KR102620034B1 - Zn-based plated steel sheet - Google Patents

Abstract

A steel sheet, a Zn-based plating layer containing Al and Zn disposed on at least one side of the steel sheet, and at least one chromate-free chemical conversion layer disposed on the Zn-based plating layer with an adhesion amount of 0.1 to 15 g/m2 per side. The chemical conversion layer contains a resin and a yellow colorant, and when the appearance is evaluated in the CIE1976 (L*, a*, b*) color space, b* is 2 or more and 60 or less, and b*/a* is -3 or more and 3 or less, 60 degree mirror gloss G _s (60°) is 50 to 200, light is incident on the surface from an angle of 60° from the surface of the chemical conversion layer, and light reflected from the surface is L* obtained when light is received at an angle of 135° from the surface is called L*1, light is incident toward the surface from an angle of 120° from the surface, and light reflected from the surface is received at an angle of 135° from the surface. When L* obtained is L*2, a Zn-based plated steel sheet that satisfies Equation 1 (10≥L*1/L*2≥2).

Description

Zn-based plated steel sheet

The present invention relates to Zn-based plated steel sheets.

The most commonly used plated steel plate with good corrosion resistance is Zn-based plated steel plate. These Zn-based plated steel sheets are used in various manufacturing industries such as automobiles, home appliances, and building materials. Among them, the use of Al-added plating has been increasing in recent years because it has high corrosion resistance.

As an example of a Zn-based plated steel sheet developed for the purpose of improving corrosion resistance, Patent Document 1 describes a hot-dip Zn-Al-Mg-Si plated steel sheet. This plated steel sheet has the characteristic of being excellent in appearance and aesthetics because its appearance shows a pear-shell pattern.

However, conventionally, in order to provide a higher level of rust prevention function to Zn-based plated steel sheets, chromate treatment using hexavalent chromate or the like is widely performed after plating, and further, as necessary, to improve designability, stain resistance, lubricity, etc. In order to provide high value-added functions, coating with organic resin was performed. However, against the backdrop of heightened environmental concerns, there is a movement to refrain from using chromate treatment. Accordingly, there is a surface-treated plated steel sheet described in Patent Document 2 below for the purpose of providing a high level of rust prevention function simply by treating one layer of a resin-based film without performing chromate treatment. It became possible to further improve corrosion resistance by using the film described in Patent Document 2 below.

However, in recent years, there has been a demand for further improvement in the aesthetic appearance of Al-containing Zn-based plated steel sheets. Specifically, the surface of the Zn-based plated steel sheet shows an achromatic pear-shell pattern with a mixture of glossy parts and white parts, but there is a desire to give it a golden appearance in order to have a splendid appearance. .

Japanese Patent No. 3179446 Publication Japanese Patent Publication No. 2006-52462

The present invention was made in consideration of the above circumstances, and its object is to provide a Zn-based plated steel sheet containing Al that has a luxurious golden appearance and improved corrosion resistance.

In order to solve the above problem, the present inventors have studied carefully and found that after reducing the surface roughness of the Zn-based plating layer to give it a metallic luster, adding a yellow colorant to the chemical conversion layer makes it appear gold to the human eye. I figured it out. The present invention adopts the following configuration.

[1] Steel plate,

a Zn-based plating layer disposed on at least one side of the steel sheet and containing 0.05 to 60% by mass of Al and Zn;

At least one chromate-free chemical conversion layer is provided on the Zn-based plating layer and has an adhesion amount of 0.1 to 15 g/m2 per side,

The chemical conversion layer contains a resin and a yellow colorant,

When the appearance is evaluated in the CIE1976 (L*, a*, b*) color space, b* is 2 or more and 60 or less, and b*/a* is -3 or more and 3 or less, as specified in JIS Z 8741:1997. 60 degree mirror gloss G _s (60°) is 50 to 200,

In a plane perpendicular to the surface of the chemical conversion layer, L obtained when light is incident on the surface from an angle of 60° from the surface and light reflected from the surface is received at an angle of 135° from the surface Let * be L*1, and in the plane, L obtained when light is incident toward the surface from an angle of 120° from the surface, and light reflected from the surface is received at an angle of 135° from the surface. When * is L*2, a Zn-based plated steel sheet in which L*1 and L*2 satisfy Equation 1 below.

10≥L*1/L*2≥2...Equation 1

[2] The Zn-based plated steel sheet according to [1], wherein the yellow colorant is an azo-based yellow pigment or an iron oxide-based yellow pigment.

[3] The Zn-based plated steel sheet according to [1] or [2], wherein the content of the yellow colorant in the chemical conversion layer is 0.1 to 10% by mass.

[4] The Zn-based plated steel sheet according to any one of [1] to [3], wherein the L*1 and the L*2 satisfy the following equation 2.

7≥L*1/L*2≥4...Equation 2

[5] The Zn-based plating according to any one of [1] to [4], wherein the chemical conversion layer contains 1 to 20% by mass of metal oxide particles with an average particle diameter of 5 to 200 nm and a refractive index of 1.3 to 2.5. Steel plate.

[6] The Zn-based plated steel sheet according to [5], wherein the metal oxide particles include silica particles.

[7] The Zn-based plated steel sheet according to [5] or [6], wherein the mixing ratio of the yellow colorant and the metal oxide particles in the chemical conversion layer is in the range of 1 to 200.

[8] The Zn-based plated steel sheet according to any one of [1] to [7], wherein the arithmetic mean roughness Ra of the surface of the Zn-based plating layer is 0.1 to 2.0 μm.

[9] Zn according to any one of [1] to [8], wherein the arithmetic mean roughness Ra of the Zn-based plating layer is 0.5 to 2.0 μm, and the arithmetic mean height Sa of the chemical conversion layer is 5 nm to 100 nm. System-plated steel sheet.

[10] The Zn-based plated steel sheet according to any one of [1] to [9], wherein the chemical conversion layer further contains one or both of a Nb compound and a phosphoric acid compound.

[11] Among [1] to [10], wherein the resin in the chemical conversion layer is made of any one or more of polyolefin resin, fluorine resin, acrylic resin, urethane resin, polyester resin, epoxy resin, and phenol resin. The Zn-based plated steel sheet according to any one of the items.

[12] The Zn-based plating layer contains, as an average composition, Al: 4 mass% to 22 mass%, Mg: more than 1 mass% to 10 mass%, and the balance consists of Zn and impurities, [1] to The Zn-based plated steel sheet according to any one of [11].

[13] The Zn-based plated steel sheet according to any one of [1] to [12], wherein the Zn-based plating layer further contains Si: 0.0001 to 2% by mass in an average composition.

[14] [1] to [13], characterized in that the Zn-based plating layer further contains a total of 0.0001 to 2 mass% of one or two or more of Ni, Sb, and Pb in average composition. The Zn-based plated steel sheet according to any one of the above.

[15] When L* is measured in a range of 0.5 mm in diameter centered on each point at five arbitrary points on the plating surface, the maximum value of L* is 1.2 times or more than the minimum value of L*. The Zn-based plated steel sheet according to any one of [1] to [14].

[16] In the Zn-based plating layer, a pattern portion and a non-pattern portion arranged to have a predetermined shape are formed,

The pattern portion and the non-pattern portion each include one or two types of a first region and a second region determined by any of the following determination methods 1 to 5,

Any one of [1] to [15], wherein the absolute value of the difference between the area ratio of the first region in the pattern portion and the area ratio of the first region in the non-pattern portion is 30% or more. Zn-based plated steel sheet described in .

[Decision method 1]

Virtual grid lines are drawn at 0.5 mm intervals on the surface of the Zn-based plating layer, and in a plurality of areas divided by the virtual grid lines, a measurement area is within a circle with a diameter of 0.5 mm centered on the center of gravity of each area. Let it be A, and measure the L* value in each measurement area A. When 50 points are randomly selected from the obtained L* values and the average of 50 points of the obtained L* values is taken as the standard L* value, the area where the L* value is higher than the standard L* value is called the first area, the reference L* value. The area below the value is called the second area.

[Decision Method 2]

Virtual grid lines are drawn at 0.5 mm intervals on the surface of the Zn-based plating layer, and in a plurality of areas divided by the virtual grid lines, a measurement area is within a circle with a diameter of 0.5 mm centered on the center of gravity of each area. Let's call it A, the L* value in each measurement area A is measured, the area where the L* value is 45 or more is called the first area, and the area where the L* value is less than 45 is called the second area.

[Decision Method 3]

Virtual grid lines are drawn at intervals of 0.5 mm on the surface of the Zn-based plating layer, and the arithmetic mean surface roughness Sa is measured in each of the plurality of regions defined by the virtual grid lines. The region where the obtained Sa is 1 μm or more is called the first region, and the region where the obtained Sa is less than 1 μm is called the second region.

[Decision Method 4]

By drawing virtual grid lines at 1 mm or 10 mm intervals on the surface of the Zn-based plating layer, and applying The diffraction peak intensity I ₀₀₀₂ of the (0002) plane of the Zn phase and the diffraction peak intensity I _10-11 of the (10-11) plane of the Zn phase were measured, and their intensity ratio (I ₀₀₀₂ /I _10-11 ) was called the orientation ratio. do. The region where the orientation ratio is 3.5 or more is called a first region, and the region where the orientation ratio is less than 3.5 is called a second region.

[Decision Method 5]

Virtual grid lines are drawn at 1 mm intervals on the surface of the Zn-based plating layer, and then, for each of the plurality of regions demarcated by the virtual grid lines, a circle S is drawn centered on the center of gravity point G of each region. The diameter R of the circle S is set so that the total length of the surface border of the Zn-based plating layer contained within the circle S is 10 mm. The average value of the largest diameter Rmax and the smallest diameter Rmin among the diameters R of circles S in a plurality of areas is called the standard diameter Rave, and the region having circles S whose diameter R is less than the standard diameter Rave is called the first region, and the diameter R is called the first region. The area having a circle S larger than or equal to the reference diameter Rave is called the second area.

[17] The Zn-based plated steel sheet according to any one of [1] to [16], which has any one of Co, Fe, and Ni on the surface of the Zn-based plating layer.

According to the present invention, it is possible to provide a Zn-based plated steel sheet containing Al that has a luxurious golden appearance and improved corrosion resistance.

The present inventors added a yellow colorant to the chemical conversion layer to color the chemical conversion layer yellow, and reduced the surface roughness of the Zn-based plating layer to give it a metallic luster, so that the appearance of the Zn-based plating layer was visible to the human eye. I found out that it appears gold. However, if the yellow color is too dark, it becomes difficult to see the metallic appearance on the surface of the plating layer and the entire thing appears yellow. In addition, in the case where incident light is reflected from the surface of the plating layer and when the incident light is reflected from the surface of the chemical conversion layer, Zn It was found that the way the color of the base plating layer appears changed, and it no longer appears gold. Therefore, after further examination, the b* value and b*/a* when evaluated in the CIE1976 (L*, a*, b*) color space and the 60-degree mirror gloss G _s (60 °) is controlled to be in a predetermined range, and light is incident toward the surface of the chemical conversion layer from an angle of 60° from the surface of the chemical conversion layer in a plane perpendicular to the surface of the chemical conversion layer, and the chemical conversion layer L* obtained when the light reflected from the surface of the chemical conversion layer is received at an angle of 135° from the surface of the chemical conversion layer is referred to as L*1, and in the above plane, the chemical conversion layer is formed at an angle of 120° from the surface of the chemical conversion layer. When light is incident toward the surface of and the light reflected from the surface of the chemical conversion layer is received at an angle of 135° from the surface of the chemical conversion layer, L*1 and L are It was found that by controlling *2 to satisfy 10≥L*1/L*2≥2 (Equation 1), a golden appearance was achieved. In addition, by controlling the relationship between b* value and b*/a*, 60-degree mirror gloss G _s (60°), and L*1 and L*2, arbitrary shapes such as letters can be displayed on the surface of the plating layer. In this case, we also found that it became easier to see arbitrary shapes. As a result, there was no need to include gold fine particles or gold-colored metal fine particles in the chemical conversion layer, and it was possible to obtain a golden appearance at low cost.

That is, the Zn-based plated steel sheet of the embodiment of the present invention includes a steel sheet, a Zn-based plating layer containing 0.05 to 60% by mass of Al and Zn disposed on at least one side of the steel plate, and disposed on the Zn-based plating layer. At least one chromate-free chemical conversion layer is provided at an adhesion amount of 0.1 to 15 g/m2 per side, the chemical conversion layer contains resin and a yellow colorant, and has an appearance that meets CIE1976 (L*, a*, b*). ) When evaluated in the color space, b* is 2 or more and 60 or less, b*/a* is -10 or more and -3 or less, and the 60-degree mirror gloss G _s (60°) specified in JIS Z 8741:1997 is 50 to 200, and in a plane perpendicular to the surface of the converted layer, light is incident toward the surface of the converted layer from an angle of 60° from the surface of the converted layer, and light is reflected from the surface of the converted layer. L* obtained when light is received at an angle of 135° from the surface of the converted layer is referred to as L*1, and in the above plane, light is incident toward the surface of the converted layer from an angle of 120° from the surface of the converted layer. And, when the L* obtained when the light reflected from the surface of the converted layer is received at an angle of 135° from the surface of the converted layer, and L*2 is taken, L*1 and L*2 are 10≥L* It is a Zn-based plated steel sheet that satisfies 1/L*2≥2 (Equation 1).

In addition, in the Zn-based plated steel sheet of this embodiment, the yellow colorant is preferably an azo-based yellow pigment or an iron oxide-based yellow pigment.

In addition, in the Zn-based plated steel sheet of this embodiment, the content of the yellow colorant in the chemical conversion layer is preferably 0.1 to 10% by mass.

Additionally, in the Zn-based plated steel sheet of this embodiment, it is preferable that L*1 and L*2 satisfy 7≥L*1/L*2≥4 (Formula 2).

In addition, in the Zn-based plated steel sheet of this embodiment, it is preferable that the chemical conversion layer contains 1 to 20% by mass of metal oxide particles with an average particle diameter of 5 to 200 nm and a refractive index of 1.3 to 2.5.

Additionally, in the Zn-based plated steel sheet of this embodiment, it is preferable that the metal oxide particles contain silica particles.

Moreover, in the Zn-based plated steel sheet of this embodiment, it is preferable that the mixing ratio of the yellow colorant and the metal oxide particles is 1 to 200.

In addition, in the Zn-based plated steel sheet of this embodiment, it is preferable that the arithmetic mean roughness Ra of the surface of the Zn-based plated layer is 0.1 to 2.0 μm.

In addition, in the Zn-based plated steel sheet of this embodiment, it is preferable that the arithmetic mean roughness Ra of the Zn-based plating layer is 0.5 to 2.0 μm, and the arithmetic mean height Sa of the chemical conversion layer is 5 nm to 100 nm.

[Zn-based plated steel sheet]

Hereinafter, the Zn-based plated steel sheet of this embodiment will be described.

There are no particular restrictions on the material of the steel sheet that becomes the base of the Zn-based plating layer. As a material, general steel, etc. can be used without any particular restrictions, and Al killed steel or some high alloy steels can also be applied, and there are no special restrictions on the shape. The Zn-based plating layer according to this embodiment is formed by applying the hot-dip plating method described later to the steel sheet.

[Zn-based plating layer]

Next, the chemical composition of the Zn-based plating layer will be explained.

The Zn-based plating layer is a Zn-based plating layer containing 0.05 to 60% by mass of Al and Zn. In addition, the Zn-based plating layer of the present embodiment preferably contains, as an average composition, 4 to 22% by mass of Al and 1 to 10% by mass of Mg, with the remainder containing Zn and impurities. More preferably, the average composition contains Al: 4 to 22% by mass, Mg: more than 1% by mass and 10% by mass or less, and the balance consists of Zn and impurities.

By containing 0.05% by mass or more of Al, the corrosion resistance of the Zn-based plating layer can be improved, and by setting the Al content to 60% by mass or less, the amount of Zn contained in the Zn-based plating layer is relatively increased, thereby improving sacrificial corrosion resistance. It becomes possible to secure In addition, by containing Al: 4 to 22% by mass, Mg: 1 to 10% by mass, balance: Zn and impurities, corrosion resistance and sacrificial corrosion resistance can be further improved. The Zn-based plating layer may contain 40% by mass or more of Zn.

Additionally, the Zn-based plating layer may contain Si: 0.001 to 2% by mass as an average composition. In addition, the Zn-based plating layer has an average composition of Ni, Ti, Zr, Sr, Fe, Sb, Pb, Sn, Ca, Co, Mn, P, B, Bi, Cr, Sc, Y, REM, Hf, C You may contain 0.001 to 2% by mass of any one or two or more types in total.

Next, the reason for limiting the composition of the Zn-based plating layer, which contains 4 to 22% by mass of Al and more than 1% by mass but not more than 10% by mass of Mg, with the remainder being Zn and impurities, will be explained.

The Al content is in the range of 4 to 22 mass%. Al may be contained to ensure corrosion resistance. If the Al content in the Zn-based plating layer is 4% by mass or more, the effect of improving corrosion resistance becomes higher. When the Al content is 22% by mass or less, the effect of improving corrosion resistance is easily secured while maintaining the golden appearance. From the viewpoint of corrosion resistance, it is preferably 5 to 18 mass%. More preferably, it is 6 to 16 mass%.

The Mg content is in the range of more than 1% by mass and 10% by mass or less. Mg may be contained to improve corrosion resistance. If the Mg content in the Zn-based plating layer is more than 1% by mass, the effect of improving corrosion resistance becomes higher. When the Mg content is 10% by mass or less, the generation of dross in the plating bath is suppressed, making it easy to stably manufacture a Zn-based plated steel sheet. From the viewpoint of the balance between corrosion resistance and dross generation, the Mg content is preferably 1.5 to 6 mass%. More preferably, the Mg content is in the range of 2 to 5 mass%.

The Zn-based plating layer containing Mg is prone to turning black, but on the other hand, when a chemical conversion layer containing a yellow colorant is placed on the plating layer, the color depth is created by turning black, so there is an advantage of creating a more luxurious golden color. there is.

The content of Al and Mg may each be 0%. That is, the Zn-based plating layer of the Zn-based plated steel sheet of this embodiment is not limited to the Zn-Al-Mg-based hot-dip plating layer, and may be a Zn-Al-based hot-dip plating layer.

Additionally, the Zn-based plating layer may contain Si in the range of 0.0001 to 2% by mass.

Since Si may improve the adhesion of the Zn-based plating layer, Si may be contained. Since the effect of improving adhesion is exhibited by containing Si in an amount of 0.0001% by mass or more, preferably 0.001% or more, more preferably 0.01% or more, it is preferable to contain 0.0001% by mass or more of Si. On the other hand, since the effect of improving plating adhesion is saturated even if Si is contained in excess of 2% by mass, the Si content is set to 2% by mass or less. From the viewpoint of plating adhesion, the range may be 0.001 to 1% by mass, and the Si content may be within the range of 0.01 to 0.8% by mass.

Among the Zn-based plating layers, the average composition is one of Ni, Ti, Zr, Sr, Fe, Sb, Pb, Sn, Ca, Co, Mn, P, B, Bi, Cr, Sc, Y, REM, Hf, C It may contain 0.001 to 2 mass% of the species or two or more species in total. By containing these elements, corrosion resistance can be further improved. REM is one or two or more types of rare earth elements with atomic numbers 57 to 71 in the periodic table.

The remainder of the chemical components of the Zn-based plating layer are zinc and impurities. Impurities include those that are inevitably included in zinc and other metals, and those that are included as a result of the steel dissolving in the plating bath.

Additionally, the average composition of the Zn-based plating layer can be measured by the following method. First, the surface layer coating film is removed with a coating film remover that does not erode the plating (e.g., Neo River SP-751, manufactured by Sansai Kako Co., Ltd.), and then an inhibitor containing an inhibitor (e.g., Hibiron, manufactured by Sugimura Chemical Co., Ltd.) is applied. It can be determined by dissolving the Zn-based plating layer in hydrochloric acid and subjecting the obtained solution to inductively coupled plasma (ICP) emission spectroscopic analysis. When removing the surface coating film, it is preferable to also remove the chemical conversion treatment layer.

Next, the structure of the Zn-based plating layer will be explained. The structure described below is the structure in which the Zn-based plating layer contains, as an average composition, 4 to 22% by mass of Al, 1 to 10% by mass of Mg, and 0 to 2% by mass of Si.

The Zn-based plating layer containing Al, Mg, and Zn contains [Al phase] and [three-way eutectic structure of Al/Zn/MgZn ₂ ]. [Al/Zn/MgZn ₂ ternary eutectic structure] has a form containing [Al phase]. Additionally, the [Al/Zn/MgZn ₂ ternary eutectic structure] may contain [MgZn ₂ phase] or [Zn phase]. In addition, when Si is added, [Mg ₂ Si phase] may be contained in the substance of [Al/Zn/MgZn ₂ ternary eutectic structure].

Here, [3-way eutectic structure of Al/Zn/MgZn ₂ ] is a 3-way eutectic structure of an Al phase, a Zn phase, and an intermetallic compound MgZn ₂ phase, and the Al phase forming this 3-way eutectic structure is, for example, It corresponds to the “Al” phase” (Al solid solution dissolving Zn and containing a small amount of Mg) at high temperature in the ternary equilibrium phase diagram of Al-Zn-Mg. The Al” phase at this high temperature is at room temperature. In general, it appears separated into a fine Al phase and a fine Zn phase. In addition, the Zn phase in the ternary eutectic structure is a Zn solid solution in which a small amount of Al is dissolved and, in some cases, a small amount of Mg is dissolved. The MgZn ₂ phase in the ternary eutectic structure is an intermetallic compound phase that exists in the vicinity of Zn: about 84 mass% in the Zn-Mg binary equilibrium phase diagram. As far as the phase diagram is concerned, it is thought that each phase does not contain any other added elements, or even if they do, it is only in trace amounts. However, since the amounts cannot be clearly distinguished by ordinary analysis, the ternary process structure consisting of these three phases is In this specification, it is referred to as [ternary eutectic structure of Al/Zn/MgZn ₂ ].

In addition, [Al phase] is a phase that appears as an island phase with clear boundaries in the body of the above-mentioned ternary eutectic structure, and this is, for example, "Al" at high temperature in the ternary equilibrium phase diagram of Al-Zn-Mg. It corresponds to the "Al solid solution that dissolves Zn and contains a small amount of Mg." The amount of Zn or Mg dissolved in the Al" phase at this high temperature varies depending on the Al or Mg concentration of the plating bath. The Al" phase at this high temperature is usually separated into a fine Al phase and a fine Zn phase at room temperature, but the shape of the island phase visible at room temperature can be considered as maintaining the shape of the Al" phase at high temperature. As far as the phase diagram is concerned, it is thought that no other added elements are dissolved in solid solution in this phase, or even if dissolved, it is only in trace amounts, but since it cannot be clearly distinguished by ordinary analysis, it is derived from the "Al" phase at this high temperature and is not morphologically The phase that maintains the shape of the "Al" phase is referred to as [Al phase] in this specification. This [Al phase] can be clearly distinguished from the Al phase forming the above-mentioned ternary eutectic structure in microscopic observation.

In addition, the [Zn phase] is a phase that appears as an island phase with clear boundaries in the body of the above-mentioned ternary eutectic structure, and may actually dissolve a small amount of Al and a small amount of Mg. As far as the phase diagram is concerned, it is thought that no other added elements are dissolved in solid solution in this phase, or that even if dissolved, it is only a trace amount. This [Zn phase] can be clearly distinguished from the Zn phase forming the above-mentioned ternary eutectic structure in microscopic observation. The Zn-based plating layer of the present invention may contain [Zn phase] depending on the manufacturing conditions, but in experiments, little effect on improving the corrosion resistance of the machined part was seen, so even if [Zn phase] is included in the plating layer, there is no particular problem. does not exist.

In addition, the [MgZn ₂ phase] is a phase that appears as an island phase with clear boundaries in the matrix of the above-mentioned ternary eutectic structure, and some actually contain a small amount of Al as a solid solution. As far as the phase diagram is concerned, it is thought that no other added elements are dissolved in solid solution in this phase, or that even if dissolved, it is only a trace amount. This [MgZn ₂ phase] can be clearly distinguished from the MgZn ₂ phase forming the above-mentioned ternary eutectic structure in microscopic observation. [MgZn _two- phase] may not be contained in the Zn-based plating layer of the present invention depending on the manufacturing conditions, but is included in the Zn-based plating layer under most manufacturing conditions.

In addition, [Mg ₂ Si phase] is a phase that has clear boundaries and appears as islands in the solidified structure of the Zn-based plating layer when Si is added. As far as the phase diagram is concerned, it is thought that Zn, Al, and other added elements are not dissolved in solid solution, or even if dissolved, it is only in very small amounts. This [Mg ₂ Si phase] can be clearly distinguished from the Zn-based plating layer during microscopic observation.

Additionally, it is preferable to have any one of Co, Fe, and Ni elements on the surface of the Zn-based plating layer. Co, Fe, and Ni are attached to the surface of the Zn-based plating layer by performing Co treatment, Fe treatment, or Ni treatment after formation of the Zn-based plating layer. By having these elements on the surface of the Zn-based plating layer, blackening resistance can be improved.

Additionally, the arithmetic mean roughness Ra of the surface of the Zn-based plating layer is preferably 0.1 to 2.0 μm. Additionally, the arithmetic mean roughness Ra may be 0.5 to 2.0 μm. When Ra is 2.0㎛ or less, the metallic luster of the Zn-based plating layer is improved, resulting in a more beautiful gold color. Additionally, since the effect is saturated even if Ra is set to less than 0.1 μm, the lower limit may be set to 0.1 μm or more. The arithmetic average roughness Ra of the Zn-based plating layer is measured and calculated using a 3D laser microscope (manufactured by Keyence Corporation). Using a 20x standard lens, the height Z is measured at a measurement interval of 50 μm. It is desirable to set the measurement score to 100 points. The measurement points are set as 100 points, and the 100 points of the obtained height Z are used as heights Z1 to height Z100 to calculate the arithmetic average roughness Ra from the following equation 3. Zave is the average of height Z of 100 points.

Ra=1/100×Σ[x=1→100] (|Height Zx-Zave|) ... Equation 3

[Formulated treatment layer]

Next, the chemical conversion layer is explained. The chemical conversion layer of this embodiment contains resin and a yellow colorant. The chemical conversion layer of this embodiment is a film obtained by applying an aqueous composition containing a resin and a yellow colorant to a Zn-based plating layer formed on a steel sheet and drying it.

(profit)

The resin contained in the chemical conversion layer is preferably made of any one or more of polyolefin resin, fluorine resin, acrylic resin, urethane resin, polyester resin, epoxy resin, and phenol resin. These resins may be water-soluble resins, or may be resins that are inherently water-insoluble but can be microdispersed in water, such as emulsions or suspensions (water-dispersible resins).

There is no particular limitation on the polyolefin resin, and for example, ethylene and unsaturated carboxylic acids such as methacrylic acid, acrylic acid, maleic acid, fumaric acid, itaconic acid, and crotonic acid are radically polymerized at high temperature and pressure, followed by ammonia or amine compounds. , KOH, NaOH, LiOH, etc., or those obtained by neutralizing the metal compounds with ammonia or amine compounds containing the metal compounds and water oxidation.

The fluororesin is not particularly limited, and examples include homopolymers or copolymers of fluoroolefins. In the case of a copolymer, a copolymer of a fluoroolefin and a fluorine-containing monomer other than the fluoroolefin and/or a monomer that does not have a fluorine atom can be mentioned.

The acrylic resin is not particularly limited and includes, for example, unsaturated monomers such as styrene, alkyl (meth)acrylates, (meth)acrylic acid, hydroxyalkyl (meth)acrylates, and alkoxysilane (meth)acrylates. and those obtained by radical polymerization in an aqueous solution using a polymerization initiator. The polymerization initiator is not particularly limited, and for example, persulfates such as potassium persulfate and ammonium persulfate, azo compounds such as azobiscyanovaleric acid, and azobisisobutyronitrile, etc. can be used.

The urethane resin is not particularly limited and includes, for example, ethylene glycol, propylene glycol, diethylene glycol, 1,6-hexanediol, neopentyl glycol, triethylene glycol, bisphenol hydroxypropyl ether, glycerin, trimethylolethane, and those obtained by reacting polyhydric alcohols such as trimethylolpropane with diisocyanate compounds such as hexamethylene diisocyanate, isophorone diisocyanate, and tolylene diisocyanate, chain extending them with diamine, etc., and water oxidation.

The polyester resin is not particularly limited and includes, for example, ethylene glycol, propylene glycol, diethylene glycol, 1,6-hexanediol, neopentyl glycol, triethylene glycol, bisphenol hydroxypropyl ether, glycerin, and trimethylolethane. , polyhydric alcohols such as trimethylolpropane, and polybasic acids such as phthalic anhydride, isophthalic acid, terephthalic acid, succinic anhydride, adipic acid, sebacic acid, maleic anhydride, itaconic acid, fumaric acid, and hymic anhydride are dehydrated and condensed into ammonia. and those obtained by neutralizing with an amine compound or the like and oxidizing in water.

The epoxy resin is not particularly limited and includes, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, resorcin type epoxy resin, hydrogenated bisphenol A type epoxy resin, hydrogenated bisphenol F type epoxy resin, and resorcin type. It is obtained by reacting an epoxy resin such as an epoxy resin or a novolak-type epoxy resin with an amine compound such as diethanolamine or N-methylethanolamine and neutralizing it with an organic or inorganic acid. In the presence of the epoxy resin, a high acid value acrylic resin is radicalized. After polymerization, it is neutralized with ammonia or an amine compound, and then obtained by water oxidation.

There is no particular limitation on the phenol resin, and examples include methylolated phenol resin obtained by addition reaction of aromatics such as phenol, resorcinol, cresol, bisphenol A, and paraxylylene dimethyl ether with formaldehyde in the presence of a reaction catalyst, etc. and those obtained by reacting the phenol resin with amine compounds such as diethanolamine and N-methylethanolamine and neutralizing it with an organic acid or inorganic acid.

The resin is preferably contained in the chemical conversion layer at a rate of 20% by mass or more. By setting the resin content to 20% by mass or more, the chemical conversion layer itself does not become brittle, and the Zn-based plating layer can be stably coated. In addition, the chemical conversion layer may contain components other than the resin, such as silica particles, Nb compounds, and phosphoric acid compounds, along with the resin and yellow colorant, and the resin content may be the remainder of these components. Additionally, there is an advantage that corrosion resistance is ensured by setting the resin content to 99.9% by mass or less.

(yellow colorant)

The chemical conversion layer contains a yellow colorant. By containing a yellow colorant in the chemical conversion layer, the chemical conversion layer is colored yellow, and in addition to the metallic luster of the Zn-based plating layer, the appearance of the Zn-based plating layer becomes gold. In order to obtain this effect, it is preferable that the content of the yellow colorant in the chemical conversion layer is in the range of 0.1 to 10 mass%. By setting the content of the yellow colorant in the chemical conversion treatment layer to 0.1% by mass or more, the appearance of the Zn-based plating layer can be made golden. Additionally, by setting the content of the yellow colorant to 10% by mass or less, the metallic luster of the Zn-based plating layer is not shielded, and a gold color can be displayed. Here, the appearance in the present invention means the appearance of the Zn-based plated steel sheet when viewed from the side of the Zn-based plating layer disposed on at least one side of the steel sheet.

As the yellow colorant, a yellow pigment is preferred. Yellow pigment has superior weather resistance compared to yellow dye. Additionally, when forming the chemical conversion layer, the chemical conversion layer may be water cooled in some cases, but the yellow dye may be eluted from the chemical conversion layer into the cooling water, so a yellow pigment that is not likely to be eluted is preferred. As the yellow pigment, an iron oxide-based yellow pigment or an azo-based yellow pigment is preferable. These pigments are preferable because they have superior weather resistance.

As the yellow pigment, generally known and well-known ones can be used, examples of which include iron oxide-based yellow pigments. As the iron oxide-based yellow pigment, generally known ones such as Pigment Yellow42 can be used. For example, iron oxide pigments sold from Lanxess Co., Ltd., Ferro Corporation, Dainichi Seika Kogyo Co., Ltd., etc. can be used. You can. Additionally, yellow lead or the like may be used as a yellow colorant. Additionally, as the azo-based yellow pigment, you may use an arylide acetoacetate-based monoazo pigment, an arylide acetoacetate-based disazo pigment, a condensed azo pigment, or a benzimidazolone-based monoazo pigment.

When the pigment in the chemical conversion layer is an iron oxide-based yellow pigment, the content is measured by the following method. First, a thin film sample of the chemical conversion layer is produced by a microtome method so that a cross section perpendicular to the rolling direction of the Zn-based plated steel sheet of this embodiment can be observed. A 200 kV field emission transmission electron microscope (FE-TEM) was used in an area of 20 ㎛ At least 5 areas are observed at a magnification of 100,000 times, and elemental mapping is performed using an energy dispersive X-ray analyzer (EDS or EDX). From the element mapping results, the area ratio of the region where Fe exists is obtained. Here, by the same method as above, the area ratio of the region where Fe is present in a plurality of comparative samples having a chemical conversion treatment layer with a known pigment content is determined, and a calibration curve is prepared in advance from the relationship with the pigment content. Be prepared. Using the calibration curve, the pigment content of the target sample is determined.

(metal oxide particles)

Here, the yellow colorant colors the chemical conversion layer yellow and makes the appearance of the Zn-based plating layer appear gold. However, if the yellow colorant is included in the chemical conversion layer, the corrosion resistance of the chemical conversion layer may decrease. Therefore, in order to prevent a decrease in the corrosion resistance of the chemical conversion layer, the chemical conversion layer of this embodiment may contain metal oxide particles. As metal oxide particles, those having an average particle diameter in the range of 5 to 200 nm are suitable. It is difficult to obtain metal oxide particles with an average particle size of less than 5 nm, and the chemical conversion layer containing metal oxide particles with an average particle size of less than 5 nm is actually difficult to manufacture and manufacture. Therefore, the average particle size of the metal oxide particle size is difficult to manufacture. The lower limit is 5 nm or more. Additionally, when the average particle diameter of the metal oxide particles is 200 nm or less, the chemical conversion layer does not become cloudy and the metallic appearance of the Zn-based plating layer is not damaged. By containing metal oxide particles of an appropriate average particle size, light is slightly reflected diffusely in the chemical conversion layer, and fluctuations in light reflection can be suppressed through effects such as microscopic flaws on the plating surface becoming less noticeable. , It can give the golden color a sense of luxury. Therefore, the average particle size of the metal oxide particles is more preferably 5 to 50 nm.

The metal oxide particles preferably have a refractive index of 1.3 to 2.5 for the reason that the diffuse reflection of light in the chemical conversion layer is appropriately controlled. The refractive index is measured by isolating the metal oxide particles from the chemical conversion layer and using a commercially available refractive index measuring device.

It is preferable to contain the metal oxide particles in a ratio of 1 to 20% by mass in the chemical conversion layer. By setting the content of metal oxide particles to 1% by mass or more, the effect of improving corrosion resistance is obtained. Additionally, by setting the content of the metal oxide particles to 20% by mass or less, the chemical conversion layer itself does not become brittle, and the Zn-based plating layer can be stably coated. The content of the metal oxide particles is more preferably 3 to 7% by mass in the chemical conversion layer from the viewpoint of appropriately controlling diffuse reflection of light.

In general, inorganic pigments such as metal oxide particles have a small particle size, and therefore may exist in the chemical conversion layer in the form of secondary particles having a particle size larger than the primary particle size. The particle size of these secondary particles (particles in which the inorganic pigment is aggregated) is hereinafter referred to as “secondary particle size.” The metal oxide particles in this embodiment may be a mixture of primary particles and secondary particles, and even if primary particles and secondary particles are mixed, the average particle diameter may be in the range of 5 to 200 nm. .

The average particle diameter of the metal oxide particles in the chemical conversion layer is measured by the following method. First, a thin film sample of the chemical conversion layer is produced by a microtome method so that a cross section perpendicular to the rolling direction of the steel sheet of the present invention can be observed. A 200 kV field emission transmission electron microscope (FE-TEM) was used in an area of 20 ㎛ Observe at least 5 areas at a magnification of 100,000x using . Using the following equation 4, the equivalent circle diameter of all silica particles in the observation area is calculated, this equivalent circle diameter is set as the particle size of each metal oxide particle, and the average particle size is obtained by averaging.

Equivalent circle diameter = 2√(S/π) … Equation 4

However, S is the area of the metal oxide particle, and π is the circumference.

The content of metal oxide particles in the chemical conversion layer is measured by the following method. First, separately from the target sample, a plurality of comparative samples having a chemical conversion layer with a known content of metal oxide particles were prepared, their surfaces were measured by a fluorescence X-ray device, and the detection intensity of the obtained metal element and the metal oxide were measured. A calibration curve is drawn based on the relationship between particle content. Next, the target sample is measured by a fluorescence

In addition, in the present invention, since the average particle diameter in the state of water-dispersed metal oxide particles before being dispersed in the paint is maintained even in the chemical conversion layer, that value may be used as the average particle diameter.

It is desirable to optimize the mixing ratio of the metal oxide particles and the yellow colorant. That is, it is preferable that the mixing ratio (mass ratio (metal oxide particles/yellow colorant)) of the metal oxide particles and the yellow colorant in the chemical conversion layer is in the range of 1 to 200. By setting the mixing ratio to 1 or more, the corrosion resistance of the chemical conversion layer can be improved even when the chemical conversion layer contains a yellow colorant. Additionally, by setting the mixing ratio to 200 or less, deterioration of the appearance of the Zn-based plating layer can be prevented.

It is more preferable that the metal oxide particles contain silica particles from the viewpoint of ensuring a balance between corrosion resistance and a luxurious golden appearance. Additionally, as metal oxide particles, titania particles, alumina particles, zirconia particles, etc., which have the same effect as silica particles, may be contained.

The chemical conversion layer may further contain either or both an Nb compound and a phosphoric acid compound. When an Nb compound or a phosphoric acid compound is contained, the corrosion resistance of the Zn-based plating layer improves.

As the Nb compound, conventionally known niobium-containing compounds can be used, and examples include niobium oxide, niobic acid and its salts, fluoroniobate salts, and fluoroxoniobate salts. Among them, it is preferable to use niobium oxide from the viewpoint of improving corrosion resistance.

Examples of phosphoric acid compounds include phosphoric acids and salts thereof such as orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, triphosphoric acid, and tetraphosphoric acid; Phosphonic acids and their salt; Organic phosphoric acids such as phytic acid and their salts can be mentioned. There are no particular restrictions on the cationic species of the salt, and examples include Cu, Co, Fe, Mn, Sn, V, Mg, Ba, Al, Ca, Sr, Nb, Y, Ni, and Zn. These may be used individually, or two or more types may be used together.

The Nb compound and the phosphoric acid compound may be contained in a total ratio of 0.5 to 30% by mass in the chemical conversion layer. If the content of the Nb compound or phosphoric acid compound is 0.5% by mass or more, the effect of improving corrosion resistance is obtained, and if the content of the Nb compound or phosphoric acid compound is 30% by mass or less, the chemical conversion treatment layer does not become brittle and stably covers the Zn-based plating layer. can do.

Additionally, the adhesion amount of the chemical conversion layer per side of the Zn-based plating layer is 0.1 to 15 g/m2. If the adhesion amount is 0.1 g/m 2 or more, the adhesion amount of the chemical conversion treatment layer becomes sufficient, the appearance of the Zn-based plating layer can be made golden, and the corrosion resistance of the Zn-based plating layer can be improved. Additionally, if the adhesion amount is 15 g/m2 or less, even if the chemical conversion layer contains a yellow colorant, reflection of light on the surface of the chemical conversion layer decreases, the metallic luster on the surface of the Zn-based plating layer is not shielded, and the Zn-based plating layer The exterior can be made gold. A more preferable adhesion amount is 0.2 to 2 g/m2. In addition, corresponding to the above-mentioned adhesion amount, it is more preferable that the thickness of the chemical conversion layer is 0.07 to 15 μm.

The chemical conversion layer may further contain at least one crosslinking agent selected from the group consisting of a silane coupling agent, a crosslinkable zirconium compound, and a crosslinkable titanium compound. These may be used individually, or two or more types may be used together.

When at least one crosslinking agent selected from the group consisting of the silane coupling agent, crosslinkable zirconium compound, and crosslinkable titanium compound is contained, the adhesion between the Zn-based plating layer and the chemical conversion treatment layer is further improved.

The silane coupling agent is not particularly limited and includes, for example, vinyltrimethoxysilane, vinyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyl ethoxysilane, N-[2- (Vinylbenzylamino)ethyl]-3-aminopropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltrimethoxysilane, 2-(3,4 -Epoxycyclohexyl)ethyltrimethoxysilane, N-β(aminoethyl)γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltriethoxysilane, N-β-( Aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, and γ-mercaptopropyltritrimethoxysilane. The said silane coupling agent may be used individually, or 2 or more types may be used together.

The crosslinkable zirconium compound is not particularly limited as long as it is a zirconium-containing compound having a plurality of functional groups capable of reacting with a carboxyl group or a hydroxyl group, but a compound soluble in water or an organic solvent is preferable, and a water-soluble zirconium compound is more preferable. do. Examples of such compounds include zirconylammonium carbonate.

The crosslinkable titanium compound is not particularly limited as long as it is a titanium-containing compound having a plurality of functional groups capable of reacting with a carboxyl group or a hydroxyl group. Dipropoxybis(triethanolaminato)titanium, dipropoxy·bis(diethanolaminato) )Titanium, propoxy·tris(diethanolaminato)titanium, dibutoxy·bis(triethanolaminato)titanium, dibutoxy·bis(diethanolaminato)titanium, dipropoxy·bis(acetylacetonato)titanium, Dibutoxy·bis(lactato)titanium, dihydroxy·bis(lactato)titanium monoammonium salt, dihydroxy·bis(lactato)titanium diammonium salt, propanedioxytitanium bis(ethylacetoacetate), oxotitanium Bis(monoammonium oxalate), isopropyltri(N-amideethyl·aminoethyl)titanate, etc. can be mentioned. The said crosslinking agent may be used individually, or 2 or more types may be used together.

The at least one crosslinking agent selected from the group consisting of the silane coupling agent, crosslinkable zirconium compound, and crosslinkable titanium compound is preferably contained in an amount of 0.1 to 50% by mass based on 100% by mass of the solid content of the resin. If the content of this crosslinking agent is less than 0.1% by mass, the effect of improving adhesion may not be obtained, and if the content of this crosslinking agent exceeds 50% by mass, the stability of the aqueous composition may decrease.

The chemical conversion layer may further contain at least one crosslinking agent selected from the group consisting of amino resins, polyisocyanate compounds, blocks thereof, epoxy compounds, and carbodiimide compounds. These crosslinking agents may be used individually, or two or more types may be used in combination.

When at least one crosslinking agent selected from the group consisting of the amino resin, polyisocyanate compound, block body thereof, epoxy compound, and carbodiimide compound is contained, the crosslinking density increases, the barrier property of the chemical conversion layer is improved, and corrosion resistance is improved. further improve.

The amino resin is not particularly limited, and examples include melamine resin, benzoguanamine resin, urea resin, and glycoluril resin.

The polyisocyanate compound is not particularly limited, and examples include hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, and tolylene diisocyanate. In addition, the blocked product is a blocked product of the polyisocyanate compound.

The epoxy compound is not particularly limited as long as it is a compound having a plurality of oxirane rings, and examples include diglycidyl adipic acid, diglycidyl phthalate, diglycidyl terephthalate, and sorbitan polyglycidyl ester. Diyl ether, pentaerythritol polyglycidyl ether, glycerin polyglycidyl ether, trimethylpropane polyglycidyl ether, neopentyl glycol polyglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl. Ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, 2,2-bis-(4'-glycidyloxyphenyl)propane, tris(2,3-epoxypropyl)isocyanurate , bisphenol A diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, etc.

As the carbodiimide compound, for example, an isocyanate-terminated polycarbodiimide is synthesized by a condensation reaction involving decarbonization of diisocyanate compounds such as aromatic diisocyanate, aliphatic diisocyanate, and cycloaliphatic diisocyanate. and compounds to which a hydrophilic segment having a functional group reactive with a group is added.

At least one crosslinking agent selected from the group consisting of the amino resin, polyisocyanate compound, block body thereof, epoxy compound, and carbodiimide compound is preferably contained in an amount of 0.1 to 50% by mass based on 100% by mass of solid content of the resin. If the content is less than 0.1% by mass, the effect of improving corrosion resistance may not be obtained because the content is small, and if the amount exceeds 50% by mass, the chemical conversion treatment layer may become brittle and corrosion resistance may decrease.

The chemical conversion layer preferably contains at least one selected from the group consisting of a vanadium compound, a tungsten compound, and a molybdenum compound. These may be used individually, or two or more types may be used together.

The corrosion resistance of the chemical conversion layer is improved by containing at least one type selected from the group consisting of the vanadium compound, tungsten compound, and molybdenum compound.

The vanadium compound is not particularly limited, and conventionally known vanadium-containing compounds can be used, for example, vanadic acid, ammonium vanadate, vanadate such as sodium vanadate, phosphorus such as phosphovanadic acid and ammonium phosphovanadate, etc. Vanadate salts, etc. can be mentioned.

The tungsten compound is not particularly limited, and conventionally known tungsten-containing compounds can be used, for example, tungstic acid, ammonium tungstate, tungstate salts such as sodium tungstate, phosphorus such as tungstic acid and ammonium phosphotungstate. Tungstate salts, etc. can be mentioned.

The molybdenum compound is not particularly limited, and conventionally known molybdenum-containing compounds can be used, such as molybdate salts. The molybdate salt is not limited in its skeleton or degree of condensation, and examples include orthomolybdate salt, paramolybdate salt, and metamolybdate salt. In addition, it includes all salts such as single salts and double salts, and examples of double salts include molybdate phosphate.

It is preferable to contain at least 1 type selected from the group consisting of the vanadium compound, tungsten compound, and molybdenum compound in an amount of 0.01 to 20% by mass based on 100% by mass of the solid content of the resin. When the content of at least one selected from the group consisting of the vanadium compound, tungsten compound and molybdenum compound is less than 0.01% by mass, the effect of improving corrosion resistance may not be obtained, and the vanadium compound, tungsten compound and molybdenum compound may not be obtained. If the content of at least one type selected from the group exceeds 20% by mass, the chemical conversion treatment layer may become brittle and corrosion resistance may decrease.

The chemical conversion layer may further contain a polyphenol compound.

By containing the polyphenol compound, the corrosion resistance of the chemical conversion treatment layer and the adhesion of the post-coating film when used for post-coating purposes, etc. are improved.

The polyphenol compound is a compound having two or more phenolic hydroxyl groups bonded to a benzene ring or a condensate thereof. Examples of compounds having two or more phenolic hydroxyl groups bonded to the benzene ring include gallic acid, pyrogallol, and catechol. The condensate of a compound having two or more phenolic hydroxyl groups bonded to a benzene ring is not particularly limited, and examples include polyphenol compounds widely distributed in the plant world, commonly called tannic acid. Tannic acid is a general term for aromatic compounds with a complex structure having a large number of phenolic hydroxyl groups widely distributed in the plant kingdom. The tannic acid may be hydrolyzable tannic acid or condensed tannic acid. The tannic acid is not particularly limited, and includes, for example, hamameli tannin, persimmon tannin, tea tannin, gallbladder tannin, molasses tannin, myrobalan tannin, DBDB tannin, algarovilla tannin, Valonia tannin, catechin tannin, etc. I can hear it.

Examples of the tannic acid include commercially available tannic acid extract A, B tannic acid, N tannic acid, commercial use tannic acid, purified tannic acid, Hi tannic acid, and F tannic acid. ”, “Koku Tannic Acid” (all manufactured by Dainippon Seiyaku Co., Ltd.), “Tannic Acid: AL” (manufactured by Fuji Chemical Industry Co., Ltd.), etc. can also be used. The above polyphenol compounds may be used individually, or two or more types may be used together.

The polyphenol compound is preferably contained in an amount of 0.1 to 50% by mass based on 100% by mass of the solid content of the resin. When the content of the polyphenol compound is less than 0.1% by mass, the effect of improving corrosion resistance may not be obtained, and when the content of the polyphenol compound exceeds 50% by mass, the stability of the aqueous composition may decrease.

The chemical conversion layer may further contain a solid lubricant.

Containing the solid lubricant improves the lubricity of the chemical conversion layer, and is effective in improving processability during press molding, preventing scratches from occurring due to molds or handling, and preventing wear and scratches when transporting molded products or coils.

The solid lubricant is not particularly limited and includes known lubricants such as fluorine-based, hydrocarbon-based, fatty acid amide-based, ester-based, alcohol-based, metal soap-based and inorganic-based lubricants. As a criterion for selecting a lubricating additive to improve processability, selecting a substance present on the surface of the chemical conversion layer rather than one dispersed in the chemical conversion layer in which the added lubricant is formed reduces the friction between the surface of the molded workpiece and the mold. This is necessary to maximize the lubrication effect. That is, when the lubricant is dispersed in the chemical conversion layer formed into a film, the surface friction coefficient is high, so the chemical conversion layer is easily destroyed, and the powdered material is peeled off and deposited, resulting in poor appearance and deterioration of processability called a powdering phenomenon. As a substance present on the surface of the chemical conversion layer, one that is not compatible with the resin and has low surface energy is selected.

The solid lubricant is preferably contained in an amount of 0.1 to 30% by mass based on 100% by mass of the solid content of the resin. If the solid lubricant content is less than 0.1%, the effect of improving processability is small, and if the solid lubricant content exceeds 30%, corrosion resistance may decrease.

The method of coating the aqueous composition used to form the chemical conversion layer is to apply the aqueous composition to the surface of the Zn-based plating layer to form a film. The coating method is not particularly limited, and commonly used roll coat, air spray, airless spray, dipping, etc. can be appropriately employed. In order to increase the curability of the chemical conversion layer, it is preferable to heat the object to be coated in advance or to heat-dry the object to be coated after coating. The heat drying method may be any of hot air, induction heating, near infrared, or far infrared, or may be used in combination. The heating temperature of the object to be coated is 50 to 250°C, preferably 70 to 220°C. If the heating temperature is less than 50°C, the evaporation rate of moisture is slow and sufficient film forming properties are not obtained, so corrosion resistance may decrease. On the other hand, if the heating temperature exceeds 250°C, thermal decomposition of the resin occurs, corrosion resistance decreases, and the appearance deteriorates due to yellowing or the like. When heat drying after coating, the drying time is preferably 1 second to 5 minutes. Additionally, in the case of heat drying, water cooling is preferable when manufacturing on a continuous line from the viewpoint of productivity.

The arithmetic mean height Sa of the chemical conversion layer is preferably 5 nm to 100 nm. The permeability of the chemical conversion layer can be maintained by the arithmetic mean height Sa of the chemical conversion layer being 100 nm or less. On the other hand, if Sa exceeds 100 nm, there is a risk that the permeability of the chemical conversion layer may decrease. The arithmetic mean height Sa of the chemical conversion layer is measured and calculated by the following method. Gold is deposited on the surface of a sample cut to a predetermined size from a Zn-based plated steel sheet to a thickness of 50 nm, the gold-deposited sample is embedded in resin, and the cross section of the sample in the plate thickness direction is exposed. The cross section of the sample is observed at a magnification of 5000 times using a scanning electron microscope, and the roughness of the gold deposition layer when observed from the direction perpendicular to the cross section is calculated to obtain the arithmetic mean height Sa of the chemical conversion layer. Gold deposition is carried out to clarify the boundary between the chemical conversion layer and the resin, and since the thickness of the gold deposition layer is negligible compared to the chemical conversion layer, the arithmetic average height of the gold deposition layer is calculated as that of the surface of the chemical conversion layer. It can be replaced by the arithmetic mean height Sa.

[Exterior]

Next, the appearance of the Zn-based plated steel sheet of this embodiment will be described. The appearance of the Zn-based plated steel sheet of this embodiment is evaluated in the CIE1976 (L*, a*, b*) color space when b* is 2 or more and 60 or less, and b*/a* is -3 or more and 3 or less. and the 60-degree mirror gloss G _s (60°) specified in JIS Z 8741:1997 is 50 to 200. Additionally, in a plane orthogonal to the surface of the converted layer, light is incident toward the surface of the converted layer from an angle of 60° from the surface of the converted layer, and the light reflected from the surface of the converted layer is directed to the converted layer. Let L*1 obtained when light is received at an angle of 135° from the surface of When L*2 is L*2 obtained when the light reflected from the surface of the treatment layer is received at an angle of 135° from the surface of the chemical conversion layer, L*1 and L*2 satisfy Equation 1 below. .

10≥L*1/L*2≥2...Equation 1

The reasons for these limitations will be explained below.

The more light is reflected from the surface of the Zn-based plating layer, the higher the light luminance, and if it is low, the reflection from the chemical treatment layer increases. Therefore, unless b* and b*/a* are specified, the metallic luster of the Zn-based plating layer cannot be recognized. Therefore, the appearance of the Zn-based plating layer does not appear gold. Therefore, in order to obtain a synergistic effect of the Zn-based plating layer showing metallic luster and the chemical conversion layer colored yellow by a yellow colorant, b* and b*/a* and 60-degree mirror gloss G _s (60°) are used. It has been found that it is necessary to set a predetermined range and ensure that L*1 and L*2 satisfy 10≥L*1/L*2≥2 (Equation 1).

When b* is less than 2 when evaluated in the CIE1976 (L*, a*, b*) color space, the color almost disappears and gold color does not appear. Additionally, if b* exceeds 60, the color becomes dark, the metallic appearance is not sufficiently recognized, and the gold color is not displayed. Therefore, b* should be in the range of 2 to 60. From the viewpoint of maintaining the golden color, the lower limit of b* is preferably 3.5, and more preferably 5. The upper limit of b* is preferably 40 and more preferably 30 from the viewpoint of maintaining the metallic appearance.

If b*/a* when evaluated in the CIE1976 (L*, a*, b*) color space is less than -3, the yellowish red color becomes darker and gold color does not appear. Additionally, when b*/a* exceeds 3, the green color becomes darker and gold color does not appear. Therefore, b*/a* is in the range of -3 to 3.

In addition, when the 60-degree mirror gloss G _s (60°) is less than 50, the appearance of the Zn-based plated steel sheet approaches white, the metallic luster of the Zn-based plated layer is damaged, and the appearance of the Zn-based plated layer no longer appears gold. . Additionally, when the 60-degree mirror gloss G _s (60°) exceeds 200, reflection from the surface of the chemical conversion layer becomes stronger, and the appearance of the Zn-based plating layer becomes yellow and no longer appears gold.

In addition, when L*1/L*2 is 10 or less, golden color development is improved. When L*1/L*2 is 2 or more, there is an effect of maintaining the metallic appearance. The lower limit of L*1/L*2 is more preferably 4 from the viewpoint of maintaining a more beautiful metallic appearance. The upper limit of L*1/L*2 is more preferably 7 from the viewpoint of developing a luxurious golden color.

In addition, the appearance of the Zn-based plated steel sheet of this embodiment is measured by measuring L* in the range of 0.5 mm in diameter centered on each point at five arbitrary points on the plating surface excluding the surface layer coating film including the chemical conversion treatment layer. When doing so, it is preferable that the maximum value of L* (L*max) is 1.2 times or more than the minimum value of L* (L*min).

When the maximum value of L* (L*max) is 1.2 times or more than the minimum value of L* (L*min), local fluctuations in the golden color occur, resulting in the effect of creating a deep sense of luxury.

Micro-surface spectral color difference for five randomly selected points on a plating surface from which the surface layer coating film including the chemical conversion layer was removed using a coating film remover that does not erode the plating (e.g., Neo River SP-751 manufactured by Sansai Kako Co., Ltd.) L* at each point is measured using a meter (VSS 7700, manufactured by Nippon Denshoku Kogyo Co., Ltd.). Among the measured L*, the largest one is called L*max and the smallest one is called L*min.

Additionally, a pattern portion and a non-pattern portion arranged to have a predetermined shape may be formed on the surface of the Zn-based plating layer according to the present embodiment.

The pattern portion is preferably arranged to have any one of straight lines, curved lines, dots, figures, numbers, symbols, shapes, or letters, or a combination of two or more of these. Additionally, the non-pattern portion is an area other than the pattern portion. Additionally, the shape of the pattern portion is acceptable as long as it can be recognized as a whole even if some parts are missing, such as missing dots. Additionally, the non-pattern portion may have a shape that forms the border and border of the pattern portion.

When any one of straight lines, curves, dots, figures, numbers, symbols, shapes, or letters, or a combination of two or more of these, is arranged on the surface of the Zn-based plating layer, these areas are called pattern areas. And the area other than that can be called a non-pattern area. The boundary between the pattern portion and the non-pattern portion can be recognized with the naked eye. The boundary between the pattern portion and the non-pattern portion may be grasped from an enlarged image using an optical microscope, a magnifying glass, or the like.

The pattern portion may be formed to a size that allows the presence of the pattern portion to be determined with the naked eye, under a magnifying glass, or under a microscope. Additionally, the non-patterned portion is an area that occupies most of the Zn-based plating layer (the surface of the Zn-based plating layer), and the patterned portion may be disposed within the non-patterned portion.

The pattern portion is arranged in a predetermined shape within the non-pattern portion. Specifically, the pattern portion, in the non-pattern portion, is arranged to be any one of straight portions, curved portions, figures, dot portions, figures, numbers, symbols, shapes, or letters, or a combination of two or more of these. It is done. By adjusting the shape of the pattern portion, any one of straight lines, curved lines, figures, dots, figures, numbers, symbols, patterns, or letters, or a combination of two or more of these, appears on the surface of the Zn-based plating layer. . For example, on the surface of the Zn-based plating layer, a character string consisting of a pattern portion, a string of numbers, a symbol, a mark, a line, a design, or a combination thereof appear. This shape is a shape formed intentionally or artificially by a manufacturing method described later, and is not formed naturally.

In this way, the pattern portion and the non-pattern portion are regions formed on the surface of the Zn-based plating layer, and the pattern portion and the non-pattern portion each include one or both of the first region and the second region.

The pattern portion and the non-pattern portion each include one or two types of a first region and a second region determined by any of the following determination methods 1 to 5, and the area ratio of the first region in the pattern portion is The absolute value of the difference between the area ratios of the first region in the non-pattern portion is 30% or more. When the difference between the area ratio of the first region in the pattern portion and the area ratio of the first region in the non-pattern portion is 30% or more in absolute value, the pattern portion and the non-pattern portion can be distinguished. If the difference in area ratio is less than 30%, the difference between the area ratio of the first region in the pattern portion and the area ratio of the first region in the non-pattern portion is small, and the appearance of the pattern portion and the non-pattern portion have a similar appearance. This makes it difficult to identify the pattern portion. The larger the difference in area ratio, the better. It is more preferable that the difference in area ratio is 40% or more, and even more preferably, the difference in area ratio is 60% or more.

That is, in the pattern portion, the area ratio of each of the first area and the second area can be obtained. And, when the area fraction of the first region exceeds 70%, the pattern portion appears relatively white or a color close to white compared to when the area fraction of the first region is 70% or less. When the area fraction of the first region is 30% or more and 70% or less, the pattern portion appears in a pear-shell pattern. Additionally, when the area fraction of the first region is less than 30%, the pattern portion appears to have a metallic luster. In this way, the appearance of the pattern portion depends on the area fraction of the first region.

On the other hand, even in the non-pattern portion, the area ratio of each of the first area and the second area can be obtained. Like the patterned portion, the appearance of the non-patterned portion depends on the area fraction of the first region.

And, when the difference between the area ratio of the first region in the pattern portion and the area ratio of the first region in the non-pattern portion is 30% or more in absolute value, the pattern portion and the non-pattern portion can be distinguished. If the difference in area ratio is less than 30%, the difference between the area ratio of the first region in the pattern portion and the area ratio of the first region in the non-pattern portion is small, and the appearance of the pattern portion and the non-pattern portion have a similar appearance. This makes it difficult to identify the pattern portion. The larger the difference in area ratio, the better. It is more preferably 40% or more, and even more preferably 60% or more.

[Decision method 1]

In decision method 1, virtual grid lines are drawn at 0.5 mm intervals on the surface of the Zn-based plating layer, and in a plurality of areas divided by the virtual grid lines, each area is within a circle with a diameter of 0.5 mm centered on the center of gravity of each area. is called measurement area A, and the L* value in each measurement area A is measured. When 50 points are arbitrarily selected from among the obtained L* values and the average of 50 points of the obtained L* values is taken as the reference L* value, the area where the L* value is higher than the reference L* value is called the first area, reference L The area below the * value is called the second area.

[Decision Method 2]

In decision method 2, virtual grid lines are drawn at 0.5 mm intervals on the surface of the Zn-based plating layer, and in a plurality of areas divided by the virtual grid lines, each area is within a circle with a diameter of 0.5 mm centered on the center of gravity of each area. is called measurement area A, the L* value in each measurement area A is measured, the area where the L* value is 45 or more is called the first area, and the area where the L* value is less than 45 is called the second area. .

[Decision Method 3]

In determination method 3, virtual grid lines are drawn at 0.5 mm intervals on the surface of the Zn-based plating layer, and the arithmetic average surface roughness Sa is measured in each of the plurality of regions defined by the virtual grid lines. The region where the obtained Sa is 1 μm or more is called the first region, and the region where the obtained Sa is less than 1 μm is called the second region. The arithmetic mean surface roughness Sa is measured using a 3D laser microscope (manufactured by Keyence Corporation). In this embodiment, a 20x standard lens is used to measure the height Z within a plurality of regions divided by virtual grid lines at a measurement interval of 50 μm. When measuring on a grid, 100 measurement points are obtained within the area. Using the obtained height Z of 100 points as height Z1 to height Z100, the arithmetic mean surface roughness Sa is calculated by the following equation 5. Zave is the average of height Z of 100 points.

Sa=1/100×Σ[x=1→100] (|Height Zx-Zave|) ... Equation 5

[Decision Method 4]

In determination method 4, virtual grid lines are drawn at 1 mm or 10 mm intervals on the surface of the Zn-based plating layer, and X-rays are incident on a plurality of regions defined by the virtual grid lines. For each region, the diffraction peak intensity I ₀₀₀₂ of the (0002) plane of the Zn phase and the diffraction peak intensity I _10-11 of the (10-11) plane of the Zn phase were measured, and these intensity ratios (I ₀₀₀₂ /I _10-11 ) were calculated. It is called the orientation ratio. The region where the orientation ratio is 3.5 or more is called the first region, and the region where the orientation ratio is less than 3.5 is called the second region.

[Decision Method 5]

In decision method 5, virtual grid lines are drawn at 1 mm intervals on the surface of the Zn-based plating layer, and then, for each of the plurality of regions divided by the virtual grid lines, a circle S is drawn centered on the center of gravity point G of each region. The diameter R of the circle S is set so that the total length of the surface boundary of the Zn-based plating layer contained inside the circle S is 10 mm. The average value of the largest diameter Rmax and the smallest diameter Rmin among the diameters R of circles S in a plurality of areas is called the standard diameter Rave, and the region having circles S whose diameter R is less than the standard diameter Rave is called the first region, and the diameter R is called the first region. The area with the circle S larger than the reference diameter Rave is called the second area.

The formation of the patterned portion and the non-patterned portion specified by determination method 1 or 2 is performed after forming the Zn-based plating layer. The patterned portion and the non-patterned portion are formed by depositing an acidic solution on the surface of the Zn-based plating layer at a temperature of 60 to 200°C. More specifically, an acidic solution may be prepared and this may be adhered to the surface of the Zn-based plating layer using a printing means. As the printing means, general printing methods such as printing methods using various plates (gravure printing, flexo printing, offset printing, silk printing, etc.) and inkjet methods can be applied.

At the location where the acidic solution adheres, the very surface of the Zn-based plating layer is dissolved, and the surface of the Zn-based plating layer changes from the plated state. As a result, the appearance of the location where the acidic solution has adhered changes compared to the location where the acidic solution has not adhered. In this way, it is assumed that the difference between the area ratio of the first region in the pattern portion and the area ratio of the first region in the non-pattern portion increases, making it possible to distinguish the pattern portion from the non-pattern portion.

The adhesion range of the acidic solution may be an area corresponding to the patterned part or an area corresponding to the non-patterned part.

As the acidic solution, it is preferable to use an inorganic acid such as hydrochloric acid, nitric acid, or sulfuric acid. Additionally, the acid concentration in the acidic solution is preferably 0.1 to 10 mass%. The temperature of the steel sheet when the acid solution is attached is preferably 60 to 200°C, preferably 50 to 80°C. By adjusting the type and concentration of the acidic solution, it is possible to adjust the area fraction of the first region and the second region on the surface of the Zn-based plating layer at the location where the acidic solution adheres.

If the surface temperature of the Zn-based plating layer when attaching the acidic solution is less than 60°C, it is not preferable because it requires time to form the patterned portion or the non-patterned portion, and if the surface temperature of the Zn-based plating layer exceeds 200°C, the acidic This is undesirable because the solution volatilizes immediately, making it impossible to form a patterned portion or a non-patterned portion.

After adhesion of the acidic solution, it is necessary to wash with water within 1 to 10 seconds.

Next, formation of the patterned portion and the non-patterned portion specified by determination method 3 is performed after forming the Zn-based plating layer. The pattern portion and the non-pattern portion are formed by pressing a roll with partially increased surface roughness against the surface of the Zn-based plating layer and transferring the surface shape of the roll to the Zn-based plating layer. For example, in order to form a pattern portion on the surface of the Zn-based plating layer, the roughness of the portion corresponding to the pattern portion on the roll surface is increased relative to other portions to form a pattern portion containing many first regions with large surface roughness. formation is possible. Alternatively, a roll may be used in which the illuminance of the portion corresponding to the pattern portion is reduced relative to other portions. The roughness (arithmetic average surface roughness, Sa (μm)) of the roll surface is set to be in the range of 0.6 to 3.0 μm at the point where the roughness is increased, and preferably 1.2 to 3.0 μm. The range of illuminance at the location where the illuminance is lowered is 0.05 to 1.0 μm, preferably 0.05 to 0.8 μm. Transfer may be performed when the surface temperature of the Zn-based plating layer is in the range of 100 to 300°C. Additionally, the difference between the illuminance at the location where the illuminance is increased and the illuminance at the location where the illuminance is lowered is set to be greater than 0.2 μm, preferably 0.3 μm or more, in terms of arithmetic mean surface roughness Sa. As the difference in illuminance decreases, it becomes difficult to distinguish between patterned portions and non-patterned portions.

The formation of the patterned portion and the non-patterned portion specified by the determination method 4 is performed by locally spraying a non-oxidizing gas onto the molten metal using a gas nozzle on the steel sheet immediately after being pulled from the hot-dip plating bath. As a non-oxidizing gas, nitrogen or argon may be used. Although the optimal temperature range varies depending on the composition, non-oxidizing gas can be sprayed when the temperature of the molten metal is in the range of (final solidification temperature -5)°C to (final solidification temperature +5)°C. Additionally, the temperature of the non-oxidizing gas is set to be lower than the final solidification temperature.

When the Zn-based plating layer is in the above temperature range, the cooling rate of the molten metal increases at the location where the non-oxidizing gas is sprayed, and as a result, the orientation ratio of the Zn-based plating layer after solidification increases. On the other hand, at locations where the non-oxidizing gas is not sprayed, the cooling rate of the molten metal decreases, and as a result, the orientation ratio of the Zn-based plating layer after solidification decreases. Therefore, by adjusting the injection range of the non-oxidizing gas, it is possible to intentionally or arbitrarily adjust the appearance points of the region with a high orientation rate and the region with a low orientation rate.

As a result, the shapes of the pattern portion and the non-pattern portion can be arbitrarily adjusted, and it is also possible to distinguish the pattern portion and the non-pattern portion. Since the lower the temperature of the injected gas, the higher the orientation rate, the orientation rate can be adjusted depending on the temperature of the injected gas. The gas temperature is preferably lower than the final solidification temperature, and for example, the gas temperature may be adjusted to 25 to 250°C.

The formation of the patterned portion and the non-patterned portion specified by Determination Method 5 involves locally applying a non-oxidizing gas higher than the final solidification temperature of plating to the molten metal using a gas nozzle on the steel sheet immediately after being pulled from the hot-dip galvanizing bath. This is done by spraying. As a non-oxidizing gas, nitrogen or argon may be used. Although the optimal temperature range varies depending on the composition, non-oxidizing gas can be sprayed when the temperature of the molten metal is in the range of (final solidification temperature -5)°C to (final solidification temperature +5)°C. Additionally, it is desirable that the temperature of the non-oxidizing gas is equal to or higher than the final solidification temperature. For example, in a plating composition of Al: 11% and Mg: 3%, when the temperature of the molten metal is 330 to 340°C, a non-oxidizing gas whose gas temperature is equal to or higher than the final solidification temperature may be sprayed.

In the vicinity where the non-oxidizing gas is sprayed, the cooling rate of the molten metal decreases, and as a result, boundaries or grain boundaries appearing on the surface become coarse. Therefore, by adjusting the injection amount and range of the non-oxidizing gas, it is possible to arbitrarily adjust the size of the boundary or grain boundary that appears on the surface.

By setting the absolute value of the difference between the area ratio of the first region in the pattern portion and the area ratio of the first region in the non-pattern portion to 30% or more, the pattern portion and the non-pattern portion can be distinguished. Since the formed pattern portion and non-pattern portion are not formed by printing or painting, durability is high. Additionally, since the patterned portion and the non-patterned portion are not formed by printing or painting, there is no effect on the corrosion resistance of the Zn-based plating layer. Therefore, the Zn-based plated steel sheet of this embodiment has excellent corrosion resistance.

In the Zn-based plating layer in which the pattern portion is formed, it is possible to provide a Zn-based plated steel sheet with high durability of the pattern portion and suitable plating characteristics such as corrosion resistance. Since the pattern portion can be shaped intentionally or artificially, the pattern portion is arranged to have any one of straight lines, curved lines, dots, figures, numbers, symbols, shapes, or letters, or a combination of two or more of these. can do. As a result, various designs, trademarks, and other identification marks can be displayed on the surface of the Zn-based plating layer without printing or painting, thereby improving the source identification and design of the steel sheet. Additionally, the pattern section can provide information necessary for process management, inventory management, etc., or arbitrary information requested by the consumer, to the hot-dip galvanized steel sheet. This can also contribute to improving the productivity of Zn-based plated steel sheets.

And, according to the Zn-based plated steel sheet of this embodiment, a chemical conversion treatment layer containing a yellow colorant is formed on the Zn-based plating layer on which the pattern portion is formed, so the visibility of the pattern portion can be further improved.

Example

Hereinafter, the present invention will be described in detail through examples.

First, a cold rolled steel sheet with a thickness of 1 mm was prepared, this was immersed in a plating bath of each composition, and the plating adhesion amount was adjusted to 80 g/m2 on one side by N ₂ wiping. Table 1 shows the plating composition of the obtained Zn-based plated steel sheet.

In addition, when forming a pattern portion on the Zn-based plating layer, the pattern was further performed by the following method. The pattern portion and the non-pattern portion each include one or two types of a first region and a second region determined by any of determination methods 1 to 5, and the area ratio of the first region in the pattern portion is The absolute value of the difference between the area ratios of the first region in the non-pattern portion was 40%.

<Pattern 1>

A hydrochloric acid solution was attached to a rubber plate having convex portions or concave portions in a square pattern with a side of 50 mm, and the rubber plate was pressed against the surface of the Zn-based plating layer, thereby causing the acid solution to adhere to the steel plate and forming a square-shaped pattern portion. . The surface temperature of the Zn-based plating layer of the hot-dip galvanized steel sheet when the acidic solution was attached was set to be in the range of 60 to 200°C. In addition, locations other than the square-shaped pattern portion were referred to as non-pattern portions. Then, based on determination method 2, virtual grid lines are drawn at 0.5 mm intervals on the surface of the Zn-based plating layer, and each of the plurality of regions demarcated by the virtual grid lines has a diameter of 0.5 centered on the center of gravity of each region. The inside of the mm circle is called measurement area A, the L* value in each measurement area A is measured, the area where the L* value is 45 or more is called the first area, and the area where the L* value is less than 45 is called the first area. It was divided into 2 areas. This Zn-based plated steel sheet was used as Example 59.

<Pattern 2>

With the surface temperature of the Zn-based plating layer set at 100 to 300°C, a roll having a square pattern with a side of 50 mm was pressed against the surface of the Zn-based plating layer to form a pattern portion. The locations of the square pattern were referred to as pattern portions, and locations other than the square pattern were referred to as non-pattern portions. Based on determination method 3, virtual grid lines were drawn at 0.5 mm intervals on the surface of the Zn-based plating layer, and the arithmetic mean surface roughness Sa was measured in each of the plurality of regions defined by the virtual grid lines. The region where the obtained Sa was 1 μm or more was designated as the first region, and the region where Sa was less than 1 μm was designated as the second region. This Zn-based plated steel sheet was used as Example 60.

<Pattern 3>

When the steel sheet is pulled out of the plating bath, when the temperature of the molten metal is in the range of (final solidification temperature -5)°C to (final solidification temperature +5)°C, a type of non-oxidizing gas is added to the molten metal on the surface of the steel sheet. Nitrogen gas was sprayed through a gas nozzle. The gas temperature was below the final solidification temperature. Afterwards, it was cooled to completely solidify the molten metal. The spray range of nitrogen gas was controlled to form a square pattern with a side of 50 mm. The locations of the square pattern were referred to as pattern portions, and locations other than the square pattern were referred to as non-pattern portions. Based on determination method 4, virtual grid lines are drawn at 1 mm or 10 mm intervals on the surface of the Zn-based plating layer, and X-rays are incident on a plurality of regions defined by the virtual grid lines. , for each of the above regions, the diffraction peak intensity I ₀₀₀₂ of the (0002) plane of the Zn phase and the diffraction peak intensity I _10-11 of the (10-11) plane of the Zn phase were measured, and their intensity ratio (I ₀₀₀₂ /I _10-11 ) is called the orientation ratio. The region where the orientation ratio was 3.5 or more was called the first region, and the region where the orientation ratio was less than 3.5 was called the second region. This Zn-based plated steel sheet was used as Example 61.

<Pattern 4>

When the steel sheet is pulled out of the plating bath, when the temperature of the molten metal is in the range of (final solidification temperature -5)°C to (final solidification temperature +5)°C, a type of non-oxidizing gas is added to the molten metal on the surface of the steel sheet. Nitrogen gas was injected from a gas nozzle in a heated state. The nitrogen gas injection conditions were as shown in Table 1. It was above the final solidification temperature. Afterwards, it was cooled to completely solidify the molten metal. The spray range of nitrogen gas was controlled to form a square pattern with one side of 50 mm. The locations of the square pattern were referred to as pattern portions, and locations other than the square pattern were referred to as non-pattern portions. Then, based on determination method 5, virtual grid lines were drawn at 1 mm intervals on the surface of the Zn-based plating layer, and then, for each of the plurality of regions demarcated by the virtual grid lines, a circle S centered on the center of gravity point G of each region was drawn. I drew it. The diameter R of the circle S was set so that the total length of the surface boundary of the Zn-based plating layer contained inside the circle S was 10 mm. The average value of the largest diameter Rmax and the smallest diameter Rmin among the diameters R of circles S in a plurality of areas is called the standard diameter Rave, and the region having circles S whose diameter R is less than the standard diameter Rave is called the first region, and the diameter R is called the first region. The area with the circle S larger than the reference diameter Rave was referred to as the second area. This Zn-based plated steel sheet was used as Example 62.

Next, as necessary, the Zn-based plated steel sheet was immersed in a Co sulfate solution, a Fe sulfate solution, or a Ni sulfate solution to deposit 1 mg/m 2 of Co, Fe, or Ni on the surface of the Zn-based plating layer. The composition of the Zn plating layer is shown in Table 3A and Table 3B.

Next, various water-based resins (urethane resin, polyester resin, olefin resin, epoxy resin, acrylic resin, phenol resin, fluororesin), metal oxide particles, and niobium oxide are applied to the surface of the Zn-based plating layer of the manufactured Zn-based plated steel sheet. , an aqueous composition containing sodium phosphate and a yellow colorant (azo-based yellow pigment, iron oxide-based yellow pigment) was applied with a bar coater to a dry adhesion amount of 1.5 g/m2, and dried in a hot air drying furnace at a plate temperature of 150°C. By water cooling, a chromate-free chemical conversion treatment layer was formed. The contents of niobium oxide and sodium phosphate were each 5%. Additionally, as metal oxide particles, silica (SiO ₂ ), titania (TiO ₂ ), alumina (Al ₂ O ₃ ), and zirconia (ZrO ₂ ) were used. Additionally, Table 2 shows details of the yellow colorant. Tables 4A to 5B show the composition of the chemical conversion layer, etc. In the “Nb oxide” column of Tables 5A and 5B, the case where niobium oxide was contained was designated as “○”, and the case where niobium oxide was not contained was designated as “×”. In addition, in the column of “Na phosphate”, the case where sodium phosphate was contained was set to “○”, and the case where it was not contained was set to “×”.

(60 degree mirror gloss Gs(60°))

Using a gloss meter, the 60° glossiness (%) of the surface of the Zn plating layer was measured based on the method specified in JIS Z 8741. The case where the gloss was 50 to 200% was referred to as “A”, and the case where the gloss was less than 50% was referred to as “B.” The results are shown in Tables 6A and 6B.

(b*value, b*/a*)

The surface of the Zn plating layer on which the chemical conversion treatment layer was formed was measured using a spectroscopic colorimeter (SE6000 manufactured by Nippon Denshoku Kogyo Co., Ltd.). The case where b* was 2 or more and 60 or less was referred to as “A,” and the case where b* was less than 2 or more than 60 was referred to as “B.” Additionally, the case where b*/a* was -3 or more and 3 or less was referred to as "A", and the case where it was less than -10 or more than -3 was referred to as "B". The results are shown in Tables 6A and 6B.

(L*1/L*2)

The case where L*1/L*2 was 4 or more and 7 or less was designated as "A", the case where it was 2 or more but less than 4 or between 7 and 10 or less was designated as "B", and the case where it was less than 2 or greater than 10 was designated as "C".

(corrosion resistance)

A salt spray test (JIS Z 2371:2015) was performed on the Zn-based plated steel sheet. The occurrence of white rust was observed 24 hours after the test time in the area where the Eriksen processing was performed, and judgment was given by giving the rating shown below. A score of 3 or higher was considered passing. The results are shown in Tables 6A and 6B.

4: White rust generation less than 5%

3: Occurrence of white rust: 5% or more but less than 10%

2: Occurrence of white rust 10% or more but less than 30%

1: White rust generation: 30% or more

(gold exterior)

When the surface of the Zn plating layer of the Zn-based plated steel sheet was shown to five panelists, it was judged based on the appearance of a gold color. The evaluation was determined by giving the ratings shown below, and a rating of 3 or higher was considered passing. The results are shown in Tables 6A and 6B.

5: More than 4 out of 5 people could recognize it as gold, and felt that there was no change in light reflection and that it had a sense of luxury.

4: More than 4 out of 5 people could recognize it as gold and also felt that there was no change in light reflection.

3: 3 out of 5 people were able to recognize it as gold.

2: 2 out of 5 people were able to recognize it as gold.

1: Less than 1 in 5 people could recognize it as gold.

As shown in Tables 1 to 6B, the Zn-based plated steel sheets of Examples 1 to 71 all had a chemical conversion treatment layer that satisfied the scope of the present invention, and had good corrosion resistance and golden appearance.

Additionally, for Examples 59 to 62 in which a pattern portion was formed on the plating layer, corrosion resistance and a golden appearance were good, and visibility of the pattern portion was significantly improved. In addition, for some examples, the adhesion amount of the chemical conversion layer was set in the range of 0.1 to 15.0 g/m2, but the results were good.

On the other hand, as shown in Tables 1 to 6B, in Comparative Example 1, since the chemical conversion layer did not contain resin, the chemical conversion layer itself became very brittle, and various evaluation tests could not be performed.

In Comparative Example 2, since the chemical conversion layer did not contain a yellow colorant, the b* value and b*/a* were outside the range of the present invention, and the golden appearance was insufficient.

In Comparative Examples 3, 4, and 5, Cu phthalocyanine, Co phthalocyanine, and quinacridone are contained in the chemical treatment layer, respectively, and these are not yellow colorants according to the present invention, that is, Comparative Examples 3 to 5 do not contain yellow colorants. As a result, at least one of the b* value and b*/a* was outside the range of the present invention, and the golden appearance was insufficient.

In Comparative Examples 6 and 7, since the adhesion amount of the chemical conversion layer was outside the range of 0.1 to 15.0 g/m2, the b* value or 60-degree mirror gloss Gs (60°) deviated from the range of the present invention, and also L*1/ L*2 was outside the range of the present invention, and the golden appearance was insufficient.

[Table 1]

[Table 2]

[Table 3A]

[Table 3B]

[Table 4A]

[Table 4B]

[Table 4C]

[Table 5A]

[Table 5B]

[Table 6A]

[Table 6B]

According to the present invention, it is possible to provide a Zn-based plated steel sheet containing Al that has a luxurious golden appearance and improved corrosion resistance, so the present invention has industrial applicability. This is high.

Claims (17)

steel plate,
a Zn-based plating layer disposed on at least one side of the steel sheet and containing 0.05 to 60% by mass of Al and Zn;
At least one chromate-free chemical conversion layer is provided on the Zn-based plating layer and has an adhesion amount of 0.1 to 15 g/m2 per side,
The chemical conversion layer contains a resin and a yellow colorant,
When the appearance is evaluated in the CIE1976 (L*, a*, b*) color space, b* is 2 or more and 60 or less, and b*/a* is -3 or more and 3 or less, as specified in JIS Z 8741:1997. 60 degree mirror gloss G _s (60°) is 50 to 200,
In a plane perpendicular to the surface of the chemical conversion layer, L obtained when light is incident on the surface from an angle of 60° from the surface and light reflected from the surface is received at an angle of 135° from the surface Let * be L*1, and in the plane, L obtained when light is incident toward the surface from an angle of 120° from the surface, and light reflected from the surface is received at an angle of 135° from the surface. When * is L*2, the Zn-based plated steel sheet is characterized in that L*1 and L*2 satisfy the following equation 1.
10≥L*1/L*2≥2...Equation 1 According to paragraph 1,
A Zn-based plated steel sheet, wherein the yellow colorant is an azo-based yellow pigment or an iron oxide-based yellow pigment. According to claim 1 or 2,
A Zn-based plated steel sheet, wherein the content of the yellow colorant in the chemical conversion layer is 0.1 to 10% by mass. According to claim 1 or 2,
A Zn-based plated steel sheet, wherein the L*1 and the L*2 satisfy Equation 2 below.
7≥L*1/L*2≥4...Equation 2 According to claim 1 or 2,
A Zn-based plated steel sheet, characterized in that the chemical conversion layer contains 1 to 20% by mass of metal oxide particles with an average particle diameter of 5 to 200 nm and a refractive index of 1.3 to 2.5. According to clause 5,
A Zn-based plated steel sheet, wherein the metal oxide particles include silica particles. According to clause 5,
A Zn-based plated steel sheet, wherein the mixing ratio of the yellow colorant and the metal oxide particles in the chemical conversion treatment layer is in the range of 1 to 200. According to claim 1 or 2,
A Zn-based plated steel sheet, characterized in that the arithmetic average roughness Ra of the surface of the Zn-based plating layer is 0.1 to 2.0 μm. According to claim 1 or 2,
A Zn-based plated steel sheet, wherein the arithmetic mean roughness Ra of the Zn-based plating layer is 0.5 to 2.0 ㎛, and the arithmetic mean height Sa of the chemical conversion layer is 5 nm to 100 nm. According to claim 1 or 2,
A Zn-based plated steel sheet, wherein the chemical conversion layer further contains one or both of a Nb compound and a phosphoric acid compound. According to claim 1 or 2,
A Zn-based plated steel sheet, wherein the resin in the chemical conversion layer is made of at least one of polyolefin resin, fluorine resin, acrylic resin, urethane resin, polyester resin, epoxy resin, and phenol resin. According to claim 1 or 2,
A Zn-based plated steel sheet characterized in that the Zn-based plating layer contains an average composition of Al: 4% by mass to 22% by mass, Mg: 1% by mass to 10% by mass, and the balance consists of Zn and impurities. . According to claim 1 or 2,
A Zn-based plated steel sheet, characterized in that the Zn-based plating layer further contains Si: 0.0001 to 2% by mass as an average composition. According to claim 1 or 2,
A Zn-based plated steel sheet, characterized in that the Zn-based plating layer further contains a total of 0.0001 to 2% by mass of one or more of Ni, Sb, and Pb as an average composition. According to claim 1 or 2,
When L* is measured in a range of 0.5 mm in diameter centered on each point at five arbitrary points on the surface of the Zn-based plating layer, the maximum value of L* is 1.2 times or more than the minimum value of L*. Zn-based plated steel sheet. According to claim 1 or 2,
A pattern portion and a non-pattern portion arranged to have a predetermined shape are formed in the Zn-based plating layer,
The pattern portion and the non-pattern portion each include one or two types of a first region and a second region determined by any of the following determination methods 1 to 5,
A Zn-based plated steel sheet, wherein the absolute value of the difference between the area ratio of the first region in the pattern portion and the area ratio of the first region in the non-pattern portion is 30% or more.
[Decision method 1]
Virtual grid lines are drawn at 0.5 mm intervals on the surface of the Zn-based plating layer, and in a plurality of areas divided by the virtual grid lines, a measurement area is within a circle with a diameter of 0.5 mm centered on the center of gravity of each area. Let it be A, and measure the L* value in each measurement area A. When 50 points are randomly selected from the obtained L* values and the average of 50 points of the obtained L* values is taken as the standard L* value, the area where the L* value is higher than the standard L* value is called the first area, the reference L* value. The area below the value is called the second area.
[Decision Method 2]
Virtual grid lines are drawn at 0.5 mm intervals on the surface of the Zn-based plating layer, and in a plurality of areas divided by the virtual grid lines, a measurement area is within a circle with a diameter of 0.5 mm centered on the center of gravity of each area. Let's call it A, the L* value in each measurement area A is measured, the area where the L* value is 45 or more is called the first area, and the area where the L* value is less than 45 is called the second area.
[Decision Method 3]
Virtual grid lines are drawn at intervals of 0.5 mm on the surface of the Zn-based plating layer, and the arithmetic mean surface roughness Sa is measured in each of the plurality of regions defined by the virtual grid lines. The region where the obtained Sa is 1 μm or more is called the first region, and the region where the obtained Sa is less than 1 μm is called the second region.
[Decision Method 4]
By drawing virtual grid lines at 1 mm or 10 mm intervals on the surface of the Zn-based plating layer, and applying The diffraction peak intensity I ₀₀₀₂ of the (0002) plane of the Zn phase and the diffraction peak intensity I _10-11 of the (10-11) plane of the Zn phase were measured, and their intensity ratio (I ₀₀₀₂ /I _10-11 ) was calculated as the orientation ratio. It is said. The region where the orientation ratio is 3.5 or more is called a first region, and the region where the orientation ratio is less than 3.5 is called a second region.
[Decision Method 5]
Virtual grid lines are drawn at 1 mm intervals on the surface of the Zn-based plating layer, and then, for each of the plurality of regions divided by the virtual grid lines, a circle S is drawn centered on the center of gravity point G of each region. The diameter R of the circle S is set so that the total length of the surface boundaries of the Zn-based plating layer contained within the circle S is 10 mm. The average value of the largest diameter Rmax and the smallest diameter Rmin among the diameters R of circles S in a plurality of areas is called the standard diameter Rave, and the region having circles S whose diameter R is less than the standard diameter Rave is called the first region, and the diameter R is called the first region. The area with the circle S larger than the reference diameter Rave is called the second area. According to claim 1 or 2,
A Zn-based plated steel sheet characterized by having any one of Co, Fe, and Ni on the surface of the Zn-based plating layer.