Plated steel sheet

Abstract

Provided is a plated steel sheet having excellent texture visibility and scratch resistance. A protective film (11) of a plated steel sheet (1) is formed on a plated layer (10) having a texture (T1) on a surface. The protective film (11) contains a binder resin (31) and a plurality of resin particles (32), and a surface of the protective film (11) includes flat portions (11F) and a plurality of convex portions (11C) formed in a manner that the resin particles (32) locally protrude more than the flat portions (11F). An average film thickness d of the protective film (11) is 10.0 µm or less, a total area ratio S of the plurality of convex portions when the surface of the protective film (11) is viewed from above is 10.0% or less, F1 of formula (1) is 10.0 or more, and F2 of formula (2) is 0.7 to 3.0. F1=D×S (1), F2=D / d (2), where in the formulas, "D" is substituted with an average particle diameter D (µm) of the resin particles (32), "S" is substituted with a total area ratio S (%) of the convex portions (11C), and "d" is substituted with an average film thickness d (µm) of the protective film (11).

Description

Technical Field

[0001] The present invention relates to a plated steel sheet, and more specifically to a plated steel sheet having a texture on the surface of the coating. Background Technology

[0002] In products such as building materials, automobiles, and electrical equipment, there are situations where aesthetic design is required. Methods to improve the aesthetic design of products include coating the product surface and applying films to the product surface.

[0003] Recently, particularly in Europe and America where a natural aesthetic is valued, there's a growing trend towards materials that effectively utilize the texture of metal. In this regard, stainless steel and aluminum sheets, which exhibit excellent corrosion resistance even when left unpainted, are commonly used as raw materials. Furthermore, to further enhance the metallic texture of stainless steel and aluminum sheets, textures such as hairline finishes have been developed. However, stainless steel and aluminum sheets are expensive. Therefore, there is a search for cheaper alternatives to stainless steel and aluminum sheets.

[0004] As a substitute for stainless steel and aluminum sheets, clad steel sheets with a coating on their surface have been developed. Clad steel sheets also possess moderate corrosion resistance similar to stainless steel and aluminum sheets, and their workability is excellent. Therefore, clad steel sheets are suitable for applications such as building materials. Consequently, various proposals have been put forward to improve the aesthetic design of clad steel sheets.

[0005] For example, in Japanese Patent Application Publication No. 2006-124824 (Patent Document 1), a brushed finish is applied to a galvanized steel sheet. Afterward, a transparent resin coating is formed on the surface of the galvanized layer with the hairline texture. This maintains corrosion resistance while allowing the surface of the coating to be visually identified through the transparent resin coating, thus improving the aesthetic appeal.

[0006] Furthermore, in Japanese Patent Publication No. 2013-536901 (Patent Document 2), a texture is formed on the surface of the galvanized layer by rolling a galvanized steel sheet. Then, an organic film (resin) with a surface roughness within a certain range is coated onto the textured galvanized layer. This maintains corrosion resistance while allowing the surface of the coating to be visually identified through the organic film, thus improving the aesthetic design.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2006-124824

[0010] Patent Document 2: Japanese Patent Publication No. 2013-536901 Summary of the Invention

[0011] The problem the invention aims to solve

[0012] However, galvanized steel sheets used in building materials and other applications are processed into predetermined shapes by methods such as stamping. In stamping, the die comes into contact with the surface of the galvanized steel sheet. There are instances where the surface of the galvanized steel sheet is damaged due to contact with the die. Furthermore, during cutting after stamping, burrs or iron filings are generated at the ends of the galvanized steel sheet. There are also instances where the surface of the galvanized steel sheet is damaged due to burrs or filings.

[0013] There may be instances where the textured, resin-coated steel sheets described in the aforementioned patent documents are subjected to processing such as stamping or cutting. Therefore, it is preferable to suppress damage during processing or cutting of these coated steel sheets. In other words, excellent scratch resistance is required in these coated steel sheets.

[0014] Furthermore, in the formation of textured coated steel sheets, the visibility of the texture is required. Therefore, in the formation of textured coated steel sheets, not only is excellent scratch resistance required, but also excellent texture visibility is required.

[0015] The purpose of this invention is to provide a coated steel sheet with excellent texture visibility and scratch resistance.

[0016] Solution for solving the problem

[0017] The coated steel sheet of the present invention comprises:

[0018] Base material: steel plate;

[0019] A coating, which is formed on the surface of the base steel sheet, has a texture on the surface; and

[0020] A protective coating is formed on the surface of the plating.

[0021] The protective coating contains adhesive resin and multiple resin particles.

[0022] The surface of the protective coating includes:

[0023] Flat part; and

[0024] Multiple protrusions are formed by locally protruding more than the flat portion from multiple of the resin particles.

[0025] The average film thickness d of the protective coating is less than 10.0 μm.

[0026] When viewed from above, the total area ratio S of the plurality of protrusions is less than 10.0%.

[0027] F1 as defined by equation (1) is 10.0 or higher.

[0028] F2, as defined by equation (2), is 0.7 to 3.0.

[0029] F1=D×S (1)

[0030] F2=D / d (2)

[0031] In Equations (1) and (2), the average particle size D (μm) of the plurality of resin particles is substituted into “D”, the total area ratio S (%) of the plurality of protrusions is substituted into “S”, and the average film thickness d (μm) of the protective coating is substituted into “d”.

[0032] The effects of the invention

[0033] The galvanized steel sheet disclosed herein exhibits excellent texture visibility and scratch resistance. Attached Figure Description

[0034] Figure 1 This is a graph showing the relationship between the total area ratio of the raised portion and the gloss of the clad steel sheet in the rolling direction.

[0035] Figure 2 This is a graph showing the relationship between F1 and scratch resistance. F1 is the product of the average particle size D of the resin particles in the protective coating of the coated steel sheet and the total area ratio S of the protrusions.

[0036] Figure 3 This is a cross-sectional view of the plated steel sheet of this embodiment.

[0037] Figure 4 yes Figure 3 A top view of the coating.

[0038] Figure 5 yes Figure 3 Enlarged view of the protective coating in the image.

[0039] Figure 6 yes Figure 3 A top view of the protective coating.

[0040] Figure 7A yes Figure 5 Enlarged view of the convex part.

[0041] Figure 7B Is with Figure 7A Different Figure 5 Enlarged view of the convex part.

[0042] Figure 7C It is used for explanation Figure 5 A schematic diagram of the method for determining the particle size of resin particles in the convex part of the image.

[0043] Figure 7D It continues Figure 7C A schematic diagram illustrating the method for determining the particle size of resin particles.

[0044] Figure 8 This is a cross-sectional view showing another example of the protective coating on the plated steel sheet of this embodiment.

[0045] Figure 9 This is a cross-sectional view showing another example of the plated steel sheet of this embodiment. Detailed Implementation

[0046] The inventors have studied a coated steel sheet having a textured coating on its surface and a protective film formed on the coating, aiming to balance texture visibility and scratch resistance. As a result, the inventors have obtained the following insights.

[0047] To enhance scratch resistance using a protective coating, the adhesive resin of the protective coating contains multiple resin particles. Furthermore, the resin particles are positioned locally to protrude more prominently from the flat portion of the protective coating, forming multiple protrusions on the surface of the protective coating.

[0048] In this case, during processing such as stamping, the die comes into contact with multiple protrusions composed of multiple resin particles. The contact between the protrusions (resin particles) and the die suppresses contact between the adhesive resin of the flat portion constituting the protective coating surface and the die. Furthermore, the contact between the adhesive resin of the flat portion constituting the protective coating surface and the burrs and chips is also suppressed by the contact of burrs and chips generated during cutting with the multiple protrusions. As a result, damage to the adhesive resin constituting the flat portion can be suppressed.

[0049] Based on the above technical concept, scratch resistance would be improved if the protective coating contained multiple resin particles forming multiple protrusions. However, it has been clarified that if the total area ratio of the multiple protrusions on the surface of the protective coating increases, the visibility of the texture formed on the surface of the coating will decrease.

[0050] Therefore, the inventors investigated the relationship between the total area ratio of the protrusions and the visibility of the texture. First, the inventors investigated the relationship between the visibility of the texture and gloss. The results showed that the visibility of the texture and gloss are positively correlated.

[0051] Therefore, the inventors further investigated the relationship between the total area ratio of the protrusions and the gloss (i.e., texture visibility). Hereinafter, the total area ratio of the protrusions will also be referred to as the total area ratio of the protrusions, S. The gloss was determined according to the specular gloss measurement method (JIS Z 8741:1997) described in the examples discussed later. The investigation results are expressed as follows: Figure 1 middle. Figure 1 The horizontal axis represents the total convex area ratio S (%). The method for determining the total convex area ratio S will be discussed later. Figure 1 The vertical axis represents the gloss (%) at 60° along the rolling direction (L direction) of the steel sheet. The method for measuring gloss is discussed later.

[0052] Reference Figure 1 This clarified that the total convexity area ratio S is negatively correlated with texture visibility. Specifically, referring to... Figure 1 As the total area ratio S of the raised portion increases, the gloss at 60° along the L direction decreases. In other words, the larger the total area ratio S of the raised portion, the lower the visibility of the texture. Therefore, the inventors believe that in order to improve texture visibility, it is necessary to suppress the total area ratio S of the raised portion to a certain extent.

[0053] On the other hand, a higher total area ratio S of the protrusions further inhibits the contact between the mold and the adhesive resin of the protective coating during processing, and further inhibits the contact between burrs or chips after cutting and the adhesive resin of the protective coating. As a result, scratch resistance is considered to be improved. Therefore, it is thought that texture visibility and scratch resistance are seemingly opposite properties.

[0054] Therefore, the inventors further investigated a method to maintain texture visibility while simultaneously improving scratch resistance by suppressing the total area ratio S of the protrusions to a certain extent. The inventors believe that not only the total area ratio S of the protrusions affects scratch resistance, but also the average particle size D of the resin particles constituting the protrusions. They believe that, for the same total area ratio S, a larger average particle size D of the resin particles results in a larger protrusion height. A larger protrusion height can suppress contact between the mold and the adhesive resin of the protective coating. On the other hand, even if the average particle size D of the resin particles increases, the effect on gloss is minimal. Therefore, even if the average particle size D of the resin particles increases, the effect on texture visibility is minimal.

[0055] Based on the above technical concept, the inventors investigated the relationship between F1, defined by formula (1), and scratch resistance. Specifically, based on the results of scratch resistance evaluation tests described in the examples discussed later, a coated steel sheet with F2 of 0.7 to 3.0 was prepared. Figure 2 . Figure 2 The horizontal axis is F1, defined by equation (1).

[0056] F1=D×S (1)

[0057] In Equation (1), the average particle size D (μm) of multiple resin particles is substituted into “D”, and the total area ratio of the protrusion S (%) is substituted into “S”. Figure 2 The vertical axis represents the damage score, which is an indicator of scratch resistance. The lower the damage score, the lower the scratch resistance; the higher the damage score, the better the scratch resistance.

[0058] Reference Figure 2 When F1 is less than 10.0, even if F1 increases, the scratch resistance remains low (damage score remains unchanged at 1). On the other hand, when F1 is above 10.0, scratch resistance increases significantly with increasing F1 (damage score increases significantly).

[0059] based on Figure 1 and Figure 2 In coated steel sheets with protective coatings and textures, texture visibility can be maintained to a certain extent by suppressing the total area ratio S of the protrusions, while scratch resistance can be improved by increasing F1.

[0060] Based on the above insights, further adjustments were made to ensure an appropriate relationship between the average film thickness d of the protective coating, the total area ratio S of the raised portions, and the average particle size D of the resin particles. As a result, the inventors discovered that as long as the coated steel sheet satisfies the following features 1 to 4, it is possible to achieve both excellent texture visibility and excellent scratch resistance.

[0061] (Feature 1) The average film thickness d of the protective coating is less than 10.0 μm.

[0062] (Feature 2) The total area ratio S of the convex part is less than 10.0%.

[0063] (Feature 3) F1 as defined by equation (1) is 10.0 or higher.

[0064] (Feature 4) F2 as defined by equation (2) is 0.7 to 3.0.

[0065] F1=D×S (1)

[0066] F2=D / d (2)

[0067] In the formula, the average particle size D (μm) of the resin particles is substituted into “D”, the total area ratio S (%) of the protrusions is substituted into “S”, and the average film thickness d (μm) of the protective coating is substituted into “d”.

[0068] The main idea of ​​the plated steel sheet of this embodiment, which utilizes the above technical concepts, is as follows.

[0069] [1] A galvanized steel sheet comprising:

[0070] Base material: steel plate;

[0071] A coating, which is formed on the surface of the base steel sheet, has a texture on the surface; and

[0072] A protective coating is formed on the surface of the plating.

[0073] The protective coating contains adhesive resin and multiple resin particles.

[0074] The surface of the protective coating includes:

[0075] Flat part; and

[0076] Multiple protrusions are formed by locally protruding more than the flat portion from each of the resin particles.

[0077] The average film thickness d of the protective coating is less than 10.0 μm.

[0078] When viewed from above, the total area ratio S of the plurality of protrusions is less than 10.0%.

[0079] F1 as defined by equation (1) is 10.0 or higher.

[0080] F2, as defined by equation (2), is 0.7 to 3.0.

[0081] F1=D×S (1)

[0082] F2=D / d (2)

[0083] In Equations (1) and (2), the average particle size D (μm) of the plurality of resin particles is substituted into “D”, the total area ratio S (%) of the plurality of protrusions is substituted into “S”, and the average film thickness d (μm) of the protective coating is substituted into “d”.

[0084] [2] According to the plated steel sheet described in [1], wherein,

[0085] The galvanized steel sheet further includes one or more internal organic resin layers layered between the protective coating and the coating.

[0086] [3] According to [1] or [2], wherein,

[0087] The galvanized steel sheet also has a chemical conversion coating, which is disposed between the galvanized layer and the protective coating and is formed by contacting the surface of the galvanized layer.

[0088] The coated steel sheet of this embodiment will be discussed in detail below.

[0089] [For galvanized steel sheet 1]

[0090] Figure 3 This is a cross-sectional view of the plated steel sheet 1 in this embodiment. Figure 3 In this design, the rolling direction of the clad steel sheet 1 is defined as the L direction. The thickness direction of the clad steel sheet 1 is defined as the T direction. The direction perpendicular to the L and T directions (that is, the width direction of the clad steel sheet 1) is defined as the W direction.

[0091] Reference Figure 3 The coated steel sheet 1 of this embodiment includes a base steel sheet 100, a coating 10, and a protective film 11. The coating 10 is formed on the surface 100S of the base steel sheet 100. The protective film 11 is formed on the surface 10S of the coating 10. Therefore, the coating 10 is disposed between the base steel sheet 100 and the protective film 11.

[0092] The following describes the base steel plate 100, the coating 10, and the protective film 11.

[0093] [For base steel plate 100]

[0094] The base steel plate 100 can be any known steel plate applicable to known clad steel plates, depending on the mechanical properties (e.g., tensile strength, workability, etc.) required by the clad steel plate 1. In other words, the type of steel used in the base steel plate 100 is not particularly limited. For example, the base steel plate 100 can be a steel plate used for construction materials, a steel plate used for automotive exterior panels, or a steel plate used for electrical equipment. The base steel plate 100 can be either a hot-rolled steel plate or a cold-rolled steel plate.

[0095] [For coating 10]

[0096] The coating 10 is formed on the surface 100S of the base steel plate 100. The coating 10 is in contact with the surface 100S of the base steel plate 100. The coating 10 is disposed between the base steel plate 100 and the protective coating 11.

[0097] There is no particular limitation on the type of coating material for coating 10. Coating 10 can be a zinc coating or a zinc alloy coating. Coating 10 can be an aluminum coating or an aluminum alloy coating. Coating 10 can also be a coating material made of other metals or alloys besides zinc-based and aluminum-based coating materials.

[0098] When coating 10 is a zinc plating layer, coating 10 is formed using well-known zinc plating methods. Specifically, coating 10 is formed, for example, using either electroplating or hot-dip galvanizing. In this specification, zinc plating also includes zinc alloy plating layers. More specifically, zinc plating is a concept that includes electroplated zinc layers, electroplated zinc alloy layers, hot-dip galvanized layers, and alloyed hot-dip galvanized layers.

[0099] When coating 10 is a zinc coating, the zinc coating may have a well-known chemical composition. The Zn content in the chemical composition of the zinc coating is 65% or more by mass%. As long as the Zn content is 65% or more by mass, the sacrificial corrosion protection function will be significantly enhanced, and the corrosion resistance of the coated steel sheet 1 will be significantly improved. The preferred lower limit for the Zn content in the chemical composition of the zinc coating is 70%, and more preferably 80%.

[0100] The chemical composition of the galvanized layer preferably contains Zn and at least one element selected from the group consisting of Al, Co, Cr, Cu, Fe, Ni, P, Si, Sn, Mg, Mn, Mo, V, W, and Zr. Furthermore, if the galvanized layer is an electroplated galvanized layer, the chemical composition further preferably contains a total of 5 to 20% by mass of an element selected from the group consisting of Fe, Ni, and Co. Additionally, if the galvanized layer is a hot-dip galvanized layer, the chemical composition further preferably contains a total of 5 to 20% by mass of an element selected from the group consisting of Mg, Al, and Si. In these cases, the galvanized layer also exhibits excellent corrosion resistance.

[0101] The zinc plating layer may also contain impurities. Impurities refer to elements that are unexpectedly mixed into the raw materials or introduced during the manufacturing process. Examples of impurities include Ti, B, S, N, C, Nb, Pb, Cd, Ca, Pb, Y, La, Ce, Sr, Sb, O, F, Cl, Zr, Ag, and H. The total impurity content in the chemical composition of the zinc plating layer is preferably less than 1%.

[0102] The chemical composition of the zinc plating layer can be determined, for example, by the following method. The protective coating 11 of the coated steel sheet 1 is removed using a solvent or stripping agent that does not dissolve the zinc plating layer (e.g., NEO REVER S-701, manufactured by Sansai Chemical Co., Ltd.). Then, the zinc plating layer is dissolved using hydrochloric acid containing a corrosion inhibitor. The solution is analyzed using an ICP (Inductively Coupled Plasma) emission spectrometer to determine the Zn content. If the determined Zn content is 65% or more by mass, the coating 10 being measured is considered a zinc plating layer.

[0103] [Regarding the texture formed on the surface of coating 10 for 10S]

[0104] Figure 4 yes Figure 3 A top view of coating 10 in the image. (Refer to...) Figure 4 When viewed from above, that is, when the coating 10 of the coated steel sheet 1 is viewed from above, the coating 10 has a texture T1 on the surface 10S.

[0105] In this specification, "texture" refers to the raised or recessed patterns formed on the surface of coating 10 using physical or chemical methods. Figure 4 The image shows a hairline texture as texture T1. However, texture T1 is not limited to a hairline texture. Texture T1 can also be, for example, an embossed pattern, vibration finishing, pear-skin surface (sandblasting) finishing, hammered pattern finishing, fabric texture (satin) finishing, etc. Preferably, texture T1 is a hairline texture.

[0106] [Regarding the adhesion amount of coating 10]

[0107] There are no particular limitations on the amount of coating 10 applied; any well-known application amount is sufficient. The preferred application amount of coating 10 is 5.0–120.0 g / m². 2 As long as the adhesion amount of coating 10 is 5.0 g / m². 2 Thus, by imparting the texture described later to the coating 10, exposure of the base metal (base steel sheet 100) can be suppressed. A further preferred lower limit for the amount of coating 10 is 7.0 g / m². 2 A further preferred value is 10.0 g / m³. 2 There is no particular upper limit to the amount of coating 10. However, from an economic point of view, when coating 10 is formed by electroplating, a preferred upper limit for the amount of coating 10 is 40.0 g / m². 2 The upper limit for further optimization is 35.0 g / m³. 2 A further preferred value is 30.0 g / m³. 2 .

[0108] [Regarding protective coating 11]

[0109] A protective coating 11 is formed on the surface 10S of the plating layer 10. Figure 3 In the middle, the protective coating 11 is in contact with the surface 10S of the coating 10. Figure 5 yes Figure 3 An enlarged view of the protective coating 11 shown. Figure 6 This is a top view of the protective coating 11. (Refer to...) Figure 5 and Figure 6 The protective coating 11 contains an adhesive resin 31 and a plurality of resin particles 32 (32A to 32E). The surface 11S of the protective coating 11 includes a flat portion 11F and a plurality of protrusions 11C.

[0110] For each of the multiple resin particles 32, from resin particles 32A to resin particles 32D, a portion of the resin particle 32 protrudes more than the flat portion 11F, with the remainder embedded in the adhesive resin 31. The protrusion 11C is formed by the resin particle 32 protruding more than the flat portion 11F.

[0111] In addition, resin particles 32 (32A to 32E) are entirely embedded in the adhesive resin 31.

[0112] The surface of the protrusion 11C can be like Figure 7A The adhesive resin 31 shown is used, and it can also be used as follows: Figure 7B The image shows a structure composed of resin particles 32. In, as shown... Figure 7B When the surface of the protrusion 11C is composed of resin particles 32, the resin particles 32 are partially exposed to the adhesive resin 31.

[0113] The protective coating 11 with the above structure maintains excellent texture visibility while also exhibiting excellent scratch resistance. The adhesive resin 31 and resin particles 32 will be described below.

[0114] [For adhesive resin 31]

[0115] The adhesive resin 31 functions as an adhesive to fix the resin particles 32. The adhesive resin 31 is composed of a light-transmitting resin. Here, "light-transmitting" means that when the plated steel sheet 1 with the protective coating 11 containing the adhesive resin 31 is placed in an environment equivalent to sunlight on a sunny morning (illuminance of about 65,000 lux), the texture T1 formed on the surface 10S of the coating 10 can be visually recognized.

[0116] There are no particular limitations on the adhesive resin 31, as long as it is a transparent resin. The adhesive resin 31 can be a well-known natural resin and / or a well-known synthetic resin. For example, the adhesive resin 31 can be one or more selected from the group consisting of epoxy resins, urethane resins, polyester resins, phenolic resins, polyethersulfone resins, melamine alkyd resins, acrylic resins, polyamide resins, polyimide resins, silicone resins, polyvinyl acetate resins, polyolefin resins, polystyrene resins, vinyl chloride resins, and vinyl acetate resins.

[0117] [For resin particles 32]

[0118] As described above, among the plurality of resin particles 32 (32A to 32D), a portion of the resin particle 32 protrudes further relative to the flat portion 11F, with the remainder embedded in the protective coating 11. The protrusion 11C is formed from the portion of the resin particle 32 that protrudes further relative to the flat portion 11F. Furthermore, in Figure 5 In the process, resin particles 32E of multiple resin particles are integrally embedded in the adhesive resin 31. However, the protective coating 11 may or may not contain resin particles 32E integrally embedded in the adhesive resin 31.

[0119] The scratch resistance of the coated steel sheet 1 is improved by forming multiple protrusions 11C in such a way that the local areas of multiple resin particles 32 are more prominent than the flat portion 11F. The improvement in scratch resistance caused by the protrusions 11C will be explained below.

[0120] The galvanized steel sheet 1 may be processed into a predetermined shape by processes such as stamping. In stamping and the like, the galvanized steel sheet 1 comes into contact with a mold or the like and is subjected to external forces from the mold or the like. Due to the contact with the mold or the like, there is a possibility that damage may occur on the surface of the galvanized steel sheet 1.

[0121] Multiple protrusions 11C protruding from the flat portion 11F suppress the occurrence of damage caused by molds, etc. Specifically, during processing, the protrusions 11C on the surface 11S of the protective coating 11 of the plated steel sheet 1, which protrude more than the flat portion 11F, preferentially contact the mold, etc., thus suppressing the contact between the flat portion 11F and the mold, etc.

[0122] The resin particles 32 are harder than the binder resin 31. Alternatively, the surface free energy of the resin particles 32 is lower than that of the binder resin 31, and the coefficient of friction of the resin particles 32 is lower than that of the binder resin 31. Therefore, it is difficult to damage the protective coating 11 during processing.

[0123] Additionally, there are cases where the galvanized steel sheet 1 is cut. Due to cutting, burrs or iron filings may be generated at the ends of the galvanized steel sheet 1. If these burrs or filings collide with or contact the surface 11S of the protective coating 11 of the galvanized steel sheet 1, damage may occur. Furthermore, there are cases where the galvanized steel sheet 1 is used as a building material, both indoors and / or outdoors. When the galvanized steel sheet 1 is used indoors, there is a possibility that everyday items or other objects may collide with or contact the surface of the galvanized steel sheet 1. Furthermore, when the galvanized steel sheet 1 is used outdoors, there is a possibility that flying objects such as stones or metal fragments may collide with or contact the surface of the galvanized steel sheet 1.

[0124] When burrs, chips, everyday items, or other flying objects collide with or come into contact with the surface of the coated steel sheet 1, these objects preferentially contact the protrusions 11C that protrude from the flat portion 11F compared to the flat portion 11F. As described above, the resin particles 32 are harder or have a lower coefficient of friction than the adhesive resin 31. Therefore, damage caused by collisions or contact with everyday items and flying objects can be suppressed.

[0125] As described above, the resin particles 32 satisfy at least one of the following (Construction 1) and (Construction 2).

[0126] (Component 1) The hardness of resin particles 32 is higher than that of binder resin 31.

[0127] (Component 2) The surface free energy of resin particles 32 is lower than that of adhesive resin 31. Therefore, the coefficient of friction of resin particles 32 is lower than that of adhesive resin 31.

[0128] There are no particular limitations as long as the resin particles 32 satisfy at least one of (Construction 1) and (Construction 2). The protective coating 11 contains a plurality of resin particles 32, for example, selected from one or more of the group consisting of urethane resin particles, acrylic resin particles, rigid polyethylene resin particles, polyethylene resin particles, polypropylene resin particles, and PTFE (polytetrafluoroethylene) particles. The resin particles 32 are composed of a type of resin different from the type of binder resin 31. Furthermore, the specific gravity of the resin particles 32 is preferably greater than or equal to that of the binder resin 31. As long as the specific gravity of the resin particles 32 is greater than or equal to that of the binder resin 31, when the thickness of the protective coating 11 is more than half the particle size (diameter) of the resin particles 32, approximately half or more of the resin particles 32 will be embedded in the binder resin 31. For example, in Figure 5 In each of the resin particles 32A to 32E, approximately more than half of each resin particle is embedded in the adhesive resin 31.

[0129] Furthermore, the resin particles 32 are composed of resin that will not melt even when baking is performed in the protective coating formation process described later.

[0130] [For features 1 through 4]

[0131] The plated steel sheet 1 in this embodiment also satisfies the following features 1 to 4.

[0132] (Feature 1) The average film thickness d of the protective coating is less than 10.0 μm.

[0133] (Feature 2) The total area ratio S of the convex part is less than 10.0%.

[0134] (Feature 3) F1 as defined by equation (1) is 10.0 or higher.

[0135] (Feature 4) F2 as defined by equation (2) is 0.7 to 3.0.

[0136] F1=D×S (1)

[0137] F2=D / d (2)

[0138] In the formula, the average particle size D (μm) of the resin particles is substituted into “D”, the total area ratio S (%) of the protrusions is substituted into “S”, and the average film thickness d (μm) of the protective coating is substituted into “d”.

[0139] The following describes features 1 through 4.

[0140] [(Feature 1) Average film thickness d for protective coating 11]

[0141] In the plated steel sheet 1 of this embodiment, the average film thickness d of the protective coating 11 is 10.0 μm or less.

[0142] When the average film thickness d of the protective coating 11 exceeds 10.0 μm, smoothing (leveling) can be easily achieved using only the protective coating 11. Therefore, the discrepancy between the impression of reflection at the surface of the protective coating 11 and the impression of a visually recognizable texture T1 increases. In this case, the metallic texture of the plated steel sheet 1 is reduced.

[0143] When the average film thickness d of the protective coating 11 is less than 10.0 μm, the texture T1 formed on the surface 10S of the coating 10 can be fully visually identified through the protective coating 11, and the metallic texture is also greatly enhanced.

[0144] The preferred upper limit for the average film thickness d of the protective coating 11 is 9.0 μm, and more preferably 8.0 μm.

[0145] The preferred lower limit for the average film thickness d of the protective coating 11 is 0.5 μm. When the average film thickness d of the protective coating 11 is 0.5 μm or more, the corrosion resistance is further improved. The preferred lower limit for the average film thickness of the protective coating 11 is 0.7 μm, more preferably 1.0 μm, and even more preferably 2.0 μm.

[0146] [Method for determining the average film thickness d of the protective coating 11]

[0147] The average film thickness d of the protective coating 11 can be determined by the following method.

[0148] Samples were collected with cross-sections (i.e., cross-sections including both the T and W directions) on the surface of the coated steel plate 1 that are orthogonal to the L direction of the coated steel plate 1. The cross-sections on the sample surface orthogonal to the L direction of the coated steel plate 1 were designated as the observation plane. A scanning electron microscope (SEM) was used to observe the observation plane, including the protective coating 11, within a 100 μm length along the W direction of the coated steel plate 1, using a 2000x backscattered electron image (BSE).

[0149] For observation using backscattered electron imaging (BSE) with a scanning electron microscope (SEM), the base steel plate 100, the coating 10, and the protective coating 11 can be easily distinguished by contrast. Within the field of view, the thickness of the protective coating 11 is measured at 10 μm intervals along the W direction (that is, the thickness is measured at a total of 11 locations). The arithmetic mean of the measured thicknesses is calculated.

[0150] In the observation field at any 5 points on the observation surface, the arithmetic mean of the film thickness is calculated using the method described above. The arithmetic mean of the 3 film thicknesses other than the largest and second largest film thicknesses is defined as the average film thickness d (μm) of the protective coating 11.

[0151] [(Feature 2) For the total area ratio S of the convex portion when viewed from above]

[0152] Reference Figure 6 Imagine viewing the surface 11S of the coated steel sheet 1 from above. In this case, the total area ratio of the protrusions 11C on the surface 11S of the protective coating 11 is defined as the total protrusion area ratio S (%). In this case, in the coated steel sheet 1 of this embodiment, the total protrusion area ratio S is 10.0% or less.

[0153] The total convexity area ratio S is negatively correlated with the visibility of texture T1. (Refer to...) Figure 1 As the total area ratio S of the raised portions increases, the gloss decreases. In other words, the larger the total area ratio S of the raised portions, the lower the visibility of the texture T1. Furthermore, even if the average particle size D of the resin particles 32 increases, the effect on gloss is minimal. Therefore, even if the average particle size D of the resin particles 32 increases, the effect on texture visibility is minimal.

[0154] As long as the gloss level is above 55%, texture T1 can be sufficiently visually identified. (Refer to...) Figure 1 As long as the total area ratio S of the raised portions is 10.0% or less, the gloss level becomes 55% or more. Therefore, in the coated steel sheet 1, the texture T1 can be sufficiently visually identified. Thus, the total area ratio S of the raised portions is 10.0% or less.

[0155] The preferred upper limit for the total area ratio S of the convex portion is 9.0%, further preferably 8.0%, further preferably 7.0%, further preferably 6.0%, further preferably 5.0%, and further preferably 4.0%.

[0156] From the perspective of the visibility of texture T1, the total area ratio S of the protrusions is preferably as small as possible. However, in order to improve scratch resistance, a certain degree of total area ratio S of the protrusions is required. Therefore, the preferred lower limit of the total area ratio S of the protrusions is 1.0%, and more preferably 1.5%.

[0157] [Method for determining the total area ratio S of convex parts]

[0158] The total area ratio S of the convex portion can be calculated using the following method.

[0159] Samples were collected from the center of the width of the coated steel sheet 1. The size of the sample was not particularly limited, but the protective coating 11 was designed to ensure at least five observation fields of 1000μm × 1000μm in size.

[0160] Select any five observation fields on the surface 11S of the protective coating 11 of the sample. In each observation area, identify the protrusions 11C on the surface 11S of the protective coating 11. The protrusions 11C are identified using the following method.

[0161] Carbon or gold vapor deposition is applied to the surface 11S of the sample. The surface irregularities of the sample after vapor deposition are measured using a laser microscope. Specifically, a laser microscope with a height resolution of 0.01 μm or higher is used. Among the measured surface irregularities, regions with a height difference of 0.1 μm or higher between themselves and adjacent concave regions (corresponding to the edge region of convex regions) are defined as "convex regions". Convex regions can be identified by image analysis of the sample surface. The convex shape of the convex region 11C can be more clearly identified by applying carbon or gold vapor deposition to the surface 11S of the sample.

[0162] Based on the total area of ​​the determined convex portion 11C and the area of ​​the observation field, the total area ratio (%) of the convex portion in each observation field is calculated. The arithmetic mean of the total area ratios of the convex portions at the five locations is defined as the total area ratio S (%) of the convex portion.

[0163] [(Feature 3) for F1]

[0164] In the plated steel sheet 1 of this embodiment, F1 as defined by formula (1) is 10.0 or higher.

[0165] F1=D×S (1)

[0166] In formula (1), the average particle size D (μm) of multiple resin particles 32 is substituted into “D”, and the total area ratio of the protrusion S (%) is substituted into “S”.

[0167] F1 is an indicator related to the scratch resistance of the coated steel sheet 1. (Refer to...) Figure 2 In the coated steel sheet 1 with an F2 of 0.7 to 3.0, when F1 is less than 10.0, the scratch resistance remains low even as F1 increases (the damage score remains constant at 1). On the other hand, in the coated steel sheet 1 with an F2 of 0.7 to 3.0, when F1 is 10.0 or higher, the scratch resistance significantly improves as F1 increases (the damage score significantly improves). Therefore, F1 is 10.0 or higher.

[0168] The preferred lower limit for F1 is 13.0, further preferred is 14.0, further preferred is 15.0, further preferred is 15.5 or higher, and further preferred is 16.0 or higher. There is no specific upper limit for F1.

[0169] [(Feature 4) for F2]

[0170] In the plated steel sheet 1 of this embodiment, F2, defined by formula (2), is 0.7 to 3.0.

[0171] F2=D / d (2)

[0172] In formula (2), the average particle size D (μm) of the multiple resin particles 32 is substituted into “D”, and the average film thickness d (μm) of the protective coating 11 is substituted into “d”.

[0173] F2 represents the relationship between the average particle size D of the resin particles 32 and the average film thickness d of the protective coating 11. F2 is an indicator of the scratch resistance of the protective coating 11.

[0174] If F2 is less than 0.7, the average particle size D of the resin particles 32 is too small relative to the average film thickness d of the protective coating 11. In this case, the resin particles 32 cannot adequately form protrusions 11C on the protective coating 11. As a result, the scratch resistance of the coated steel sheet 1 is reduced.

[0175] On the other hand, if F2 exceeds 3.0, the average particle size D of the resin particles 32 becomes too large relative to the average film thickness d of the protective coating 11. In this case, the resin particles 32 will easily peel off from the protective coating 11. As a result, the scratch resistance of the coated steel sheet 1 decreases.

[0176] Therefore, F2 is 0.7 to 3.0.

[0177] The preferred lower limit for F2 is 0.8, the further preferred value is 0.9, and the even more preferred value is 1.0.

[0178] The preferred upper limit for F2 is 2.8, the further preferred value is 2.6, and the even more preferred value is 2.4.

[0179] [Method for determining the average particle size D of resin particles 32]

[0180] The average particle size of the resin particles 32 in the protective coating 11 can be determined by the following method.

[0181] The surface 11S of the protective coating 11 is ground parallel to the flat portion 11F. For example... Figure 7C As shown, by means of this grinding, the vertex portion of the protrusion 11C, which is more prominent than the flat portion 11F, is ground, and a cross section 11CC parallel to the flat portion 11F is formed on the protrusion 11C.

[0182] The cross-section 11CC also includes the cross-section of the resin particles 32. The particle size of the resin particles 32 at the cross-section 11CC (hereinafter referred to as the resin particle size at the cross-section 11CC) 32CD gradually increases with each repeated grinding. Furthermore, as... Figure 7D As shown, the resin particle size 32CD at section 11CC soon reaches its maximum value. This maximum value corresponds to the particle size (diameter) of resin particles 32. If grinding continues further, the resin particle size 32CD at section 11CC decreases.

[0183] Therefore, the above-described grinding is performed on any protrusion 11C on the surface 11S of the protective coating 11, parallel to the flat portion 11F. Furthermore, the resin particle size 32CD at the cross-section 11CC is measured at each grinding operation using the method described above. Additionally, the resin particle size 32CD is measured using well-known image analysis. The depth (spacing) of each grinding operation is set to 0.05 μm. The maximum value of the measured resin particle size 32CD is set as the particle size (μm) of the resin particles 32 at that protrusion 11C.

[0184] The particle size of resin particles 32 is determined for any 50 protrusions 11C using the method described above. The arithmetic mean of the obtained particle sizes of resin particles 32 at the 50 protrusions 11C is defined as the average particle size D (μm) of resin particles 32.

[0185] There are no particular limitations on the grinding method; any known method can be used. For example, Cryo FIB-SEM (cryo-focused ion beam scanning electron microscopy) can be used as the grinding method. In Cryo FIB-SEM, the sample temperature is set to approximately -100°C, and the sample is processed (ground) using an ion beam. Under these conditions, the heat generated by the ion beam irradiation causes less damage to the coating, allowing for sub-nanometer level grinding. Therefore, the particle size of resin particles 32 can be determined.

[0186] [Preferred size for the average particle size D of resin particles 32]

[0187] The average particle size D of resin particles 32 is not specifically limited.

[0188] The preferred upper limit for the average particle size D of the resin particles 32 is 10.0 μm. The average particle size D of the resin particles 32 is 10.0 μm, satisfying equations (1) and (2), and it is envisioned that the diameter of the protrusion 11C when viewed from above the surface 11S is 10.0 μm. When the average particle size D of the resin particles 32 is 10.0 μm and the diameter of the protrusion 11C is 10.0 μm, the diameter of the protrusion 11C is substantially the largest diameter. In this case, for every 10000 μm of resin particles 32 constituting the protrusion 11C... 2 Number density (numbers / 10000μm) 2 ) becomes 0.6 per 10000μm 2 Therefore, assuming that when viewing the surface 11S in the protective coating 11 from above, and assuming that the resin particles 32 constituting the protrusions 11C are arranged in a matrix, the average spacing between adjacent protrusions 11C is 125.0 μm, and the average spacing between the protrusions 11C on the diagonal is 176.8 μm.

[0189] The smallest tip diameter of any of the aforementioned impactors, such as burrs, chips, everyday items, and incoming objects, that could cause damage to the flat portion 11F of the protective coating 11, is approximately 200 μm. If the average particle size D of the resin particles 32 is 10.0 μm, then the average spacing of the protrusions 11C is less than 200 μm. Therefore, even tiny impactors with a tip diameter of approximately 200 μm will come into contact with the protrusions 11C, but are unlikely to come into contact with the flat portion 11F. As a result, damage can be further effectively suppressed.

[0190] The preferred upper limit of the average particle size D of the resin particles 32 is 9.5 μm, more preferably 9.0 μm, more preferably 8.5 μm, more preferably 8.0 μm, more preferably 7.5 μm, and more preferably 7.0 μm.

[0191] The preferred lower limit for the average particle size D of the resin particles 32 is 0.7 μm, more preferably 1.0 μm, more preferably 1.1 μm, and more preferably 1.5 μm.

[0192] [Summarize]

[0193] As described above, the plated steel sheet 1 of this embodiment has the following characteristics.

[0194] (Feature 1) The average film thickness d of the protective coating 11 is less than 10.0 μm.

[0195] (Feature 2) The total area ratio S of the convex part 11C is less than 10.0%.

[0196] (Feature 3) F1 as defined by equation (1) is 10.0 or higher.

[0197] (Feature 4) F2 as defined by equation (2) is 0.7 to 3.0.

[0198] By having these features, it is possible to achieve both excellent visibility of the texture T1 and excellent scratch resistance in the plated steel sheet 1 of this embodiment.

[0199] Furthermore, the resin particles 32 in the protective coating 11 are uniformly dispersed. For example, in a 1000μm × 1000μm field of view on the surface of the protective coating 11, when the field of view is divided into 100μm × 100μm micro-regions, the average number density of resin particles 32 in each micro-region is 0.4 particles / 10000μm. 2 The coefficient of variation calculated based on the average number density and standard deviation in each micro-region is less than 50.0%. The preferred average number density of resin particles 32 in each micro-region is 0.6 particles / 10000 μm. 2 The preferred variation coefficient is below 40.0%.

[0200] [Other structures of galvanized steel sheet 1]

[0201] The protective coating 11 of the aforementioned plated steel sheet 1 is composed of a single organic resin layer. However, it is also possible that one or more organic resin layers are laminated between the protective coating 11 and the plating layer 10.

[0202] Figure 8 This is a cross-sectional view showing another example of the plated steel sheet 1 in this embodiment. (Refer to...) Figure 8 The clad steel sheet 1 includes a base steel sheet 100, a coating 10, and a protective film 11, and also includes one or more internal organic resin layers 12. Figure 8 In this configuration, one internal organic resin layer 12 may be provided, but multiple internal organic resin layers 12 may also be provided. One or more internal organic resin layers 12 are stacked between the protective coating 11 and the plating layer 10.

[0203] The inner organic resin layer 12 is composed of adhesive resin 31. That is, the inner organic resin layer 12 does not contain resin particles 32. The adhesive resin 31 of the inner organic resin layer 12 can be composed of a type of resin that is the same type as the adhesive resin 31 constituting the protective coating 11, or it can be composed of a type of resin that is different from the adhesive resin 31 constituting the protective coating 11.

[0204] As described above, even when the protective coating 11 is composed of multiple organic resin layers, it is possible to achieve both excellent visibility of the texture T1 and excellent scratch resistance by satisfying the features 1 to 4 described above.

[0205] In addition, Figure 8 In the plated steel sheet 1 shown, the preferred total thickness of the protective coating 11 and the inner organic resin layer 12 is 10.0 μm or less. In this case, the texture T1 formed on the surface 10S of the coating 10 can be fully visually discerned through the protective coating 11 and the inner organic resin layer 12, and the metallic texture is also significantly enhanced.

[0206] [Other structures of galvanized steel sheet 1 2]

[0207] like Figure 9 As shown, the plated steel sheet 1 of this embodiment may also have a chemical conversion coating 13 between the plating layer 10 and the protective coating 11. The chemical conversion coating 13 is formed by contacting the surface 10S of the plating layer 10. The chemical conversion coating 13 is a transparent coating. The chemical conversion coating 13 is formed, for example, by an inorganic compound, or by a mixture of organic and inorganic compounds. The average thickness of the chemical conversion coating 11 is less than 1.0 μm.

[0208] When the plated steel sheet 1 includes a chemical conversion coating 13, the adhesion of the protective coating 11 to the plating layer 10 is improved. The chemical conversion coating 13 is, for example, a phosphate coating, an oxalate coating, a chromate coating, a lithium silicate coating, a silane coupling agent coating, and a coating containing rust-inhibiting components. The chemical conversion coating 13 is formed using well-known chemical conversion processes.

[0209] Furthermore, one or more organic resin layers 12 may be formed between the protective coating 11 and the chemical conversion treated coating 13. Both the protective coating 11 and the organic resin layers 12 are composed of adhesive resin 31. Therefore, the protective coating 11 has a high adhesion to the organic resin layers 12. The chemical conversion treated coating 13 further enhances the adhesion between the inner organic resin layers 12 and the plating layer 10. As a result, the adhesion between the protective coating 11 and the plating layer 10 is improved.

[0210] [Manufacturing Method]

[0211] This section describes an example of a method for manufacturing the galvanized steel sheet 1 according to this embodiment. The manufacturing method described below is an example for manufacturing the galvanized steel sheet 1 according to this embodiment. Therefore, the galvanized steel sheet 1 having the above-described structure can also be manufactured using other manufacturing methods besides the method described below. However, the manufacturing method described below is a preferred example of the method for manufacturing the galvanized steel sheet 1 according to this embodiment.

[0212] The manufacturing method of this embodiment includes the following steps.

[0213] (Process 1) Preparation of 100mm base steel plate (Preparation Process)

[0214] (Process 2) The process of forming a coating 10 on the base steel plate 100 (plating process).

[0215] (Process 3) The process of forming texture T1 in coating 10 (texture processing process)

[0216] (Step 4) Step 4: Forming a protective coating 11 on the coating 10 (coating formation step)

[0217] The following is a description of each process.

[0218] [(Process 1) Preparation Process]

[0219] In the preparation process, a base steel plate 100 is prepared. As mentioned above, the base steel plate 100 can be either a hot-rolled steel plate or a cold-rolled steel plate.

[0220] [(Process 2) Plating process]

[0221] In the plating process, the prepared base steel plate 100 is subjected to a well-known plating process, and a plating layer 10 is formed on the surface of the base steel plate 100.

[0222] For example, when forming a zinc-plated coating 10 using a well-known electroplating method, it is sufficient to use a well-known electroplating bath and an electroplating zinc alloy bath. Examples of electroplating baths include sulfuric acid baths, chloride baths, zincate baths, cyanide baths, pyrophosphate baths, boric acid baths, citric acid baths, other complex baths, and combinations thereof. Alternatively, the electroplating zinc alloy bath may contain, for example, one or more ions selected from the group consisting of Al, Co, Cr, Cu, Fe, Ni, P, Si, Sn, Mg, Mn, Mo, V, W, and Zr, in addition to Zn ions.

[0223] The chemical composition, temperature, flow rate, and conditions (current density, energizing mode, etc.) of the electro-zinc plating bath and the electro-zinc alloy plating bath can be adjusted appropriately during the electro-zinc plating process.

[0224] The thickness of the coating 10 in the electro-zinc plating process can be adjusted by adjusting the current density and time during the electro-zinc plating process.

[0225] When forming a zinc-based coating 10 using hot-dip galvanizing or alloyed hot-dip galvanizing, a well-known zinc plating bath is prepared. The zinc plating bath may, for example, be primarily composed of Zn and contain one or more elements selected from the group consisting of Al, Co, Cr, Cu, Fe, Ni, P, Si, Sn, Mg, Mn, Mo, V, W, and Zr.

[0226] When the coating 10 is a hot-dip galvanized layer, the base steel plate 100 is immersed in a galvanizing bath in which the bath temperature and chemical composition have been adjusted, and a coating 10 (hot-dip galvanized layer) consisting of hot-dip galvanization is formed on the surface of the base steel plate 100.

[0227] When the coating 10 is set as an alloyed hot-dip galvanized layer, the base steel plate 100 on which the hot-dip galvanized layer is formed is subjected to a well-known heat treatment in a well-known alloying furnace, and the coating 10 is set as an alloyed hot-dip galvanized layer.

[0228] The thickness of the coating 10 in the hot-dip galvanizing process can be adjusted by adjusting the pull-out speed from the galvanizing bath and the amount of galvanizing removed by gas wiping.

[0229] Alternatively, well-known degreasing treatments such as electrolytic degreasing can be performed on the base steel plate 100 before plating.

[0230] The above manufacturing process is used to manufacture a coated steel sheet 1 (hereinafter referred to as an intermediate coated steel sheet) having a base steel sheet 100 and a coating 10.

[0231] [(Process 3) Texture Processing]

[0232] In the texturing process, a texture T1 is formed on the surface 10S of the coating 10 of the intermediate coated steel sheet by performing well-known texturing processes.

[0233] When texture T1 is a hairline finish, a well-known brushing process is performed. Brushing methods include, for example, forming a hairline finish by grinding the surface with a well-known abrasive belt, forming a hairline finish by grinding the surface with a well-known abrasive brush, and forming a hairline finish by rolling and transferring it using a roller with a hairline shape. The length, depth, and frequency of the hairline can be adjusted by changing the grit size of the well-known abrasive belt, the grit size of the well-known abrasive brush, and the surface shape of the roller. Furthermore, from the viewpoint of surface quality, it is preferable to form a hairline finish by grinding the surface with an abrasive belt or an abrasive brush.

[0234] The intermediate clad steel sheet is manufactured using the above manufacturing process. The intermediate clad steel sheet has a base steel sheet 100 and a coating 10, and a texture T1 is formed on the surface 10S of the coating 10.

[0235] [(Process 4) Coating Formation Process]

[0236] In the coating formation process, a protective coating 11 is formed on the surface 10S of the coating 10 of the intermediate plated steel sheet with texture T1. The coating formation process will be described in detail below.

[0237] First, a coating material is prepared for the formation of the protective coating 11. The coating material is a liquid composition containing a plurality of resin particles 32 and a binder resin 31 when cured.

[0238] The method for forming a protective coating 11 on the coating 10 is a well-known method and is preferred. For example, the above-mentioned coating is applied to the surface 10S of the coating 10 by means of blowing, roller coating, curtain coating or dip-coating.

[0239] Subsequently, the coating on the plating layer 10 is allowed to dry naturally or by baking to form a protective film 11. The drying temperature, drying time, baking temperature, and baking time can be appropriately adjusted within well-known ranges.

[0240] F1 and F2 can be adjusted to the ranges described above by adjusting the mixing of the liquid composition of the coating used to form the protective coating 11 with the resin particles 32, the size of the resin particles 32, and the film thickness of the protective coating 11. Furthermore, when one or more internal organic resin layers 12 are formed between the protective coating 11 and the plating layer 10, one or more internal organic resin layers 12 are first formed using the method described above, and then the protective coating 11 is formed using the method described above.

[0241] Alternatively, a well-known chemical conversion treatment process can be performed after the texturing process and before the protective coating formation process. In this case, such as Figure 9 As shown, a plated steel sheet 1 with a chemically converted coating 13 disposed between the plating layer 10 and the protective coating 11 can be manufactured.

[0242] The galvanized steel sheet 1 of this embodiment can be manufactured using the above manufacturing process. Furthermore, the galvanized steel sheet 1 of this embodiment is not limited to the above manufacturing method; as long as a galvanized steel sheet 1 having the above structure can be manufactured, other manufacturing methods besides the above-described method can also be used to manufacture the galvanized steel sheet 1 of this embodiment. However, the above-described manufacturing method is suitable for manufacturing the galvanized steel sheet 1 of this embodiment.

[0243] Example

[0244] The effects of one aspect of the present invention will be further described in detail below using examples. The conditions in the following examples are examples of conditions adopted to confirm the feasibility and effectiveness of the plated steel sheet 1 of this embodiment. Therefore, the present invention is not limited to this one example of conditions. Various conditions can be adopted in the present invention as long as they do not depart from the spirit of the present invention and achieve the purpose of the present invention.

[0245] [Manufacturing of galvanized steel sheets for each test number]

[0246] The plated steel sheets with the test numbers listed in Table 1 were prepared. The base steel sheets were SPCC as specified in JIS G 3141:2017, with a thickness of 0.6 mm.

[0247] [Table 1]

[0248] Table 1

[0249]

[0250] Pre-plating treatment was performed on the base steel plates for each test number. Specifically, a Na₄SiO₄ treatment solution with a concentration of 30 g / L was used, the treatment solution temperature was set to 60℃, and the current density was set to 20 A / dm². 2 The base steel plates were electrolytically degreased and washed with water for a processing time of 10 seconds. After electrolytic degreasing and washing, the base steel plates were further immersed in a 50 g / L H2SO4 aqueous solution at 60°C for 10 seconds, followed by washing with water.

[0251] The following plating treatment was applied to the base steel plates of each test number after pre-plating treatment.

[0252] A Zn plating layer was formed on the base steel plates of test numbers 1 to 8 and 15 to 31 using the following method. Specifically, a plating bath containing 1.0 M Zn sulfate heptahydrate and 50 g / L anhydrous sodium sulfate at pH 2.0 was prepared. Using this plating bath, a plating temperature of 50°C and a current density of 50 A / dm³ were applied. 2 The plating time was adjusted under the given conditions to achieve an adhesion amount of 35 g / m. 2 The above plating process forms a Zn plating layer.

[0253] Zn-Ni coatings, containing 11% Ni by mass and the balance Zn, were formed on base steel plates from tests 9 and 10 using the following method. Specifically, a plating bath with a pH of 2.0 and containing a total of 1.2 M Zn sulfate heptahydrate and Ni sulfate hexahydrate, and 50 g / L anhydrous sodium sulfate was prepared. The Zn sulfate heptahydrate and Ni sulfate hexahydrate in the plating bath were adjusted to achieve a plating temperature of 50°C and a current density of 50 A / dm³. 2 When the plating process was performed, the resulting Zn-Ni coating contained 11% Ni by mass, with the balance being Zn. Using the aforementioned plating bath, at a bath temperature of 50°C and a current density of 50 A / dm³... 2 The plating time was adjusted under the given conditions to achieve an adhesion amount of 35 g / m. 2 The above plating process was used to form a Zn-Ni coating.

[0254] The following method was used to form a Zn-Fe coating, containing 15% Fe by mass and the balance Zn, on the base steel plates of Test No. 11 and Test No. 12. Specifically, a plating bath with a pH of 2.0 and containing a total of 1.2 M of Zn sulfate heptahydrate and Fe(II) sulfate heptahydrate, and 50 g / L of anhydrous sodium sulfate was prepared. The Zn sulfate heptahydrate and Fe(II) sulfate heptahydrate in the plating bath were adjusted to achieve a plating temperature of 50 °C and a current density of 50 A / dm³. 2 When the plating treatment was performed, the resulting Zn-Fe coating contained 15% Fe by mass, with the balance being Zn. Using the above-mentioned plating bath, at a bath temperature of 50°C and a current density of 50 A / dm³... 2 The plating time was adjusted under the given conditions to achieve an adhesion amount of 35 g / m. 2 The above plating process was used to form a Zn-Fe coating.

[0255] Zn-Co coatings, containing 2% Co by mass and the balance Zn, were formed on the base steel plates of Test No. 13 and Test No. 14 using the following method. Specifically, a plating bath with a pH of 2.0 and containing a total of 1.2 M of Zn sulfate heptahydrate and Co sulfate heptahydrate, and 50 g / L of anhydrous sodium sulfate was prepared. The Zn sulfate heptahydrate and Co sulfate heptahydrate in the plating bath were adjusted to achieve a plating temperature of 50°C and a current density of 50 A / dm³. 2 When the plating treatment was performed, the resulting Zn-Co coating contained 2% Co by mass, with the balance being Zn. Using the above-mentioned plating bath, at a bath temperature of 50°C and a current density of 50 A / dm³... 2 The plating time was adjusted under the given conditions to achieve an adhesion amount of 35 g / m. 2The above plating process was used to form a Zn-Co coating.

[0256] A hairline texture is applied to the coated base steel sheet along the L-direction (rolling direction). This is achieved by pressing sandpaper of various grits against the base steel sheet and adjusting the pressing force and the number of grinding passes.

[0257] Chemical conversion treatment was applied to the base steel plates with coatings formed in tests 1-18 and 20-31, resulting in a chemical conversion coating on the coating. Specifically, silane coupling agent A and silane coupling agent B were prepared.

[0258] Silane coupling agent A: 3-aminopropyltrimethoxysilane

[0259] Silane coupling agent B: 3-epoxypropoxypropyltrimethoxysilane

[0260] The solid component mass ratio (silane coupling agent A / silane coupling agent B) was set to 1.0, and silane coupling agent A and silane coupling agent B were added to water adjusted to pH 4. The mixture was then stirred for a predetermined time to produce an organosilicon compound. The produced organosilicon compound also contained phosphoric acid as a phosphoric acid compound, thus creating a treatment solution.

[0261] The treatment solution is transferred onto the coating by using a roller to lift it up. At this point, the adhesion weight of the chemical conversion treated film after baking and drying is 0.3 g / m². 2 The treatment solution is transferred onto the coating in this way.

[0262] The steel sheet onto which the treatment solution was transferred to the coating was baked and dried. Specifically, the steel sheet onto which the treatment solution was transferred to the coating was placed in a furnace maintained at 180°C and held in the furnace until the temperature of the steel sheet reached 130°C. After the temperature of the steel sheet reached 130°C, it was removed from the furnace and air-cooled to room temperature. This process formed a chemical conversion treatment coating on the coating. Furthermore, no chemical conversion treatment was performed on the steel sheet of test number 19. That is, no chemical conversion treatment coating was formed on the steel sheet of test number 19.

[0263] Protective coatings were formed on steel plates with chemical conversion treatment coatings (test numbers 1-18, 20-31) and on steel plate without chemical conversion treatment coating (test number 19). As the adhesive resin for the protective coating, a urethane-based resin (trade name: HUX-232 manufactured by ADEKA Co., Ltd.) was used. As the resin particles, polyethylene-based resin particles (trade name: CHEMIPEARL manufactured by Mitsui Chemicals Co., Ltd.) were used. Various coatings with different resin particle concentrations were prepared by dispersing the above-mentioned adhesive resin and resin particles in water.

[0264] The prepared coating is transferred onto a steel plate using a roller. At this time, the coating adhesion is adjusted so that the average film thickness of the protective coating after baking and drying is the average film thickness d recorded in Table 1. The steel plate with the transferred coating is placed in a furnace maintained at 250°C. The steel plate is held in the furnace until its temperature reaches 180°C. After the steel plate reaches 180°C, it is removed from the furnace and air-cooled to room temperature. The protective coating is formed using the above process. Furthermore, in Test No. 7 and Test No. 17, a protective coating and an inner organic resin layer are formed. The binder resin for both the protective coating and the inner organic resin layer uses the aforementioned urethane-based resin. The inner organic resin layer does not contain resin particles. The protective coating contains the aforementioned polyethylene-based resin particles as resin particles. In Test No. 7 and Test No. 17, firstly, after transferring the coating onto the steel plate using the above method, it is baked and dried to form the inner organic resin layer. After transferring the coating onto the steel plate using the method described above, it was baked and dried to form a protective film. The above manufacturing process was used to produce coated steel plates for each test number.

[0265] [Evaluation Test]

[0266] The following evaluation tests were conducted on the coated steel sheets of each test number manufactured.

[0267] (Experiment 1) Test on determination of average film thickness d of protective coating

[0268] (Experiment 2) Determination of the total area ratio S of the convex part

[0269] (Experiment 3) Determination of the average particle size D of resin particles

[0270] (Experiment 4) L-direction gloss measurement test

[0271] (Experiment 5) Scratch resistance evaluation test

[0272] (Experiment 6) Evaluation Test of Metallic Texture

[0273] The following is a description of each experiment.

[0274] [(Experiment 1) Determination of the average film thickness d of the protective coating]

[0275] The average film thickness d (μm) of the protective coating of the coated steel sheet for each test number was determined using the method described in the "Method for Determining the Average Film Thickness d of Protective Coating 11". The calculated average film thickness d is shown in Table 1. Among them, the total film thickness of the protective coating and the inner organic resin layer in test number 7 is 9.4 μm, and the total film thickness of the protective coating and the inner organic resin layer in test number 17 is 4.0 μm. In addition, in test numbers 7 and 17, the layer containing resin particles was identified as the protective coating, and the layer without resin particles was identified as the inner organic resin layer, and the film thickness of each layer (protective coating and inner organic resin layer) was determined.

[0276] [(Experiment 2) Determination of Total Area Ratio S of Convex Parts]

[0277] Using a laser microscope (trade name: VK-9710) manufactured by Keyence Corporation, the total area ratio S (%) of the convex parts for each test number of the coated steel sheet was determined using the method described in the "Method for Determination of Total Area Ratio S of Convex Parts" above. The determined total area ratio S of convex parts is shown in Table 1.

[0278] [(Experiment 3) Determination of the average particle size D of resin particles]

[0279] The average particle size D (μm) of the resin particles in the coated steel sheets for each test number was determined using the method described above in [Method for Determining the Average Particle Size D of Resin Particles 32]. The determined average particle sizes are shown in Table 1.

[0280] [(Experiment 4) L-direction gloss measurement test]

[0281] The gloss in the L-direction of the coated steel sheets for each test number was determined using the following method. Specifically, the gloss at an incident angle of 60° in the L-direction (the direction of hairline extension) of the coated steel sheets was measured using a gloss meter according to the specular gloss determination method of JIS Z 8741:1997 (60° gloss). A gloss meter manufactured by Suga Test Instruments Co., Ltd. (trade name: UGV-6P) was used. The obtained L-direction gloss (%) is shown in Table 1.

[0282] [(Experiment 5) Scratch resistance evaluation test]

[0283] The scratch resistance of the coated steel sheets for each test number was evaluated using the following method.

[0284] Test pieces, including the protective coating, were collected from the coated steel sheets of each test number. These test pieces, including the protective coating, were mounted and fixed onto the sample stage of a friction testing machine equipped with diamond needles with a tip diameter of 180 μm. The friction testing machine used was a TriboGear TYPE: 14FW manufactured by Shinto Science Co., Ltd.

[0285] A diamond needle was brought into perpendicular contact with the surface of the protective coating on the test piece. With the diamond needle in contact with the surface of the protective coating, the test stage, to which the test piece was fixed, was slid at a scratching speed of 60 mm / s. The load applied to the diamond needle was varied, and the presence or absence of damage was visually assessed. The scratch resistance of the protective coating was evaluated based on the load at which damage was visually identified, as follows.

[0286] Damage rating 1: Visually identifiable damage when the load is less than 30 gf.

[0287] Damage Score 2: Visually identifiable damage occurs when the load is above 30gf but below 50gf.

[0288] Damage score 3: Visually identifiable damage occurs when the load is above 50gf but below 70gf.

[0289] Damage score 4: Visually identifiable damage occurs when the load exceeds 70 gf.

[0290] A damage score of 2 or higher is considered excellent scratch resistance.

[0291] [(Experiment 6) Evaluation of Metallic Texture]

[0292] The metallic texture of the plated steel sheets for each test number was determined using the following method.

[0293] At any point on the coated steel sheet of each test number, the 60° gloss level Gl at an incident angle of 60° in the rolling direction L and the 60° gloss level Gw at an incident angle of 60° in the W direction (width direction) were measured using a gloss meter according to JIS Z 8741:1997. A gloss meter manufactured by Suga Test Instruments Co., Ltd. (trade name: UGV-6P) was used. Gw / Gl was calculated based on the obtained gloss levels Gl and Gw.

[0294] As long as the texture can be visually identified and Gw / Gl≤0.90, it is judged to have achieved an excellent metallic texture.

[0295] [Evaluation Results]

[0296] Referring to Table 1, in the coated steel sheets tested from test number 1 to test number 19, the average film thickness d of the protective coating was 10.0 μm or less. Furthermore, the total area ratio S of the raised portion was 10.0% or less. Also, F1 was 10.0 or more, and F2 was 0.7 to 3.0. As a result, the 60° gloss in the L direction was 55% or more, and even with a protective coating or a chemical conversion coating formed on the coating, the texture formed on the surface of the coating was visually discernible, demonstrating excellent texture visibility. Moreover, Gw / Gl was 0.90 or less, achieving an excellent metallic texture. Furthermore, the scratch resistance evaluation consistently showed a damage score of 2 or more, indicating excellent scratch resistance.

[0297] On the other hand, in test number 20, the average film thickness d of the protective coating exceeded 10.0 μm. Therefore, the Gw / Gl ratio exceeded 0.90, resulting in a lower metallic appearance.

[0298] In tests 21 and 22, the average film thickness d of the protective coating exceeded 10.0 μm. Therefore, the Gw / Gl ratio exceeded 0.90, indicating a low metallic appearance. Furthermore, F1 was less than 10.0 and F2 was less than 0.7. Consequently, both tests received a damage score of 1, indicating low scratch resistance.

[0299] In tests 23 to 25, the total area ratio S of the protrusions exceeded 10.0%. As a result, the gloss at 60° in the L direction was less than 55%, and the visibility of the texture formed on the surface of the coating was low.

[0300] In tests 26 and 27, F1 was less than 10.0. As a result, the scratch resistance evaluation was a damage score of 1, indicating low scratch resistance.

[0301] In tests 28 and 29, F2 was less than 0.7. Therefore, F1 was also less than 10.0. As a result, the scratch resistance evaluation was a damage score of 1 in both tests, indicating low scratch resistance.

[0302] In tests 30 and 31, F2 exceeded 3.0. As a result, the scratch resistance evaluation was a damage score of 1, indicating low scratch resistance.

[0303] The embodiments of the present invention have been described above. However, the above embodiments are merely illustrative examples for carrying out the present invention. Therefore, the present invention is not limited to the above embodiments, and can be implemented by appropriately modifying the above embodiments without departing from its spirit.

[0304] Explanation of reference numerals in the attached figures

[0305] 1. Coated steel sheet; 10. Coating; T1. Texture; 11. Protective coating; 31. Adhesive resin; 32. Resin particles.

Claims

1. A galvanized steel sheet, comprising: Base material: steel plate; A coating, which is formed on the surface of the base steel sheet, has a texture on the surface; and A protective coating is formed on the surface of the plating. The protective coating contains adhesive resin and multiple resin particles. The surface of the protective coating includes: Flat area; and Multiple protrusions are formed by locally protruding more than the flat portion from multiple of the resin particles. The average film thickness d of the protective coating is less than 10.0 μm. When viewed from above, the total area ratio S of the plurality of protrusions is less than 10.0%. F1, as defined by equation (1), is 10.0 or higher. F2, as defined by equation (2), is 0.7~1.

4. F1=D×S (1) F2=D / d (2) In Equations (1) and (2), the average particle size D of the plurality of resin particles is substituted into "D", the unit of the average particle size D is μm, the total area ratio S of the plurality of protrusions is substituted into "S", the unit of the total area ratio S is %, and the average film thickness d of the protective coating is substituted into "d", the unit of the average film thickness d is μm.

2. The galvanized steel sheet according to claim 1, wherein, The galvanized steel sheet also includes one or more internal organic resin layers stacked between the protective coating and the coating.

3. The plated steel sheet according to claim 1 or claim 2, wherein, The galvanized steel sheet also has a chemical conversion coating, which is disposed between the galvanized layer and the protective coating and is formed by contacting the surface of the galvanized layer.

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