking the applied coating material is not limited to a specific method as long as it can vaporize the dispersion medium (mainly water or organic solvent). Here, if heated at an excessively high temperature, it is feared that the uniformity of the colored film layer may be deteriorated, and conversely, if heated at an excessively low temperature, there is a concern that productivity may be deteriorated. Therefore, in order to stably and efficiently produce a colored coating layer having excellent characteristics, the colored coating layer after coating should be heated at a temperature of about 150 ° C. to 250 ° C. for about 5 to 80 seconds. preferable. By setting the heating temperature in the above range, it becomes possible to appropriately and sufficiently move each particle in the treatment liquid, and it is possible to more reliably realize a desired distribution state of each particle.

In addition, it is economical and preferable that the formation of the colored film layer is performed in-line in the production line of the plated steel sheet, but it may be formed in another line, or after blanking for forming is performed. It may be formed.

[Second Embodiment]
FIG. 2 is a schematic diagram showing a layer structure of a precoated steel sheet 200 according to the second embodiment of the present invention. The pre-coated steel sheet 200 is provided on the steel sheet 1, contains 1 to 25 mass% Al, 0.1 to 13 mass% Mg, and 0 to 2.0 mass% Si. The balance includes a zinc alloy plating layer 10 composed of Zn and impurities, and a colored film layer 120 provided on the zinc alloy plating layer 10 and containing a vanadium compound, a color pigment, and a binder resin. That is, the precoated steel sheet 200 is different from the first embodiment in that the colored coating layer 120 contains the vanadium compound.
The description of the points common to the first embodiment will be omitted.

(Colored film layer 120)
A colored film layer (more specifically, a single colored film layer) 120 is provided on the zinc alloy plating layer 10. The colored film layer 120 according to this embodiment contains at least a vanadium compound, a color pigment, and a binder resin.

<Vanadium compound>
It is important that the vanadium compound contained in the colored coating layer 120 according to the present embodiment is distributed near the interface 140 of the colored coating layer 120 on the zinc alloy plating layer 10 side. The form in which the vanadium compound is contained is not particularly limited, as long as the vanadium compound is distributed as such. Hereinafter, the vanadium compound will be described in detail.

Vanadium compounds release vanadate ions in corrosive environments. The released vanadate ions react with the plating components of the zinc alloy plating layer 10 and the components of the steel plate 1 to form a protective film (not shown) on the surfaces of the zinc alloy plating layer 10 and the steel plate 1 at the end face, The formed protective film has an effect of improving corrosion resistance.
In order to facilitate the reaction of vanadate ions with the plating component and the base steel plate component, it is important that the vanadium compound exists near the interface 140 on the zinc alloy plating layer 10 side of the colored coating layer 120. Particularly, when the end surface of the precoated steel sheet 200 is exposed, the state of existence of the vanadium compound becomes extremely important.

When a solvent-based paint is used to form a multi-layer coating such as a primer layer, a colored coating layer, a clear coating layer, ... By adding a large amount of vanadium compound to the primer layer, it is possible to obtain the effect of improving the corrosion resistance. On the other hand, in the case of improving the corrosion resistance with only one colored film layer as in the embodiment of the present invention, when a large amount of the vanadium compound is present in the colored film layer 520, as schematically shown in FIG. 6, In the corrosive environment, the location where the vanadium compound is eluted serves as a path for the corrosive agent to enter, and the barrier property of the colored film layer 520 itself is reduced. Therefore, the vanadium compound used for the colored coating layer 120 according to the present embodiment is present in a fixed amount near the interface 140 on the zinc alloy plating layer 10 side of the colored coating layer 120, as schematically shown in FIG. However, it is important that the distribution is not too dense.

FIG. 8 is a schematic diagram showing the presence state of the vanadium compound in the colored film layer 120. As shown in FIG. 8, when the cross section of the colored film layer 120 in the thickness direction is observed by mapping with FE-EPMA, 1 μm in the thickness direction from the interface 140 toward the surface side and a direction parallel to the interface 140 (hereinafter, There are 1 to 10 second regions 130 having a vanadium element concentration of 3% or more within a range of 200 μm (which may be referred to as an interface direction).

When the number of the second regions 130 existing within the range of 200 μm along the interface direction is less than 1, the distribution of the vanadium compound becomes sparse and a sufficient corrosion resistance improving effect cannot be obtained. On the other hand, when the number of the second regions 130 existing within the range of 200 μm along the interface direction exceeds 10, the distribution of the vanadium compound becomes too dense and the barrier property of the colored film layer 120 itself. Is decreased, which is not preferable.
It is preferable that 1 to 10 second regions 130 are present within the range of 1 μm in the thickness direction from the interface 140 toward the surface side and 40 μm in the interface direction. More preferably, 1 to 10 second regions 130 are present within the range of 1 μm in the thickness direction from the interface 140 toward the surface side and 20 μm in the interface direction.

FIG. 11 is a schematic diagram for explaining the layer thickness center 190 and the layer thickness in the precoated steel sheet 200 according to the second embodiment of the present invention.
When the layer thickness of the colored coating layer 120 is T, the vanadium element concentration detected using FE-EPMA in the range of T from the surface of the colored coating layer 120 in the thickness direction and 200 μm in the interface direction is PD, and the colored coating layer is FE-EPMA is used in a range of T / 2 from the layer thickness center 190 of the 120 toward the interface 140 in the thickness direction (that is, a range from the layer thickness center 190 to the interface 140 in the thickness direction) and 200 μm in the interface direction. When the concentration of vanadium element detected by PE is PE, PE / PD is preferably 1.0 to 5.0.

The method of measuring the vanadium element concentration by FE-EPMA mapping observation is as follows. That is, a precoated steel plate is cut into a suitable size, embedded with resin, and the cross section is polished. Then, FE-EPMA mapping analysis of the colored film layer is carried out from the cross-sectional direction at an acceleration voltage of 15 kV and a magnification of 5000 times. At this time, V is selected as the detection target element, and the existing position and element concentration of each element are mapped.

More specifically, in the mapping analysis as described above, first, focusing on “a region up to 1 μm in the film thickness direction from the interface 140 on the zinc alloy plating layer 10 side of the colored film layer 120 toward the surface side”, Based on the measurement result of the vanadium element concentration in such a region, the portion where the vanadium element concentration is 3% or more is the position of the second region 130 in the focused visual field. Next, the number of the second regions 130 is measured for an arbitrary portion having a length of 200 μm in the plane direction, and the obtained number exists within the range of 200 μm in length along the interface direction of the colored film layer 120. The number of the second areas 130 to be processed is set.

The distribution state of the specific vanadium compound as described above is realized by including a vanadium compound having a specific shape in the colored film layer 120 at a specific concentration, as described below. That is, since the vanadium compound has a larger specific gravity than the binder resin that functions as the matrix of the colored film layer 120, after the treatment liquid for forming the colored film layer is applied, the treated liquid is dried and solidified. By the time it is carried out, it is in a state where it is likely to settle downward (that is, in the direction toward the plated steel sheet). Furthermore, by using a water-dispersible water-based resin as the binder resin, the vanadium compounds are in a state of being easily aggregated and not dispersed. By containing a vanadium compound having a specific shape in a specific concentration in the colored film layer, the precipitation of the vanadium compound as described above is appropriately realized, and the distribution state of the specific vanadium compound as described above. Is realized.

The vanadium compound contained in the colored film layer according to the present embodiment is a vanadate compound or vanadium oxide. The vanadium compound contained in the colored film layer according to the present embodiment, for example, calcium vanadate, magnesium vanadate, ammonium vanadate, vanadium oxide, sodium vanadate, potassium vanadate, phosphorus vanadate, ammonium metavanadate, Pigments such as potassium metavanadate may be mentioned. Of these vanadium compounds, one vanadium compound may be used alone, or a plurality of vanadium compounds may be used in combination. Among these vanadium compounds, it is particularly preferable to use at least one of calcium vanadate and magnesium vanadate.
In this specification, phosphorus vanadate is classified as a phosphate compound.

Whether or not the vanadium compound is a "vanadate compound" or "vanadium oxide" and whether or not the phosphorus compound is a "phosphate compound" can be analyzed by determining the binding energy from the narrow spectrum of XPS. It can also be confirmed from the infrared absorption peak due to IR or the like.

The average particle size of the vanadium compound is preferably 0.10 μm or more.

When the average particle size of the vanadium compound is less than 0.10 μm, it becomes difficult to properly precipitate the vanadium compound in the treatment liquid for forming the colored film layer, and the vanadium compound distribution state as described above is realized. It is not preferable because it is difficult to do. Further, when the average particle diameter of the vanadium compound is less than 0.10 μm, the vanadium compound is distributed near the interface 140 of the colored coating layer 120 on the zinc alloy plating layer 10 side at a close interval. In that case, the location where the vanadium compound is eluted in the corrosive environment may serve as an entry path for the corrosion factor, which may reduce the barrier properties of the colored coating layer 120 itself, which is not preferable.

The average particle size of the vanadium compound is preferably 10 μm or less. If the average particle diameter of the vanadium compound exceeds 10 μm, it may adversely affect the color tone of the precoated steel sheet according to the present embodiment, which is not preferable. The average particle size of the vanadium compound is more preferably within the range of 1 to 5 μm.

The concentration of the vanadium compound in the colored film layer 120 is 8.0 mass% or less in terms of V amount with respect to the total solid content mass of the colored film layer 120. When the concentration of the vanadium compound exceeds 8.0% by mass, the concentration of the vanadium compound in the colored film layer 120 becomes too large, and it is difficult to realize the above-mentioned distribution state of the vanadium compound. Further, when the concentration of the vanadium compound exceeds 8.0 mass%, the vanadium compound is distributed in the vicinity of the interface 140 on the zinc alloy plating layer 10 side of the colored film layer 120 at a close interval. In that case, the part where the vanadium compound is eluted in the corrosive environment becomes a path for the corrosive agent to enter, and the barrier property of the colored film itself may be deteriorated, which is not preferable.

The concentration of the vanadium compound in the colored film layer 120 is preferably 0.5% by mass or more in terms of V amount with respect to the total solid mass of the colored film layer 120. If the concentration of the vanadium compound is less than 0.5% by mass, the corrosion resistance of the precoated steel sheet according to this embodiment may be insufficient, which is not preferable.
The concentration of the vanadium compound in the colored film layer 120 is more preferably 1.5 to 6.5 mass% in terms of V amount.

Here, the concentration of the vanadium compound in the colored coating layer 120 is substantially the same as the concentration of the vanadium compound contained in the colored coating material used to form the colored coating layer 120.
The concentration of the vanadium compound converted into the amount of V in the colored coating layer 20 is analyzed by FE-EPMA on the cross section of the colored coating layer 20.

(Method of manufacturing precoated steel sheet 200)
Next, a method for manufacturing the precoated steel sheet 200 according to this embodiment will be described.
The method for manufacturing the precoated steel sheet 200 according to the present embodiment includes a step of applying a colored coating material containing a vanadium compound, a color pigment and a binder resin to the steel sheet 1 on which the zinc alloy plating layer 10 is formed. Here, the above-mentioned colored paint is a colored paint treatment liquid used for forming the colored film layer 120.
Except that the colored paint contains a vanadium compound, the method is the same as the method for manufacturing the precoated steel sheet 100, and therefore the description is omitted.

[Third Embodiment]
FIG. 3 is a schematic diagram showing a layer structure of a precoated steel sheet 300 according to the third embodiment of the present invention. The precoated steel sheet 300 is provided on the steel sheet 1, contains 1 to 25% by mass of Al, 0.1 to 13% by mass of Mg, and 0 to 2.0% by mass of Si. A zinc alloy plating layer 10 with the balance being Zn and impurities, and a colored film layer 220 provided on the zinc alloy plating layer 10 and containing a phosphoric acid compound, a vanadium compound, a color pigment, and a binder resin. That is, in the pre-coated steel sheet 300, the point that the colored film layer 220 contains both the phosphoric acid compound and the vanadium compound is different from the first embodiment and the second embodiment.
The description of the points common to the first embodiment and the second embodiment will be omitted.

(Colored film layer 220)
A colored film layer (more specifically, a single colored film layer) 220 is provided on the zinc alloy plating layer 10. The colored film layer 220 according to the present embodiment contains at least a phosphoric acid compound, a vanadium compound, a color pigment, and a binder resin.

Although the colored film layer 220 contains both a phosphoric acid compound and a vanadium compound, the phosphoric acid compound and the vanadium compound in the colored film layer 220 exist independently (that is, in the colored film). This is the same as the existing mode of the phosphoric acid compound in the layer 20 and the existing mode of the vanadium compound in the colored film layer 120).

(Method of manufacturing precoated steel sheet 300)
Next, a method for manufacturing the precoated steel sheet 300 according to this embodiment will be described.
The method for manufacturing the precoated steel sheet 300 according to the present embodiment includes a step of applying a colored coating material containing a phosphoric acid compound, a vanadium compound, a color pigment and a binder resin to the steel sheet 1 on which the zinc alloy plating layer 10 is formed. .. Here, the above-mentioned colored paint is a colored paint treatment liquid used for forming the colored film layer 220.
The description is omitted because it is common to the manufacturing method of the precoated steel sheet 100 and the precoated steel sheet 200, except that the coloring paint contains both the phosphoric acid compound and the vanadium compound.

In the following, the precoated steel sheet according to the present invention will be specifically described with reference to Examples and Comparative Examples. The examples described below are merely examples of the precoated steel sheet according to the present invention, and the precoated steel sheet according to the present invention is not limited to the following examples.

(1) Plated Steel Sheets Five kinds of zinc-plated steel sheets A1 to A5 shown in Table 1 below were prepared. Further, a plated steel sheet was prepared by subjecting these zinc-based plated steel sheets to a chromate-free chemical conversion treatment (CT-E300 / manufactured by Nippon Parkerizing Co., Ltd.) at 60 mg / m ² . The treatment liquid used for the chemical conversion treatment contains a silane coupling agent as its component, and the chemical conversion treatment film layer formed by such chemical conversion treatment functions as an undercoat layer. The presence / absence of chemical conversion treatment is shown in Tables 5-1 to 5-5.

(2) Preparation of Colored Paint A colored paint used for forming the colored film layer was prepared.
As the binder resin, the resins shown in Table 4 below were prepared, and a melamine-based curing agent as a curing agent was added to each resin solution at a solid content of 15% by mass. Furthermore, the rust preventive pigments shown in Table 2 below were prepared as the rust preventive pigments. The average particle size and concentration of the rust preventive pigment contained in the manufactured colored film layer were measured by the following methods.
<Average particle size>
The average particle diameter of the rust preventive pigment was determined by the following method. The steel sheet was observed from the cross-sectional direction, and phosphorus (P) element or vanadium (V) element was mapped by FE-EPMA. At this time, continuous particles of 9 pixels or more are regarded as one particle, and the area Sp thereof is obtained. The particle size of the phosphoric acid compound is determined by φp = 2 × (Sp / π) ^0.5 . An arbitrary width of 200 μm was measured, and the average of the particle diameter φp of the phosphoric acid compound particles or the vanadium compound particles confirmed in that range was obtained.
<Concentration>
The concentration of the rust preventive pigment was measured by analyzing the cross section of the colored film layer by FE-EPMA.
The average particle size and concentration of the rust preventive pigment are shown in Tables 5-1 to 5-5. The concentrations of the rust preventive pigments shown in Tables 5-1 to 5-5 are the concentration converted into the amount of P in the case of the phosphoric acid compound and the concentration converted into the amount of V in the case of the vanadium compound.
The types of color pigments used are shown in Table 3, and the concentrations, average particle diameters and average aspect ratios are shown in Tables 5-1 to 5-5.
The concentration of the color pigment was measured by dissolving the color film and quantitatively analyzing the color pigment element with an ICP emission spectrophotometer. Further, the average particle diameter and the average aspect ratio of the color pigment were measured by the above-mentioned method using FE-EPMA.

(3) Sample preparation The colored coating material prepared as described above was applied to a plated steel sheet using a bar coater so that the dry film thickness was as shown in Tables 5-1 to 5-5, and 60 seconds Then, it was heated so that the maximum reached plate temperature (PMT) was 200 ° C. to form a colored film layer.

(4) Evaluation of sample The performance of each sample manufactured by the above method was evaluated based on the following criteria. In the performance evaluation, VeryGood, Good, and Fair were accepted, and Poor was rejected. The obtained evaluation results are shown in Tables 6-1 to 6-3.

<Distribution of phosphate compound>
The distribution of the phosphoric acid compound in the colored film layer was analyzed by the following method.
Each of the prepared samples was cut into a size of 15 × 20 mm, embedded with resin, the cross section was polished, and FE-EPMA mapping analysis of the colored film layer was performed from the cross section direction at an acceleration voltage of 15 kV and a magnification of 5000 times. At this time, in any region of the colored film layer, the number of first regions having a phosphorus element concentration of 3% or more within the range of 2 μm in the film thickness direction × 200 μm in the plane direction It was confirmed.
Similarly, the values of PA / PB and PA / PC were measured. In addition, when the film thickness is 8 μm or less, slash is described in the item of PA / PB.

<Distribution of vanadium compound>
The distribution of the vanadium compound in the colored film layer was analyzed by the following method.
Each of the prepared samples was cut into a size of 15 × 20 mm, embedded with resin, the cross section was polished, and FE-EPMA mapping analysis of the colored film layer was carried out from the cross section direction at an acceleration voltage of 15 kV and a magnification of 5000 times. At this time, in the region of 1 μm in the film thickness direction from the interface of the colored film layer with the zinc plating layer toward the surface layer side, the second region in which the concentration of vanadium element is 3% or more is the length in the plane direction. The number existing within the range of 200 μm was confirmed.
Similarly, the value of PE / PD was measured.

<Distribution of color pigment>
The distribution of the aluminum pigment in the colored film layer of the sample using the aluminum pigment as the coloring pigment was analyzed by the following method.
Each of the produced samples was cut into a size of 15 × 20 mm, embedded with a resin, the cross section was polished, and an electron microscope observation was performed from the cross section direction at an acceleration voltage of 15 kV and a magnification of 5000 times. It was confirmed whether or not aluminum element was present within a range of 0.5 μm from the interface of the colored film layer on the zinc alloy plating layer side and within a range of 0.5 μm from the outermost layer of the colored film layer. The evaluation criteria are as follows.
In Examples and Comparative Examples in which no aluminum pigment is used, "-" is entered in the evaluation result column of "distribution of color pigment".

Good: Not present in either of the two parts Fair: Present in only one of the two parts Poor: Present in either of the two parts

<Corrosion resistance of processed part>
The sample was extruded by 7 mm by an Erichsen tester, and after 30 cycles of the combined cycle corrosion test specified in JASO-M609, the rust generation area ratio in the processed part was evaluated. The evaluation criteria are as follows.

Very Good: less than 5 mm Good: 5 mm or more, less than 8 mm Fair: 8 mm or more, less than 10 mm Poor: 10 mm or more

<End face corrosion resistance>
A salt spray test (SST) according to JIS Z2371 was carried out for 480 hours, and the rust development distance from the end face was evaluated according to the following criteria.

Very Good: less than 5 mm Good: 5 mm or more and less than 8 mm Fair: 8 mm or more and less than 10 mm Poor: 10 mm or more

<Weather resistance>
A sunshine carbon arc lamp type accelerated weathering test was carried out for 500 hours, and the color difference ΔE on the surface of the colored film before and after the test was evaluated according to the following criteria. The color difference ΔE was measured using a spectrophotometer (manufactured by Suga Test Instruments Co., Ltd., model: SC-T45).

VeryGood: Color difference ΔE is less than 3 Good: Color difference ΔE is 3 or more and less than 4 Fair: Color difference ΔE is 4 or more and less than 6 Poor: Color difference ΔE is 6 or more

<Appearance>
The appearance of the produced sample was evaluated according to the following criteria.

VeryGood: The color tone and surface gloss are uniform, and the base cannot be seen through.
Good: The color tone and surface gloss are slightly non-uniform (a level that can be confirmed by squinting eyes), and the base cannot be seen through.
Fair: The color tone and surface gloss are slightly non-uniform (a level that can be confirmed by squinting), and the base is slightly transparent.
Poor: The color tone and surface gloss are non-uniform (at a level that can be easily confirmed), or the base is visible.

<Workability>
After bending the produced sample by 180 ° in an atmosphere of 20 ° C, the appearance of the folded portion was evaluated according to the following criteria.

VeryGood: There are no defects such as cracks in the colored film layer.
Good: A slight crack is observed in the colored film layer (a level that can be seen by squinting with the sample before processing)
Fair: A slight crack is observed in the colored film layer (a level that can be easily seen when aligned with the sample before processing)
Poor: A crack is observed in the colored film layer (a level that can be easily seen by looking at only the sample after processing).

As is clear from Tables 5-1 to 5-5 and Tables 6-1 to 6-3, the precoated steel sheets corresponding to the examples of the present invention have excellent designability, corrosion resistance, workability, and weather resistance. You can see that it has both. On the other hand, it can be seen that the precoated steel sheet corresponding to the comparative example of the present invention is inferior in any of the designability, corrosion resistance, workability, or weather resistance.

The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various alterations or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

According to each of the above-described embodiments, it is possible to provide a precoated steel sheet having excellent designability, corrosion resistance, workability, and weather resistance while achieving a thin colored film.

1 Steel plate 10 Zinc alloy plating layer 20, 120, 220 Colored film layer 100, 200, 300 Pre-coated steel plate 30 First region 130 Second region 40, 140 (Zinc alloy plating layer and colored film layer) Interface

Claims (20)

1. Steel plate;
   Zinc provided on the steel sheet, containing 1 to 25% by mass of Al, 0.1 to 13% by mass of Mg, and 0 to 2.0% by mass of Si, with the balance being Zn and impurities. Alloy plating layer;
   A colored film layer which is provided on the zinc alloy plating layer and contains at least one of a phosphoric acid compound and a vanadium compound, a color pigment and a binder resin;
   Equipped with
   When the colored film layer contains the phosphoric acid compound,
   The concentration of the phosphoric acid compound is 0.3 to 5.0% by mass in terms of P amount with respect to the total solid mass of the colored film layer;
   When the cross section in the thickness direction of the colored film layer was observed by mapping with FE-EPMA, it was within a range of 2 μm in the thickness direction and 200 μm in the direction parallel to the interface between the colored film layer and the zinc alloy plating layer. , There are 1 to 15 first regions having a phosphorus element concentration of 3% or more,
   When the colored film layer contains the vanadium compound,
   The vanadium compound is a vanadate compound or vanadium oxide;
   The concentration of the vanadium compound is 0.5 to 8.0% by mass in terms of V amount with respect to the total solid mass of the colored film layer;
   When the cross section of the colored film layer in the thickness direction is observed by mapping with FE-EPMA, vanadium is present within a range of 1 μm in the thickness direction from the interface toward the surface side and 200 μm in the direction parallel to the interface. A precoated steel sheet, wherein 1 to 10 second regions having an element concentration of 3% or more are present.
2. The precoated steel sheet according to claim 1, wherein the colored coating layer contains the phosphoric acid compound.
3. When the cross section of the colored film layer in the thickness direction is observed by mapping with FE-EPMA, the phosphorus element concentration is 3% or more within a range of 2 μm in the thickness direction and 40 μm in the direction parallel to the interface. The precoated steel sheet according to claim 1 or 2, wherein 1 to 15 first regions are present.
4. When the cross section of the colored film layer in the thickness direction is observed by mapping with FE-EPMA, the phosphorus element concentration is 3% or more within a range of 2 μm in the thickness direction and 20 μm in the direction parallel to the interface. The precoated steel sheet according to any one of claims 1 to 3, wherein 1 to 15 first regions are present.
5. The precoated steel sheet according to any one of claims 1 to 4, wherein the phosphoric acid compound has an average particle diameter of 0.10 to 10 µm.
6. The layer thickness of the colored film layer is more than 8 μm and 15 μm or less,
   A surface portion within a range of 2 μm from the surface of the colored coating layer in the thickness direction, a central portion within a range of 2 μm in the thickness direction around the layer thickness center of the colored coating layer, and the surface side from the interface. Toward the depth direction, the concentration of the phosphorus element detected in the range of 2 μm × 200 μm is measured using FE-EPMA for each of the deep parts in the range of 2 μm in the thickness direction, and the concentration of the phosphate compound in the surface portion is measured. Is PA, the central phosphate compound concentration is PB, and the deep phosphate compound concentration is PC, PA / PB is 0.5 to 2.0, and PA / PC is 0. The precoated steel sheet according to claim 1, wherein the precoated steel sheet has a thickness of 5 to 2.0.
7. The layer thickness of the colored film layer is 8 μm or less,
   FE-EPMA is used for each of the surface portion within the range of 2 μm in the thickness direction from the surface of the colored film layer and the deep portion within the range of 2 μm in the thickness direction from the interface toward the surface side. Then, the cross section in the thickness direction is observed by mapping, and PA / PC is 0.5 to 2.0 when the phosphate compound concentration in the surface portion is PA and the phosphate compound concentration in the deep portion is PC. The precoated steel sheet according to any one of claims 1 to 6, characterized in that
8. The precoated steel sheet according to any one of claims 1 to 7, wherein the colored coating layer contains the vanadium compound.
9. 9. The precoated steel sheet according to claim 8, wherein the vanadium compound has an average particle diameter of 0.10 to 10 μm.
10. When the layer thickness of the colored coating layer is T, the concentration of vanadium element detected by FE-EPMA in the range of T from the surface of the colored coating layer in the thickness direction and 200 μm in the direction parallel to the interface is PD. When the concentration of vanadium element detected by FE-EPMA is PE in a range of T / 2 in the thickness direction from the center of the thickness of the colored film layer to the interface and 200 μm in the interface direction, The precoated steel sheet according to claim 8 or 9, wherein PE / PD is 1.0 to 5.0.
11. The zinc alloy plating layer,
    4-22% by mass of Al;
    1 to 5 mass% Mg;
    The precoated steel sheet according to any one of claims 8 to 10, characterized by containing.
12. The precoated steel sheet according to any one of claims 8 to 11, wherein the zinc alloy plated layer contains 0.01 to 2.0 mass% of Si.
13. The precoated steel sheet according to any one of claims 8 to 12, wherein the color pigment is an aluminum pigment.
14. The precoated steel sheet according to claim 13, wherein the color pigment has an average particle diameter of 7 to 30 μm and an average aspect ratio of 20 or more.
15. The color pigment is not present in the range of 0.5 μm in the thickness direction from the surface of the colored film layer or in the range of 0.5 μm in the thickness direction from the interface toward the surface. The precoated steel sheet according to claim 13 or 14.
16. The precoated steel sheet according to any one of claims 1 to 15, wherein the binder resin contained in the colored film layer is a polyester resin and an acrylic resin.
17. The precoated steel sheet according to any one of claims 1 to 16, wherein the colored coating layer further contains melamine.
18. The precoated steel sheet according to claim 17, wherein a melamine concentrated layer is provided on the surface of the colored coating layer.
19. The precoated steel sheet according to any one of claims 1 to 18, further comprising a chemical conversion treatment coating layer between the colored coating layer and the zinc alloy plating layer.
20. The precoated steel sheet according to any one of claims 1 to 19, wherein the colored film layer has a layer thickness of 2 µm or more.

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