CN116547405A

CN116547405A - Zn-based coated steel sheet

Info

Publication number: CN116547405A
Application number: CN202180076021.XA
Authority: CN
Inventors: 鸟羽哲也; 东新邦彦; 森下敦司
Original assignee: Nippon Steel and Sumitomo Metal Corp
Current assignee: Nippon Steel Corp
Priority date: 2021-12-03
Filing date: 2021-12-03
Publication date: 2023-08-04
Also published as: WO2023100349A1; JP7107474B1; KR102620034B1; KR20230084519A; JPWO2023100349A1

Abstract

A Zn-based plated steel sheet is provided with: a steel plate; a Zn-based coating layer which is disposed on at least one surface of the steel sheet and contains Al and Zn; and a single-sided adhesion amount of 0.1 to 15g/m disposed on the Zn-based plating layer ² At least 1 or more of the chromate-free chemical conversion treatment layers comprising a resin and a yellow colorant, and the resin and the yellow colorant being formed by CIE1976 (L ^* ，a ^* ，b ^* ) B in case of evaluating appearance in color space ^* 2 to 60, b ^* /a ^* A specular gloss G of-3 to 3 at 60 DEG _s (60) is 50-200, and L is obtained when light is incident from the surface at an angle of 60 DEG to the surface of the chemical conversion treatment layer and light reflected at the surface is received at an angle of 135 DEG to the surface ^* Denoted as L1, obtained when light is incident from an angle of 120 ° to the surface towards the surface and light reflected at the surface is received at an angle of 135 ° to the surface ^* When denoted as L2, formula 1 is satisfied: 10. and (2) is equal to or more than L1/L2.

Description

Zn-based coated steel sheet

Technical Field

The present invention relates to a Zn-based coated steel sheet.

Background

The most used coated steel sheet is a Zn-based coated steel sheet as a coated steel sheet having excellent corrosion resistance. These Zn-based coated steel sheets are used in various manufacturing industries such as automobiles, home appliances, and building material fields. Among these, the plating layer containing Al has a high corrosion resistance, and therefore, the amount of Al used has been increasing in recent years.

As an example of a Zn-based coated steel sheet developed for the purpose of improving corrosion resistance, patent document 1 describes a zn—al—mg—si hot dip coated steel sheet. The coated steel sheet has a pear-shaped appearance, and thus has a characteristic of excellent appearance and beauty.

Conventionally, in order to impart a higher rust preventing function to a Zn-based plated steel sheet, a step of performing a chromate treatment using 6-valent chromate or the like after plating has been widely performed, and further, a coating using an organic resin has been performed in order to impart a high added value function such as design property, stain resistance, lubricity or the like as required. However, in view of the increase in environmental problems, there is a trend to inhibit the use of chromate treatment. Accordingly, there is a surface-treated plated steel sheet described in patent document 2 below, in order to simply impart a high rust preventive function by a single-layer treatment of a resin film without chromate treatment. By using the coating film described in patent document 2 below, corrosion resistance can be further improved.

Recently, however, there has been an urgent need for further improvement in appearance of Zn-based plated steel sheets containing Al. Specifically, the surface of the Zn-based coated steel sheet has a pear skin-like pattern of a non-colored type in which a glossy portion and a white portion are mixed, but in order to make the appearance thereof gorgeous, it is highly desired to have a gold appearance.

Prior art literature

Patent literature

Patent document 1: japanese patent No. 3179446

Patent document 2: japanese patent application laid-open No. 2006-52462

Disclosure of Invention

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a Zn-based plated steel sheet having an improved corrosion resistance and exhibiting a gold appearance with a high-quality feel in a Zn-based plated steel sheet containing Al.

As a result of intensive studies to solve the above problems, the inventors have found that the surface roughness of a Zn-based plating layer is reduced to give a metallic luster, and that a chemical conversion-treated layer contains a yellow colorant and looks golden to the naked human eye. The present invention adopts the following constitution.

[1] A Zn-based plated steel sheet is provided with:

a steel plate;

a Zn-based coating layer which is disposed on at least one surface of the steel sheet and contains 0.05 to 60 mass% of Al and Zn; and

the amount of one surface of the Zn-based coating layer is 0.1-15 g/m ² At least 1 or more of the chromate-free chemical conversion treatment layers,

the chemical conversion treatment layer contains a resin and a yellow colorant,

using CIE1976 (L) ^* ，a ^* ，b ^* ) B in case of evaluating appearance in color space ^* 2 to 60, b ^* /a ^* Is-3 or more and 3 or less, in JIS Z8741: 60 degree specular gloss G as defined in 1997 _s (60 DEG) is 50-200,

incident light from an angle of 60 DEG to the surface of the chemical conversion treatment layer toward the surface in a plane orthogonal to the surface, and receiving light reflected at the surface at an angle of 135 DEG to the surface ^* Denoted by L1, in the plane, L obtained when light is incident from an angle of 120 ° to the surface towards the surface and light reflected at the surface is received at an angle of 135 ° to the surface ^* When written as L.times.2, the L ^* 1 and said L ^* 2 satisfies the following formula 1.

10. Not less than 1/2 not less than 2. Formula 1

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

[4]According to [1]]～[3]The Zn-based coated steel sheet according to any one of the above, wherein L is ^* 1 and said L ^* 2 satisfies the following formula 2.

7. Not less than 1/2 not less than 4.2

[5] The Zn-coated steel sheet according to any one of [1] to [4], wherein the chemical conversion treatment layer comprises 1 to 20 mass% of metal oxide particles having an average particle diameter of 5 to 200nm and a refractive index of 1.3 to 2.5.

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

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

[8] The Zn-coated steel sheet according to any one of [1] to [7], wherein the surface of the Zn coating layer has an arithmetic average roughness Ra of 0.1 to 2.0. Mu.m.

[9] The Zn-coated steel sheet according to any one of [1] to [8], wherein the Zn-coated layer has an arithmetic average roughness Ra of 0.5 to 2.0. Mu.m, and the chemical conversion treatment layer has an arithmetic average height Sa of 5 to 100nm.

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

[11] The Zn-coated steel sheet according to any one of [1] to [10], wherein the resin in the chemical conversion treatment layer is composed of at least one resin selected from the group consisting of polyolefin resins, fluororesin, acrylic resins, polyurethane resins, polyester resins, epoxy resins, and phenolic resins.

[12] The Zn-coated steel sheet according to any one of [1] to [11], wherein the Zn-coated steel sheet comprises, in terms of average composition: 4 mass% or more and 22 mass% or less, mg: more than 1 mass% and not more than 10 mass%, the balance being Zn and impurities.

[13] The Zn-coated steel sheet according to any one of [1] to [12], wherein the Zn-coated steel sheet further comprises, in terms of average composition, si:0.0001 to 2 mass percent.

[14] The Zn-coated steel sheet according to any one of [1] to [13], wherein the Zn-coated steel sheet further comprises, in terms of average composition, at least one of Ni, sb and Pb in an amount of 0.0001 to 2% by mass.

[15]According to [1]]～[14]The Zn-based coated steel sheet according to any one of the preceding claims, characterized in that L having a diameter in the range of 0.5mm centered on each point is measured at any 5 points on the surface of the coating layer ^* When L ^* Has a maximum value of L ^* Is more than 1.2 times the minimum value of (2).

[16] The Zn-coated steel sheet according to any one of [1] to [15], wherein the Zn-coated layer is formed with pattern portions and non-pattern portions, which are arranged so as to have a predetermined shape,

the pattern portion and the non-pattern portion include one or both of the 1 st region and the 2 nd region determined by any one of the following determination methods 1 to 5,

an absolute value of a difference between the area ratio of the 1 st region in the pattern portion and the area ratio of the 1 st region in the non-pattern portion is 30% or more.

[ determination method 1]

Virtual grid lines are drawn at 0.5mm intervals on the surface of the Zn-based plating layer, and L in each measurement region A is measured in a circle having a diameter of 0.5mm centered on the center of gravity of each region among a plurality of regions divided by the virtual grid lines as measurement regions A ^* Values. From the L thus obtained ^* Selecting arbitrary 50 points from the values, and obtaining L ^* The 50-point average of the values is taken as a reference L ^* When the value is, L ^* The value becomes the reference L ^* The 1 st region is the region with the value above L ^* A value smaller than the reference L ^* Region of valuesIs zone 2.

[ determination method 2]

Virtual grid lines are drawn at 0.5mm intervals on the surface of the Zn-based plating layer, and L in each measurement region A is measured in a circle having a diameter of 0.5mm centered on the center of gravity of each region among a plurality of regions divided by the virtual grid lines as measurement regions A ^* Value, L ^* An area having a value of 45 or more is defined as the 1 st area, L ^* The region with a value less than 45 is referred to as the 2 nd region.

[ determination method 3]

Virtual lattice lines are drawn at intervals of 0.5mm on the surface of the Zn-based plating layer, and the arithmetic average surface roughness Sa is measured in each of a plurality of regions divided by the virtual lattice lines. The 1 st region was defined as a region having a Sa of 1 μm or more, and the 2 nd region was defined as a region having a Sa of less than 1 μm.

[ determination method 4]

Drawing virtual grid lines at intervals of 1mm or 10mm on the surface of the Zn-based plating layer, and measuring the diffraction peak intensity I of the (0002) plane of Zn phase for each of the regions by an X-ray diffraction method in which X-rays are incident on each of the regions divided by the virtual grid lines ₀₀₀₂ Diffraction peak intensity I of (10-11) plane of Zn phase _10-11 Their intensity ratio (I ₀₀₀₂ /I _10-11 ) As the orientation ratio. The 1 st region is the region having the orientation ratio of 3.5 or more, and the 2 nd region is the region having the orientation ratio of less than 3.5.

[ determination method 5]

Virtual grid lines are drawn at 1mm intervals on the surface of the Zn-based plating layer, and then, circles S centered on the center of gravity point G of each region are drawn for each of a plurality of regions divided by the virtual grid lines. The diameter R of the circle S is set so that the total length of the surface boundary lines of the Zn-based plating layer contained in the inside of the circle S becomes 10 mm. The average value of the maximum diameter Rmax and the minimum diameter Rmin among the diameters R of the circles S of the plurality of regions is set as a reference diameter Rave, the region having the circle S with the diameter R smaller than the reference diameter Rave is set as the 1 st region, and the region having the circle S with the diameter R equal to or larger than the reference diameter Rave is set as the 2 nd region.

[17] The Zn-coated steel sheet according to any one of [1] to [16], wherein the Zn-coated steel sheet comprises Co, fe or Ni on the surface of the Zn-coated layer.

According to the present invention, a Zn-based plated steel sheet having an improved corrosion resistance and exhibiting a gold appearance with a high-quality feel can be provided.

Detailed Description

The inventors found that: the chemical conversion treatment layer is colored yellow by containing a yellow colorant, and the surface roughness of the Zn-based plating layer is reduced to give a metallic luster, and the Zn-based plating layer looks gold in appearance to the naked human eye. However, it was found that: if the yellow color is too intense, the metallic appearance of the plating surface becomes difficult to visually recognize, and the plating surface looks yellow as a whole, and if the incident light is reflected on the plating surface or the surface of the chemical conversion treatment layer, the look of the color of the Zn-based plating changes, and the plating surface cannot look gold. Thus, further studies have found that: will utilize CIE1976 (L ^* ，a ^* ，b ^* ) B in the case of color space evaluation ^* Value and b ^* /a ^* And in JIS Z8741: 60 degree specular gloss G as defined in 1997 _s (60 DEG) controlling so that they are within a prescribed range, and, in a plane orthogonal to the surface of the chemical conversion treatment layer, incident light from an angle of 60 DEG to the surface of the chemical conversion treatment layer toward the surface of the chemical conversion treatment layer, and receiving L obtained when light reflected at the surface of the chemical conversion treatment layer is received at an angle of 135 DEG to the surface of the chemical conversion treatment layer ^* Denoted by L1, in the plane described above, L obtained when light is incident from an angle of 120 ° to the surface of the chemical conversion treatment layer toward the surface of the chemical conversion treatment layer and light reflected at the surface of the chemical conversion treatment layer is received at an angle of 135 ° to the surface of the chemical conversion treatment layer ^* When denoted as L.times.2, control is performed such that L ^* 1 and L ^* 2 satisfies 10 is more than or equal to L ^* 1/L.times.2.gtoreq.2 (formula 1), thereby becoming a gold appearance. In addition, it was found that: by controlling b ^* Value and b ^* /a ^* 60 degree specular gloss G _s (60°)、L ^* 1 and L ^* 2, even when an arbitrary shape such as a letter is displayed on the surface of the plating layer, the arbitrary shape is easily seen. As a result, it is not necessary to include gold fine particles or gold-colored metal fine particles in the chemical conversion treatment layer, and the gold appearance can be obtained at low cost.

That is, a Zn-based plated steel sheet according to an embodiment of the present invention includes: a steel plate; a Zn-based coating layer which is disposed on at least one surface of the steel sheet and contains 0.05-60 mass% of Al and Zn; and a single-sided adhesion amount of 0.1 to 15g/m disposed on the Zn-based plating layer ² At least 1 or more of the chromate-free chemical conversion treatment layers comprising a resin and a yellow colorant, and the resin and the yellow colorant being formed by CIE1976 (L ^* ，a ^* ，b ^* ) B in case of evaluating appearance in color space ^* 2 to 60, b ^* /a ^* Is-10 to-3, under JIS Z8741: 60 degree specular gloss G as defined in 1997 _s (60 DEG) 50 to 200, in a plane orthogonal to the surface of the chemical conversion treatment layer, incident light from an angle of 60 DEG to the surface of the chemical conversion treatment layer toward the surface of the chemical conversion treatment layer, and receiving light reflected at the surface of the chemical conversion treatment layer at an angle of 135 DEG to the surface of the chemical conversion treatment layer ^* Denoted by L1, in the plane described above, L obtained when light is incident from an angle of 120 ° to the surface of the chemical conversion treatment layer toward the surface of the chemical conversion treatment layer and light reflected at the surface of the chemical conversion treatment layer is received at an angle of 135 ° to the surface of the chemical conversion treatment layer ^* When the value is recorded as L.times.2, L ^* 1 and L ^* 2 satisfies 10 is more than or equal to L ^* 1/L ^* 2. Not less than 2 (formula 1).

In the Zn-based coated steel sheet of the present embodiment, the yellow colorant is preferably an azo-based yellow pigment or an iron oxide-based yellow pigment.

In the Zn-based coated steel sheet of the present embodiment, the content of the yellow colorant in the chemical conversion treatment layer is preferably 0.1 to 10 mass%.

In the Zn-based coated steel sheet of the present embodiment, it is preferable that L1 and L2 satisfy 7.gtoreq.l 1/L2.gtoreq.4 (formula 2).

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

In the Zn-based coated steel sheet of the present embodiment, the metal oxide particles preferably contain silica particles.

In the Zn-based coated steel sheet of the present embodiment, the mixing ratio of the yellow colorant to the metal oxide particles is preferably 1 to 200.

In the Zn-based plated steel sheet of the present embodiment, the arithmetic average roughness Ra of the surface of the Zn-based plated layer is preferably 0.1 to 2.0 μm.

In the Zn-based plated steel sheet of the present embodiment, it is preferable that: the arithmetic average roughness Ra of the Zn plating layer is 0.5-2.0 mu m, and the arithmetic average height Sa of the chemical conversion treatment layer is 5-100 nm.

[ Zn-based coated steel sheet ]

Hereinafter, a Zn-based plated steel sheet according to the present embodiment will be described.

The material of the steel sheet to be the base of the Zn-based plating layer is not particularly limited. As a material thereof, ordinary steel or the like can be used without particular limitation, al-killed steel or a part of high alloy steel can be used, and the shape is not particularly limited. The Zn-based plating layer according to the present embodiment can be formed by applying a hot dip plating method described later to a steel sheet.

[ Zn-based coating ]

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

The Zn-based coating layer is a Zn-based coating layer containing 0.05 to 60 mass% of Al and Zn. The Zn-based plating layer of the present embodiment is preferably: contains Al in terms of average composition: 4-22 mass percent of Mg:1 to 10 mass% of Zn and impurities as the balance. More preferably: contains Al in terms of average composition: 4-22 mass percent of Mg: more than 1 mass% and not more than 10 mass%, the balance being Zn and impurities.

By containing 0.05 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 mass% or less, the Zn content in the Zn-based plating layer can be relatively increased to ensure the sacrificial corrosion resistance. In addition, by containing Al: 4-22 mass percent of Mg: 1-10 mass percent and the balance: zn and impurities, can further improve corrosion resistance and sacrifice corrosion resistance. The Zn-based plating layer may contain Zn in an amount of 40 mass% or more.

The Zn-based plating layer may contain Si in terms of average composition: 0.001 to 2 mass%. The Zn-based plating layer may contain one or two or more of Ni, ti, zr, sr, fe, sb, pb, sn, ca, co, mn, P, B, bi, cr, sc, Y, REM, hf, C in an amount of 0.001 to 2 mass% in total, based on the average composition.

Next, the Zn-based plating layer containing Al: 4-22 mass percent of Mg: the reason why the composition of the Zn-based plating layer is limited to more than 1 mass% and not more than 10 mass% with the balance being Zn and impurities.

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

The content of Mg is in a range of more than 1 mass% and 10 mass% or less. Mg may be contained in order to improve corrosion resistance. If the Mg content in the Zn-based plating layer exceeds 1 mass%, the effect of improving the corrosion resistance is further improved. When the Mg content is 10 mass% or less, occurrence of dross (dross) in the plating bath is suppressed, and a Zn-based plated steel sheet can be easily and stably produced. From the viewpoint of balance between corrosion resistance and occurrence of scum, the Mg content is preferably 1.5 to 6 mass%. More preferably, the Mg content is in the range of 2 to 5 mass%.

On the other hand, when a chemical conversion treatment layer containing a yellow colorant is disposed on the plating layer, the Zn-based plating layer containing Mg is likely to be blackened, and the color thereof is deep due to the blackening, and therefore, there is an advantage that the Zn-based plating layer becomes golden yellow with a higher quality feeling.

The contents of Al and Mg may be 0%, respectively. That is, the Zn-based plating layer of the Zn-based plated steel sheet of the present 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.

The Zn-based plating layer may contain Si in a range of 0.0001 to 2 mass%.

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

The Zn-based plating layer may contain one or two or more of Ni, ti, zr, sr, fe, sb, pb, sn, ca, co, mn, P, B, bi, cr, sc, Y, REM, hf, C in an amount of 0.001 to 2 mass% in total in terms of the average composition. By containing these elements, corrosion resistance can be further improved. REM is one or more than two rare earth elements with atomic numbers of 57-71 in the periodic table.

The remainder (balance) of the chemical components of the Zn-based coating layer is zinc and impurities. Examples of the impurities include impurities which are inevitably contained in zinc and other raw metals, and impurities which are contained in the plating bath due to dissolution of steel.

The average composition of the Zn-based plating layer can be measured by the following method. First, a top coating film is removed by a coating film remover (for example, coating film SP-751 manufactured by trichromatic chemical company), and then a Zn-based coating layer is dissolved by hydrochloric acid to which a corrosion inhibitor (for example, coating solution manufactured by the chemical industry company) is added, and the resulting solution is subjected to Inductively Coupled Plasma (ICP) emission spectrometry to obtain the coating film. In removing the top coating film, the chemical conversion treatment layer is preferably removed together.

Next, the structure of the Zn-based plating layer will be described. The structure described below is that the Zn-based plating layer contains Al in terms of average composition: 4-22 mass percent of Mg:1 to 10 mass% of Si:0 to 2 mass% of a tissue.

A Zn-based coating layer containing Al, mg and Zn comprises [ Al phase ]]And [ Al/Zn/MgZn ] ₂ Ternary eutectic structure of (C)]. Has the structure of [ Al/Zn/MgZn ] ₂ Ternary eutectic structure of (C)]Comprises [ Al phase in the matrix ]Is in the form of (a). In addition, the composition may be [ Al/Zn/MgZn ] ₂ Ternary eutectic structure of (C)]Comprises [ MgZn ] in the matrix ₂ Phase (C)][ Zn phase ]]. In addition, when Si is added, the composition may be [ Al/Zn/MgZn ] ₂ Comprises [ Mg ] in a matrix of the ternary eutectic structure ] ₂ Si phase).

Here, the term [ Al/Zn/MgZn ] ₂ Is Al phase, zn phase and intermetallic compound MgZn ₂ The ternary eutectic structure of the phases, the Al phase forming the ternary eutectic structure corresponds to, for example, "Al" phase "at high temperature in a ternary equilibrium state diagram of al—zn—mg (Al solid solution that is solid solution Zn, containing a small amount of Mg). The Al "phase at high temperature generally separates into a fine Al phase and a fine Zn phase at normal temperature and appears. The Zn phase in the ternary eutectic structure is a Zn solid solution in which a small amount of Al and, in some cases, a small amount of Mg are dissolved. MgZn in the ternary eutectic structure ₂ The phase is Zn in a binary equilibrium state diagram of Zn-Mg: about 84 mass% of an intermetallic compound phase present in the vicinity. It is considered that, when the three phases are observed in the state diagram, other additive elements are not dissolved in the respective phases or are dissolved in very small amounts, but the amounts thereof cannot be clearly distinguished in a normal analysis, so that the ternary eutectic structure composed of these 3 phases is expressed as [ Al/Zn/MgZn ] in the present specification ₂ Ternary eutectic structure of (C)]。

The "Al phase" is a phase having a clear boundary in the matrix of the ternary eutectic structure and appearing to be island-like, and corresponds to, for example, an "Al" phase "at high temperature in a ternary equilibrium state diagram of al—zn—mg (which is an Al solid solution of solid solution Zn and contains a small amount of Mg). The Al' phase at high temperature differs in the amount of Zn and the amount of Mg to be dissolved depending on the concentration of Al and Mg in the plating bath. The Al "phase at high temperature is generally separated into a fine Al phase and a fine Zn phase at normal temperature, but the island shape seen at normal temperature can be regarded as a shape of a debris retaining the Al" phase at high temperature. It is considered that, when the state diagram is viewed, other additive elements are not dissolved in this phase or are very small even if they are dissolved in solid, but they cannot be clearly distinguished in ordinary analysis, so that the phase derived from the Al "phase at high temperature and having the Al" phase remaining in shape is referred to as "Al phase" in the present specification. The [ Al phase ] is clearly distinguishable from the Al phase forming the ternary eutectic structure in microscopic observation.

The [ Zn phase ] is a phase having a clear boundary and appearing island-like in the matrix of the ternary eutectic structure, and may be a phase in which a small amount of Al and, in fact, a small amount of Mg are dissolved in solid solution. It is considered that other additive elements are not dissolved in this phase or are very small even if dissolved in the state diagram. The [ Zn phase ] is clearly distinguishable from the Zn phase forming the ternary eutectic structure in microscopic observation. The Zn-based plating layer of the present invention may contain [ Zn phase ] depending on the production conditions, but since the effect on the improvement of the corrosion resistance of the processed portion is hardly seen in the experiment, there is no particular problem even if the [ Zn phase ] is contained in the plating layer.

In addition, so-called [ MgZn ] ₂ The phase is a phase having a clear boundary and appearing island-like in the matrix of the ternary eutectic structure, and may be practically dissolved with a small amount of Al. It is considered that other additive elements are not dissolved in this phase or are very small even if dissolved in the state diagram. The (MgZn) ₂ Phase and MgZn forming the ternary eutectic structure ₂ Phases can be clearly distinguished in microscopic observation. In the Zn system of the present inventionThe coating layer may not contain [ MgZn ] depending on the production conditions ₂ But is contained in the Zn-based plating layer under most of the manufacturing conditions.

In addition, so-called [ Mg ₂ The Si phase is a phase which has a clear boundary in the solidification structure of the Zn-based coating layer when Si is added and appears as an island shape. It is considered that Zn, al, and other additive elements are not solid-dissolved or are very trace even if solid-dissolved, as long as they are observed in the state diagram. This [ Mg ] ₂ Si phase is clearly distinguishable from Zn-based plating by microscopic observation.

Further, it is preferable that the surface of the Zn-based plating layer has any one element of Co, fe, and Ni. Co, fe and Ni are adhered to the surface of the Zn-based coating layer by Co treatment, fe treatment or Ni treatment after the Zn-based coating layer is formed. The presence of these elements on the surface of the Zn-based plating layer can improve blackening resistance.

The arithmetic average roughness Ra of the surface of the Zn-based plating layer is preferably 0.1 to 2.0. Mu.m. The arithmetic average roughness Ra may be 0.5 to 2.0 μm. When Ra is 2.0 μm or less, the metallic luster of the Zn-based coating layer is improved to exhibit a more beautiful gold color. Further, even if Ra is smaller than 0.1 μm, the effect is saturated, and therefore the lower limit may be set to 0.1 μm or more. The arithmetic average roughness Ra of the Zn-based plating layer was measured and calculated by a 3D laser microscope (k-gram, inc.). The height Z was measured at 50 μm measurement intervals using a 20-fold standard lens. The number of measurement points is preferably set to 100 points. The number of measurement points was set to 100 points, the obtained 100 points were designated as the heights Z1 to Z100, and the arithmetic average roughness Ra was calculated using the above values by using the following equation 3. Zave is the average of the heights Z at 100 points.

Ra=1/100×Σ [ x=1→100] (|height Zx-zave|) … type 3

[ chemical conversion treatment layer ]

Next, the chemical conversion treatment layer will be described. The chemical conversion treatment layer of the present embodiment contains a resin and a yellow colorant. The chemical conversion coating layer according to the present embodiment is a coating 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 the Zn-based plating layer.

(resin)

The resin contained in the chemical conversion treatment layer is preferably one or more resins selected from polyolefin resins, fluorine resins, acrylic resins, polyurethane resins, polyester resins, epoxy resins, and phenolic resins. These resins may be water-soluble resins or water-insoluble resins (water-dispersible resins) which are capable of being finely dispersed in water such as emulsions and suspensions.

The polyolefin resin is not particularly limited, and examples thereof include: and polyolefin resins obtained by radical polymerization of ethylene with an unsaturated carboxylic acid such as methacrylic acid, acrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, etc., at high temperature and high pressure, neutralization with a metal compound such as ammonia, amine compound, KOH, naOH, liOH, or ammonia, amine compound containing the above metal compound, etc., and water dispersion.

The fluororesin is not particularly limited, and examples thereof include homopolymers and copolymers of fluoroolefins. In the case of the copolymer, there can be mentioned a copolymer of a fluoroolefin and a fluoromonomer other than the fluoroolefin and/or a monomer having no fluorine atom.

The acrylic resin is not particularly limited, and examples thereof include: an acrylic resin obtained by radical polymerization of an unsaturated monomer such as styrene, an alkyl (meth) acrylate, a (meth) acrylic acid, a hydroxyalkyl (meth) acrylate, or an alkoxysilane (meth) acrylate 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 azobiscyano valeric acid (azobiscyanovaleric acid) and azobisisobutyronitrile (azodiisobutyronitrile) can be used.

The urethane resin is not particularly limited, and examples thereof include: polyurethane resins obtained by reacting polyols such as ethylene glycol, propylene glycol, diethylene glycol, 1, 6-hexanediol, neopentyl glycol, triethylene glycol, bisphenol hydroxypropyl ether, glycerin, trimethylolethane, and trimethylolpropane with diisocyanate compounds such as hexamethylene diisocyanate, isophorone diisocyanate, and benzylidene diisocyanate, chain-extending with diamines, and dispersing with water.

The polyester resin is not particularly limited, and examples thereof include: and polyester resins obtained by dehydrating and condensing polyhydric alcohols such as ethylene glycol, propylene glycol, diethylene glycol, 1, 6-hexanediol, neopentyl glycol, triethylene glycol, bisphenol hydroxypropyl ether, glycerin, trimethylolethane, and trimethylolpropane with polybasic acids such as phthalic anhydride, isophthalic acid, terephthalic acid, succinic anhydride, adipic acid, sebacic acid, maleic anhydride, itaconic acid, fumaric acid, and maleic anhydride (hymic anhydride), neutralizing with ammonia, an amine compound, and dispersing with water.

The epoxy resin is not particularly limited, and examples thereof include: epoxy resins obtained by reacting an epoxy resin such as bisphenol a epoxy resin, bisphenol F epoxy resin, resorcinol epoxy resin, hydrogenated bisphenol a epoxy resin, hydrogenated bisphenol F epoxy resin, resorcinol epoxy resin, novolac epoxy resin (novolac type epoxy resin), etc., with an amine compound such as diethanolamine, N-methylethanolamine, etc., and neutralizing with an organic acid or an inorganic acid; and an epoxy resin obtained by subjecting a high acid value acrylic resin to radical polymerization in the presence of the epoxy resin, neutralizing with ammonia, an amine compound or the like, and dispersing with water.

The phenolic resin is not particularly limited, and examples thereof include: phenolic resins obtained by reacting phenol, resorcinol, cresol, bisphenol a, para-xylylene dimethyl ether (paraxylylene dimethyl ether) and other aromatic compounds with formaldehyde in the presence of a reaction catalyst, reacting phenolic resins such as methylolated phenolic resins obtained by the addition reaction with amine compounds such as diethanolamine and N-methylethanolamine, and neutralizing the reaction products with an organic acid or an inorganic acid.

The chemical conversion treatment layer preferably contains a resin in an amount of 20 mass% or more. When the resin content is 20 mass% or more, the chemical conversion treatment layer itself does not become brittle, and the Zn-based plating layer can be stably coated. In addition, the chemical conversion treatment layer may contain components other than the resin such as silica particles, nb compounds, and phosphoric acid compounds, together with the resin and the yellow colorant, and the content of the resin may be the balance other than these components. In addition, the resin content is 99.9 mass% or less, which has the advantage of ensuring corrosion resistance.

(yellow colorant)

The chemical conversion treatment layer contains a yellow colorant. By containing a yellow colorant in the chemical conversion treatment layer, the chemical conversion treatment layer is colored yellow, and the appearance of the Zn-based plating layer is gold in combination with the metallic luster of the Zn-based plating layer. In order to obtain this effect, the content of the yellow colorant in the chemical conversion treatment layer is preferably in the range of 0.1 to 10 mass%. The appearance of the Zn-based plating layer can be made golden by setting the content of the yellow colorant in the chemical conversion treatment layer to 0.1 mass% or more. Further, by setting the content of the yellow colorant to 10 mass% or less, the metallic luster of the Zn-based plating layer can be kept clear and gold color can be exhibited. Here, the appearance in the present invention means an appearance when the Zn-based coated steel sheet is viewed from the Zn-based coated side disposed on at least one surface of the steel sheet.

As the yellow colorant, a yellow pigment is preferable. The yellow pigment has excellent weather resistance as compared with the yellow dye. In addition, the chemical conversion treatment layer may be water-cooled when the chemical conversion treatment layer is formed, but the yellow dye may be eluted from the chemical conversion treatment layer into the cooling water, and thus, a yellow pigment which is free from elution is preferable. As the yellow pigment, an iron oxide-based yellow pigment or an azo-based yellow pigment is preferable. These pigments are preferable because they are more excellent in weather resistance.

As the yellow pigment, a generally known yellow pigment can be used, and examples thereof include iron oxide yellow pigments. As the iron oxide yellow pigment, a generally known yellow pigment such as pigment yellow 42 can be used, and for example, an iron oxide pigment sold by the company of the kukan, the company of the feban, the company of the dada refinement industry, etc. can be used. As the yellow colorant, chrome yellow or the like may be used. Further, as the azo-based yellow pigment, an acetoacetic acid arylate (acetoacetic arylide) -based monoazo pigment, an acetoacetic acid arylate-based disazo pigment, a condensed azo pigment, a benzimidazolone (benzomidazolone) -based monoazo pigment, or the like can be used.

In the case where the pigment in the chemical conversion treatment layer is an iron oxide yellow pigment, the content thereof is measured by the following method. First, a thin film sample of a chemical conversion treatment layer was prepared by a slicing method (microtome method) so that a cross section perpendicular to the rolling direction of the Zn-based coated steel sheet of the present embodiment can be observed. In a region of 20 μm×t μm (region of 20 μm in a direction parallel to a plate width direction and film thickness t μm in a plate thickness direction) of the obtained thin film sample, at least 5 regions were observed at a magnification of 10 ten thousand times using a 200kV field emission type transmission electron microscope (FE-TEM), and element mapping (elemental mapping) was performed using an energy dispersive X-ray analysis device (EDS or EDX). And (5) obtaining the area ratio of the area where Fe exists according to the element mapping result. In the same manner as described above, the area ratio of the region where Fe is present in the plurality of comparative samples having the chemical conversion treatment layer having a known pigment content was determined, and a calibration curve (calibration curve: calibration curve) was prepared in advance based on the relationship between the area ratio and the pigment content. The pigment content of the target sample was determined using the calibration curve.

(Metal oxide particles)

Here, the yellow colorant colors the chemical conversion treatment layer to yellow to make the Zn-based plating layer look golden, but if the yellow colorant is contained in the chemical conversion treatment layer, the corrosion resistance of the chemical conversion treatment layer may be lowered. Therefore, in order to prevent the corrosion resistance of the chemical conversion treatment layer from being lowered, the chemical conversion treatment layer of the present embodiment may contain metal oxide particles. As the metal oxide particles, metal oxide particles having an average particle diameter in the range of 5 to 200nm are preferable. The metal oxide particles having an average particle diameter of less than 5nm are difficult to obtain, and the chemical conversion treatment layer containing the metal oxide particles having an average particle diameter of less than 5nm is actually difficult to produce and manufacture, so that the lower limit of the average particle diameter of the metal oxide particles is set to 5nm or more. In addition, the average particle diameter of the metal oxide particles is 200nm or less, so that the chemical conversion treatment layer is not clouded and the metallic appearance of the Zn-based plating layer is not impaired. Since light is slightly diffusely reflected in the chemical conversion treatment layer by containing metal oxide particles having an appropriate average particle diameter, the deviation of light reflection can be suppressed by the effect that the minute flaws on the surface of the plating layer become insignificant, and the like, and thus, a gold color can be perceived as high-quality. Therefore, the average particle diameter of the metal oxide particles is more preferably 5 to 50nm.

The refractive index of the metal oxide particles is preferably 1.3 to 2.5, for the reason of properly controlling the diffuse reflection of light in the chemical conversion treatment layer. The metal oxide particles were isolated from the chemical conversion treatment layer, and the refractive index was measured using a commercially available refractive index measuring device.

The chemical conversion treatment layer preferably contains metal oxide particles in an amount of 1 to 20 mass%. By setting the content of the metal oxide particles to 1 mass% or more, the effect of improving the corrosion resistance can be obtained. In addition, by setting the content of the metal oxide particles to 20 mass% or less, the chemical conversion treatment 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 mass% in the chemical conversion treatment layer from the viewpoint of appropriately controlling the diffuse reflection of light.

Generally, since the particle size of an inorganic pigment such as metal oxide particles is small, secondary particles having a larger particle size than the primary particle size may be present in the chemical conversion treatment layer. Hereinafter, the particle diameter of the secondary particles (particles obtained by agglomerating the inorganic pigment) will be referred to as "secondary particle diameter". In the metal oxide particles of the present embodiment, primary particles and secondary particles may be mixed and present, and even if primary particles and secondary particles are mixed and present, 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 treatment layer was measured by the following method. First, a thin film sample of a chemical conversion treatment layer was produced by a slicing method so that a cross section perpendicular to the rolling direction of the steel sheet of the present invention could be observed. Of the 20 μm×t μm regions of the obtained thin film sample (20 μm in the direction parallel to the plate width direction and t μm in the plate thickness direction), at least 5 regions were observed at a magnification of 10 ten thousand times using a 200kV field emission type transmission electron microscope (FE-TEM). The equivalent circle diameter (equivalent circle diameter) of all the silica particles in the observation region was calculated using the following formula 4, and the average particle diameter was obtained by averaging the equivalent circle diameter as the particle diameter of each metal oxide particle.

Equivalent circle diameter=2 (S/pi) ^1/2 … type 4

Where S is the area of the metal oxide particles and pi is the circumference ratio.

The content of the metal oxide particles in the chemical conversion treatment layer was measured by the following method. First, a plurality of comparative samples having a chemical conversion treatment layer having a known content of metal oxide particles were prepared separately from a target sample, the surfaces thereof were measured by a fluorescent X-ray apparatus, and a calibration curve was drawn from the relationship between the detected intensity of the obtained metal element and the content of the metal oxide particles. Then, the target sample was measured by a fluorescent X-ray apparatus under the same conditions as those of the comparative sample, and the content of the metal oxide particles was determined from the obtained detection intensity of the metal element by using the above-mentioned calibration curve.

In the present invention, the average particle diameter of the metal oxide particles dispersed in water before being dispersed in the coating material is maintained in the chemical conversion treatment layer, and therefore, this value can be used as the average particle diameter.

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

From the viewpoint of ensuring a balance between corrosion resistance and golden appearance having a high-quality feel, the metal oxide particles more preferably contain silica particles. The metal oxide particles may contain titanium dioxide particles, aluminum oxide particles, zirconium oxide particles, or the like having the same effect as the silicon dioxide particles.

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

As the Nb compound, a conventionally known niobium-containing compound can be used, and examples thereof include niobium oxide, niobic acid and salts thereof, fluoroniobate, and the like. Among them, niobium oxide is preferably used from the viewpoint of improving corrosion resistance.

Examples of the phosphoric acid compound include phosphoric acids such as orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, triphosphoric acid, tetraphosphoric acid, and salts thereof; phosphonic acids such as aminotri (methylenephosphonic acid), 1-hydroxyethylidene-1,1-diphosphonic acid (1-hydroxyyethyidene-1, 1-diphosphonic acid), ethylenediamine tetra (methylenephosphonic acid), diethylenetriamine penta (methylenephosphonic acid), and salts thereof; organic phosphoric acids such as phytic acid and salts thereof. The cation type of the salt is not particularly limited, and examples thereof include Cu, co, fe, mn, sn, V, mg, ba, al, ca, sr, nb, Y, ni and Zn. These may be used alone or in combination of two or more.

The chemical conversion treatment layer preferably contains a Nb compound and a phosphoric acid compound in a total amount of 0.5 to 30 mass%. When the content of the Nb compound and the phosphoric acid compound is 0.5 mass% or more, the effect of improving the corrosion resistance can be obtained, and when the content of the Nb compound and the phosphoric acid compound is 30 mass% or less, the chemical conversion treatment layer is not embrittled, and the Zn-based plating layer can be stably coated.

Furthermore, the amount of the chemical conversion treatment layer attached to one surface of the Zn-based plating layer is 0.1-15 g/m ² . If the adhesion amount is 0.1g/m ² As described above, the amount of the chemical conversion treatment layer deposited becomes sufficient, the appearance of the Zn-based plating layer can be gold, and the corrosion resistance of the Zn-based plating layer can be improved. In addition, if the adhesion amount is 15g/m ² In the following, even if the chemical conversion treatment layer contains a yellow colorant, the reflection of light at the surface of the chemical conversion treatment layer is reduced, and the appearance of the Zn-based plating layer can be gold without masking the metallic luster of the surface of the Zn-based plating layer. More preferably, the adhesion amount is 0.2 to 2g/m ² . The thickness of the chemical conversion treatment layer is more preferably 0.07 to 15 μm in accordance with the amount of the adhesion.

The chemical conversion treatment 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 alone or in combination of two or more.

When at least one crosslinking agent selected from the silane coupling agent, the crosslinkable zirconium compound and the 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 examples thereof include: vinyl trimethoxysilane, vinyl triethoxysilane, gamma-aminopropyl trimethoxysilane, gamma-aminopropyl ethoxysilane, N- [2- (vinylbenzylamino) ethyl ] -3-aminopropyl trimethoxysilane, gamma-methacryloxypropyl methyldimethoxysilane, gamma-methacryloxypropyl trimethoxysilane, gamma-methacryloxypropyl methyldiethoxysilane, gamma-methacryloxypropyl triethoxysilane, gamma-glycidoxypropyl methyldiethoxysilane, gamma-glycidoxypropyl trimethoxysilane, 2- (3, 4-epoxycyclohexyl) ethyl trimethoxysilane, N-beta (aminoethyl) -gamma-aminopropyl trimethoxysilane, N-beta- (aminoethyl) -gamma-aminopropyl triethoxysilane, N-beta- (aminoethyl) -gamma-aminopropyl methyldimethoxysilane, N-phenyl-gamma-aminopropyl trimethoxysilane, gamma-mercaptopropyl trimethoxysilane, and the like. The silane coupling agent may be used alone, or two or more of them may be used in combination.

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 carboxyl groups and hydroxyl groups, but is preferably a compound soluble in water or an organic solvent, and more preferably a water-soluble zirconium compound. Examples of such a compound include ammonium zirconium 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 carboxyl groups and hydroxyl groups, and examples thereof include dipropoxy-bis (triethanolamine) titanium, dipropoxy-bis (diethanolamine) titanium, propoxy-tris (diethanolamine) titanium, dibutoxy-bis (triethanolamine) titanium, dibutoxy-bis (diethanolamine) titanium, dipropoxy-bis (acetylacetonato) titanium, dibutoxy-bis (acetylacetonato) titanium, dihydroxy-bis (lactate) titanium monoammonium salt (di hydroxy-bis (lacto) titanium monoammonium salt), dihydroxy-bis (lactate) titanium diammonium salt (di hydroxy-bis (lacto) titanium diammonium salt), propane-dioxytitanium bis (acetoacetate ethyl), oxo-titanium bis (monoammonium oxalate) (monoammonium oxalate)), isopropyl-tris (N-amidoethyl) titanate, and the like. The above-mentioned crosslinking agents may be used alone or in combination of two or more.

It is preferable that the resin contains 0.1 to 50% by mass of at least one crosslinking agent selected from the silane coupling agent, the crosslinkable zirconium compound and the crosslinkable titanium compound, based on 100% by mass of the solid content of the resin. When the content of the crosslinking agent is less than 0.1 mass%, the effect of improving the adhesion may not be obtained, and when the content of the crosslinking agent exceeds 50 mass%, the stability of the aqueous composition may be lowered.

The chemical conversion treatment layer may further contain at least one crosslinking agent selected from the group consisting of an amino resin, a polyisocyanate compound, a block body thereof, an epoxy compound, and a carbodiimide compound. These crosslinking agents may be used alone or in combination of two or more.

When the resin composition contains at least one crosslinking agent selected from the group consisting of the amino resin, the polyisocyanate compound, the blocked product thereof, the epoxy compound and the carbodiimide compound, the crosslinking density increases, the barrier property of the chemical conversion coating layer increases, and the corrosion resistance further increases.

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

The polyisocyanate compound is not particularly limited, and examples thereof include hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, and benzylidene diisocyanate. The blocked products are blocked compounds of the polyisocyanate compounds.

The epoxy compound is not particularly limited as long as it has a plurality of oxirane rings, and examples thereof include diglycidyl adipate, diglycidyl phthalate, diglycidyl terephthalate, polyglycidyl sorbitan ether, pentaerythritol polyglycidyl ether, polyglycidyl ether of glycerin, trimethylolpropane polyglycidyl ether, neopentyl glycol polyglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, 2-bis- (4' -glycidoxyphenyl) propane, tris (2, 3-epoxypropyl) isocyanurate, bisphenol a diglycidyl ether, hydrogenated bisphenol a diglycidyl ether, and the like.

Examples of the carbodiimide compound include: and a compound obtained by synthesizing an isocyanate-terminated polycarbodiimide by a condensation reaction of a diisocyanate compound such as an aromatic diisocyanate, an aliphatic diisocyanate, or an alicyclic diisocyanate accompanied by decarbonation, and further adding a hydrophilic segment (hydrophilic segment) having a functional group reactive with an isocyanate group.

It is preferable that the resin contains 0.1 to 50% by mass of at least one crosslinking agent selected from the group consisting of the amino resin, the polyisocyanate compound, the blocked product thereof, the epoxy compound and the carbodiimide compound, based on 100% by mass of the solid content of the resin. When the content is less than 0.1 mass%, the effect of improving the corrosion resistance may not be obtained in some cases, and when the content exceeds 50 mass%, the chemical conversion treatment layer may become brittle and the corrosion resistance may be lowered.

Preferably, the chemical conversion treatment layer further contains at least one selected from the group consisting of vanadium compounds, tungsten compounds and molybdenum compounds. These may be used alone or in combination of two or more.

By containing at least one selected from the above vanadium compounds, tungsten compounds and molybdenum compounds, the corrosion resistance of the chemical conversion treatment layer is improved.

The vanadium compound is not particularly limited, and conventionally known vanadium-containing compounds can be used, and examples thereof include vanadates such as vanadate and ammonium vanadate, sodium vanadate, and the like, phosphovanadates such as phosphovanadate and ammonium phosphovanadate, and the like.

The tungsten compound is not particularly limited, and conventionally known tungsten-containing compounds can be used, and examples thereof include tungstates such as tungstic acid and ammonium tungstate, sodium tungstate, and phosphotungstates such as phosphotungstic acid and ammonium phosphotungstate.

The molybdenum compound is not particularly limited, and conventionally known molybdenum-containing compounds can be used, for example, molybdates and the like can be used. The above-mentioned molybdate is not limited in terms of skeleton and degree of condensation, and examples thereof include orthomolybdate, secondary molybdate, and meta molybdate. Examples of the double salts include all salts such as single salts and double salts, and as the double salts, phosphomolybdates and the like are mentioned.

It is preferable that the resin contains 0.01 to 20% by mass of at least one selected from the group consisting of the vanadium compounds, tungsten compounds and molybdenum compounds, 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 above-mentioned vanadium compound, tungsten compound and molybdenum compound is less than 0.01 mass%, the effect of improving the corrosion resistance may not be obtained, and when the content of at least one selected from the group consisting of the above-mentioned vanadium compound, tungsten compound and molybdenum compound exceeds 20 mass%, the chemical conversion treatment layer may become brittle and the corrosion resistance may be lowered.

The chemical conversion treatment 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 applications and the like are improved.

The polyphenol compound is a compound having 2 or more phenolic hydroxyl groups bonded to a benzene ring, or a condensate thereof. Examples of the compound having 2 or more phenolic hydroxyl groups bonded to a benzene ring include gallic acid, pyrogallol, catechol, and the like. The condensate of a compound having 2 or more phenolic hydroxyl groups bonded to a benzene ring is not particularly limited, and examples thereof include polyphenol compounds widely distributed in the plant kingdom, which are generally called tannic acid. Tannic acid is a generic term for aromatic compounds having a complex structure with a large number of phenolic hydroxyl groups, which are widely distributed in the plant kingdom. The tannic acid may be a hydrolyzable tannic acid or a condensed tannic acid. The tannic acid is not particularly limited, and examples thereof include Hamamelis tannin (hamameli tanin), persimmon tannin (persimmon tanin), tea tannin, gallnut tannin, gallotannin, mi Luoba lantanin (myrobalan tanin), canola tannin (dipyridin), albira tannin (algarovilla tannin), valonea tannin (valonea tanin), and catechin tannin.

As the tannic acid, commercially available products such as "tannic acid extract a", "B tannic acid", "N tannic acid", "industrial tannic acid", "refined tannic acid", "Hi tannic acid", "F tannic acid", "office tannic acid" (all manufactured by japan pharmaceutical corporation), "tannic acid: AL "(manufactured by Fuji chemical Co., ltd.). The above polyphenol compounds may be used alone or in combination of two or more.

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 mass%, the effect of improving the corrosion resistance may not be obtained, and when the content of the polyphenol compound exceeds 50 mass%, the stability of the aqueous composition may be lowered.

The chemical conversion treatment layer may further contain a solid lubricant.

By containing the above solid lubricant, the lubricity of the chemical conversion treatment layer is improved, and the chemical conversion treatment layer has an effect of improving the workability at the time of press forming, preventing scratches caused by a die, handling, and the like, and preventing abrasion damage at the time of conveying a formed article and a coil.

The solid lubricant is not particularly limited, and known lubricants such as fluorine-based, hydrocarbon-based, fatty acid amide-based, ester-based, alcohol-based, metal soap-based, and inorganic-based lubricants may be used. As a selection criterion of a lubricating additive for improving workability, it is necessary to select a substance that can be present on the surface of a chemical conversion treatment layer, compared with a case where an additive lubricant is present in a film-formed chemical conversion treatment layer in a dispersed manner, in order to reduce friction between the surface of a molded product and a mold and to maximize a lubricating effect. That is, when the lubricant is present in a dispersed state in the formed chemical conversion treatment layer, the surface friction coefficient is high, the chemical conversion treatment layer is easily broken, and the powdery material is peeled off and deposited, so that appearance defects called chalking phenomenon and workability are reduced. As a substance which can be present on the surface of the chemical conversion treatment layer, a substance which is not compatible with the resin and has a small surface energy can be 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. When the content of the solid lubricant is less than 0.1%, the effect of improving the workability is small, and when the content of the solid lubricant exceeds 30%, the corrosion resistance may be lowered.

The coating method of the aqueous composition used for forming the chemical conversion treatment layer is a method of forming a coating film by applying the aqueous composition to the surface of the Zn-based plating layer. The coating method is not particularly limited, and a generally used roll coating, air spraying (air spraying), airless spraying, dipping, or the like can be suitably employed. In order to improve the hardenability of the chemical conversion treatment layer, it is preferable to heat the coating material in advance or to thermally dry the coating material after coating. The heat drying method may be any method such as 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 ℃, preferably 70 to 220 ℃. When the heating temperature is less than 50 ℃, the evaporation rate of moisture is slow, and sufficient film forming property cannot be obtained, so that the corrosion resistance may be lowered. On the other hand, when the heating temperature exceeds 250 ℃, thermal decomposition of the resin occurs, corrosion resistance decreases, and appearance deteriorates due to yellowing or the like. The drying time in the case of heat drying after coating is preferably 1 second to 5 minutes. In the case of thermal drying, water cooling is preferable from the viewpoint of productivity in the case of manufacturing by a continuous production line.

The arithmetic average height Sa of the chemical conversion treatment layer is preferably 5nm to 100nm. The arithmetic average height Sa of the chemical conversion treatment layer is 100nm or less, whereby the permeability of the chemical conversion treatment layer can be maintained. On the other hand, if Sa exceeds 100nm, the permeability of the chemical conversion treatment layer may be lowered. The arithmetic average height Sa of the chemical conversion treatment layer was measured and calculated by the following method. Gold was deposited on the surface of a sample cut out from a Zn-based coated steel sheet to a predetermined size to a thickness of 50nm, and the gold deposited sample was buried in a resin and polished so that the cross section of the sample in the plate thickness direction was exposed. The cross section of the sample was observed at a magnification of 5000 times by using a scanning electron microscope, and the roughness of the gold plating layer was calculated when observed from the direction perpendicular to the cross section, thereby obtaining the arithmetic average height Sa of the chemical conversion treatment layer. Since gold vapor deposition is performed to clarify the boundary between the chemical conversion treatment layer and the resin, the thickness of the gold vapor deposition layer is negligible compared to the chemical conversion treatment layer, and therefore the arithmetic average height Sa of the surface of the chemical conversion treatment layer can be replaced with the arithmetic average height of the gold vapor deposition layer.

[ appearance ]

Next, the appearance of the Zn-based plated steel sheet of the present embodiment will be described. The appearance of the Zn-based plated steel sheet according to the present embodiment was measured by CIE1976 (L ^* ，a ^* ，b ^* ) B in the case of color space evaluation ^* 2 to 60, b ^* /a ^* Is-3 or more and 3 or less, in JIS Z8741: 60 degree specular gloss G as defined in 1997 _s (60 DEG) is 50 to 200. In addition, in a plane orthogonal to the surface of the chemical conversion treatment layer, light is incident from an angle of 60 DEG to the surface of the chemical conversion treatment layer toward the surface of the chemical conversion treatment layer, and L obtained when light reflected at the surface of the chemical conversion treatment layer is received at an angle of 135 DEG to the surface of the chemical conversion treatment layer ^* Denoted by L1, in the plane described above, L obtained when light is incident from an angle of 120 ° to the surface of the chemical conversion treatment layer toward the surface of the chemical conversion treatment layer and light reflected at the surface of the chemical conversion treatment layer is received at an angle of 135 ° to the surface of the chemical conversion treatment layer ^* When the value is recorded as L.times.2, L ^* 1 and L ^* 2 satisfies the following formula 1.

10. Not less than 1/2 not less than 2. Formula 1

Hereinafter, the reason for this limitation will be described.

The higher the surface light reflection at the Zn-based plating layer, the higher the brightness, and if the reflection is lower, the reflection in the chemical conversion treatment layer increases, and from this point, the reflection is not the prescribed b ^* B ^* /a ^* When the metallic luster of the Zn-based plating layer is not visually recognized, the Zn-based plating layer does not exhibit gold in appearance. Here, it was found that: in order to obtain a synergistic effect between a Zn-based plating layer exhibiting metallic luster and a chemical conversion treatment layer colored yellow by a yellow colorant, it is necessary to make b ^* B ^* /a ^* And 60 degree specular gloss G _s (60 DEG) is within a predetermined range, and L is ^* 1 and L ^* 2 satisfies 10 is more than or equal to L ^* 1/L ^* 2. Not less than 2 (formula 1).

When CIE1976 (L) ^* ，a ^* ，b ^* ) B in case of evaluating color space ^* At less than 2, the color substantially disappears, becoming non-gold. In addition, if b ^* If the number exceeds 60, the color becomes a dark color, the metallic appearance cannot be recognized sufficiently, and the gold color is not developed. Thus b ^* The range is 2 to 60 inclusive. From the viewpoint of maintaining golden color, b ^* The lower limit of (2) is preferably 3.5, more preferably 5. B from the viewpoint of maintaining metallic appearance ^* The upper limit of (2) is preferably 40, more preferably 30.

If CIE1976 (L) ^* ，a ^* ，b ^* ) B in case of evaluating color space ^* /a ^* Less than-3, the yellow-red color becomes rich and thus becomes non-gold. In addition, if b ^* /a ^* Above 3, the green color becomes rich and becomes non-gold. Therefore, b/a is set to a range of-3 or more and 3 or less.

In addition, if 60 degrees specular gloss G _s When the (60 °) is less than 50, the appearance of the Zn-based coated steel sheet is close to white, the metallic luster of the Zn-based coating is impaired, and the appearance of the Zn-based coating does not show gold. In addition, if 60 degrees specular gloss G _s When the (60 °) exceeds 200, the reflection at the surface of the chemical conversion treatment layer becomes strong, and the Zn-based plating layer becomes yellow in appearance, and does not become gold.

In addition, through L ^* 1/L ^* The color development of the color is improved when the color is less than or equal to 2, and the color development is improved when the color is less than or equal to 10. Through L ^* 1/L ^* 2 is 2 or more, and has the effect of maintaining the metallic appearance. The lower limit value of L1/L2 is more preferably 4 from the viewpoint of maintaining a more attractive metallic appearance. From the viewpoint of showing a high-quality gold color, the upper limit value of L1/L2 is more preferably 7.

In addition, regarding the appearance of the Zn-based plated steel sheet of the present embodiment, it is preferable that: l was measured in a range of 0.5mm in diameter around any 5 points on the surface of the plating layer from which the surface coating film including the chemical conversion treatment layer was removed ^* When, L ^* Maximum value (L) ^* max) is L ^* Minimum value (L) ^* min) is more than 1.2 times of the total weight of the composition.

Through L ^* Maximum value (L) ^* max) is L ^* Minimum value (L) ^* min) is 1.2 times or more, and local fluctuation occurs in golden yellow, and thus has an effect of producing a deep sense of high quality as a result.

L was measured at 5 points selected arbitrarily for the surface of the coating layer from which the top coating film including the chemical conversion treatment layer was removed by using a coating film remover (for example, coating film from three color chemical Co., ltd.) which does not attack the coating layer, using a micro-area spectrocolorimeter (VSS 7700 from Nippon electric color Co., ltd.) ^* . At the measured L ^* Among them, the largest L ^* The value is recorded as L ^* max, will be the smallest L ^* The value is recorded as L ^* min。

The Zn-based plating layer according to the present embodiment may have a pattern portion and a non-pattern portion arranged so as to have a predetermined shape on the surface thereof.

The pattern portion is preferably arranged in a shape of one or a combination of two or more of a straight line portion, a curved line portion, a dot portion, a figure, a number, a symbol, a pattern, and a character. The non-pattern portion is a region other than the pattern portion. In addition, the shape of the pattern portion is allowed to be recognized as a whole even if a part of the pattern portion is missing as if the dots were missing. The non-pattern portion may have a shape in which a boundary of the pattern portion is decorated.

When a Zn-based plating layer has a surface in which any one of straight portions, curved portions, dot portions, figures, numerals, signs, figures, or characters, or a shape in which two or more of them are combined is arranged, a region of the Zn-based plating layer may be used as a pattern portion, and the other regions may be used as non-pattern portions. The boundaries between the pattern portions and the non-pattern portions can be grasped with the naked eye. The boundaries between the pattern portion and the non-pattern portion can be grasped from a magnified image by an optical microscope, a magnifying glass, or the like.

The pattern portion may be formed to a size that can discriminate the presence of the pattern portion under the naked eye, under a magnifying glass, or under a microscope. The non-pattern portion is a region occupying most of the Zn-based plating layer (surface of the Zn-based plating layer), and the pattern portion may be disposed in the non-pattern portion.

The pattern portion is arranged in a predetermined shape in the non-pattern portion. Specifically, the pattern portion is arranged in the non-pattern portion so as to be any one of a straight line portion, a curved line portion, a figure, a dot portion, a figure, a numeral, a symbol, a pattern, and a character, or a shape in which two or more of them are combined. By adjusting the shape of the pattern portion, any one or a combination of two or more of a straight portion, a curved portion, a pattern, a dot portion, a pattern, a number, a symbol, a pattern, and a character is formed on the surface of the Zn-based plating layer. For example, character strings, number strings, marks (marks), line drawings, design drawings, combinations thereof, or the like, which are formed of pattern portions, are displayed on the surface of the Zn-based plating layer. The shape is a shape formed intentionally or manually by a manufacturing method described later, and is not a shape 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 one or both of the 1 st region and the 2 nd region are included in the pattern portion and the non-pattern portion, respectively.

The pattern portion and the non-pattern portion include one or both of the 1 st region and the 2 nd region determined by any one of the determination methods 1 to 5 described below, respectively, and an absolute value of a difference between an area ratio of the 1 st region in the pattern portion and an area ratio of the 1 st region in the non-pattern portion is 30% or more. When the difference between the area ratio of the 1 st region in the pattern portion and the area ratio (area ratio) of the 1 st region in the non-pattern portion is 30% or more in absolute value, it becomes possible to identify the pattern portion and the non-pattern portion. When the difference in the area ratio is less than 30%, the difference in the area ratio of the 1 st region in the pattern portion and the area ratio of the 1 st region in the non-pattern portion is small, and the appearance of the pattern portion and the non-pattern portion is similar, and it becomes difficult to recognize the pattern portion. The larger the difference in the area ratios, the more preferably the difference in the area ratios is 40% or more, and further preferably the difference in the area ratios is 60% or more.

That is, the area ratio of each of the 1 st region and the 2 nd region can be obtained in the pattern portion. When the area fraction of the 1 st region exceeds 70%, the pattern portion appears to be a relatively white or nearly white color, relative to the case where the area fraction of the 1 st region is 70% or less. When the area fraction of the 1 st region is 30% or more and 70% or less, the pattern portion appears pear-shaped. In addition, when the area fraction of the 1 st region is less than 30%, the pattern portion appears to have metallic luster. Thus, the appearance of the pattern portion depends on the area fraction of the 1 st region.

On the other hand, the area ratio of each of the 1 st region and the 2 nd region can be obtained also in the non-pattern portion. The appearance of the non-pattern portion depends on the area fraction of the 1 st region, as in the pattern portion.

Further, in the case where the difference between the area ratio of the 1 st region in the pattern portion and the area ratio of the 1 st region in the non-pattern portion is 30% or more in absolute value, it becomes possible to identify the pattern portion and the non-pattern portion. When the difference in the area ratio is less than 30%, the difference in the area ratio of the 1 st region in the pattern portion and the area ratio of the 1 st region in the non-pattern portion is small, and the appearance of the pattern portion and the non-pattern portion is similar, and it becomes difficult to recognize the pattern portion. The difference in area ratio is preferably 40% or more, more preferably 60% or more.

[ determination method 1]

In the determination method 1, virtual grid lines are drawn at 0.5mm intervals on the surface of the Zn-based plating layer, and L in each measurement region A is measured in a circle having a diameter of 0.5mm centered on the center of gravity of each region among a plurality of regions divided by the virtual grid lines, as the measurement region A ^* Values. From the L thus obtained ^* Selecting arbitrary 50 points from the values, and obtaining L ^* The 50-point average of the values is taken as a reference L ^* When the value is, L ^* The value becomes the reference L ^* The 1 st region is the region with the value above L ^* A value smaller than the reference L ^* The region of values is taken as region 2.

[ determination method 2]

In the determination method 2, virtual grid lines are drawn at 0.5mm intervals on the surface of the Zn-based plating layer, and L in each measurement region A is measured in a circle having a diameter of 0.5mm centered on the center of gravity of each region among a plurality of regions divided by the virtual grid lines, as the measurement region A ^* Value, L ^* An area having a value of 45 or more is defined as the 1 st area, L ^* The region with a value less than 45 is referred to as the 2 nd region.

[ determination method 3]

In the determination method 3, virtual lattice lines are drawn at intervals of 0.5mm on the surface of the Zn-based plating layer, and the arithmetic average surface roughness Sa is measured in each of a plurality of areas divided by the virtual lattice lines. The 1 st region was defined as a region having a Sa of 1 μm or more, and the 2 nd region was defined as a region having a Sa of less than 1 μm. The arithmetic average roughness Ra was measured by a 3D laser microscope (manufactured by k-gram, inc.). In the present embodiment, the height Z in each of the regions divided by the virtual grid line is measured at 50 μm measurement intervals using a standard lens of 20 times. In the case of measurement on a grid, a measurement point of 100 points is obtained in the region. The obtained height Z at 100 points was designated as a height Z1 to a height Z100, and the arithmetic average roughness Ra was calculated using these heights and using the following equation 5. Zave is the average of the heights Z at 100 points.

Ra=1/100×Σ [ x=1→100] (|height Zx-zave|) … type 5

[ determination method 4]

In the determination method 4, virtual grid lines are drawn at 1mm intervals or 10mm intervals on the surface of the Zn-based plating layer, and the diffraction peak intensity I of the (0002) plane of the Zn phase is measured for each of the regions by an X-ray diffraction method in which X-rays are incident on each of the regions divided by the virtual grid lines ₀₀₀₂ Diffraction peak intensity I of (10-11) plane of Zn phase _10-11 Their intensity ratio (I ₀₀₀₂ /I _10-11 ) As the orientation ratio. The 1 st region was a region having an orientation ratio of 3.5 or more, and the 2 nd region was a region having an orientation ratio of less than 3.5.

[ determination method 5]

In the determination method 5, virtual grid lines are drawn at 1mm 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 centered on the center of gravity point G of each region is drawn. The circle S has a diameter R set so that the total length of the surface boundary lines of the Zn-based plating layer contained in the interior of the circle S becomes 10 mm. The average value of the maximum diameter Rmax and the minimum diameter Rmin among the diameters R of the circles S of the plurality of regions is set as a reference diameter Rave, the region having the circle S with the diameter R smaller than the reference diameter Rave is set as the 1 st region, and the region having the circle S with the diameter R equal to or larger than the reference diameter Rave is set as the 2 nd region.

The formation of the patterned portion and the non-patterned portion specified by the determination method 1 or 2 is performed after the Zn-based plating layer is formed. The formation of the pattern portion and the non-pattern portion is performed by adhering an acidic solution to the surface of the Zn-based plating layer at 60 to 200 ℃. More specifically, the acidic solution may be prepared and attached to the surface of the Zn-based plating layer by a printing method. As the printing method, a general printing method using various types of printing methods (gravure printing, flexography (flexographic printing), offset printing, screen printing (silk printing), or the like), an inkjet method, or the like can be applied.

The surface of the Zn-based plating layer is changed from the plated state by dissolving the polar surface of the Zn-based plating layer at the site where the acidic solution adheres. Thereby, the appearance of the portion to which the acidic solution is attached is changed as compared with the portion to which the acidic solution is not attached. In this way, it is estimated that the difference between the area ratio of the 1 st region in the pattern portion and the area ratio of the 1 st region in the non-pattern portion becomes large, and it becomes possible to identify the pattern portion and the non-pattern portion.

The adhesion range of the acidic solution may be set to a region corresponding to the pattern portion or a region corresponding to the non-pattern portion.

As the acidic solution, an inorganic acid such as hydrochloric acid, nitric acid, sulfuric acid, or the like is preferably used. The concentration of the acid in the acidic solution is preferably 0.1 to 10 mass%. The temperature of the steel sheet at the time of adhesion of the acidic solution may be 60 to 200 ℃, and is desirably 50 to 80 ℃. By adjusting the type and concentration of the acidic solution, the area fraction of the 1 st region and the 2 nd region on the Zn-based plating layer surface can be adjusted at the site where the acidic solution adheres.

When the surface temperature of the Zn-based plating layer at the time of adhesion of the acidic solution is lower than 60 ℃, it takes time for forming the pattern portion or the non-pattern portion, and therefore, it is not preferable, and when the surface temperature of the Zn-based plating layer exceeds 200 ℃, the acidic solution immediately volatilizes, and it becomes impossible to form the pattern portion or the non-pattern portion, and therefore, it is not preferable.

After the acid solution is adhered, it is necessary to wash with water within 1 to 10 seconds.

Next, the patterned portion and the non-patterned portion specified by the determination method 3 were formed after the Zn-based plating layer was formed. The patterned portion and the non-patterned portion are formed by pressing a roller having a partially increased surface roughness against the surface of the Zn-based plating layer, and transferring the surface shape of the roller 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 in the roller surface is increased relative to other portions, whereby a pattern portion including a large number of 1 st regions having a large surface roughness can be formed. In addition, conversely, a roller may be used which reduces the roughness of the portion corresponding to the pattern portion relative to other portions. Regarding the roughness of the roller surface (arithmetic average surface roughness, sa (μm)), the range of the roughness of the portion where the roughness is improved is set to 0.6 to 3.0 μm, preferably 1.2 to 3.0 μm. The roughness of the roughness-reduced portion may be in the range of 0.05 to 1.0. Mu.m, preferably 0.05 to 0.8. Mu.m. The transfer can be performed at a surface temperature of the Zn-based plating layer in the range of 100 to 300 ℃. The difference between the roughness of the roughness-increased portion and the roughness of the roughness-reduced portion is set to be more than 0.2 μm, preferably 0.3 μm or more, in terms of the arithmetic average surface roughness Sa. If the difference in roughness becomes small, it becomes difficult to distinguish between the pattern portion and the non-pattern portion.

The pattern portion and the non-pattern portion are specified by the determination method 4, and the non-oxidizing gas is locally injected into the molten metal by the gas nozzle with respect to the steel sheet immediately after the steel sheet is lifted from the hot dip plating bath. As the non-oxidizing gas, nitrogen or argon may be used. Although the optimum temperature range varies depending on the composition, it is preferable to perform the blowing of the non-oxidizing gas when the temperature of the molten metal is in the range of (final solidification temperature-5) to (final solidification temperature +5). The temperature of the non-oxidizing gas is set lower than the final solidification temperature.

When the Zn-based coating is in the above temperature range, the cooling rate of the molten metal increases at the portion to which the non-oxidizing gas is blown, and thus the orientation rate of the Zn-based coating after solidification increases. On the other hand, in the portion where the non-oxidizing gas is not blown, the cooling rate of the molten metal is lowered, and thus the orientation rate of the Zn-based plating layer after solidification is lowered. Therefore, by adjusting the blowing range of the non-oxidizing gas, the appearance positions of the regions having a high orientation ratio and the regions having a low orientation ratio can be intentionally or arbitrarily adjusted.

This makes it possible to arbitrarily adjust the shapes of the pattern portions and the non-pattern portions, and to identify the pattern portions and the non-pattern portions. Since the orientation ratio is higher as the temperature of the blown gas is lower, the orientation ratio can be adjusted by using the temperature of the blown gas. The gas temperature is preferably set lower than the final solidification temperature, and the gas temperature may be adjusted to 25 to 250 ℃.

The pattern portion and the non-pattern portion are specified by the determination method 5, and the non-oxidizing gas at a temperature equal to or higher than the final solidification temperature of the plating layer is locally sprayed onto the molten metal by the gas nozzle with respect to the steel sheet immediately after the steel sheet is lifted from the hot dip plating bath. As the non-oxidizing gas, nitrogen or argon may be used. Although the optimum temperature range varies depending on the composition, it is preferable to perform the blowing of the non-oxidizing gas when the temperature of the molten metal is in the range of (final solidification temperature-5) to (final solidification temperature +5). The temperature of the non-oxidizing gas is preferably equal to or higher than the final solidification temperature. For example, in Al:11%, mg: at a plating composition of 3%, it is preferable to blow a non-oxidizing gas having a gas temperature equal to or higher than the final solidification temperature at a temperature of 330 to 340 ℃.

The cooling rate of the molten metal is lowered around the portion to which the non-oxidizing gas is blown, and thus the boundary or grain boundary appearing on the surface becomes coarse. Therefore, by adjusting the amount and the range of the non-oxidizing gas to be injected, the size of the boundary or grain boundary appearing on the surface can be arbitrarily adjusted.

By setting the absolute value of the difference between the area ratio of the 1 st region in the pattern portion and the area ratio of the 1 st region in the non-pattern portion to 30% or more, it becomes possible to identify the pattern portion and the non-pattern portion. Since the patterned portion and the non-patterned portion are not formed by printing and painting, durability is improved. Further, since the pattern portion and the non-pattern portion are not formed by printing or painting, the corrosion resistance of the Zn-based plating layer is not affected. Therefore, the Zn-based plated steel sheet of the present embodiment is excellent in corrosion resistance.

A Zn-coated steel sheet having suitable coating characteristics such as high durability and corrosion resistance of a pattern part in a Zn-coated layer on which the pattern part is formed can be provided. Since the pattern portion can be formed in an intentional or artificial shape, the pattern portion can be arranged so as to be any one of a straight line portion, a curved line portion, a dot portion, a figure, a numeral, a symbol, a pattern, and a character, or a shape in which two or more of them are combined. This makes it possible to display various designs, trademarks, and other identification marks on the surface of the Zn-based plating without printing or coating, and to improve the identification of the origin (source) of the steel sheet, design, and the like. Further, any information required for process management, inventory management, and the like, and any information required by the user may be provided to the hot-dipped steel sheet by the pattern portion. This can contribute to improvement in productivity of the Zn-based plated steel sheet.

Further, according to the Zn-based coated steel sheet of the present embodiment, the chemical conversion treatment layer containing the yellow colorant is formed on the Zn-based coating layer on which the pattern portion is formed, so that the visibility of the pattern portion can be further improved.

Examples

Hereinafter, the present invention will be specifically described with reference to examples.

First, a cold-rolled steel sheet having a thickness of 1mm was prepared, immersed in a plating bath of each composition, and passed through N ₂ Wiping to adjust the coating adhesion to 80g/m on one side ² . The coating composition of the obtained Zn-based coated steel sheet is shown in table 1.

When the Zn-based plating layer is formed into a pattern portion, the pattern is further applied by the following method. The pattern portion and the non-pattern portion each include one or both of the 1 st region and the 2 nd region determined by any one of the determination methods 1 to 5, and an absolute value of a difference between the area ratio of the 1 st region in the pattern portion and the area ratio of the 1 st region in the non-pattern portion is 40%.

Pattern 1 >, pattern

The hydrochloric acid solution was adhered to a rubber plate having a square pattern of convex portions or concave portions with a single side of 50mm, and the rubber plate was pressed against the surface of the Zn-based plating layer, whereby the acidic solution was adhered to the steel sheet to form square pattern portions. The surface temperature of the Zn-based coating layer of the hot-dip coated steel sheet at the time of the adhesion of the acidic solution is set to be in the range of 60 to 200 ℃. In addition, a portion other than the square pattern portion is used as the non-pattern portion. Then, based on the determination method 2, virtual grid lines were drawn at 0.5mm intervals on the surface of the Zn-based plating layer, and, among the plurality of regions divided by the virtual grid lines, L in each measurement region a was measured using, as measurement region a, a circle having a diameter of 0.5mm centered on the center of gravity of each region ^* Value, L ^* An area having a value of 45 or more is defined as the 1 st area, L ^* The region with a value less than 45 is referred to as the 2 nd region. The Zn-coated steel sheet was used in example 59.

Pattern 2 >, pattern 2

A roller having a square pattern with a single side of 50mm is pressed against the surface of the Zn-based plating layer in a state where the surface temperature of the Zn-based plating layer is 100 to 300 ℃, thereby forming a pattern portion. The square pattern portions are used as pattern portions, and the portions other than the square pattern portions are used as non-pattern portions. Based on determination method 3, virtual grid lines were drawn at 0.5mm intervals on the surface of the Zn-based plating layer, and the arithmetic average surface roughness Sa was measured in each of a plurality of areas divided by the virtual grid lines. The 1 st region was defined as a region where the obtained Sa was 1 μm or more, and the 2 nd region was defined as a region where the obtained Sa was less than 1 μm. The Zn-coated steel sheet was used in example 60.

Pattern 3 >, pattern

When the temperature of the molten metal is in the range of (final solidification temperature-5) DEG C to (final solidification temperature +5) DEG C when the steel sheet is lifted from the plating bath,nitrogen gas, which is one of non-oxidizing gases, is blown onto the molten metal on the surface of the steel sheet by means of a gas nozzle. The gas temperature is below the final solidification temperature. Then, cooling is performed to completely solidify the molten metal. The nitrogen gas blowing range was controlled so as to form a square pattern having a single side of 50 mm. The square pattern portions are used as pattern portions, and the portions other than the square pattern portions are used as non-pattern portions. Based on the determination method 4, virtual grid lines were drawn at 1mm intervals or 10mm intervals on the surface of the Zn-based plating layer, and the diffraction peak intensity I of the (0002) plane of the Zn phase was measured for each of the regions by an X-ray diffraction method in which X-rays were incident on each of the regions divided by the virtual grid lines ₀₀₀₂ Diffraction peak intensity I of (10-11) plane of Zn phase _10-11 Their intensity ratio (I ₀₀₀₂ /I _10-11 ) As the orientation ratio. The 1 st region was a region having an orientation ratio of 3.5 or more, and the 2 nd region was a region having an orientation ratio of less than 3.5. The Zn-coated steel sheet was used in example 61.

Pattern 4 >, pattern

When the steel sheet is lifted from the plating bath, nitrogen gas, which is one of the non-oxidizing gases, is blown from the gas nozzle toward the molten metal on the surface of the steel sheet in a heated state when the temperature of the molten metal is in the range of (final solidification temperature-5) to (final solidification temperature +5). The nitrogen blowing conditions are shown in table 1. The temperature is above the final solidification temperature. Then, cooling is performed to completely solidify the molten metal. The nitrogen gas blowing range was controlled so as to form a square pattern having a single side of 50 mm. The square pattern portions are used as pattern portions, and the portions other than the square pattern portions are used as non-pattern portions. Then, based on the determination method 5, virtual grid lines were drawn at 1mm 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 centered on the center of gravity point G of each region was drawn. The diameter R of the circle S is set so that the total length of the surface boundary lines of the Zn-based plating layer contained in the interior of the circle S becomes 10 mm. The average value of the maximum diameter Rmax and the minimum diameter Rmin among the diameters R of the circles S of the plurality of regions is set as a reference diameter Rave, the region having the circle S with the diameter R smaller than the reference diameter Rave is set as the 1 st region, and the region having the circle S with the diameter R equal to or larger than the reference diameter Rave is set as the 2 nd region. The Zn-coated steel sheet was used in example 62.

Next, if necessary, the Zn-based coated steel sheet was immersed in a Co sulfate solution, an Fe sulfate solution, or a Ni sulfate solution to deposit 1mg/m on the surface of the Zn-based coating layer ² Co, fe or Ni of (C). The composition of the Zn plating layer is shown in table 3A and table 3B.

Next, the surface of the Zn-based coating layer of the Zn-based coated steel sheet thus produced was dried by a bar coater to give a dry adhesion amount of 1.5g/m ² An aqueous composition containing various aqueous resins (urethane resin, polyester resin, polyolefin resin, epoxy resin, acrylic resin, phenolic resin, and fluororesin), metal oxide particles, niobium oxide, sodium phosphate, and a yellow colorant (azo yellow pigment, and iron oxide yellow pigment) was applied, dried in a hot air drying oven at a plate temperature of 150 ℃, and then cooled with water, thereby forming a chromate-free chemical conversion treatment layer. The contents of niobium oxide and sodium phosphate were set to 5% respectively. Further, as the metal oxide particles, silica (SiO ₂ ) Titanium dioxide (TiO) ₂ ) Alumina (Al) ₂ O ₃ ) Zirconium oxide (ZrO) ₂ ). In addition, details of the yellow colorant are shown in table 2. The chemical conversion treatment layer composition and the like are shown in tables 4A to 5B. In the columns "Nb oxide" in table 5A and table 5B, the case containing niobium oxide was marked "o", and the case not containing niobium oxide was marked "x". In the column "sodium phosphate", the case containing sodium phosphate is indicated by "o", and the case not containing sodium phosphate is indicated by "x".

(60-degree specular gloss Gs (60 °))

The 60 ° glossiness (%) of the surface of the Zn plating layer was measured based on the method specified in JIS Z8741 using a glossmeter. The case where the glossiness is 50 to 200% is referred to as "a", and the case where the glossiness is less than 50% is referred to as "B". The results are shown in Table 6A and Table 6B.

(b, b/a)

The surface of the Zn plating layer on which the chemical conversion treatment layer was formed was measured by using a spectrocolorimeter (SE 6000, manufactured by Nippon Denshoku Co., ltd.). Will b ^* The cases of 2 to 60 inclusive are denoted as "A", and b is defined as ^* Cases less than 2 or more than 60 are denoted as "B". And, will b ^* /a ^* A is a number of-3 or more and 3 or less, b is represented by "A" ^* /a ^* Cases less than-10 or exceeding-3 are noted as "B". The results are shown in Table 6A and Table 6B.

(L ^* 1/L ^* 2)

Will L ^* 1/L ^* The cases where 2 is 4 or more and 7 or less are denoted as "A", and L ^* 1/L ^* 2 is 2 or more and less than 4, or more than 7 and 10 or less, denoted as "B", L ^* 1/L ^* Cases where 2 is less than 2 or greater than 10 are denoted as "C".

(Corrosion resistance)

The Zn-coated steel sheet was subjected to a salt spray test (JIS Z2371:2015). White rust occurrence after 24 hours of the test time of the portion subjected to Erichsen (Erichsen) processing was observed, and the evaluation was performed according to the following score. And judging the score of 3 or more as qualified. The results are shown in Table 6A and Table 6B.

4: white rust occurrence is less than 5%

3: white rust is generated by more than 5% and less than 10%

2: white rust occurs by more than 10% and less than 30%

1: white rust occurrence of more than 30 percent

(golden appearance)

When 5 panelists observed the surface of the Zn-plated layer of the Zn-plated steel sheet, the evaluation was made based on the appearance of gold. The evaluation was judged according to the following score, and a score of 3 or more was judged as being acceptable. The results are shown in Table 6A and Table 6B.

5: more than 4 out of 5 people can recognize gold, and feel no deviation of light reflection and have high-grade feeling.

4: more than 4 out of 5 people can recognize gold, and no deviation of light reflection is perceived.

3: 3 of the 5 people can recognize the gold color.

2: 2 out of 5 people can recognize gold.

1: of the 5, 1 or less can recognize gold.

As shown in tables 1 to 6B, the Zn-based plated steel sheets of examples 1 to 71 each had a chemical conversion treatment layer satisfying the scope of the present invention, and were excellent in corrosion resistance and golden appearance.

Further, in examples 59 to 62 in which the pattern portion was formed on the plating layer, the corrosion resistance and golden appearance were good, and the visibility of the pattern portion was greatly improved. In some examples, the amount of the chemical conversion treatment layer to be adhered was set to 0.1 to 15.0g/m ² But the results were good.

On the other hand, as shown in tables 1 to 6B, in comparative example 1, since the chemical conversion treatment layer contained no resin, the chemical conversion treatment layer itself became extremely brittle, and various evaluation tests could not be performed.

In comparative example 2, since the chemical conversion treatment layer does not contain a yellow colorant, b ^* Value sum b ^* /a ^* The golden appearance was insufficient outside the scope of the present invention.

Comparative examples 3, 4 and 5, which contain Cu phthalocyanine, co phthalocyanine, quinacridone in the chemical conversion treatment layer, respectively, are not yellow colorants according to the present invention, that is, comparative examples 3 to 5 do not contain yellow colorants, so b ^* Value sum b ^* /a ^* At least one of them is out of the scope of the present invention, and the golden appearance is insufficient.

Comparative examples 6 and 7, wherein the adhesion amount of the chemical conversion treatment layer was 0.1 to 15.0g/m ² Out of range of (b), thus b ^* The value or 60 degree specular gloss Gs (60 DEG) deviates from the scope of the invention, and in addition, L ^* 1/L ^* 2 deviate from the scope of the present invention, the golden appearance is insufficient.

TABLE 1

TABLE 2

	Detailed description
		Condensed azo pigments	AF yellow E-12 manufactured by Dai refining industry Co., ltd
Iron oxide	NAF502 manufactured by Dai refining industry Co., ltd
		Chrome yellow	Reagent manufactured by Kanto Chemie Co., ltd
Cu phthalocyanine	NAF1052 manufactured by Dai refining industry Co., ltd
		Co phthalocyanine	Dari refining industry Co., ltd
Quinacridones	NAF1032 manufactured by Dai refining industry Co., ltd

TABLE 3A

TABLE 3B

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TABLE 5A

TABLE 5B

The underlined section indicates that it is outside the scope of the present invention.

TABLE 6A

TABLE 6B

Industrial applicability

According to the present invention, a Zn-based plated steel sheet having a gold appearance with a high quality feeling and improved corrosion resistance can be provided, and therefore the present invention has high industrial applicability.

Claims

1. A Zn-based coated steel sheet is characterized by comprising:

a steel plate;

the chemical conversion treatment layer contains a resin and a yellow colorant,

incident light from an angle of 60 DEG to the surface of the chemical conversion treatment layer toward the surface in a plane orthogonal to the surface, and receiving light reflected at the surface at an angle of 135 DEG to the surface ^* Denoted by L1, in the plane, L obtained when light is incident from an angle of 120 ° to the surface towards the surface and light reflected at the surface is received at an angle of 135 ° to the surface ^* When written as L.times.2, the L ^* 1 and said L ^* 2 satisfies the following formula 1: 10. not less than 1L/2 not less than 2.1.

2. The Zn-based coated steel sheet as set forth in claim 1, wherein said yellow colorant is an azo-based yellow pigment or an iron oxide-based yellow pigment.

3. The Zn-based coated steel sheet as set forth in claim 1 or 2, wherein the content of said yellow colorant in said chemical conversion treatment layer is 0.1 to 10 mass%.

4. A Zn-based plated steel sheet according to any one of claims 1 to 3, wherein the L ^* 1 and said L ^* 2 satisfies the following formula 2: 7. and (2) not less than 1/2 of L and not less than 4.cndot.2 of formula (2).

5. The Zn-based coated steel sheet according to any one of claims 1 to 4, wherein the chemical conversion treatment layer contains 1 to 20 mass% of metal oxide particles having an average particle diameter of 5 to 200nm and a refractive index of 1.3 to 2.5.

6. The Zn-based plated steel sheet according to claim 5, wherein the metal oxide particles comprise silica particles.

7. The Zn-based coated steel sheet as set forth in claim 5 or 6, wherein the mixing ratio of said yellow colorant to said metal oxide particles in said chemical conversion treatment layer is in the range of 1 to 200.

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

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

10. The Zn-based plated steel sheet according to any one of claims 1 to 9, wherein either one or both of a Nb compound and a phosphoric acid compound is further contained in the chemical conversion treatment layer.

11. The Zn-based coated steel sheet as defined in any one of claims 1 to 10 wherein said resin in said chemical conversion treatment layer is composed of any one or more resins selected from polyolefin resins, fluorine resins, acrylic resins, polyurethane resins, polyester resins, epoxy resins, and phenolic resins.

12. The Zn-based plated steel sheet according to any one of claims 1 to 11, wherein the Zn-based plated layer contains, in terms of average composition: 4 mass% or more and 22 mass% or less, mg: more than 1 mass% and not more than 10 mass%, the balance being Zn and impurities.

13. The Zn-based plated steel sheet according to any one of claims 1 to 12, further comprising, in terms of average composition, si:0.0001 to 2 mass percent.

14. The Zn-based plated steel sheet according to any one of claims 1 to 13, wherein the Zn-based plated layer further contains any one or two or more of Ni, sb, and Pb in a total amount of 0.0001 to 2 mass% on an average composition basis.

15. The Zn-based plated steel sheet according to any one of claims 1 to 14, wherein for any 5 points on the surface of the plated layer, L having a diameter in the range of 0.5mm centered on each point is measured ^* When L ^* Has a maximum value of L ^* Is more than 1.2 times the minimum value of (2).

16. The Zn-coated steel sheet according to any one of claims 1 to 15, wherein the Zn-coated steel sheet comprises pattern portions and non-pattern portions formed so as to have a predetermined shape,

The absolute value of the difference between the area ratio of the 1 st region in the pattern portion and the area ratio of the 1 st region in the non-pattern portion is 30% or more,

decision method 1: the surface of the Zn-based plating layer was drawn at 0.5mm intervalsDrawing virtual lattice lines, and measuring L in each measurement region A as measurement region A in a circle having a diameter of 0.5mm centered on the center of gravity of each region among a plurality of regions divided by the virtual lattice lines ^* Value from the resulting L ^* Selecting arbitrary 50 points from the values, and obtaining L ^* The 50-point average of the values is taken as a reference L ^* When the value is, L ^* The value becomes the reference L ^* The 1 st region is the region with the value above L ^* A value smaller than the reference L ^* The region of values is taken as the 2 nd region;

decision method 2: virtual grid lines are drawn at 0.5mm intervals on the surface of the Zn-based plating layer, and L in each measurement region A is measured in a circle having a diameter of 0.5mm centered on the center of gravity of each region among a plurality of regions divided by the virtual grid lines as measurement regions A ^* Value, L ^* An area having a value of 45 or more is defined as the 1 st area, L ^* A region having a value less than 45 is regarded as a 2 nd region;

decision method 3: drawing virtual grid lines at intervals of 0.5mm on the surface of the Zn-based plating layer, measuring arithmetic average surface roughness Sa in each of a plurality of regions divided by the virtual grid lines, wherein the 1 st region is a region where the obtained Sa is 1 μm or more, and the 2 nd region is a region where the obtained Sa is less than 1 μm;

Decision method 4: drawing virtual grid lines at intervals of 1mm or 10mm on the surface of the Zn-based plating layer, and measuring the diffraction peak intensity I of the (0002) plane of Zn phase for each of the regions by an X-ray diffraction method in which X-rays are incident on each of the regions divided by the virtual grid lines ₀₀₀₂ Diffraction peak intensity I of (10-11) plane of Zn phase _10-11 Their intensity ratio (I ₀₀₀₂ /I _10-11 ) As the orientation ratio, a region having the orientation ratio of 3.5 or more is referred to as a 1 st region, and a region having the orientation ratio of less than 3.5 is referred to as a 2 nd region;

decision method 5: a virtual grid line is drawn on the surface of the Zn-based plating layer at 1mm intervals, then, for each of a plurality of regions divided by the virtual grid line, a circle S centered on a center of gravity point G of each region is drawn, the circle S having a diameter R set such that a total length of surface boundary lines of the Zn-based plating layer contained in the inside of the circle S becomes 10mm, an average value of a maximum diameter Rmax and a minimum diameter Rmin among the diameters R of the circle S of the plurality of regions is set as a reference diameter Rave, a region having a circle S with a diameter R smaller than the reference diameter Rave is set as a 1 st region, and a region having a circle S with a diameter R equal to or greater than the reference diameter Rave is set as a 2 nd region.

17. The Zn-based plated steel sheet according to any one of claims 1 to 16, wherein any one of Co, fe, and Ni is provided on the surface of the Zn-based plated layer.