Hot-dip plated steel product and method for manufacturing hot-dip plated steel product

Abstract

This hot dipped steel material has: a steel material; and a plating layer that is formed on the surface of the steel material and has a specific chemical composition. The thickness of the plating layer is 5 μm or more. The plating layer has a first region and a second region, and satisfies the following formulae (1) to (6): (1) Ra_A ≤ 10.0; (2) Ra_B ≤ 10.0; (3) 1.5 ≤ |Ra_A - Ra_B|; (4) 150 ≤ HV_x ≤ 350; (5) 200 ≤ HV_max; and (6) 0.80 ≤ HV_big / HV_sml ≤ 1.50.

Description

[Technical Field]

[0001] The present disclosure relates to hot-dip galvanized steel products and methods for producing hot-dip galvanized steel products. This application claims priority based on Japanese Patent Application No. 2023-191984, filed on November 10, 2023, the contents of which are incorporated herein by reference. [Background technology]

[0002] Hot-dip galvanized steel is widely used in the building, civil engineering, and automotive industries. This hot-dip galvanized steel undergoes various processes, and the resulting steel structures are then used to manufacture them. For example, metallic-colored hot-dip galvanized steel is often seen in urban areas, used in guardrails, windbreak fences, distribution boards, cable racks, and other applications. Unlike standard galvanized steel, steel structures that form part of roads, railways, and cityscapes often require aesthetic considerations. For example, there is a growing need to add color and design to hot-dip galvanized steel, such as anti-glare coatings for safety in road and railway infrastructure, or black-based colors and logos for advertising and brand names in modern urban spaces. While painting is the most commonly used method, significant drawbacks include the need for periodic repairs due to deterioration and the high cost proportional to the area of ​​application. While stainless steel and aluminum are sometimes used for durability, they are often difficult to adopt due to material costs and strength considerations.

[0003] One way to solve these problems is to apply markings to the plated metal itself without painting before shipping hot-dip plated steel products. For example, Patent Documents 1 to 3 show examples of hot-dip plated steel products to which designs are imparted by controlling the internal constituent phases of the plating layer, which is a metal coating, and combining it with a resin-based coating. In these examples, the differences in the metal constituent phases in the plating layer are utilized to impart the design. Therefore, these examples have issues with achieving clarity like reading, permanence due to corrosion of the plating layer, and large-area markings using patterning. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2021-85089 [Patent Document 2] Japanese Patent Publication No. 2021-172880 [Patent Document 3] Japanese Patent Publication No. 2021-85085 Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure has been made in consideration of the above circumstances, and aims to provide a hot-dip plated steel material and a method for manufacturing hot-dip plated steel material that can display letters, designs, etc. on a plating layer, that has excellent clarity and permanence of the letters, designs, etc., and that allows the letters, designs, etc. to be formed over a large area. [Means for solving the problem]

[0006] In order to solve the above problems, the present disclosure employs the following configuration. [1] A hot-dip galvanized steel material according to one embodiment of the present disclosure is a hot-dip galvanized steel material having a steel material and a coating layer formed on a surface of the steel material, wherein the coating layer has an average chemical composition, in mass%, of Al: more than 10.0% and less than 40.0%, Mg: more than 4.0% and 15.0% or less, Si: 0% or more and 1.00% or less, Sn: 0% or more and 0.7% or less, Bi: 0% or more and 0.3% or less, In: 0% or more and 0.3% or less, a total amount ΣX of Sn, Bi, and In: 0% or more and 0.7% or less, Ca: 0% or more and 0.60% or less, Y : 0% or more, 0.30% or less, La: 0% or more, 0.30% or less, Ce: 0% or more, 0.30% or less, Sr: 0% or more, 0.30% or less, Li: 0% or more, 0.30% or less, total amount of Ca, Y, La, Ce, Sr and Li ΣYa: 0% or more, 0.60% or less, Cr: 0% or more, 1.00% or less, Ni: 0% or more, 1.0% or less, Mo: 0% or more, 0.25% or less, Cu: 0% or more, 1.0% or less, Ag: 0% or more, 0.25% or less, Sb: 0% or more, 0.25% or less, Pb: 0% or more, 0.25% or less, total amount of Cr, Ni, Mo, Cu, Ag, Sb and Pb ΣYb: 0% or more, 1.0% or less, B: 0% or more, 0.50% or less, P : 0% or more, 0.50% or less, total amount of B and P ΣYc: 0% or more, 0.50% or less, Ti: 0% or more, 0.25% or less, Co: 0% or more, 0.25% or less, V: 0% or more, 0.25% or less, Nb: 0% or more, 0.25% or less, Mn: 0% or more, 0.25% or less, Zr: 0% or more, 0.25% or less, W a total content ΣZ of Ti, Co, V, Nb, Mn, Zr, and W: 0% or more and 0.25% or less; Fe: 0% or more and 5.0% or less; Zn: more than 42.0% and 85.0% or less; the coating layer has a thickness of 5 μm or more; the coating layer has a first region and a second region, and one of the first region and the second region is arranged to have a predetermined shape; the arithmetic mean roughness Ra (μm) of the surface of the first region of the hot-dip coated steel material is Ra_A, the arithmetic mean roughness Ra (μm) of the surface of the second region of the hot-dip coated steel material is Ra_B, the larger value of Ra_A or Ra_B is Ra_L, and the surface of the coating layer has a thickness of (Ra_L+1.When the average Vickers hardness HV between a depth position of (Ra_L + 1.0) μm from the surface of the plating layer and a depth position of half the thickness of the plating layer is defined as HV_x and the maximum Vickers hardness HV is defined as HV_max, the following formulas (1) to (5) are satisfied; when the average Vickers hardness HV between a depth position of (Ra_L + 1.0) μm from the surface of the plating layer and a depth position of half the thickness of the plating layer in the region of the first region or the second region, whichever has the larger arithmetic mean roughness Ra, is defined as HV_big; and when the average Vickers hardness HV between a depth position of (Ra_L + 1.0) μm from the surface of the plating layer and a depth position of half the thickness of the plating layer in the region of the first region or the second region, whichever has the smaller surface roughness Ra, is defined as HV_sml, the following formula (6) is satisfied: death, One of the first region and the second region is arranged to have any one of the shapes of a straight line portion, a curved line portion, a dot portion, a figure, a number, a symbol, a pattern, or a letter, or an intentional shape that combines two or more of these. Hot-dip galvanized steel. Ra_A≦10.0 …(1) Ra_B≦10.0 …(2) 1.5≦|Ra_A−Ra_B| …(3) 150≦HV_x≦350 …(4) 200≦HV_max …(5) 0.80≦HV_big / HV_sml≦1.50 …(6) [ 2 ] A hot-dip galvanized steel material according to another embodiment of the present disclosure is a hot-dip galvanized steel material having a steel material and a coating layer formed on a surface of the steel material, wherein the coating layer has an average chemical composition, in mass%, of Al: more than 10.0% and less than 40.0%, Mg: more than 4.0% and 15.0% or less, Si: 0% or more and 1.00% or less, Sn: 0% or more and 0.7% or less, Bi: 0% or more and 0.3% or less, In: 0% or more and 0.3% or less, a total amount ΣX of Sn, Bi, and In: 0% or more and 0.7% or less, Ca: 0% or more and 0.60% or less, Y : 0% or more, 0.30% or less, La: 0% or more, 0.30% or less, Ce: 0% or more, 0.30% or less, Sr: 0% or more, 0.30% or less, Li: 0% or more, 0.30% or less, total amount of Ca, Y, La, Ce, Sr and Li ΣYa: 0% or more, 0.60% or less, Cr: 0% or more, 1.00% or less, Ni: 0% or more, 1.0% or less, Mo: 0% or more, 0.25% or less, Cu: 0% or more, 1.0% or less, Ag: 0% or more, 0.25% or less, Sb: 0% or more, 0.25% or less, Pb: 0% or more, 0.25% or less, total amount of Cr, Ni, Mo, Cu, Ag, Sb and Pb ΣYb: 0% or more, 1.0% or less, B: 0% or more, 0.50% or less, P : 0% or more, 0.50% or less, total amount of B and P ΣYc: 0% or more, 0.50% or less, Ti: 0% or more, 0.25% or less, Co: 0% or more, 0.25% or less, V: 0% or more, 0.25% or less, Nb: 0% or more, 0.25% or less, Mn: 0% or more, 0.25% or less, Zr: 0% or more, 0.25% or less, W a total content ΣZ of Ti, Co, V, Nb, Mn, Zr, and W: 0% or more and 0.25% or less; Fe: 0% or more and 5.0% or less; Zn: more than 42.0% and 85.0% or less; the coating layer has a thickness of 5 μm or more; the coating layer has a first region and a second region, and one of the first region and the second region is arranged to have a predetermined shape; the arithmetic mean roughness Ra (μm) of the surface of the first region of the hot-dip coated steel material is Ra_A, the arithmetic mean roughness Ra (μm) of the surface of the second region of the hot-dip coated steel material is Ra_B, the larger value of Ra_A or Ra_B is Ra_L, and the surface of the coating layer has a thickness of (Ra_L+1.When the average value of Vickers hardness HV between a depth position of (Ra_L + 1.0) μm from the surface of the plating layer and a depth position of half the thickness of the plating layer is defined as HV_x and the maximum value of Vickers hardness HV is defined as HV_max, the following formulas (1) to (5) are satisfied; when the average value of Vickers hardness HV between a depth position of (Ra_L + 1.0) μm from the surface of the plating layer and a depth position of half the thickness of the plating layer in the region of the first region or the second region, whichever has the larger arithmetic mean roughness Ra, is defined as HV_big; and when the average value of Vickers hardness HV between a depth position of (Ra_L + 1.0) μm from the surface of the plating layer and a depth position of half the thickness of the plating layer in the region of the first region or the second region, whichever has the smaller surface roughness Ra, is defined as HV_sml, the following formula (6) is satisfied; The steel material is a steel plate, and the plating layer is provided on both one surface of the steel plate and the other surface opposite to the one surface, and in either or both of the plating layer on the one surface side or the plating layer on the other surface side, one of the first region and the second region is arranged so as to have one type of shape selected from the group consisting of straight line portions, curved portions, dot portions, figures, numbers, symbols, patterns, and letters, or an intentional shape combining two or more of these. R . Ra_A≦10.0 …(1) Ra_B≦10.0 …(2) 1.5≦|Ra_A−Ra_B| …(3) 150≦HV_x≦350 …(4) 200≦HV_max …(5) 0.80≦HV_big / HV_sml≦1.50 …(6) [ 3 A method for producing a hot-dip plated steel material according to another embodiment of the present disclosure includes: [1] In this method for manufacturing hot-dip plated steel material, either the first region or the second region is formed by colliding iron or non-ferrous metal particles (shot) with the surface of a plating layer formed on the surface of the steel material by a hot-dip plating method using centrifugal force or air pressure. [ 4 A method for producing a hot-dip plated steel material according to another embodiment of the present disclosure includes: [2] In this method for manufacturing a hot-dip plated steel material, one of the first region and the second region is formed on the surface of one or both of the plating layers formed on one side or the other side of a steel sheet by a hot-dip plating method, by causing particles (shot) of iron or non-ferrous metal to collide with the hot-dip plated steel material by centrifugal force or air pressure. [Effects of the Invention]

[0007] According to the above aspects of the present disclosure, it is possible to provide a hot-dip galvanized steel product and a method for manufacturing the hot-dip galvanized steel product that allows characters, designs, etc. to appear on the plating layer, has excellent clarity and permanence, and enables large-area characters, designs, etc. This makes it possible to provide inexpensive materials with excellent aesthetic appeal, and contributes to industrial development. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a photograph showing an example of a design imparted to a plated steel sheet by shot blasting. [Figure 2] FIG. 1 is a schematic diagram of a cross section of a hot-dip plated steel material according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present inventors have intensively investigated means for making characters, designs, etc. appear on the surface (plating layer) of hot-dip plated steel material, improving the clarity and permanence of the characters, designs, etc., and further enabling the characters, designs, etc. to be displayed over a large area.

[0010] In order to express designs such as letters or designs in specific areas of a metal surface, it is possible to create differences in color, gloss, reflectivity, etc. between the area showing the letters or design and the background area.

[0011] Of these, color differences have the greatest potential for clarifying a design. While the surface of metal materials generally has a uniform color tone, with the exception of titanium and stainless steel oxide coatings and aluminum after anodizing, alloys among metal materials can change their surface color tone by varying the chemical composition ratio. However, with hot-dip galvanized steel products with a Zn-Al-Mg plating layer, whose chemical composition is uniform, it is difficult to partially change the chemical composition during the manufacturing process, making it difficult to intentionally change the color difference in specific areas of the plating layer.

[0012] Furthermore, gloss poses a problem of design permanence over long-term use of metal materials. In other words, as corrosion of the metal surface progresses over time, the difference in gloss between the visible and background areas of the design may decrease, making the design less noticeable. Furthermore, gloss is related to properties such as anti-glare, so it must be carefully controlled. Furthermore, while gloss, like color difference, is affected by the composition ratio of the alloy's chemical components, for the same reasons as above, it is difficult to intentionally change the gloss in specific areas of a Zn-Al-Mg plating layer.

[0013] On the other hand, since reflectivity can be changed by controlling the surface roughness of the metal material, it is believed that even in a Zn-Al-Mg-based plating layer, where partial control of chemical composition is not easy, it is possible to express a design by partially changing the reflectivity. Therefore, in this disclosure, we attempted to impart a design to a plating layer by controlling the surface roughness of the plating layer surface.

[0014] In this disclosure, we have investigated the application of shot blasting to a coating surface as a means of changing the surface roughness of a specific region of a coating layer. In the steel industry, shot blasting is used to remove rust and scale, and to create surface irregularities by striking a projectile against a steel surface, etc., to form a paint base. However, typical hot-dip coating layers, such as Zn and Al coatings, are relatively soft and thin, with thicknesses of up to several tens of micrometers. Therefore, if shot blasting is performed on such hot-dip coating layers, there is a risk that the hot-dip coating layer will deform and disappear within a short treatment time, making it difficult to achieve a design. In response to this issue, the present inventors have found that, if the coating layer is sufficiently hard, it is possible to impart a design by adjusting the shot blasting treatment time. However, it has also been found that excessively hard coating layers reduce productivity due to the long shot blasting treatment time and also cause peeling of the coating layer due to cracks that occur after shot blasting. Therefore, the inventors conducted further studies and found that it is preferable to apply a plating layer having a Vickers hardness in the range of 150 to 350 Hv, as this is moderately hard and moderately soft, and further that it is preferable for a hard phase and a soft phase to be mixed within the plating layer.

[0015] Regarding the permanence of designs, shot-blasted plating layers, which have a partially increased surface roughness and larger surface area than before, tend to have a longer wetting time and are more susceptible to corrosion. Therefore, when a design is applied to a conventional Zn-plated steel material by shot-blasting, white rust readily develops on the surface, making it difficult to maintain the clarity of the design, for example, when exposed to outdoor environments in Japan for more than one year. Furthermore, Al- or Al-Zn-plated steels are often plated on thin steel sheets for sacrificial corrosion protection. However, when subjected to external forces such as shot-blasting, the steel warps and deforms, making it unsuitable for use as a structural steel material. In light of these circumstances, hot-dip galvanized steel with a Zn-Al-Mg-based plating layer is suitable for maintaining the clarity of the design over a period equivalent to 10 years in outdoor environments in Japan.

[0016] In order to enlarge the area of ​​the design, it is possible to do so using either the batch or continuous method by fully automating the shot blasting process and applying masking or partial shot blasting.

[0017] It was discovered that shot blasting has a favorable effect in the design application process due to the unique properties of the Zn-Al-Mg plating layer. The mixture of hard and soft structures within the plating layer suppresses the propagation of cracks within the plating layer, preventing cracks that occur during shot blasting from penetrating all the way to the base steel, preventing peeling of the plating layer and a decrease in corrosion resistance.

[0018] Hereinafter, a hot-dip plated steel material according to an embodiment of the present disclosure will be described.

[0019] The hot-dip plated steel material of this embodiment has a steel material and a coating layer formed on the surface of the steel material, and the coating layer has an average chemical composition, in mass%, of Al: more than 10.0% and less than 40.0%, Mg: more than 4.0% and 15.0% or less, Si: 0% or more and 1.00% or less, Sn: 0% or more and 0.7% or less, Bi: 0% or more and 0.3% or less, In: 0% or more and 0.3% or less, a total amount ΣX of Sn, Bi, and In: 0% or more and 0.7% or less, Ca: 0% or more and 0.60% or less, Y: 0% or more and 0.30% or less, and La: 0% or more and 0.30% or less. %, Ce: 0% or more, 0.30% or less, Sr: 0% or more, 0.30% or less, Li: 0% or more, 0.30% or less, total of Ca, Y, La, Ce, Sr and Li ΣYa: 0% or more, 0.60% or less, Cr: 0% or more, 1.00% or less, Ni: 0% or more, 1.0% or less, Mo: 0% or more, 0.25% or less, Cu: 0% or more, 1.0% or less, Ag: 0% or more, 0.25% or less, Sb: 0% or more, 0.25% or less, Pb: 0% or more, 0.25% or less, total of Cr, Ni, Mo, Cu, Ag, Sb and Pb Amount ΣYb: 0% or more, 1.0% or less, B: 0% or more, 0.50% or less, P: 0% or more, 0.50% or less, total amount of B and P ΣYc: 0% or more, 0.50% or less, Ti: 0% or more, 0.25% or less, Co: 0% or more, 0.25% or less, V: 0% or more, 0.25% or less, Nb: 0% or more, 0.25% or less, Mn: 0% or more, 0.25% or less, Zr: 0% or more, 0.25% or less, W: 0% or more, 0.25% or less, total amount ΣZ of Ti, Co, V, Nb, Mn, Zr and W: 0% or more, 0.25% or less, Fe: The coating layer has a thickness of 5 μm or more, and contains a first region and a second region, and one of the first region and the second region is arranged to have a predetermined shape. The arithmetic mean roughness Ra (μm) of the surface of the first region of the hot-dip coated steel material is defined as Ra_A, the arithmetic mean roughness Ra (μm) of the surface of the second region of the hot-dip coated steel material is defined as Ra_B, and the larger value of Ra_A or Ra_B is defined as Ra_L, and the distance from the surface of the coating layer to the surface of the first region is defined as (Ra_L+1.The hot-dip galvanized steel material satisfies the following formulas (1) to (5), where HV_x is the average value of Vickers hardness HV between a depth position of (Ra_L+1.0) μm from the coating layer surface and a depth position of half the coating layer thickness, and HV_max is the maximum value of Vickers hardness HV; and HV_big is the average value of Vickers hardness HV between a depth position of (Ra_L+1.0) μm from the coating layer surface and a depth position of half the coating layer thickness, in the region of either the first region or the second region, whichever has the larger arithmetic mean surface roughness Ra, and HV_sml is the average value of Vickers hardness HV between a depth position of (Ra_L+1.0) μm from the coating layer surface and a depth position of half the coating layer thickness, in the region of either the first region or the second region, which has the smaller surface roughness Ra, and HV_sml is the average value of Vickers hardness HV between a depth position of (Ra_L+1.0) μm from the coating layer surface and a depth position of half the coating layer thickness. Ra_A≦10.0 …(1) Ra_B≦10.0 …(2) 1.5≦|Ra_A−Ra_B| …(3) 150≦HV_x≦350 …(4) 200≦HV_max …(5) 0.80≦HV_big / HV_sml≦1.50 …(6)

[0020] Here, the thickness of the plating layer is calculated based on the plating weight. The plating weight is calculated by measuring the change in weight when the plating layer is dissolved in acid. There are no particular restrictions on the type of acid as long as it can dissolve the plating layer, but it is preferable to use an acid containing an inhibitor that suppresses corrosion of the base steel (steel material). If the area and weight are measured before and after dissolution, the plating weight (g / m 2 ) can be obtained. 2 ) can be calculated not only for steel sheets but also for steel wire rods or steel wires, and it is possible to calculate the coating weight from the weight of the dissolved coating layer based on the surface area of ​​the steel wire rods or steel wires (diameter x π x length). The coating weight can be calculated using the coating specific gravity (g / m 3 ) to obtain the thickness of the plating layer.

[0021] Furthermore, by measuring the obtained acid solution using ICP atomic emission spectroscopy or ICP-MS, the chemical composition (average chemical composition) of the plating layer can be obtained, as described below, and the plating specific gravity can be calculated from the value of the chemical composition.

[0022] In addition, in the hot-dip galvanized steel material of this embodiment, it is preferable that one of the first region and the second region is arranged to have the above-mentioned predetermined shape, which is one of a straight line portion, a curved line portion, a dot portion, a figure, a number, a symbol, a pattern, or a letter, or a shape that combines two or more of these. The shape of one of the first region and the second region may be formed intentionally.

[0023] In the following description, the "%" used to indicate the content of each element in the chemical composition means "mass %." Furthermore, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. Furthermore, when the numerical values ​​before and after "to" are followed by "greater than" or "less than," the numerical range does not include these numerical values ​​as the lower or upper limit.

[0024] <Steel> First, we will explain steel materials. Steel materials are, for example, mainly steel sheets, steel wire rods, or steel wires, but there are no particular limitations on their size. For example, steel sheets may be any steel sheets that are applicable to a typical hot-dip galvanizing process. Specifically, this applies to steel sheets that are applicable to processes in which the steel is immersed in molten metal and solidified, such as continuous hot-dip galvanizing lines (CGLs). For example, hot-dip galvanized steel sheets that satisfy JIS G3323:2022 "Hot-dip zinc-aluminum-magnesium alloy-coated steel sheets and steel strips" are applicable, but this is not limited thereto. For example, steel sheets with a thickness of 10 mm or less and a width of 2000 mm or less may be applicable, but the steel sheet size is not limited thereto. Steel sheet shapes also include checkered steel sheets, which have macroscopic surface irregularities previously applied. Steel wire rods or steel wires may also be any steel sheets that are applicable to a typical hot-dip galvanizing process.

[0025] There are no particular limitations on the quality of the steel material, and examples of applicable steel materials include general steel, pre-plated steel thinly plated with various metals, Al-killed steel, ultra-low carbon steel, high carbon steel, various high-tensile steels, and some high alloy steels (such as steels containing elements that strengthen corrosion resistance, such as Ni and Cr).

[0026] Furthermore, the manufacturing process of steel materials includes common processes such as iron and steel making processes using blast furnaces or electric furnaces, hot rolling processes, pickling processes, cold rolling processes, and heat treatment processes, but the steel materials of this embodiment may be those that have undergone any of these processes, and the processing conditions for each process are not limited.

[0027] <Plating layer> Next, the plating layer will be described. The plating layer according to this embodiment includes a Zn-Al-Mg alloy layer. This selection is due to the fact that the hardness distribution of the plating layer is suitable for imparting a design, and the plating layer has high corrosion resistance and is excellent in terms of the durability of the design. The plating layer may also include an Al-Fe interfacial alloy layer.

[0028] The thickness of the plating layer is the sum of the thicknesses of the Zn-Al-Mg alloy layer and the Al-Fe layer, and in order to impart a design by shot blasting, the plating layer needs to have a certain thickness, specifically a thickness of 5 μm or more, in order to impart surface roughness. On the other hand, since the maximum thickness of the plating layer formed on steel wire material or steel wire by a normal hot-dip plating method is often 100 μm or less, the thickness of the plating layer of the hot-dip plated steel material of this embodiment may be, for example, 100 μm or less.

[0029] The Zn-Al-Mg alloy layer is made of a Zn-Al-Mg alloy. The Zn-Al-Mg alloy refers to a ternary alloy whose main elements are Zn, Al, and Mg, and which may contain optional elements. The main elements refer to elements other than Fe that make up the coating layer, and the total amount is 95.0% or more.

[0030] The Al-Fe interfacial alloy layer is an interfacial alloy layer between the steel material and the Zn-Al-Mg alloy layer, and is in contact with the surface of the steel material.

[0031] That is, the plating layer may have a single-layer structure of a Zn-Al-Mg alloy layer, or a laminated structure including a Zn-Al-Mg alloy layer and an Al-Fe interfacial alloy layer. In the case of a laminated structure, the Zn-Al-Mg alloy layer is preferably a layer that forms the surface of the plating layer.

[0032] As will be described later, when a hot-dip galvanized steel material (in the form of a steel sheet, steel wire, or steel wire) produced by a CGL or a hot-dip zinc alloy-plated steel material produced by a batch-type hot-dip galvanizing method is used as the base material for plating, traces of the interfacial alloy layer of the base material for plating may remain on the hot-dip galvanized steel material according to this embodiment. In particular, when the base material for plating is a plated steel sheet, the Al-Fe-based interfacial alloy layer tends to become thinner due to the high sheet passing speed through the plating bath during hot-dip plating. Furthermore, when a Ni-preplated steel material, an Sn-preplated steel material, a Cr-preplated steel material, or the like is used as the base material for plating, these metals may be mixed into the Al-Fe-based interfacial alloy layer.

[0033] The Al-Fe interfacial alloy layer bonds the steel material to the Zn-Al-Mg alloy layer, and the thickness of the Al-Fe interfacial alloy layer can be controlled to some extent by controlling the plating bath temperature during the production of the hot-dip galvanized steel material, the plating bath immersion time, the steel material passing speed during plating, and the wiping pressure.

[0034] The Al-Fe-based interface alloy layer is formed between the steel material and the Zn-Al-Mg-based alloy layer, and its main phase is the Al5Fe2 phase. The Al-Fe-based interface alloy layer is formed by atomic diffusion between the steel substrate (steel material) and the hot-dip coating during or after the steel material passes through a hot-dip coating bath. When a continuous hot-dip coating method is used as a manufacturing method, the Al-Fe-based interface alloy layer is likely to form in a coating layer containing Al. In this embodiment, since the coating bath contains a certain concentration of Al or higher, the Al5Fe2 phase is the most abundant phase in the Al-Fe-based interface alloy layer. However, because atomic diffusion takes time, the Fe concentration in the Al-Fe-based interface alloy layer is not uniform, and the Fe concentration may be higher in the portion closer to the steel substrate. Therefore, the Al-Fe-based interface alloy layer may partially contain small amounts of AlFe phase, Al3Fe phase, Al5Fe2 phase, etc. Furthermore, since the coating bath also contains a certain concentration of Zn, the Al-Fe-based interface alloy layer may also contain small amounts of Zn or Si, which tends to accumulate at the interface.

[0035] In this embodiment, the plating layer may contain Si. When Si is incorporated into an Al-Fe-based interfacial alloy layer, it forms an Al-Fe-Si intermetallic compound phase. Identified intermetallic compound phases include the AlFeSi phase, and isomers such as α-, β-, q1-, and q2-AlFeSi phases exist. Therefore, these AlFeSi phases may be detected in the Al-Fe-based interfacial alloy layer. An Al-Fe-based interfacial alloy layer containing these AlFeSi phases is also referred to as an Al-Fe-Si alloy layer. This intermetallic compound is determined solely by the plating component concentration (presence or absence), regardless of the manufacturing method. Therefore, if Si is contained in the plating layer, an intermetallic compound phase containing Si will certainly be formed.

[0036] Although the morphology of the Al-Fe-based interfacial alloy layer contributes little to corrosion resistance, which is the primary required characteristic of the coating layer, it does influence the adhesion of the coating layer during processing of hot-dip galvanized steel and its workability, specifically, whether or not cracks occur during processing. In particular, the morphology of the Al-Fe-based interfacial alloy layer can affect powdering resistance, which indicates the degree of peeling of the coating layer during processing. Generally, a thinner Al-Fe-based interfacial alloy layer reduces the number of crack initiation points in the coating layer during processing, thereby improving powdering resistance. Therefore, for hot-dip galvanized steel that may be subjected to heavy processing during use, it is preferable that the Al-Fe-based interfacial alloy layer be as thin as possible. Specifically, the thickness of the Al-Fe-based interfacial alloy layer is preferably 2.0 μm or less, but may also be 1.0 μm or less, 0.7 μm or less, or more preferably 0.5 μm or less, or even 0.3 μm or less. Typically, the Al-Fe-based interfacial alloy layer is thinner than the Zn-Al-Mg-based alloy layer, often accounting for less than 10% of the total coating layer.

[0037] Furthermore, if the plating layer contains optional elements (Mg, Si, Cr, Ni, Co, Mn, V, Nb, Sn, Bi, In, B, La, Ca, Ce, Y), these elements may be mixed into the Al-Fe interfacial alloy layer or may exist as intermetallic compounds containing these elements. For example, Ni can form Al3Ni or Al-Ca-Si-Ni intermetallic compounds. Among optional elements, elements with particularly high melting points tend to remain in layer form in the Al-Fe interfacial alloy layer. On the other hand, low-melting-point metals such as Sn do not leave traces and may not be detectable. Furthermore, when steel with a pre-plated layer of Ni, Cr, etc. is used as the plating base material, Ni, Cr, etc. may remain in layer form in the interfacial alloy layer. These metals may exist in a thickness of less than 1 μm as a metal layer formed by prior displacement electroplating, i.e., a pure Ni or Cr layer.

[0038] <Chemical composition of plating layer> Next, the average chemical composition of the plating layer will be described.

[0039] The average chemical composition of the entire plating layer is the average chemical composition of the Zn-Al-Mg alloy layer when the plating layer has a single-layer structure of the Zn-Al-Mg alloy layer. Furthermore, when the plating layer has a laminate structure of an Al-Fe interfacial alloy layer and a Zn-Al-Mg alloy layer, it is the average chemical composition of the combined Al-Fe interfacial alloy layer and the Zn-Al-Mg alloy layer. In this embodiment, the thickness of the Al-Fe interfacial alloy layer is preferably 10% or less of the entire plating layer, and therefore the Fe content of the plating layer is often within 5.0%. Therefore, the average chemical composition of the plating layer can be safely considered to be roughly the composition of the Zn-Al-Mg alloy layer. Furthermore, traces of the original plating material are unlikely to remain as chemical components of the plating layer. Therefore, the average chemical composition of the plating layer can be considered to be approximately equivalent to the composition of the plating bath used in its production.

[0040] The chemical composition of the coating layer determines its hardness. In other words, coating layers produced on a typical coating production line often reach the top roll within 60 seconds of hot-dip plating, and while the internal morphology of the coating layer is controlled by the solidification process, the chemical composition cannot be significantly changed. Therefore, if the component composition is the same, there will be no significant variation in the hardness of the coating layer, and hardness variation will be within a range of ±20%.

[0041] The hot-dip plated steel material of this embodiment is produced by a continuous hot-dip plating method, and therefore, Fe may diffuse from the base material to the plated layer during production. As described above, in this embodiment, the Al content of the plated layer is high, and an Al-Fe-based interfacial alloy layer may be formed, but the thickness of the Al-Fe-based interfacial alloy layer is thin. As a result, the plated layer may contain up to 5.0% Fe.

[0042] The elements contained in the plating layer and their contents (concentrations) will be described below.

[0043] Al: Over 10.0% and less than 40.0% Like Zn, Al is an element that mainly constitutes the plating layer. In Zn-Al-Mg-based plating, it mainly forms the Al phase in the plating layer. If the Al content is 10.0% or less, the corrosion resistance of the plating layer decreases and the hardness of the plating layer falls outside the appropriate range, which is undesirable. If the Al content is 40.0% or more, the Zn content decreases relatively, which is undesirable, resulting in a decrease in sacrificial corrosion protection. The Al content is preferably 15.0% or more or 19.0% or more. Furthermore, the Al content is preferably 35.0% or less or 30.0% or less.

[0044] Mg: more than 4.0%, less than 15.0% Like Al and Zn, Mg is an element that mainly constitutes the coating layer. A lack of Mg reduces sacrificial corrosion protection, so the Mg content is set to more than 4.0%. The Mg content is preferably 5.0% or more or 6.0% or more. A Mg content of more than 15.0% reduces corrosion resistance. Therefore, the Mg content is set to 15.0% or less. The Mg content is preferably less than 15.0%, 14.0% or less, 12.0% or less, 10.0% or less, 8.0% or less, 7.5% or less, or 7.0% or less.

[0045] Zn: more than 42.0%, less than 85.0% The hot-dip plated steel material of this embodiment is a Zn-based plated steel material with high versatility, and therefore the element that constitutes the main phase of the plated layer is Zn. If the Zn content is 42.0% or less, the corrosion resistance becomes insufficient, and if it exceeds 85.0%, the corrosion resistance improving effect of other elements such as Al and Mg cannot be obtained. Therefore, the Zn content is set to more than 42.0% and 85.0% or less.

[0046] The plating layer may further contain the elements listed below. All of the elements described below are optional elements, and within the composition ranges described below, they form new intermetallic compounds, substitution products of major elements, etc. If the elements are contained in amounts greater than the composition ranges, the hardness of the plating layer increases significantly, making it difficult to impart roughness by shot blasting and significantly impairing the properties of the plating layer surface. Therefore, the content must be kept within an appropriate range.

[0047] Si: 0% or more, 1.00% or less Although Si may or may not be contained in the coating layer, the inclusion of Si in the coating layer results in the formation of intermetallic compounds therein. The coating composition in this embodiment has a high melting point, and therefore, hot-dip coating is performed at an operating temperature of approximately 500°C. At such operating temperatures, when a steel material is immersed in a coating bath, active interdiffusion of Al and Zn with Fe occurs, forming Fe-based intermetallic compounds. However, Si suppresses this excessive reaction. Therefore, if Si is contained in an amount of 0.01% or more, the Fe diffusion reaction is significantly suppressed, making it easier to control the formation of Fe-based intermetallic compounds contained in the coating layer. On the other hand, excessive Si content may combine with Mg to form a large amount of intermetallic compounds having the composition MgSi, significantly increasing the hardness of the coating layer. Therefore, the Si content is set to 1.00% or less. The Si content is preferably 0.05% or more or 0.25% or more. The Si content is preferably 0.75% or less.

[0048] Element group X Sn: 0% or more, 0.7% or less Bi: 0% or more, 0.3% or less In: 0% or more, 0.3% or less Total amount of Sn, Bi and InΣX: 0% or more, 0.7% or less Each element in element group X (Sn, Bi, In) can be optionally contained, so the content of each is set to 0% or more. When Sn is contained, Mg2Sn and Mg9Sn5 tend to form in the plating layer. Bi forms Mg3Bi2, and In forms Mg3In. These elements are softer than the MgZn2 phase and have good workability, so their inclusion clearly improves workability. At the same time, they exhibit very base electrochemical properties, providing a high sacrificial corrosion protection effect. Therefore, their inclusion improves corrosion resistance.

[0049] Each element has an upper limit, and if too much is added, the plating layer will become excessively hard. Therefore, the content of these elements must be limited to 0.7% or less for Sn, 0.3% or less for Bi and In, and the total amount ΣX must also be limited to 0.7% or less.

[0050] Element group Ya Ca: 0% or more, 0.60% or less Y: 0% or more, 0.30% or less La: 0% or more, 0.30% or less Ce: 0% or more, 0.30% or less Sr: 0% or more, 0.300% or less Li: 0% or more, 0.30% or less Total amount of Ca, Y, La, Ce, Sr and Li ΣYa: 0% or more, 0.60% or less These elements, along with Si, control the reaction rate of the coating layer and can also control Fe diffusion in the coating bath. Furthermore, the formation of intermetallic compounds containing these elements between the base steel and the interfacial alloy layer ensures adhesion between the base steel and the Al-Fe alloy layer. Ca can form Al2CaSi2 and Zn-Ca compounds. To achieve these effects, a Ca content of 0.03% or more is recommended. However, excessive Ca can form various floating dross in the coating bath, increasing coating defects, and extremely increasing the viscosity of the coating bath, reducing the amount of molten metal adhered to the steel when it is removed from the coating bath, resulting in an extremely thin coating layer and poor corrosion resistance. Furthermore, the coating layer becomes excessively hard. Therefore, the Ca content is limited to 0.60% or less.

[0051] Each element in the element group Ya other than Ca can be added as a substitute for Ca because it has almost the same effect as Ca. However, it cannot be added in as large an amount as Ca. That is, the content of each element in the element group Ya other than Ca is 0 to 0.30%, preferably 0.01 to 0.30%. Furthermore, the total amount ΣYa of the element group Ya including Ca is 0 to 0.60%.

[0052] Element group Yb Cr: 0% or more, 1.00% or less Ni: 0% or more, 1.0% or less Mo: 0% or more, 0.25% or less Cu: 0% or more, 1.0% or less Ag: 0% or more, 0.25% or less Sb: 0% or more, 0.25% or less Pb: 0% or more, 0.25% or less ΣYb: 0% or more and 1.0% or less of the total amount of the element group Yb of Cr, Ni, Mo, Cu, Ag, Sb, and Pb The elements in the element group Yb can be optionally contained, so their respective contents must be 0% or greater. Elements in the element group Yb have properties similar to those of Zn and can be contained in relatively large amounts. Cr and Mo form Mg-Al-Cr and Mg-Al-Mo compounds. When both the element group Yb and the element group Ya are contained, some of the Mg in the Mg-Al-Cr or Mg-Al-Mo compounds may be replaced by the Ya element. Ni also forms Al-Ni compounds. Cu, Ag, Sb, and Pb form Zn-Cu compounds, Zn-Ag compounds, Zn-Sb compounds, and Zn-Sb compounds. When these elements are contained within the above ranges, they effectively improve corrosion resistance. This effect is apparent at a content of around 0.1%. However, if the total content of these elements is excessive, the hardness of the plating layer will be excessively high. Therefore, the Cr content is 0 to 1.00%, preferably 0.01 to 1.00%, the Ni and Cu contents are 0 to 1.0%, and the Mo, Ag, Sb, and Pb contents are 0 to 0.25%. The total amount ΣYb is 0% or more and 1.0% or less.

[0053] Element group Yc B: 0% or more, 0.50% or less P: 0% or more, 0.50% or less Total amount of B and P ΣYc: 0% or more, 0.50% or less The elements in the element group Yc can be contained arbitrarily, and therefore the content of each is set to 0% or more. The elements in the element group Yc tend to form Al-B compounds and Al-P compounds. Furthermore, when these elements are contained within the above ranges, they have the effect of improving corrosion resistance. This effect is apparent when the total content is about 0.05%. On the other hand, if these elements are contained in large amounts, the hardness of the coating layer becomes excessively high. Therefore, the content of each element in the element group Yc is set to 0 to 0.50%. The total amount ΣYc is set to 0% or more and 0.50% or less.

[0054] Element group Z Ti: 0% or more, 0.25% or less Co: 0% or more, 0.25% or less V: 0% or more, 0.25% or less Nb: 0% or more, 0.25% or less Mn: 0% or more, 0.25% or less Zr: 0% or more, 0.25% or less W: 0% or more, 0.25% or less Total amount of element group Z of Ti, Co, V, Nb, Mn, Zr and W ΣZ: 0% or more, 0.25% or less The elements included in element group Z can be contained arbitrarily, and therefore the content of each is set to 0% or more. Although elements in element group Z are difficult to contain in the plating layer of this embodiment, they tend to bond with Al to form intermetallic compounds. When elements in element group Z are contained in the plating bath, corrosion resistance is improved. This effect is apparent when the total content (concentration) is about 0.10%. On the other hand, if these elements are contained in large amounts, the hardness of the plating layer becomes excessively high. Therefore, the content of each element in element group Z is set to 0 to 0.25%. The total amount ΣZ is set to 0% or more and 0.25% or less.

[0055] Fe: 0% or more, 5.0% or less The hot-dip plated steel material of this embodiment is produced by a continuous hot-dip plating method, and therefore Fe may diffuse from the base material to be plated into the plated layer during production. As described above, in this embodiment, the Al content of the plated layer is high, and an Al-Fe-based interfacial alloy layer may be formed, but its thickness is thin. As a result, the plated layer may contain up to 5.0% Fe, but as long as the Fe content is limited to 5.0% or less, there is no effect on the frequency of cracks in the plated layer, etc. Therefore, the Fe content is set to 0 to 5.0%. The Fe content may be greater than 0%.

[0056] The remainder other than the above may be impurities. That is, the above elements may be contained, with the remainder consisting of impurities. Impurities refer to components contained in raw materials or components mixed in during the manufacturing process, but not intentionally added. For example, trace amounts of components other than Fe may be mixed into the coating layer as impurities due to mutual atomic diffusion between the steel material (base steel) and the coating bath.

[0057] The average chemical composition of the plating layer can be determined using the acid solution prepared when measuring the thickness of the plating layer. Specifically, the plating layer is stripped and dissolved using an acid containing an inhibitor that suppresses corrosion of the steel substrate (steel material). The resulting acid solution can then be analyzed using ICP atomic emission spectroscopy or ICP-MS to determine the chemical composition.

[0058] <Plating layer structure> The plating layer of this embodiment includes Zn, Al, MgZn2, Mg2Zn 11 , MgZn, η-MgZn, Mg 32 (Zn, Al) 39The coating layer contains one or more of the above phases. The total volume fraction of these phases is often 90% or more. When observed in a cross section in the thickness direction of the coating layer, the total area fraction of these phases is often 90% or more. The coating layer may contain one or more of these phases as a single phase, or may also contain a mixed structure made up of these phases. For example, it may contain a Zn-Al phase (Zn: 16.5 to 67%) containing a fine Zn phase and a fine Al phase, or a ternary eutectic structure containing a Zn phase, an Al phase, and an MgZn2 phase.

[0059] These area fractions can be determined by obtaining EPMA images of Zn, Al, MgZn2 phases, etc. in a horizontal cross section to identify the structure of the same component. To measure area fractions, image analysis software such as ImageJ can be used to map the compositional region of the target component, making it easy to identify the area occupied by the constituent phases of the main component.

[0060] The main constituent phases in the coating layer determine the Vickers hardness of the coating layer. Relatively hard phases are Mg-Zn compounds such as MgZn2, which exhibit a Vickers hardness of 200 to 400 Hv. On the other hand, soft phases are Zn phase, Al phase, and Zn-Al phase, which exhibit a Vickers hardness of 50 to 100 Hv. As for the ternary eutectic structure, the proportion of the MgZn2 phase in the eutectic structure is relatively small, so the Vickers hardness is in the range of 100 to 200 Hv. Therefore, a coating layer in which the ternary eutectic structure is the main constituent phase, in particular, has a hardness of less than 200 Hv. By setting the Al content to more than 10.0% and the Mg content to more than 4.0%, as in this embodiment, it is possible to prevent the ternary eutectic structure from becoming the main phase (50% or more), and the Vickers hardness of the coating layer can be controlled within the desired range. As for the structure of the coating layer, it is preferable that the area fraction of a ternary eutectic structure containing a Zn phase, an Al phase, and an MgZn2 phase is less than 50 area %.

[0061] Other compounds are less than 10% in terms of volume fraction and area fraction. Therefore, although various elements can be contained in the plating layer, they do not affect the average hardness of the plating layer by more than 10%.

[0062] <First and second regions of plating layer> In this embodiment, the surface layer (the coating layer or the portion including the coating layer and the steel material) of the hot-dip coated steel material has a first region and a second region. The first region is a region where the surface has a relatively small Ra (arithmetic mean roughness), and the second region is a region where the surface has a relatively large Ra. Either the first region or the second region is arranged to have a predetermined shape. More specifically, the first region is arranged to have one of the following shapes: straight lines, curved lines, dotted lines, figures, numbers, symbols, patterns, or letters, or a combination of two or more of these shapes. In the following description, the straight lines, curved lines, dotted lines, figures, numbers, symbols, patterns, or letters, or a combination of two or more of these shapes, may be referred to as patterned sections, and regions other than the patterned sections may be referred to as non-patterned sections. For example, the first region may be a patterned section and the second region a non-patterned section. Conversely, the first region may be a non-patterned section and the second region a patterned section. The shape of the patterned section is acceptable even if it is partially missing, such as a missing dot, as long as it can be recognized as a whole. Furthermore, the non-patterned section may have a shape that outlines the boundary of the patterned section.

[0063] In this way, the pattern portion constituting either the first region or the second region and the non-pattern portion constituting the other of the first region or the second region are regions formed on the surface of the hot-dip galvanized steel material. The first region and the second region are preferably formed within the same plane.

[0064] The boundary between the first and second regions can be seen with the naked eye. The boundary between the first and second regions may also be seen from a magnified image using an optical microscope or a magnifying glass. The arithmetic mean roughness Ra, which is the criterion for determining whether a region is the first region or the second region, can be measured using a non-contact white light interference microscope, as described below.

[0065] The pattern portion constituting either the first region or the second region is preferably formed to a size that allows the presence of the pattern portion to be discerned with the naked eye, under a magnifying glass, or under a microscope. The non-pattern portion is a region that occupies the majority of the plating layer (surface of the hot-dip plating layer), and the pattern portion may be disposed within the non-pattern portion.

[0066] The patterned portion constituting either the first region or the second region is arranged in a predetermined shape within the non-patterned portion constituting the other of the first region or the second region. Specifically, the patterned portion is arranged within the non-patterned portion to form a shape consisting of one or a combination of two or more of straight lines, curved lines, dots, figures, numbers, symbols, patterns, or letters. By adjusting the shape of the patterned portion, a shape consisting of one or a combination of two or more of straight lines, curved lines, dots, figures, numbers, symbols, patterns, or letters appears on the surface of the plating layer. For example, the surface of the plating layer may appear as a character string, a number string, a symbol, a mark, a line drawing, a design, or a combination thereof, consisting of the patterned portion. This shape is intentionally or artificially formed by the manufacturing method described below, and is not naturally formed.

[0067] In this embodiment, if the arithmetic mean roughness Ra (μm) (sometimes simply referred to as surface roughness) on the surface of the first region of the hot-dip plated steel material is Ra_A and the arithmetic mean roughness Ra (μm) on the surface of the second region of the hot-dip plated steel material is Ra_B, the following equations (1) to (3) must be satisfied.

[0068] Ra_A≦10.0 …(1) Ra_B≦10.0 …(2) 1.5≦|Ra_A−Ra_B| …(3)

[0069] As shown in equations (1) and (2), Ra_A, the arithmetic mean roughness (surface roughness) Ra (μm) of the surface of the first region, and Ra_B, the arithmetic mean roughness Ra (μm) of the surface of the second region, must both be 10.0 μm or less. Surface roughness Ra refers to the arithmetic mean roughness Ra of the surface. By having the surface roughness Ra (μm) of the first region and the second region be 10.0 μm or less, the specific surface area of ​​the surface of the plating layer is reduced, thereby slowing the corrosion rate and suppressing changes in the appearance of the plating layer due to corrosion. Therefore, when a pattern portion consisting of the first region or the second region is formed, the durability of the pattern portion can be ensured. In addition, the appearance of the entire plating layer is also improved.

[0070] Furthermore, as shown in formula (3), |Ra_A-Ra_B|, which is the absolute value of the difference between the roughness (surface roughness) Ra (μm) of the surface of the first region and the roughness Ra (μm) of the surface of the second region, must be 1.5 μm or more. When |Ra_A-Ra_B| is 1.5 μm or more, the difference in reflectance between the first region and the second region becomes large, making it possible to distinguish the first region from the second region with the naked eye. When |Ra_A-Ra_B| is less than 1.5 μm, the difference in reflectance between the first region and the second region is small, making it impossible to distinguish the first region from the second region with the naked eye. More preferably, |Ra_A-Ra_B| is 2.0 μm or more.

[0071] Furthermore, if the larger of Ra_A and Ra_B is defined as Ra_L, the average Vickers hardness HV between a depth of (Ra_L + 1.0) μm from the surface of the coating layer (whether the surface of the first region or the surface of the second region) and a depth of half the thickness of the coating layer is defined as HV_x, and the maximum Vickers hardness HV is defined as HV_max, the following formulas (4) and (5) must be satisfied. The Vickers hardness measurement range is set between a depth of (Ra_L + 1.0) μm and a depth of half the thickness of the coating layer to avoid the influence of surface roughness when measuring Vickers hardness. Of the depths of (Ra_L + 1.0) μm and half the thickness of the coating layer, the depth of (Ra_L + 1.0) μm is preferably closer to the surface of the coating layer. This is to avoid the influence of the Fe-Al interfacial alloy layer. That is, HV_x represents the average value of the Vickers hardness of the Zn-Al-Mg alloy layer among the plating layers, and HV_max represents the maximum value of the Vickers hardness of the Zn-Al-Mg alloy layer. Here, the reference surface (surface of the plating layer) at a depth position of Ra_L+1.0 μm, i.e., a depth position of 1 / 2 the thickness of the plating layer, is the distance from the average surface of the roughness in the measurement area (first area or second area).

[0072] 150≦HV_x≦350 …(4) 200≦HV_max …(5)

[0073] If the average Vickers hardness (HV_x) is less than 150 Hv, the deformation of the plating layer during shot blasting increases, significantly reducing the remaining amount of the plating layer after shot blasting. Such a plating layer reduces the clarity of the pattern due to the exposure of the base iron, increases the amount of corrosion, and fails to maintain the durability of the pattern. On the other hand, if the average Vickers hardness exceeds 350 Hv, the plating layer itself loses flexibility, causing numerous cracks to form in the plating layer after shot blasting, making the plating layer more susceptible to peeling. Therefore, the average Vickers hardness of the plating layer is set to a range of 150 to 350 Hv. A plating layer having the average chemical composition specified in this embodiment and including a Zn-Al-Mg alloy layer will have an average Vickers hardness within this range. From the viewpoint of clarity of the pattern, the range of 200 to 300 Hv is preferred, and the range of 230 to 280 Hv is even more preferred.

[0074] Furthermore, a plating layer with a maximum Vickers hardness (HV_max) of 200 Hv or more means that it contains a certain amount of Mg-Zn compounds. The Mg-Zn compounds are moderately deformed by shot blasting, preventing strain and processing from concentrating on the surrounding soft phase. This suppresses the occurrence of cracks. The moderate deformation of the Mg-Zn compounds during shot blasting gradually forms a fine structure with the surrounding soft phase. On the other hand, a plating layer with a maximum Vickers hardness of less than 200 Hv contains a large amount of ternary eutectic structure, as mentioned above. Such a plating layer is undesirable because it undergoes a large amount of deformation after shot blasting, reducing the clarity and permanence of the pattern.

[0075] Furthermore, the hot-dip galvanized steel material of this embodiment preferably satisfies the following formula (6), where HV_big is the average Vickers hardness HV measured in the region of either the first or second region, whichever has the larger surface roughness Ra, between a depth position of (Ra_L+1.0) μm from the coating layer surface and a depth position of half the coating layer thickness, and HV_sml is the average Vickers hardness HV measured in the region of either the first or second region, whichever has the smaller surface roughness Ra, between a depth position of (Ra_L+1.0) μm from the coating layer surface and a depth position of half the coating layer thickness. That is, HV_big / HV_sml is the ratio of the Vickers hardness in the region of either the first or second region, which has the larger surface roughness Ra, divided by the Vickers hardness in the region of the first or second region, which has the smaller surface roughness Ra, and this ratio is 0.80 to 1.50.

[0076] 0.80≦HV_big / HV_sml≦1.50 …(6)

[0077] If HV_big / HV_sml is 0.80 or more and 1.50 or less, the difference in hardness between the first region and the second region becomes small, and cracks are less likely to occur near the boundary between the first region and the second region when an external force is applied to the plating layer, thereby preventing a decrease in the corrosion resistance of the plating layer.

[0078] If the structure of the plating layer is rich in relatively hard phases, shot blasting may cause the plating layer to become softer. On the other hand, if the structure is rich in relatively soft phases, shot blasting may cause the plating layer to become harder. If the difference in hardness within the plating layer becomes too large, cracks will occur, so it is necessary to adjust the hardness ratio (HV_big / HV_sml) to the above range. This can be achieved by changing the shot blasting conditions or the plating composition. For example, increasing the shot blasting time increases the difference between HV_big and HV_sml. The preferred range is a lower limit of 0.85 to 0.90 and an upper limit of 1.20 to 1.30.

[0079] The surface roughness Ra is measured by a non-contact white light interferometric microscope. First, test pieces for evaluation are taken from the hot-dip plated steel material. The test pieces for evaluation are taken from each of the first and second regions. The size of the test pieces for evaluation is 10 mm2 in terms of the surface area of ​​the plating layer. 2 It is advisable to harvest so that the above area is secured. The arithmetic mean roughness (Ra) of the surface of the sampled specimen is measured using a white light interferometer microscope (manufactured by Bruker Corporation). In this embodiment, the surface height of a rectangular area with sides of 3.5 mm is acquired, and then surface height information is obtained for each pixel with a size of 0.67 μm x 0.67 μm arranged in a grid pattern. The arithmetic mean roughness (Ra) within the 3.5 mm x 3.5 mm area can be calculated from the height of each pixel. The Ra calculation method complies with ISO 4287. By previously matching the observation range of the white light interferometer microscope with the observation range of the optical microscope, the mean roughness corresponding to each area can be obtained. The rectangular measurement area with sides of 3.5 mm is selected to be close to the center of the first or second area. More specifically, all measurement points in the rectangular measurement area with sides of 3.5 mm are selected to be at least 1 mm away from the boundary between the first and second areas. The arithmetic mean roughness (Ra) (μm) of the first area is designated as Ra_A, and the arithmetic mean roughness (Ra) of the second area is designated as Ra_B.

[0080] Vickers hardness is measured using a micro Vickers hardness tester. In this embodiment, a sample for hardness measurement is taken from any location on the hot-dip plated steel material. If the steel material has irregularities, a flat portion is selected for hardness measurement. Before measuring the Vickers hardness, the measurement sample is polished to a depth of (Ra_L + 1.0 μm) from the surface of the plating layer to create a mirror finish. The polished surface is a rectangular area with sides of 20 mm. The polishing is performed using emery paper up to #2400 grit, followed by further polishing using a buff with an alumina suspension to create a mirror finish. The polishing depth is determined by measuring the thickness of the sample using a micrometer or the like. Next, Vickers hardness measurement is performed.

[0081] Vickers hardness is measured using a micro Vickers hardness tester with a load of 10 gf in accordance with JIS Z 2244. A total of 25 measurement positions are selected from each region to prevent adjacent Vickers marks from affecting each other, and the Vickers hardness is measured at each measurement position. The measurement positions are arranged in a grid pattern consisting of 5 vertical and 5 horizontal positions. The hardness measurement interval is 100 μm. The average value of the Vickers hardness measurements at the 25 positions is defined as HV_x, and the maximum value is defined as HV_max. The Vickers hardness measurement positions are selected as the first and second regions using an optical microscope attached to the micro Vickers hardness tester, and hardness measurements are performed for each region. The above measurements were also performed in the area with the larger surface roughness Ra and the area with the smaller surface roughness Ra, and the average value of the Vickers hardness HV at 25 locations in the area with the larger surface roughness Ra between a depth position of (Ra_L+1.0) μm from the plating layer surface and a depth position of 1 / 2 the thickness of the plating layer was designated HV_big, and the average value of the Vickers hardness HV at 25 locations in the area with the smaller surface roughness Ra between a depth position of (Ra_L+1.0) μm from the plating layer surface and a depth position of 1 / 2 the thickness of the plating layer was designated HV_sml.

[0082] <Evaluation of the permanence of a design> By intentionally forming the first and second regions, a design is imparted to the plating layer. The hot-dip plated steel material of this embodiment is required to have a durable design. To evaluate the durability of the design, whether the design can be recognized after corrosion is determined visually. White rust is usually formed by corrosion of the plating layer, but if there is a large amount of white rust, and it appears as raindrops or accumulates on the plating surface, the white rust affects the surface roughness of the first and second regions, making it difficult to recognize the design.

[0083] The cyclic corrosion test (CCT) is a test that shows a relatively high correlation with exposure environments in Japan. Unlike the salt spray test (SST), which is a type of accelerated corrosion test, the CCT involves repeated salt spray, drying, and wetting processes, which results in a corrosion condition closer to that in an atmospheric environment, and a certain degree of correlation with exposure environments in Japan is observed. The CCT uses the JASO cycle (M609-91), with 30 cycles equivalent to 10 years of general corrosive environments in Japan. The durability of the design is evaluated by determining the degree of design identity before and after the CCT.

[0084] Specifically, the hot-dip galvanized steel material after the design was applied was cut to an appropriate size, for example, 100 x 50 mm, and the cut end surfaces were coated with an epoxy resin paint to prepare evaluation samples. The following two types of evaluation samples were prepared: Evaluation sample (S1) had a 35 x 35 mm rectangular patterned portion in the center, surrounded by non-patterned portions; evaluation sample (S2) had a 35 x 35 mm rectangular non-patterned portion in the center, surrounded by patterned portions. The patterned portions of evaluation samples (S1) and (S2) were regions formed by shot blasting, and the non-patterned portions were regions that were not subjected to shot blasting. In this case, the non-patterned portions correspond to the first region of this embodiment, and the patterned portions correspond to the second region of this embodiment.

[0085] Five evaluation samples (S1) and (S2) are prepared, and a total of 10 samples are subjected to a corrosion test of 30 cycles using the CCT (JASO cycle).

[0086] Before and after the test, the white rust area ratio on the evaluation surface was measured, and the white rust area ratio within a 35 mm square was measured, and the durability was evaluated by ranking as follows.

[0087] S: White rust area rate on the evaluation surface is less than 5% A: The white rust area rate on the evaluation surface is less than 5-10% B: The white rust area rate on the evaluation surface is less than 10-15% C: White rust area rate on the evaluation surface is 15% or more

[0088] The evaluation samples (S1) and (S2) are evaluated using the above criteria, and the combination of (S1, S2) (S, S), (S, A), (A, S), (S, B), (B, S), (A, A), (A, B) or (B, A) is considered a pass, and any other combination is considered a fail.

[0089] With ordinary galvanized steel sheets, white rust is likely to form in both shot-blasted and unshot-blasted areas, making it difficult to obtain a rating of S to B. With aluminum-plated steel sheets, while white rust formation is suppressed in unshot-blasted areas, it occurs frequently in shot-blasted areas, making it difficult to obtain a rating of S to B.

[0090] In contrast, a Zn-Al-Mg-based coating layer is less susceptible to white rust than a Zn-coated steel sheet, both in shot-blasted and unshot-blasted areas.

[0091] Increasing the Mg and Al contents of the coating layer, as in the hot-dip galvanized steel material of this embodiment, can improve corrosion resistance, particularly in the shot-blasted region. That is, the Mg content is preferably greater than 4.0% and less than 15.0%, and the Al content is preferably greater than 10.0%. More preferably, the Mg content is 5.0% to 8.0%, and the Al content is 15.0% to 35.0%. Even more preferably, the Mg content is 6.0 to 7.0%, and the Al content is 19.0 to 30.0%, resulting in a hot-dip galvanized steel material with excellent design durability. Other optional elements are either not significantly involved in corrosion within 30 JASO cycles or are not substances that form clear white rust, so the durability index does not change significantly depending on the content of these elements.

[0092] In areas where shot blasting has been applied, the continuity of the plating layer structure is lost compared to areas where shot blasting has not been applied. When the continuity of the plating layer structure is lost, the propagation of cracks in the plating layer changes significantly. In areas where shot blasting has been applied, for example, the corrosion resistance of the processed part is improved.

[0093] Furthermore, when plated steel is bent, cracks may occur in the plating layer due to its inability to follow the deformation of the base steel (the steel that is the base material). However, cracks that occur near the interface between the base steel and the plating layer change their propagation direction on the surface of the plating layer that has been shot blasted. As a result, the exposed area of ​​the base steel observed from the surface of the plating layer in the bent area is significantly reduced. This improves the corrosion resistance of the processed area in the area where shot blasting has been applied, i.e., the area with the greater surface roughness in the first or second region.

[0094] When a plated steel material having a plating layer with the chemical composition according to this embodiment is produced, cracks that occur near the interface between the base steel and the plating layer typically propagate linearly from the interface to the surface of the plating layer. Therefore, when cracks that occur in the interfacial alloy layer are observed from the surface of the plating layer using an optical microscope or the like, exposed areas of the base steel are confirmed in the processed area. On the other hand, when shot blasting, as described below, is applied, the structure of the plating layer becomes finer and softer, and the continuity of the structure of the plating layer is lost, making it more difficult for cracks that occur in the interfacial alloy layer to propagate to the surface of the plating layer.

[0095] Therefore, the effect of shot blasting is not only to impart a design, but also to improve the corrosion resistance of the processed portion, resulting in desirable properties for the formed plated steel material.

[0096] In the hot-dip plated steel material of the present embodiment, the steel material may be a steel sheet. In this case, a plating layer is provided on both one surface (rolled surface) of the steel sheet and the other surface (rolled surface) opposite to the one surface, and in either the plating layer on the one surface or the plating layer on the other surface, or both, one of the first region and the second region may be arranged in the shape of one type of straight line portion, curved portion, dot portion, figure, number, symbol, pattern, or letter, or a shape combining two or more types of these, more preferably an intentional shape.

[0097] <Method for manufacturing hot-dip galvanized steel sheet according to this embodiment> Next, a method for producing the hot-dip plated steel material of this embodiment will be described. Annealing of the steel material to be plated is carried out in a reducing atmosphere. The reducing atmosphere and annealing conditions are not particularly limited. By this annealing, oxides present on the surface of the steel material are removed as much as possible.

[0098] Next, the steel material immediately after annealing is immersed in a hot-dip galvanizing bath. The chemical composition of the galvanizing bath may be appropriately adjusted so as to obtain the chemical composition of the coating layer described above. The temperature of the galvanizing bath is not particularly limited, and a temperature at which hot-dip galvanizing can be performed may be appropriately selected. For example, the temperature of the galvanizing bath may be set to a value approximately 20°C or more higher than the melting point of the galvanizing bath.

[0099] Next, the steel material is pulled up from the coating bath. The coating weight of the coating layer can be controlled by controlling the pulling speed of the steel sheet. If necessary, the coating weight of the coating layer may be controlled by wiping the steel sheet to which the coating layer is attached. The coating weight of the coating layer is not particularly limited and can be, for example, within the range described above. When the steel material is a steel sheet (when the hot-dip plated steel material is a hot-dip plated steel sheet), a coating layer is formed on both one surface of the steel sheet and the other surface that is the reverse side of the one surface.

[0100] The plating layer is then cooled under any cooling conditions, including the application of a cooling gas or mist, or by allowing the plating layer to cool naturally.

[0101] The resulting plated steel product is then shot blasted. While various shapes and materials are possible for the shot material (media), spherical steel shot (Hv 390-510), 0.5 mm-SB-6 (JIS R 6001) is suitable. Using other materials is not recommended because it alters the degree of roughness imparted to the Zn-Al-Mg-based coating and may introduce cracks into the coating layer. In accordance with the General Rules for Blasting Methods for Surface Conditioning (JIS Z 0310:2016), iron or nonferrous metal particles (shot) are collided with the coating layer using centrifugal force or air pressure. In this way, first and second regions are formed on the surface of the coating layer. Furthermore, if the steel product is a steel plate with a coating layer on both sides, shot blasting can be performed on either one or both of the coating layers on the first or second side.

[0102] The surface roughness Ra in the first region and the second region must satisfy the above (1) to (3). Therefore, when performing shot blasting, the region where shot blasting is performed is designated as the second region.

[0103] In forming the first and second regions, it is preferable to mask predetermined regions on the surface of the hot-dip plated steel material with a sufficiently thick material such as steel or wood so as to obtain a desired pattern portion. After the masking treatment, shot blasting treatment may be applied.

[0104] An example of the conditions for shot blasting is as follows: 0.5 mm SB-6 steel shot as the projectile, projection amount: 3 to 7 kg / min, projection speed: 50 to 70 m / s, area: 1200 cm 2 Treatment time per shot blast: 60 seconds or more. If the treatment time is too short, it becomes difficult to form a clear pattern. Preferably, it is 150 seconds or more. The size of the area to be shot blasted depends on the size of the design to be formed on the surface. More suitable conditions are an area of ​​1200 cm 2The treatment time per test piece is in the range of 150 to 600 seconds. If the treatment time is too long, the plating layer may deform significantly, increasing the Hv_big / Hv_sml value or even disappearing, which is undesirable. If the Mg content is high, the above effects become more pronounced, so when the Mg content is relatively high, the more preferable upper limit is 550 seconds, 500 seconds, or 450 seconds.

[0105] An example of a pattern formed by shot blasting is shown in Figure 1. Figure 1 also shows an example of an alphabet or heart mark formed by shot blasting on a plating layer with a matte appearance.

[0106] After shot blasting (or roll transfer) is applied to the hot-dip plated steel material of this embodiment, a coating may be formed on the plating layer. One or more coatings may be formed. Examples of types of coatings that may be formed directly on the plating layer include chromate coatings, phosphate coatings, and chromate-free coatings. The chromate treatment, phosphate treatment, and chromate-free treatment that form these coatings can be performed by known methods.

[0107] Chromate treatments include electrolytic chromate treatments, which form a chromate film by electrolysis; reactive chromate treatments, which form a film by utilizing a reaction with the material and then wash away excess treatment solution; and paint-on chromate treatments, which apply a treatment solution to the substrate and then dry it without rinsing to form a film. Any of these treatments may be used. A nearly colorless and transparent finish is preferable to distinguish the design.

[0108] Examples of electrolytic chromate treatments include those using chromic acid, silica sol, resin (phosphoric acid, acrylic resin, vinyl ester resin, vinyl acetate acrylic emulsion, carboxylated styrene butadiene latex, diisopropanolamine-modified epoxy resin, etc.), and hard silica.

[0109] Chromate-free treatments are particularly suitable because they do not place a burden on the environment. Chromate-free treatments include electrolytic chromate-free treatments that form a chromate-free film by electrolysis, reactive chromate-free treatments that form a film by utilizing a reaction with the material and then wash away excess treatment liquid, and paint-on chromate-free treatments that apply a treatment liquid to the substrate and dry it without rinsing with water to form a film. Any of these treatments may be used.

[0110] Furthermore, one or more organic resin coatings may be provided on the coating directly on the plating layer. The organic resin is not limited to a specific type, and examples include polyester resin, polyurethane resin, epoxy resin, acrylic resin, polyolefin resin, and modified versions of these resins. Here, the term "modified version" refers to a resin in which a reactive functional group contained in the structure of these resins is reacted with another compound (such as a monomer or a crosslinking agent) containing a functional group capable of reacting with the functional group.

[0111] Such organic resins may be a mixture of one or more organic resins (unmodified), or a mixture of one or more organic resins obtained by modifying at least one other organic resin in the presence of at least one organic resin. The organic resin film may also contain any coloring pigment or anti-rust pigment. Aqueous solutions prepared by dissolving or dispersing in water may also be used. [Example]

[0112] The following plated steel sheets were prepared as steel sheets to which shot blasting was applied.

[0113] The plated steel sheets were produced by preparing an alloy by mixing predetermined amounts of pure metals and the like, melting the alloy, and hot-dipping the alloy using a hot-dip galvanizing simulator manufactured by Rhesca. The base sheet used for plating was a cold-rolled steel sheet (equivalent to SPCC JIS G3141:2021) or a hot-rolled checkered steel sheet (manufactured by Otomi Steel Co., Ltd.) measuring 200 mm x 100 mm x 1.2 mm in thickness. Prior to hot-dip coating, the surface of the base steel sheet was fully reduced by holding it at 800°C for 1 minute in a 25% N2-H2 atmosphere (dew point -40°C). It was then immersed in a coating bath at a temperature 30°C above the bath's melting point for 3 seconds, removed, and then wiped with N2 gas to adjust the thickness of the coating layer. Immediately after wiping, the sheet was cooled to room temperature at an average cooling rate of -10°C / s. The resulting coated steel sheet was then skin-pass rolled to achieve a surface roughness Ra in the range of 0.8 to 1.5 μm, with a reduction of 1% or less.

[0114] The shot blasting conditions were: 0.5 mm SB-6 steel shot, 5 kg / min shot volume, 60 m / s shot speed, 1200 cm area. 2 The treatment time per shot was set to 50 to 720 seconds. The shot blasting machine used was the SNT-1PE manufactured by Shinto Kogyo. The range of shot blasting treatment was changed for each evaluation item. After masking a specified area with steel material, shot blasting was performed to randomly print 100 numbers from "0" to "9" in Gothic font at 100pt in bold.

[0115] The average chemical composition of the plating layer, the surface roughness (Ra_A, Ra_B) of the plating layer in a predetermined area, and the Vickers hardness (Hv_x, Hv_max, Hv_big, Hv_sml) were measured and evaluated as described in the embodiment.

[0116] (Evaluation of corrosion resistance of processed parts) Plated steel sheets before and after shot blasting were cut into 100 x 50 x 1.2 mm pieces, the cut edges coated with epoxy resin paint, and a 70 x 40 mm test surface was positioned in the center of the steel sheet to create a test specimen. After shot blasting, the plated steel sheets were cut so that the shot-blasted area served as the test surface. An Erichsen treatment was then used to create an Erichsen treatment zone measuring 40 mm in diameter and 5 mm in height in the center of the test surface. A CCT test was then conducted (JASO M609-91) to determine the white rust area ratio after 30 cycles. The corrosion resistance of the treated zone was evaluated according to the following criteria. S, A, and B were considered acceptable.

[0117] S: The white rust area ratio after shot blasting is 20% or more lower than the white rust area ratio before shot blasting. A: The white rust area ratio after shot blasting is 10% or more but less than 20% lower than the white rust area ratio before shot blasting. B: The white rust area ratio after shot blasting is 5% or more but less than 10% lower than the white rust area ratio before shot blasting. C: The white rust area ratio after shot blasting is 0 to less than 5% lower than the white rust area ratio before shot blasting, or the white rust area ratio after shot blasting is higher than the white rust area ratio before shot blasting.

[0118] (Evaluation of clarity) Clarity was evaluated using a computerized character recognition function, including character recognition, based on machine learning. The numbers "0" through "9" formed by shot blasting were illuminated at a 45-degree angle with a white LED light source, and photographs of the areas where each number was formed were taken with a digital camera from a vertical angle. The photographs were saved at a resolution of 1000 x 1000 pixels. The number areas were then cropped, mosaicked to 100 x 100 pixels, and binarized. One hundred binarized number images extracted from the sample using the above method were prepared. Each number image was classified into 0 through 9 by processing it with a convolutional neural network using the MNIST database, a collection of images of numbers 0 through 9, as training data. The formed numbers were compared with the numbers classified by the convolutional neural network. If they were identical, they were considered correct, and the accuracy rate for the 100 number images was calculated. Clarity was then evaluated using the following criteria. A was considered a pass.

[0119] A: The overall matching rate for numbers 1 to 10 is 80% or more. B: The overall match rate for numbers 1 to 10 is less than 80%.

[0120] <Evaluation of the permanence of a design> The hot-dip plated steel material after shot blasting was cut into pieces measuring 100 x 50 mm, and the cut end surfaces were coated with an epoxy resin paint to prepare evaluation samples. Two types of evaluation samples were prepared: Evaluation sample (S1) had a 35 x 35 mm rectangular patterned portion in the center, with non-patterned portions arranged around the patterned portion; and Evaluation sample (S2) had a 35 x 35 mm rectangular non-patterned portion in the center, with patterned portions arranged around the non-patterned portion. The patterned portions of evaluation samples (S1) and (S2) were regions formed by shot blasting, and the non-patterned portions were regions that were not subjected to shot blasting.

[0121] Five evaluation samples (S1) and (S2) were prepared, and a total of 10 samples were subjected to 30 cycles of CCT (JASO Cycle Test (M609-91)). The white rust area ratio on the evaluation surface was measured before and after the test, and the white rust area ratio within a 35mm square was measured, and the durability was evaluated by ranking as follows. Evaluation samples (S1) and (S2) were evaluated according to the following evaluation criteria, and a combination of (S1, S2) of (S, S), (S, A), (A, S), (S, B), (B, S), (A, A), (A, B), or (B, A) was deemed to have passed.

[0122] S: White rust area rate on the evaluation surface is less than 5% A: The white rust area rate on the evaluation surface is less than 5-10% B: The white rust area rate on the evaluation surface is less than 10-15% C: White rust area rate on the evaluation surface is 15% or more

[0123] As shown in Tables 1 to 4, in Comparative Examples 1 to 4, the Al content in the chemical composition of the plating layer was 10.0 mass% or less, the hardness of the plating layer was low, and the surface roughness caused by shot blasting exceeded 10.0 μm, resulting in poor durability and corrosion resistance of the processed part.

[0124] In Comparative Examples 5 to 8, the Mg content in the chemical composition of the plating layer was 4.0 mass% or less, the plating layer hardness was low, and the surface roughness caused by shot blasting exceeded 10.0 μm, resulting in poor durability and corrosion resistance of the processed part.

[0125] In Example No. 9, the plating composition was within the specified range, the plating layer had sufficient hardness, and clarity and corrosion resistance of the processed portion were ensured even after shot blasting.

[0126] In Comparative Example No. 10, the Mg content in the chemical composition of the plating layer was 4.0% or less, the hardness of the plating layer was low, and the surface roughness caused by shot blasting exceeded 10.0 μm, resulting in poor durability and corrosion resistance of the processed part.

[0127] In Examples 11 to 28 and 30 to 32, the plating composition was within the specified range, the hardness of the plating layer was sufficient, and clarity, durability, and corrosion resistance of the processed portion were ensured.

[0128] In Comparative Examples 29 and 39, the shot blasting time was insufficient, and the change in roughness on the shot blasted surface was not large enough, resulting in inferior clarity, durability, and corrosion resistance of the processed portion.

[0129] In Comparative Example No. 33, the shot blasting time was long. Therefore, HV_big / HV_sml was outside the range of the present invention. As a result, durability was insufficient. In Comparative Examples 34 to 37 and 41, the Mg content in the chemical composition of the plating layer did not satisfy the range of more than 4.0% and not more than 15.0%. In Comparative Examples 34 to 37, the Al content also fell outside the range of the invention (more than 10.0% and less than 40.0%). As a result, the hardness of the plating layer was not within the optimum range, and the surface roughness achieved during shot blasting was either too small or exceeded 10.0 μm. Consequently, clarity, durability, and corrosion resistance of the processed area were inferior. In Comparative Example No. 38, shot blasting was not performed and no pattern was formed. In Comparative Example No. 40, the shot blasting time was too long, resulting in excessively large Ra_B and HV_big / HV_sml. As a result, durability and corrosion resistance of the processed part were poor.

[0130] [Table 1]

[0131] [Table 2]

[0132] [Table 3]

[0133] [Table 4] [Industrial Applicability]

[0134] According to the present disclosure, it is possible to provide a hot-dip galvanized steel product and a method for manufacturing the hot-dip galvanized steel product that allows letters, designs, etc. to appear on the plating layer, has excellent clarity and permanence, and enables large-area letters, designs, etc. This makes it possible to provide inexpensive materials with excellent aesthetic appeal, and contributes to industrial development. [Explanation of symbols]

[0135] 1. Hot-dip galvanized steel 11 Steel materials 12 plating layer 21 First area 22 Mean surface of the first region 31 Second area 32 Mean surface of the second region L1: The depth position (Ra_L+1.0μm) from the surface of the plating layer when the second area is the measurement area L2: When the second area is the measurement area, the depth position is half the thickness of the plating layer.

Claims

1. A hot-dip plated steel material having a steel material and a plating layer formed on a surface of the steel material, The average chemical composition of the plating layer is, in mass%, Al: more than 10.0% and less than 40.0%; Mg: more than 4.0%, 15.0% or less, Si: 0% or more, 1.00% or less, Sn: 0% or more, 0.7% or less, Bi: 0% or more, 0.3% or less, In: 0% or more, 0.3% or less, Total amount ΣX of Sn, Bi and In: 0% or more and 0.7% or less; Ca: 0% or more, 0.60% or less, Y: 0% or more, 0.30% or less, La: 0% or more, 0.30% or less, Ce: 0% or more, 0.30% or less, Sr: 0% or more, 0.30% or less, Li: 0% or more, 0.30% or less, Total amount ΣYa of Ca, Y, La, Ce, Sr and Li: 0% or more and 0.60% or less, Cr: 0% or more, 1.00% or less, Ni: 0% or more, 1.0% or less, Mo: 0% or more, 0.25% or less, Cu: 0% or more, 1.0% or less, Ag: 0% or more, 0.25% or less, Sb: 0% or more, 0.25% or less, Pb: 0% or more, 0.25% or less, Total amount ΣYb of Cr, Ni, Mo, Cu, Ag, Sb and Pb: 0% or more and 1.0% or less, B: 0% or more, 0.50% or less, P: 0% or more, 0.50% or less, The total amount of B and P ΣYc: 0% or more and 0.50% or less, Ti: 0% or more, 0.25% or less, Co: 0% or more, 0.25% or less, V: 0% or more, 0.25% or less, Nb: 0% or more, 0.25% or less, Mn: 0% or more, 0.25% or less, Zr: 0% or more, 0.25% or less, W: 0% or more, 0.25% or less, Total content ΣZ of Ti, Co, V, Nb, Mn, Zr and W: 0% or more and 0.25% or less, Fe: 0% or more, 5.0% or less, Zn: more than 42.0%, less than 85.0%, Including, The thickness of the plating layer is 5 μm or more, the plating layer has a first region and a second region, One of the first region and the second region is arranged to have a predetermined shape, The arithmetic mean roughness Ra (μm) of the surface of the first region of the hot-dip plated steel material is defined as Ra_A, The arithmetic mean roughness Ra (μm) on the surface of the second region of the hot-dip plated steel material is defined as Ra_B, The larger value of the Ra_A or the Ra_B is defined as Ra_L, When the average value of Vickers hardness HV between a depth position of (Ra_L+1.0) μm from the surface of the plating layer and a depth position of ½ of the thickness of the plating layer is defined as HV_x and the maximum value of Vickers hardness HV is defined as HV_max, The following formulas (1) to (5) are satisfied: an average value of Vickers hardness HV between a depth position of (Ra_L+1.0) μm from the surface of the plating layer and a depth position of ½ of the thickness of the plating layer in the region of the first region or the second region which has the larger arithmetic mean roughness Ra is defined as HV_big; When the average value of Vickers hardness HV between a depth position of (Ra_L+1.0) μm from the surface of the plating layer and a depth position of ½ of the thickness of the plating layer in the region having the smaller surface roughness Ra of either the first region or the second region is defined as HV_sml, The following formula (6) is satisfied: One of the first region and the second region is arranged to have any one of the shapes of a straight line portion, a curved line portion, a dot portion, a figure, a number, a symbol, a pattern, or a letter, or an intentional shape that combines two or more of these. Hot-dip galvanized steel. Ra_A≦10.0…(1) Ra_B≦10.0…(2) 1.5≦|Ra_A−Ra_B| …(3) 150≦HV_x≦350 ... (4) 200≦HV_max…(5) 0.80≦HV_big / HV_sml≦1.50…(6)

2. A hot-dip plated steel material having a steel material and a plating layer formed on the surface of the steel material, The average chemical composition of the plating layer is, in mass%, Al: more than 10.0% and less than 40.0%; Mg: more than 4.0%, 15.0% or less, Si: 0% or more, 1.00% or less, Sn: 0% or more, 0.7% or less, Bi: 0% or more, 0.3% or less, In: 0% or more, 0.3% or less, Total amount ΣX of Sn, Bi and In: 0% or more and 0.7% or less; Ca: 0% or more, 0.60% or less, Y: 0% or more, 0.30% or less, La: 0% or more, 0.30% or less, Ce: 0% or more, 0.30% or less, Sr: 0% or more, 0.30% or less, Li: 0% or more, 0.30% or less, Total amount ΣYa of Ca, Y, La, Ce, Sr and Li: 0% or more and 0.60% or less, Cr: 0% or more, 1.00% or less, Ni: 0% or more, 1.0% or less, Mo: 0% or more, 0.25% or less, Cu: 0% or more, 1.0% or less, Ag: 0% or more, 0.25% or less, Sb: 0% or more, 0.25% or less, Pb: 0% or more, 0.25% or less, Total amount ΣYb of Cr, Ni, Mo, Cu, Ag, Sb and Pb: 0% or more and 1.0% or less, B: 0% or more, 0.50% or less, P: 0% or more, 0.50% or less, The total amount of B and P ΣYc: 0% or more and 0.50% or less, Ti: 0% or more, 0.25% or less, Co: 0% or more, 0.25% or less, V: 0% or more, 0.25% or less, Nb: 0% or more, 0.25% or less, Mn: 0% or more, 0.25% or less, Zr: 0% or more, 0.25% or less, W: 0% or more, 0.25% or less, Total content ΣZ of Ti, Co, V, Nb, Mn, Zr and W: 0% or more and 0.25% or less, Fe: 0% or more, 5.0% or less, Zn: more than 42.0%, less than 85.0%, Including, The thickness of the plating layer is 5 μm or more, the plating layer has a first region and a second region, One of the first region and the second region is arranged to have a predetermined shape, The arithmetic mean roughness Ra (μm) of the surface of the first region of the hot-dip plated steel material is defined as Ra_A, The arithmetic mean roughness Ra (μm) on the surface of the second region of the hot-dip plated steel material is defined as Ra_B, The larger value of the Ra_A or the Ra_B is defined as Ra_L, When the average value of Vickers hardness HV between a depth position of (Ra_L+1.0) μm from the surface of the plating layer and a depth position of ½ of the thickness of the plating layer is defined as HV_x and the maximum value of Vickers hardness HV is defined as HV_max, The following formulas (1) to (5) are satisfied: an average value of Vickers hardness HV between a depth position of (Ra_L+1.0) μm from the surface of the plating layer and a depth position of ½ of the thickness of the plating layer in the region of the first region or the second region which has the larger arithmetic mean roughness Ra is defined as HV_big; When the average value of Vickers hardness HV between a depth position of (Ra_L+1.0) μm from the surface of the plating layer and a depth position of ½ of the thickness of the plating layer in the region having the smaller surface roughness Ra of either the first region or the second region is defined as HV_sml, The following formula (6) is satisfied: The steel material is a steel plate, The plating layer is provided on both one surface of the steel sheet and the other surface that is the reverse side of the one surface, In either or both of the plating layer on the one surface side and the plating layer on the other surface side, one of the first region and the second region is arranged to have one of the shapes of a straight line portion, a curved portion, a dot portion, a figure, a number, a symbol, a pattern, or a letter, or an intentional shape that combines two or more of these. Ra_A≦10.0…(1) Ra_B≦10.0…(2) 1.5≦|Ra_A−Ra_B| …(3) 150≦HV_x≦350 ... (4) 200≦HV_max…(5) 0.80≦HV_big / HV_sml≦1.50…(6)

3. The method for producing a hot-dip plated steel material according to claim 1, A method for manufacturing hot-dip plated steel material, in which either the first region or the second region is formed by colliding iron or non-ferrous metal particles (shot) with the surface of a plating layer formed on the surface of a steel material by a hot-dip plating method using centrifugal force or air pressure.

4. The method for producing a hot-dip plated steel material according to claim 2, A method for manufacturing a hot-dip plated steel product, in which a plating layer formed on one side of a steel sheet or on the other side opposite to the one side by a hot-dip plating method is collided with iron or non-ferrous metal particles (shot) on the surface of one or both of the plating layers on the one side or the other side by centrifugal force or air pressure, thereby forming either the first region or the second region.

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