Plated steel material

Abstract

The plating layer of the plated steel material includes, in terms of mass%, 10.0 to 40.0% of Al, 5.0 to 12.5% of Mg, 0 to 1.0% of Ti, 0 to 1.0% of Zr, and a balance including 50.0% or more of Zn and impurities; Ti and Zr are included in a total amount of 0.001% or more; and the plating layer has a diffraction intensity satisfying a formula (1) below, the diffraction intensity being obtained from an X-ray diffraction measurement result: I200Al / I111Al+I220Al+I200Al+I311Al≥0.40 wherein, in the formula (1), I(200)Al is a diffraction intensity of (200) of Al, I(111)Al is a diffraction intensity of (111) of Al, I(220)Al is a diffraction intensity of (220) of Al, and I(311)Al is a diffraction intensity of (311) of Al.

Description

TECHNICAL FIELD

[0001] The present invention relates to a plated steel material.

[0002] The present application claims priority based on Japanese Patent Application No. 2023-131415 filed in Japan on August 10, 2023, the contents of which are incorporated herein by reference.BACKGROUND ART

[0003] Plated steel materials, having excellent corrosion resistance, are used in the fields of building materials and civil engineering. In particular, molten Zn-Al-Mg-based plated steel materials, having excellent corrosion resistance, are widely used in the above-described fields. The molten Zn-Al-Mg-based plated steel materials may be worked into various shapes before being formed into various final products.

[0004] The molten Zn-Al-Mg-based plating layer includes an MgZn 2 phase, a [Al / Zn / MgZn 2 ] ternary eutectic structure, and an Al primary crystal formed therein as its representative phase structures. The Al primary crystal is an Al dendrite structure containing Zn. Among these phase structures, the MgZn 2 phase and the [Al / Zn / MgZn 2 ] ternary eutectic structure are considered to have low plastic deformability. The Al primary crystal is considered to have higher plastic deformability than the MgZn 2 phase and the [Al / Zn / MgZn 2 ] ternary eutectic structure, which is insufficient, though. Therefore, the plating layer of the molten Zn-Al-Mg-based plated steel material has poor workability. As a result, there is a problem that the plating layer of the molten Zn-Al-Mg-based plated steel material cannot follow working deformation, and the plating layer cracks at the worked portion, so that the corrosion resistance of the worked portion is inferior to that of the flat surface.

[0005] Patent Document 1 discloses a technique in which MgZn 2 is precipitated in the Al primary crystal to suppress the corrosion progress of the Al primary crystal. Patent Document 1 attempts to improve the corrosion resistance of the worked portion by suppressing the corrosion rate of the Al primary crystal, and does not consider improving the workability of the plating layer itself.Citation ListPatent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application, First Publication No. 2005-336546SUMMARY OF INVENTIONTechnical Problem

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a plated steel material excellent in corrosion resistance and also excellent in the workability of the plating layer thereof.Solution to Problem

[0008] In order to solve the above problem, the present invention adopts the following configuration. [1] A plated steel material including: a steel material; and a plating layer on the steel material, wherein the plating layer includes, as an average chemical composition, in terms of mass%, 10.0 to 40.0% of Al, 5.0 to 12.5% of Mg, 0 to 1.0% of Ti, 0 to 1.0% of Zr, 0 to 5.00% of Si, 0 to 3.00% of Ca, 0 to 0.50% of Y, 0 to 0.50% of La, 0 to 0.50% of Ce, 0 to 0.50% of Sr, 0 to 3.00% of Sn, 0 to 1.00% of Bi, 0 to 1.00% of In, 0 to 1.00% of B, 0 to 0.50% of P, 0 to 0.25% of Cr, 0 to 0.25% of V, 0 to 1.0% of Ni, 0 to 0.25% of Co, 0 to 0.25% of Nb, 0 to 1.0% of Cu, 0 to 0.25% of Mn, 0 to 0.25% of Mo, 0 to 0.25% of W, 0 to 1.00% of Ag, 0 to 0.50% of Li, 0 to 0.05% of Na, 0 to 0.25% of Ba, 0 to 0.05% of K, 0 to 5.0% of Fe, 0 to 0.50% of Sb, 0 to 0.50% of Pb, and a balance including 50.0% or more of Zn and impurities; the plating layer includes Ti and Zr in a total amount of 0.001% or more; and the plating layer has a diffraction intensity satisfying a formula (1) below, the diffraction intensity being obtained from an X-ray diffraction measurement result: I 200 AI / I 111 AI + I 220 AI + I 200 AI + I 311 AI ≥ 0.40 wherein, in the formula (1), I(200) Al is a diffraction intensity of (200) of Al, I(111) Al is a diffraction intensity of (111) of Al, I(220) Al is a diffraction intensity of (220) of Al, and I(311) Al is a diffraction intensity of (311) of Al. [2] The plated steel material according to [1], wherein the plating layer includes Ti and Zr in a total amount of 0.020% or more. [3] The plated steel material according to [1] or [2], wherein a total area of an Al phase having a circle equivalent diameter of 20 µm or less is included in a ratio of 50% or more based on a total area of an Al phase in a cross section in a thickness direction of the plating layer. Advantageous Effects of Invention

[0009] According to the present invention, it is possible to provide a plated steel material excellent in corrosion resistance and also excellent in the workability of the plating layer thereof.BRIEF DESCRIPTION OF DRAWING

[0010] [FIG. 1] FIG. 1 is a schematic cross-sectional view of a plated steel material according to an embodiment of the present invention.DESCRIPTION OF EMBODIMENTS

[0011] When a plated steel material is bent and the plating layer cracks to expose the base metal of the steel material, sacrificial corrosion protection function of the plating layer acts in the vicinity thereof, so that the constituent elements of the plating layer elute and the plating layer itself is partially consumed. Therefore, the plating layer in the vicinity of the worked portion may have lower corrosion resistance than the plating layer other than that of the worked portion. For the prevention thereof, it is necessary to prevent the cracking of the plating layer at the worked portion. The plating layer is less likely to crack as the plating layer has higher plastic deformability.

[0012] The Zn-Al-Mg-based plating layer has a phase structure containing a plurality of phases and microstructures, and for example, includes an MgZn 2 phase, a [Al / Zn / MgZn 2 ternary eutectic structure], and an Al primary crystal. The Al primary crystal has an Al dendrite crystal structure containing Zn. The MgZn 2 phase and the [Al / Zn / MgZn 2 ternary eutectic structure] are considered to have low plastic deformability and low workability. On the other hand, it is known that Al changes in workability depending on the crystal orientation state thereof. Therefore, if the crystal orientation state of Al mainly included in the Al primary crystal can be controlled, it is expected that the workability of the entire plating layer can be improved to reduce the cracking of the plating layer at the worked portion.

[0013] The inventors have studied for the purpose of improving the workability of the plating layer by controlling the crystal orientation of the Al phase, and found that when the plating layer contains one or both of Zr and Ti, the Al crystal orientation plane at the surface of the plating layer includes the (100) plane in an increased ratio, thereby improving the workability of the plating layer.

[0014] Zr and Ti form a compound with Al in the plating layer, specifically, an intermetallic compound such as Al 3 Zr and Al 3 Ti. When Si is further present, Al 2.7 Si 0.3 Zr and Al 2.5 Si 0.5 Ti are formed. These intermetallic compounds act as a solidified nucleus of the Al primary crystal and refine the Al primary crystal. The inventors have found that this further improves the workability of the plating layer.

[0015] A steel structure produced by such a plated steel material is excellent in workability and corrosion resistance.

[0016] Hereinafter, the plated steel material according to an embodiment of the present invention will be described.

[0017] The plated steel material according to the embodiment includes: a steel material; and a plating layer provided on the surface of the steel material, wherein the plating layer includes, as an average chemical composition, in terms of mass%, 10.0 to 40.0% of Al, 5.0 to 12.5% of Mg, 0 to 1.0% of Ti, 0 to 1.0% of Zr, 0 to 5.00% of Si, 0 to 3.00% of Ca, 0 to 0.50% of Y, 0 to 0.50% of La, 0 to 0.50% of Ce, 0 to 0.50% of Sr, 0 to 3.00% of Sn, 0 to 1.00% of Bi, 0 to 1.00% of In, 0 to 1.00% of B, 0 to 0.50% of P, 0 to 0.25% of Cr, 0 to 0.25% of V, 0 to 1.0% of Ni, 0 to 0.25% of Co, 0 to 0.25% of Nb, 0 to 1.0% of Cu, 0 to 0.25% of Mn, 0 to 0.25% of Mo, 0 to 0.25% of W, 0 to 1.00% of Ag, 0 to 0.50% of Li, 0 to 0.05% of Na, 0 to 0.25% of Ba, 0 to 0.05% of K, 0 to 5.0% of Fe, 0 to 0.50% of Sb, 0 to 0.50% of Pb, and a balance including 50.0% or more of Zn and impurities; the plating layer includes Ti and Zr in a total amount of 0.001% or more; and the plating layer has a diffraction intensity satisfying a formula (1) below, the diffraction intensity being obtained from an X-ray diffraction measurement result: The surface of the steel material mentioned herein refers to the interface between the plating layer and the steel material. The plating layer provided on the surface of the steel material is a plating layer provided on the steel material. I 200 Al / I 111 Al + I 220 Al + I 200 Al + I 311 Al ≥ 0.40 wherein, in the formula (1), I(200) Al is a diffraction intensity of (200) of Al, I(111) A1 is a diffraction intensity of (111) of Al, I(220) Al is a diffraction intensity of (220) of Al, and I(311) A1 is a diffraction intensity of (311) of Al.

[0018] The plating layer preferably includes Ti and Zr in a total amount of 0.020% or more.

[0019] In the plated steel material according to the embodiment, a total area of an Al phase having a circle equivalent diameter of 20 µm or less is preferably included in a ratio of 50% or more based on a total area of an Al phase in a cross section in a thickness direction of the plating layer.

[0020] In the following description, the expression "%" of the content of each element in a chemical composition means "mass%". In addition, a numerical range represented by "to" means a range including numerical values described before and after "to" as the lower limit and the upper limit. Note that a numerical range in which "more than" or "less than" is attached to the numerical values described before and after "to" means a range not including these numerical values as the lower limit or the upper limit.

[0021] "Corrosion resistance" indicates a property that a plating layer itself is hardly corroded. The Zn-based plating layer has a sacrificial corrosion protection action on the steel material. Thus, in the corrosion process of the plated steel sheet, the plating layer corrodes and turns into white rust before the steel material corrodes, and after the plating layer turns into white rust and disappears, the steel material corrodes and generates red rust.

[0022] The "workability" indicates a property that the plating layer is less likely to crack when the plated steel material is bent.

[0023] As illustrated in FIG. 1, a plated steel material 1 according to the embodiment includes a steel material 11. The shape of the steel material 11 is not particularly limited, and an example of the steel material 11 is a steel sheet. In addition, the steel material 11 may be, for example, a formed base steel material, such as a steel pipe, a civil engineering and construction material (fence culvert, corrugated pipe, drain channel lid, splash preventing plate, bolt, wire mesh, guard rail, water stop wall, and the like), a home electric appliance member (a housing of an outdoor unit of an air conditioner, or the like), and a vehicle component (a suspension member, or the like). The forming is, for example, various deformation working methods, such as pressing, roll forming, and bending.

[0024] The material of the steel material 11 is not particularly limited. As the steel material 11, for example, various steel materials, such as general steel, Ni pre-plated steel, Al-killed steel, ultra-low carbon steel, high carbon steel, various high tensile strength steels, and some high alloy steels (a steel containing a reinforcing element such as Ni, Cr, etc.) are applicable. In addition, the steel material 11 is not particularly limited in terms of conditions such as a method for manufacturing the steel material and a method for manufacturing a steel sheet (a hot rolling method, a pickling method, a cold rolling method, or the like). Furthermore, as the steel material 11, a steel material on which a metal film or an alloy film made of Zn, Ni, Sn, an alloy thereof, or the like and having a thickness of less than 1 µm is formed may be used.

[0025] Next, the plating layer 12 will be described. The plated steel material 1 according to the embodiment has a plating layer 12 arranged on the surface of the steel material 11. When the steel material 11 is a steel sheet, the plating layer 12 is arranged at least on one surface of the steel sheet and the other surface opposite to the one surface. The plating layer 12 is also arranged on the end surface between one surface and the other surface of the steel sheet.

[0026] The plating layer 12 according to the embodiment is mainly made of a Zn-Al-Mg alloy layer due to the chemical composition described later. The Zn-Al-Mg-based alloy layer is made of a Zn-Al-Mg-based alloy. The Zn-Al-Mg-based alloy means a ternary alloy containing Zn, Al, and Mg. The Zn-Al-Mg-based alloy layer in which alloying elements such as Al and Mg are added to Zn has improved corrosion resistance as compared with a normal Zn plating layer. For example, even when the thickness of the Zn-Al-Mg-based alloy layer is about a half of that of a normal Zn plating layer, the Zn-Al-Mg-based alloy layer has corrosion resistance equivalent to that of the Zn plating layer. Therefore, the plating layer of the embodiment also has corrosion resistance equivalent to or higher than that of the Zn plating layer.

[0027] In addition, the plating layer 12 of the plated steel material 1 according to the embodiment may include an Fe-Al-based interfacial alloy layer (hereinafter, referred to as Al-Fe alloy layer) between the steel material 11 and the Zn-Al-Mg alloy layer. The Al-Fe alloy layer is an interfacial alloy layer between the steel material and the Zn-Al-Mg alloy layer.

[0028] The plating layer according to the embodiment may have a single-layer structure of the Zn-Al-Mg alloy layer or a multi-layer structure including the Zn-Al-Mg alloy layer and the Al-Fe alloy layer. In the case of the multi-layer structure, the Zn-Al-Mg alloy layer is preferably a layer constituting the surface of the plating layer. On the outermost surface of the plating layer, an oxide film of the constituent elements of the plating layer is formed with a thickness of about less than 1 µm. The oxide film is thin with respect to the thickness of the entire plating layer, and thus may be ignored from the main constituent of the plating layer.

[0029] In general, the thinner the plating layer, the better the workability. However, considering the consumption of the plating layer due to corrosion, the thicker the plating layer, the easier it is to secure corrosion resistance. Therefore, the thickness of the entire plating layer is preferably 10 to 70 µm. Since the thickness of the entire plating layer depends on plating conditions, the thickness of the entire plating layer is not limited to the range of 10 to 70 µm. The thickness of the entire plating layer is affected by the viscosity and specific gravity of the plating bath in an ordinary hot-dip plating method. Then, the thickness of the entire plating layer is adjusted by the drawing speed of the steel material (original sheet to be plated) and the intensity of the wiping.

[0030] The Al-Fe alloy layer is formed on the surface of the steel material (specifically, between the steel material and the Zn-Al-Mg alloy layer), and is a layer having an Al 5 Fe 2 phase as a main phase in the microstructure. The Al-Fe alloy layer is formed by mutual atomic diffusion between the base metal (steel material) and the plating bath. When a hot-dip plating method is used as a manufacturing method, the Al-Fe alloy layer is easily formed in a plating layer containing the Al element. Since a certain concentration or more of Al is contained in the plating bath, an Al 5 Fe 2 phase is formed most. However, the atomic diffusion takes time, and there is a portion where the Fe concentration is high in a portion close to the base metal. Therefore, the Al-Fe alloy layer may partially contain a small amount of an AlFe phase, an Al 3 Fe phase, an Al 2 Fe phase, or the like. In addition, since a certain concentration of Zn is also contained in the plating bath, a small amount of Zn is also contained in the Al-Fe alloy layer.

[0031] When Si is contained in the plating layer, Si is particularly easily incorporated into the Al-Fe alloy layer, and an Al-Fe-Si intermetallic compound phase may be formed. The intermetallic compound phase to be identified includes an AlFeSi phase, and the isomer thereof includes α, β, q1, q2-AlFeSi phases. Therefore, these AlFeSi phases and the like may be detected in the Al-Fe alloy layer. The Al-Fe alloy layer containing these AlFeSi phases and the like is also referred to as Al-Fe-Si alloy layer.

[0032] Next, the average chemical composition of the plating layer will be described. When the plating layer has a single-layer structure of the Zn-Al-Mg alloy layer, 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 multi-layer structure of the Al-Fe alloy layer and the Zn-Al-Mg alloy layer, the average chemical composition of the entire plating layer is the average chemical composition of the total of the Al-Fe alloy layer and the Zn-Al-Mg alloy layer.

[0033] In the hot-dip plating method, the chemical composition of the Zn-Al-Mg alloy layer is ordinarily almost the same as that of the plating bath because the formation reaction of the plating layer is almost completed in the plating bath. In the hot-dip plating method, the Al-Fe alloy layer is instantaneously formed and grown immediately after immersion in the plating bath. The formation reaction of the Al-Fe alloy layer is completed in the plating bath, and the thickness thereof is often sufficiently smaller than that of the Zn-Al-Mg alloy layer. Therefore, unless a special heat treatment such as a heat alloying treatment is performed after plating, the average chemical composition of the entire plating layer is substantially equal to the chemical composition of the Zn-Al-Mg alloy layer, and the components of the Al-Fe alloy layer and the like can be ignored.

[0034] The plating layer according to the embodiment includes, as a chemical composition, Zn, other alloy elements, and impurities. The plating layer according to the embodiment may be composed of, as a chemical composition, Zn, other alloy elements, and impurities. The chemical composition of the plating layer will be described in detail below. Note that the elements the concentration of which has a lower limit of 0% as described are not essential for solving the problem of the plated steel material according to the embodiment, but are optional elements which are allowed to be included in the plating layer for the purpose of improving characteristics or the like.Al: 10.0 to 40.0%

[0035] Similarly to Zn, Al is an element mainly constituting the plating layer. Although the sacrificial corrosion protection action of Al is small, flat portion corrosion resistance is improved when Al is contained in the plating layer. In addition, when Al is not present, Mg cannot be stably held in the plating bath. Therefore, Al is contained in the plating bath as an essential element in the manufacturing.

[0036] The Al content is 10.0% or more, because the content is necessary for containing a large amount of Mg to be described later, and the content is necessary for securing workability. When the Al content is less than the content, the plating bath is difficult to prepare, and the plating layer is difficult to secure workability and corrosion resistance. The Al content is 40.0% or less, because Al has a weak sacrificial corrosion protection action on steel material, and sacrificial corrosion protection properties cannot be sufficiently obtained when the Al content exceeds the content. Therefore, the upper limit is 40.0% or less.Mg: 5.0 to 12.5%

[0037] Mg is an element that has a sacrificial corrosion protection effect and enhances corrosion resistance of the plating layer. When a certain amount or more of Mg is contained, an MgZn 2 phase is formed in the plating layer. As the Mg content in the plating layer is high, more MgZn 2 phase is formed. The MgZn 2 phase is known to have a structure called a Laves phase, and the hardness thereof is known to be high. The Mg content is 5.0% or more, because the concentration is necessary for exhibiting corrosion resistance, and corrosion resistance cannot be sufficiently obtained when the Mg content is less than 5.0%. In addition, the MgZn 2 phase is not sufficiently formed in the plating layer, and the corrosion resistance of the plating layer itself is low. When the Mg content is excessively large, it is difficult to manufacture the plating layer, and the workability of the plating layer is deteriorated, so that the upper limit thereof is 12.5% or less. The Mg content is more preferably 6.0 to 8.0%.Ti: 0 to 1.0%Zr: 0 to 1.0%

[0038] When one or both of Ti and Zr are contained in the plating bath, each form Al 3 Zr and Al 3 Ti as an intermetallic compound, respectively. When Si is present, Al 2.7 Si 0.3 Zr and Al 2.5 Si 0.5 Ti are formed. These have good lattice matching with the Al phase in the crystal structure, and act as a solidification nucleus of the Al primary crystal. When the intermetallic compound containing Ti or Zr acts as a solidification nucleus of the Al primary crystal, the (100) plane of Al is preferentially oriented at the surface of the plated steel material in parallel with the surface of the plating layer. When the total concentration of Ti and Zr is 0.001% or more, the (100) plane of Al starts to form in parallel with the surface of the plating layer, and the orientation of the (100) plane tends to increase as the concentration of Ti and Zr increases. Therefore, the lower limit of the total concentration of Ti and Zr is 0.001% or more, and more preferably 0.020% or more.

[0039] In addition, when the total concentration of Ti and Zr is 0.020% or more, the Al primary crystal starts to be refined, and the Al primary crystal tends to be refined as the concentration increases. When the total concentration of Ti and Zr is 0.5%, the grain refinement effect is saturated. Since the refinement of the crystal structure contributes to the improvement of workability, the total concentration of Ti and Zr is preferably 0.020% or more for the refinement of the Al primary crystal. On the other hand, when the concentration of Ti and Zr is high, the plating bath tends to be difficult to prepare. When each of Ti and Zr is more than 1.0%, there is a tendency that a large amount of dross is generated, and bare spots frequently occur, so that the external appearance and corrosion resistance deteriorate. Therefore, the concentration of Ti and the concentration of Zr are 1.0% or less, respectively. The total concentration of Ti and Zr is 0.001 to 2.0%, more preferably 0.001 to 1.5%, or 0.010 to 0.5%, and still more preferably 0.1 to 0.5%.

[0040] Furthermore, when one or both of Ti and Zr are contained in the plating bath, precipitation of a Mg 2 Zn 11 phase tends to be suppressed, and workability is improved.Si: 0 to 5.00%

[0041] Si is an optionally added element. When Si is contained in the plating bath, the plating layer includes an Si single phase or Mg 2 Si precipitated therein. When Ca is further contained, an Al-Ca-Si compound is precipitated. When these Si or Si-based compounds are precipitated on the surface of the plating layer, there are effects of improving water wet resistance and water flow resistance. In addition, Si is incorporated into the Al-Fe alloy layer to form an Al-Fe-Si phase, thereby suppressing the growth of the Al-Fe alloy layer, so that there is an effect of improving bending workability, and plating adhesion is also improved. Si is preferably contained in an amount of 0.05% or more. In addition, when Si exceeds 5.00%, a large amount of dross is generated and bare spots frequently occur. Therefore, the Si concentration is 5.00% or less. The Si concentration is preferably 0 to 5.00%, 0.05 to 3.00%, 0.05 to 1.0%, or 0.10 to 0.50%.Element group A

[0042] Ca: 0 to 3.00% Y: 0 to 0.50% La: 0 to 0.50% Ce: 0 to 0.50% Sr: 0 to 0.50%

[0043] Ca, Y, La, Ce, and Sr as the element group A are optionally added elements. These elements are easily oxidized in the atmosphere, and when present in the plating bath, exhibit an effect of forming a dense oxide film on the bath surface to prevent oxidation of Mg. Through the effect, the Mg concentration is stabilized, and the plated steel sheet having a target composition is easily manufactured. In order to suitably exhibit such an effect, the content of each of these elements is more than 0%, and more preferably 0.01% or more. In addition, there is an upper limit to the content of each element, and when the content exceeds the upper limit, the plating bath tends to be difficult to prepare. In addition, adhesion of dross or the like increases, and external appearance and corrosion resistance tend to deteriorate.

[0044] Therefore, Ca is included in an amount of 0 to 3.00%, preferably more than 0% and less than 2.00%, more preferably 0.01% or more and less than 2.00%, and still more preferably 0.01% or more and 1.50% or less. Ca may be included in an amount of 1.00% or less, 0.60% or less, or 0.50% or less.

[0045] In addition, each of Y, La, Ce, and Sr is included in an amount of 0 to 0.50%, preferably more than 0% and less than 0.50%, and more preferably 0.01% or more and less than 0.50%. Furthermore, each element may be included in an amount of 0.01% or more, and may be included in an amount of 0.40% or less, or 0.30% or less. The element group A forms a compound with Al or Zn in the plating structure. Taking Ca as an example, when Ca is contained in an amount of more than 0%, preferably 0.01% or more, an Al-Ca-Zn-based compound is formed, and when Si is further present, an Al-Ca-Si-based compound is easily formed. In addition, when Y, La, Ce, and Sr are contained, those in which Ca of the compound is replaced by each element are formed.Element group B

[0046] Sn: 0 to 3.00% Bi: 0 to 1.00% In: 0 to 1.00%

[0047] The elements of the element group B are optionally added elements, and these elements have a function of improving sacrificial corrosion protection properties. Note that, since these elements tend to be bonded to Mg stronger than Zn and the effect of Mg contained is reduced, there is an upper limit to the content of each of these elements. When the upper limit is exceeded, adhesion of dross or the like increases, and corrosion resistance tends to deteriorate. Therefore, Sn is contained in an amount of 0 to 3.00%, more preferably more than 0% and less than 3.00%. Sn may be contained in an amount of 0.01% or more, 0.05% or more, 2.50% or less, 2.00% or less, or 1.50% or less. Bi is contained in an amount of 0 to 1.00%, more preferably more than 0% and less than 1.00%. Bi may be contained in an amount of 0.01% or more, 0.05% or more, 0.80% or less, 0.50% or less, or 0.40% or less. In is contained in an amount of 0 to 1.00%, more preferably more than 0% and less than 1.00%. In may be contained in an amount of 0.01% or more, 0.05% or more, 0.80% or less, 0.50% or less, or 0.40% or less.Element group C

[0048] B: 0 to 1.00% P: 0 to 0.50%

[0049] B and P as the element group C are elements belonging to metalloids. These elements are optionally added elements. B, as AlB 2 , acts as a solidification nucleus of the Al primary crystal to refine the Al primary crystal, thereby improving the workability of the Al primary crystal. However, the effect thereof is not large and lower than the effects of Ti and Zr. P has no effect of refining the Al primary crystal, but improves corrosion resistance. There is an upper limit to the content of each of the elements, and when the content exceeds the upper limit, adhesion of dross or the like increases, and external appearance and corrosion resistance tend to deteriorate. Therefore, B is contained in an amount of 0 to 1.00%, preferably more than 0% and 0.50% or less, and more preferably more than 0% and 0.10% or less. B may be contained in an amount of 0.01% or more, or 0.05% or more. P is contained in an amount of 0 to 0.50%, more preferably more than 0% and less than 0.50%, and still more preferably more than 0% and 0.01% or less. P may be contained in an amount of 0.001% or more, or 0.005% or more.Element group D

[0050] Cr: 0 to 0.25% V: 0 to 0.25% Ni: 0 to 1.0% Co: 0 to 0.25% Nb: 0 to 0.25% Cu: 0 to 1.0% Mn: 0 to 0.25% Mo: 0 to 0.25% W: 0 to 0.25% Ag: 0 to 1.00% Li: 0 to 0.50% Na: 0 to 0.05% Ba: 0 to 0.25% K: 0 to 0.05% Fe: 0 to 5.0%

[0051] The element group D includes metal elements as optionally added elements. These elements are incorporated into the plating layer to improve the corrosion resistance thereof. There is an upper limit to the content of each element. When the content exceeds the upper limit, adhesion of dross or the like tends to increase. Therefore, Cr, V, Co, Nb, Mn, Mo, W, and Ba are each 0 to 0.25%, preferably more than 0% and 0.25% or less, more than 0.01% and 0.20% or less, or more than 0% and 0.10% or less. Ni, Cu, and Ag are contained in an amount of 0 to 1.0%, preferably more than 0% and 1.0% or less, more than 0% and 0.5% or less, more than 0% and 0.20% or less, or more than 0% and 0.10% or less. Each of Ni, Cu, and Ag may be contained in an amount of 0.01% or more, or 0.05% or more. Li is contained in an amount of 0 to 0.50%, and preferably more than 0% and 0.10% or less. Li may be contained in an amount of 0.01% or more. Na and K are 0 to 0.05%, and preferably more than 0% and 0.03% or less. Na and K may be contained in an amount of 0.01% or more. In addition, Fe may be inevitably contained in the plating layer. This is because Fe may be diffused from the base metal into the plating layer during manufacture of plating. Therefore, the Fe content is 0 to 5.0%, and may be preferably more than 0% and 2.0% or less, more than 0% and 1.5% or less, more than 0% and 1.2% or less, or more than 0% and 1.0% or less. Fe may be contained in an amount of 0.1% or more, 0.3% or more, 0.5% or more, or 0.9% or less.Element group E

[0052] Sb: 0 to 0.50% Pb: 0 to 0.50%

[0053] Sb and Pb, belonging to the element group E, are optionally added elements, and elements having properties similar to those of Zn. Therefore, when these elements are contained, there is an effect that a spangle pattern is easily formed on the external appearance of plating, or the like. However, when these elements are contained in an excessively large amount, corrosion resistance may be deteriorated. Therefore, Sb and Pb are each contained in an amount of 0 to 0.50%, and preferably more than 0% and 0.50% or less, more than 0% and 0.40% or less, or more than 0% and 0.10% or less. Sb and Pb may be contained in an amount of 0.01% or more, or 0.05% or more, respectively.Balance: Zn: 50.0% or more and impurities

[0054] Zn is a metal having a low melting point, and exists as a main phase of the plating layer on the steel material. Zn is an element necessary for securing corrosion resistance and obtaining a sacrificial corrosion protection action on the steel material. When the Zn content is less than 50.0%, the main constituent of the metallographic structure of the Zn-Al-Mg alloy layer becomes the Al phase, and the Zn phase exhibiting sacrificial corrosion protection properties is insufficient. Therefore, the Zn content is 50.0% or more, and more preferably 60.0% or more, or 70.0% or more. Note that the upper limit of the Zn content is the amount of the balance other than elements excluding Zn and impurities. The Zn content may be 85.0% or less.

[0055] The impurities in the plating layer refer to components contained in raw materials, components mixed in the manufacturing process, and components which are other than the optionally added elements and contained in a range where the effect of the present invention is not affected. For example, in the plating layer, a small amount of components other than Fe may be mixed as the impurities due to mutual atomic diffusion between the steel material (base metal) and the plating bath.

[0056] Note that the plating layer according to the embodiment does not exclude elements contained therein other than the elements listed above as long as the effects of the present invention are not affected. The phrase "the effects of the present invention are not affected" refers to a case where the rating is A or higher in the corrosion resistance evaluation and the workability evaluation as described later.

[0057] In the plating layer according to the embodiment, Al, Mg, and Zn are preferably contained in a total amount of 83.7% or more, 90.0% or more, or 94.7% or more.

[0058] In order to identify the average chemical composition of the plating layer, the plating layer is peeled off and dissolved with an acid containing an inhibitor that suppresses corrosion of the base metal (steel material) to obtain an acid solution. Next, the obtained acid solution is measured by ICP emission spectrometry or ICP-MS to determine the chemical composition. The acid species is not particularly limited as long as it is an acid capable of dissolving the plating layer. In a case where the area and weight before and after peeling are measured, the plating adhesion amount (g / m 2< ) can also be determined at the same time.

[0059] Next, the microstructure of the plating layer will be described.

[0060] The proportion of the phases contained in the plating layer greatly affects the performance of the plating layer. Even if the plating layers have the same composition, phases or microstructures included in the metallographic structure change depending on the manufacturing method, and the properties thereof differ from each other. The metallographic structure of the plating layer can be easily confirmed by a scanning electron microscope with an energy dispersive X-ray analyzer (SEM-EDS). The state of the approximate metallographic structure of the plating layer can be confirmed by, for example, obtaining a reflected electron image in an arbitrary vertical cross section (thickness direction) of a mirror-finished plating layer. Since the thickness of the plating layer according to the embodiment is about 10 to 70 µm, it is preferable to confirm the metallographic structure thereof in a visual field at a magnification of 500 to 5000 times in SEM. For example, when a plating layer having a thickness of 25 µm is confirmed at a magnification of 2000 times, a cross section of the plating layer in a region of 25 µm (plating thickness) × 40 µm (SEM field width) = 1000 µm 2< can be confirmed per one visual field. In the embodiment, with a SEM visual field, the plating layer may be observed by a local visual field. Therefore, in order to obtain average information of the plating layer, 25 visual fields may be selected from the arbitrary cross section for the average information. That is, the area fraction and the size of the phases or microstructures constituting the metallographic structure of the plating layer may be determined by observing the metallographic structure in a visual field of 25000 µm 2< in total.

[0061] The reflected electron image by SEM is preferable in that a phase or a microstructure included in the plating layer can be easily distinguished. An element having a small atomic number such as Al is imaged in black, and an element having a large atomic number such as Zn is imaged in white. Therefore, the ratio of each of these microstructures can be easily read.

[0062] In order to confirm each phase, the composition of the phase is confirmed at pinpoint in the EDS analysis, and phases having substantially equivalent components are read from element mapping or the like to specify the phase. When EDS analysis can be used, phases having almost the same composition can be discriminated by element mapping. When phases having almost the same composition can be specified, the area of the crystal phase in an observed visual field can be found. When the area is grasped, the equivalent circle diameter can be determined by calculation.

[0063] In addition, the area percentage of each phase in the observed visual field can be determined. The area fraction of a specific phase in the plating layer corresponds to the volume percentage of the phase in the plating layer.

[0064] The plating layer according to the embodiment includes an MgZn 2 phase, an Al primary crystal containing an Al phase, and a [Al / Zn / MgZn 2 ternary eutectic structure]. The plating layer may further include a remainder in microstructure. The Al primary crystal is made of an Al phase alone, or is made in a form in which an Al phase occupies the central portion of the dendrite and an Al-Zn phase occupies the outer peripheral portion.

[0065] As for the content ratio of phases and microstructures in the plating layer, in an arbitrary vertical cross section (thickness direction) of the plating layer, in terms of the area fraction observed by the visual field of scanning electron microscope observation, it is preferable that the area fraction of the MgZn 2 phase is 15% or more and 50% or less, the area fraction of the total of the Al phase and the Al-Zn phase is 15% or more and 70% or less, the area fraction of the [Al / Zn / MgZn 2 ternary eutectic structure] is 0% or more and 60% or less, and the area fraction of other phases is 0% or more and 10% or less. The plating layer according to the embodiment, satisfying the above chemical composition and the formula (1), is excellent in corrosion resistance and workability. Therefore, the area fraction of phases and microstructures in the plating layer is not limited to the above ranges.MgZn 2 phase

[0066] The MgZn 2 phase according to the embodiment is a region where Mg is contained in an amount of 16 mass% (± 5%) and Zn is contained in an amount of 84 (± 5%) in the plating layer. The MgZn 2 phase is often photographed in a gray having an intermediate color between the colors of Al and Zn in a reflected electron image of SEM. In the reflected electron image of SEM, the MgZn 2 phase can be clearly distinguished from the Al phase, the Al-Zn phase, the [Al / Zn / MgZn 2 ternary eutectic structure], and the like.

[0067] When the proportion of the MgZn 2 phase in the plating layer is increased, corrosion resistance is improved. On the other hand, the MgZn 2 phase, called Laves phase, may lower the workability of the plating layer. Therefore, from the viewpoint of corrosion resistance, the MgZn 2 phase is preferably contained more and more, but there may be an upper limit from the viewpoint of securing workability. The proportion of the MgZn 2 phase in the plating layer may be 15% or more and 50% or less in terms of area fraction in order to balance corrosion resistance and workability. The area fraction of the MgZn 2 phase may be 20% or more, 25% or more, 45% or less, or 40% or less.Al phase

[0068] In the embodiment, the Al phase constituting the Al primary crystal is a region where the Al content is more than 40 mass% in the plating layer. The Al phase may contain Zn, but the Zn content is less than 60 mass%. The Al phase can be clearly distinguished from other phases and microstructures in a SEM reflected electron image. That is, the Al phase is often indicated in the blackest color in the SEM reflected electron image. In the embodiment, the Al phase takes various forms, for example, the Al phase appears as a block-shaped cross section or a dendritic cross section such as a circular cross section or a flat cross section in any cross section. In the embodiment, Al contained in the [Al / Zn / MgZn 2 ternary eutectic structure] is not included in the Al phase.

[0069] The area fraction of the Al phase in the plating layer is not particularly limited, and may be 5% or more, 10% or more, 20% or more, or 25% or more. The Al phase may be contained in an amount of 60% or less, 55% or less, or 50% or less.

[0070] The Al phase is excellent in plastic deformability as compared with the MgZn 2 phase and the [Al / Zn / MgZn 2 ternary eutectic structure]. It is known that the Al phase takes a face-centered cubic structure as its crystal structure, and the workability thereof depends on its orientation. In the case of bending, when the preferential orientation at the surface of the plating layer is the (100) plane, the plastic deformability of the plating layer is improved, and the plating layer extends following the working, so that the plating in the worked portion is less likely to crack. In addition, the tendency of development of the preferential orientation also varies depending on the Al content of the plating layer, and when the Al content is small and the Zn content is large, the (110) plane becomes the preferential orientation, and the preferential orientation changes to the (100) plane as the Al content increases.

[0071] The preferential orientation of the Al phase at the surface of the plating layer can be determined by performing X-ray diffraction. For example, when X-ray diffraction is measured under an output condition of 50 KV-300 mA using a Cu radiation source, the (111) plane appears near 38.47°, the (200) plane appears near 44.74°, the (220) plane appears near 65.13°, and the (311) plane appears near 78.23° in terms of 2θ peak. Since the (200) plane is parallel to the (100) plane and the (220) plane is parallel to the (110) plane, the preferential orientation at the surface of the plating layer can be evaluated by X-ray diffraction, while the (200) plane is replaced with the (100) plane and the (220) plane is replaced with the (110) plane.

[0072] Whether the (100) plane appears at the surface of the plating layer as the preferential orientation is confirmed by the ratio between the peak intensity of the (200) plane and the peak intensity of another orientation plane. As the peak intensity of the (200) plane increases, the (100) plane appears as the preferential orientation. In the embodiment, when the diffraction intensity of the plating layer obtained from the X-ray diffraction measurement result satisfies the following formula (1), the (100) plane is the preferential orientation at the surface of the plating layer, so that the workability of the plating layer can be improved. I 200 Al / I 111 Al + I 220 Al + I 200 Al + I 311 Al ≥ 0.4 wherein, in the formula (1), I(200) Al is a diffraction intensity of (200) of Al, I(111) Al is a diffraction intensity of (111) of Al, I(220) Al is a diffraction intensity of (220) of Al, and I(311) Al is a diffraction intensity of (311) of Al. In the plating composition of the present invention, the value of the formula (1) may be 0.7 or less.

[0073] The method for measuring I 200 Al / I 111 Al + I 220 Al + I 200 Al + I 311 Al as defined by the formula (1) is as follows. First, the surface of the plating layer is mechanically polished and chemically polished as necessary to bring the surface of the plating layer into a mirror surface state. Next, for example, X-ray diffraction measurement is performed using an X-ray diffractometer (manufactured by Rigaku Corporation (model number RINT-TTR III) under the conditions of X-ray output: 50 kV and 300 mA; copper target; goniometer TTR (horizontal goniometer); slit width of Kβ filter: 0.05 mm; longitudinal limiting slit width: 2 mm; light receiving slit width: 8 mm; and light receiving slit 2: open, and under the measurement conditions of scan speed: 5 deg. / min; step width: 0.01 deg; and scan axis: 2θ (5 to 90°). Then, the diffraction intensity of the (200) of Al (maximum intensity in the range of 44.74° ± 0.20°), the diffraction intensity of the (111) of Al (maximum intensity in the range of 38.47° ± 0.20°), the diffraction intensity of the (220) of Al (maximum intensity in the range of 65.13° ± 0.20°), and the diffraction intensity of the (311) of Al (maximum intensity in the range of 78.23° ± 0.20°) are measured, respectively. The diffraction intensity is an intensity excluding the background intensity. From the obtained diffraction intensity, I 200 Al / I 111 Al + I 220 Al + I 200 Al + I 311 Al is determined.

[0074] In an arbitrary vertical cross section (thickness direction) of the plating layer, within the Al phase included in the plating layer, the total area of the Al phase having a circle equivalent diameter of 20 µm or less is preferably 50% or more, in terms of percentage based on the total area of the entire Al phase. That is, the total area of the Al phase having a circle equivalent diameter of 20 µm or less is preferably included in a ratio of 50% or more based on the total area of the Al phase in a cross section in the thickness direction of the plating layer. As described above, the Al phase having a circle equivalent diameter of 20 µm or less occupies 50% or more of the total area of the Al phase, so that the Al primary crystal is further refined, and the workability of the plating layer can be further improved. Since the workability of the plating layer tends to be improved when the Al primary crystal is refined, the total area of the Al phase having a circle equivalent diameter of 20 µm or less may be included in an area percentage of 70% or more based on the entire Al phase in the thickness direction of the plating layer. The upper limit thereof may be 100%.

[0075] In the method for measuring the area percentage of the Al phase having a circle equivalent diameter of 20 µm or less, the Al phases are extracted by image extraction in a predetermined observed visual field, and the area of each Al phase is measured, thereby deriving the circle equivalent diameter. Hereinafter, the specific measurement method will be described.

[0076] The observed visual field is 25000 µm 2< in total, which is used to confirm phases and microstructures in the plating layer as described above. In the EDS analysis on the observed visual field, the composition of the phase is confirmed at pinpoint, and phases having substantially equivalent components are read from the contrast of the SEM image, element mapping, or the like to specify the Al phase. The Al phase, which is a light element, can be grasped as the black region in the reflected electron image of SEM. In the EDS analysis, the Al phase can be discriminated by element mapping. The method for discriminating the Al phase is not limited to the above, and for example, EPMA mapping may be used. Next, the Al phase in the observed visual field is extracted by image processing, and each area is measured. After the area is grasped, the equivalent circle diameter of each Al phase can be calculated. Then, the Al phase having a circle equivalent diameter of 20 µm or less is extracted, and the total area thereof is determined. Then, the area fraction (%) of the Al phase having a circle equivalent diameter of 20 µm or less based on the total area of the Al phase in the observed visual field is determined.Al-Zn phase

[0077] The Al-Zn phase in the embodiment is a phase containing Zn in an amount of 60 mass% or more and Al. The Al-Zn phase is an aggregate of a fine Zn phase having a grain size of about 1 µm (hereinafter, referred to as fine Zn phase) and a fine Al phase having a grain size of less than 1 µm (hereinafter, referred to as fine Al phase). In the plating layer in a molten state, Al has a structure different from the crystal structure at room temperature (for example 25°C), a large amount of the Zn phase can form a solid solution in Al, and Al exists as a high-temperature stable phase containing about 60% of Zn phase. On the other hand, at room temperature, the content of the Zn phase extremely decreases in this high-temperature stable phase, and Al and Zn are equilibrium-separated, and exist as an Al-Zn phase including a fine Al phase and a fine Zn phase. That is, the Al-Zn phase is a phase containing 60 mass% or more of the fine Zn phase. The Al-Zn phase has different properties from the Al phase and the Zn phase contained in the plating layer, and therefore is distinguished in a reflected electron SEM image and wide-angle X-ray diffraction. In wide-angle X-ray diffraction, it is said to have specific diffraction peaks such as Al 0.403 Zn 0.597 (JCODF #00-052-0856) and Al 0.71 Zn 0.29 (PDF#00-019-0057). Therefore, in the embodiment, a phase containing 15 to 40 mass% of an Al component and 60 to 85 mass% of a Zn component is defined as the Al-Zn phase.

[0078] As described above, the Al-Zn phase is an aggregate of a fine Al phase and a fine Zn phase, and therefore is excellent in plastic deformability as compared with the MgZn 2 phase and the [Al / Zn / MgZn 2 ternary eutectic structure]. On the other hand, the Al-Zn phase has poor corrosion resistance as compared with the MgZn 2 phase, the [Al / Zn / MgZn 2 ternary eutectic structure], and the Al phase.

[0079] The area fraction of the Al-Zn phase is not particularly limited, and may be 5% or more, or 10% or more. The area fraction of the Al-Zn phase may be 20% or less, or 15% or less.

[0080] In the present invention, the total area ratio of the Al primary crystal, that is, the Al phase and the Al-Zn phase may be 15% or more and 70% or less. The total area ratio of the Al phase and the Al-Zn phase may be 20% or more, 25% or more, or 30% or more, and may be 65% or less, 60% or less, 55% or less, or 50% or less.[Al / Zn / MgZn 2 ternary eutectic structure]

[0081] The [Al / Zn / MgZn 2 ternary eutectic structure] is a eutectic structure including an Al phase, an MgZn 2 phase, and a Zn phase, and is clearly distinguished from the MgZn 2 phase contained as the main phase of the plating layer and the above-described Al phase in the reflected electron SEM image.

[0082] When the [Al / Zn / MgZn 2 ternary eutectic structure] including a Zn phase is present to some extent, sacrificial corrosion protection properties are secured and corrosion resistance at the end surface is improved. On the other hand, since water wet resistance and water flow resistance deteriorate, the [Al / Zn / MgZn 2 ternary eutectic structure] may be included in an area fraction of 60 area% or less in consideration of water wet resistance and water flow resistance. Further, the area fraction thereof may be 40 area% or less, 35 area% or less, or 30 area% or less. The lower limit of the area fraction of the [Al / Zn / MgZn 2 ternary eutectic structure] is not particularly limited, and may be 0%, 5 area% or more, 10 area% or more, or 15 area% or more.Mg 2 Zn 11 phase

[0083] The Mg 2 Zn 11 phase according to the embodiment is a region where Mg is contained in an amount of 5 mass% (±3%) and Zn is contained in an amount of 93 (±4%). The Mg 2 Zn 11 phase is often photographed in a gray having an intermediate color between the colors of Al and Zn, and brighter than the MgZn 2 phase, in a reflected electron image of SEM.

[0084] Since the Mg 2 Zn 11 phase is further poor in plastic deformability than the MgZn 2 phase, and it is preferable that the Mg 2 Zn 11 phase is not precipitated in the plating structure. That is, the existence form of Mg in the plating structure is preferably the MgZn 2 phase, the [Al / Zn / MgZn 2 ternary eutectic structure], or the Mg 2 Si phase to be described later. Specifically, in the X-ray diffraction intensity, the ratio between the diffraction intensity of the (322) plane of the Mg 2 Zn 11 phase (maximum intensity in the range of 43.60° ± 0.20°, hereinafter referred to as I(322) Mg2Zn11 ) and the diffraction intensity of the (201) plane of the MgZn 2 phase (maximum intensity in the range of 41.30° ± 0.20°, hereinafter referred to as I(201) MgZn2 ) satisfies I(322) Mg2Zn11 / I(201) MgZn2 / ≤ 0.2, and more preferably satisfies that of 0.1 or less. The composition of the plating bath and the cooling rate after pulling up from the plating bath affect the precipitation of the Mg 2 Zn 11 phase. The plated steel sheet produced in the embodiment satisfies I(322) Mg2Zn11 / I(201) MgZn2 / ≤ 0.2, and the percentage of the Mg 2 Zn 11 phase in the plating structure is less than 1 area%.

[0085] The above phases and microstructures constitute the main phase of the plating layer, and these constitute 90% or more of the plating layer in terms of area fraction. Meanwhile, when elements other than Zn, Mg, and Al are contained in the plating layer, other metal phases are formed. For example, Si forms a Mg 2 Si phase or the like, and Ca forms an Al-Zn-Ca phase or the like. The remainder in microstructure may include, as a typical composition, a Mg 2 Si phase, an AlZnCa phase, and an AlCaSi phase. Some of them are effective in improving weldability and corrosion resistance, but the effects thereof are not remarkable. In the composition of the plating layer, the total thereof is difficult to be more than 10 area%, and may be 10 area% or less.

[0086] Next, a case where the plated steel material of the embodiment is manufactured by a hot-dip plating method will be described. The plated steel material of the embodiment can be manufactured by either an immersion type plating method (batch type) or a continuous type plating method.

[0087] The size, shape, surface form, and the like of the steel material to be plated are not particularly limited. Ordinary steel material, high tensile strength steel, stainless steel, and the like are applicable as long as they are steel materials. A steel strip of general structural steel is most preferable. The surface may be finished by shot blasting, brush grinding, or the like in advance. There is no problem even if plating is performed after a metal film or an alloy film of Ni, Fe, Zn, Sn, plating, or the like is attached at a thickness of 3 g / m 2< or less to the surface. In addition, as a pretreatment for the steel material, it is preferable to sufficiently clean the steel material by degreasing and pickling.

[0088] After the surface of the steel material is sufficiently heated and reduced by a reducing gas such as H 2 , the steel material is immersed in a plating bath prepared to contain predetermined components. In high tensile strength steel and the like, it is common to humidify the atmosphere during annealing and to ensure plating adhesion of high Si, Mn steel and the like by utilizing an internal oxidation method and the like. By performing such a treatment, a plated steel material with less bare spots and fewer external appearance defects can be usually plated in a similar manner to a general steel material. In such a steel material, a steel material surface having a fine crystal grain size and an internal oxide film layer are observed on the base metal side, but they do not affect the performance of the present invention.

[0089] In the case of the hot-dip plating method, the components of the plating layer can be controlled by the components of the plating bath to be prepared. When a plating bath is prepared, an alloy having the plating bath components is prepared by mixing predetermined amounts of pure metals, for example, through a dissolution method under an inert atmosphere.

[0090] By immersing the steel material whose surface has been reduced in the plating bath maintained at a predetermined concentration, a plating layer having substantially the same components as those of the plating bath is formed. When the immersion time is prolonged or it takes a long time to complete the solidification, the formation of the interfacial alloy layer becomes active, so that the Fe concentration may increase. When the temperature is less than 500°C, the reaction with the plating layer rapidly slows down, so that the concentration of Fe contained in the plating layer ordinarily falls 5.0% or less.

[0091] In order to form a hot-dip plating layer, it is preferable to keep the plating bath at 450 to 550°C. Then, it is preferable to immerse the reduced steel material for several seconds. On the surface of the reduced steel material, Fe may diffuse into the plating bath and react with the plating bath to form an interfacial alloy layer at the interface between the plating layer and the steel material. The interfacial alloy layer is mainly an Al-Fe-based intermetallic compound layer (Al-Fe alloy layer). When the interfacial alloy layer (Al-Fe alloy layer) is formed, the steel material below the interfacial alloy layer (Al-Fe alloy layer) and the plating layer above are metal-chemically bonded to each other more firmly.

[0092] After the steel material is immersed in the plating bath for a predetermined time, the steel material is pulled up from the plating bath. When the metal attached to the surface is in a molten state, N 2 wiping is performed, whereby the thickness of the plating layer is adjusted to a predetermined thickness. The thickness of the plating layer is preferably adjusted to 10 to 70 µm. When the thickness is converted into the adhesion amount of the plating layer, the adhesion amount is 40 to 450 g / m 2< (one surface).

[0093] After adjusting the adhesion amount of the plating layer, the adhered molten metal is solidified. Cooling means in the solidification of the plating may be performed by blowing nitrogen, air, or a mixed gas of hydrogen and helium; mist cooling; or immersion in water. Mist cooling is preferable, and mist cooling in which water is contained in nitrogen is preferable. The cooling rate may be adjusted by the content of water.

[0094] In the embodiment, when cooling is performed under plating solidification conditions of ordinary operating conditions, for example, at an average cooling rate of 5 to 20 °C / sec between the plating bath temperature and 150°C, the microstructure cannot be controlled in some cases, and this may cause an unsatisfactory result in predetermined performance. Therefore, a cooling step capable of obtaining the plating layer of the embodiment will be described below.Average cooling rate between bath temperature and 380°C: more than 20 °C / sec and less than 50 °C / sec

[0095] Between the bath temperature and 380°C, the Al phase precipitates as a primary phase, and then the MgZn 2 phase precipitates. Even in the plating composition range of the present invention, when the supercooling degree is large, orientation planes other than the (100) plane of the Al phase tend to easily grow. Therefore, in order that the Al phase preferentially grows in the (100) plane, the average cooling rate needs to be less than 50 °C / sec, at least. On the other hand, when the cooling rate is 20 °C / sec or less in terms of average cooling rate, the Al primary crystal tends to become coarse, leading to deterioration of workability. Therefore, in the region between the bath temperature and 380°C, the average cooling rate needs to be more than 20 °C / sec and less than 50 °C / sec.Average cooling rate between 380°C and 300°C: 5 °C / sec or more and less than 15 °C / sec

[0096] Between 380°C and 300°C, the Al-Zn phase precipitates from the liquid phase, and the Zn-Al-MgZn 2 undergoes a ternary eutectic reaction, so that the liquid phase is no longer present and the plating layer is completely solidified. In the temperature range between 380°C and 300°C, the Mg 2 Zn 11 phase may be formed when the supercooling degree is large. Since workability tends to deteriorate when the Mg 2 Zn 11 phase is precipitated, the average cooling rate between 380°C and 300°C is preferably less than 15 °C / sec. On the other hand, when the average cooling rate is lower than 5 °C / sec, the Al phase is recrystallized, and the percentage of orientation planes other than the (100) plane increases, so that workability tends to deteriorate. Therefore, the average cooling rate is preferably 5 °C / sec or more and less than 15 °C / sec, and more preferably 5 °C / sec or more and 10 °C / sec or less.Average cooling rate between 300°C and 150°C: more than 10 °C / sec and 20 °C / sec or less

[0097] In the temperature range between 300°C and 150°C, the fine Zn phase incorporated into the Al-Zn phase is rapidly discharged from the Al-Zn phase. Therefore, when cooling is performed slowly in the temperature range, the Al primary crystal includes the Al phase in a large percentage. In particular, when the Al concentration is high, the tendency becomes strong, and when the cooling rate between 300 to 150°C is 20 °C / sec or less, the Al-Zn phase is separated into the Al phase and the Zn phase. On the other hand, when the cooling rate is 10 °C / sec or less, the ternary eutectic structure undergoes grain growth to form a coarse MgZn 2 phase or Mg 2 Zn 11 phase, so that workability tends to deteriorate. Therefore, in the temperature range between 300°C and 150°C, it is preferable to perform cooling at an average cooling rate of more than 10 °C / sec and 20 °C / sec or less.Temperature range of lower than 150°C

[0098] In the temperature range of less than 150°C in the solidification process, the cooling rate does not affect the constituent phase in the plating layer, and thus cooling conditions are not particularly limited, and natural cooling may be employed.

[0099] After the plating layer is cooled, various chemical conversion treatments and coating treatments may be performed. In addition, in order to further enhance corrosion resistance, repair touch-up paint, a thermal spraying treatment, and the like may be performed in a weld, a worked portion, and the like.

[0100] In the plated steel material of the embodiment, a film may be formed on the plating layer. A film having a single layer or two or more layers may be formed. Examples of the type of the film immediately above the plating layer include a chromate film, a phosphate film, and a chromate-free film. The chromate treatment, the phosphating treatment, and the chromate-free treatment for forming these films can be performed by known methods. It is noted that many chromate treatments may deteriorate weldability on the surface of the plating layer. Therefore, the thickness of the film is preferably less than 1 µm in order to sufficiently obtain weldability improving effect in the plating layer.

[0101] The chromate treatment includes an electrolytic chromate treatment in which a chromate film is formed by electrolysis, a reaction type chromate treatment in which a film is formed by utilizing a reaction with the material and then the excess treatment liquid is washed away, and an application type chromate treatment in which a film is formed by applying a treatment liquid to an object to be coated and drying the treatment liquid without washing with water. Any treatment may be adopted.

[0102] Examples of the electrolytic chromate treatment include an electrolytic chromate treatment using chromic acid, a silica sol, a resin (phosphoric acid, an acrylic resin, a vinyl ester resin, a vinyl acetate acrylic emulsion, a carboxylated styrene-butadiene latex, a diisopropanolamine-modified epoxy resin, and the like), and hard silica.

[0103] Examples of the phosphating treatment include a zinc phosphate treatment, a zinc calcium phosphate treatment, and a manganese phosphate treatment.

[0104] The chromate-free treatment, which does not impose a burden on the environment, is particularly suitable. The chromate-free treatment includes an electrolytic chromate-free treatment in which a chromate-free film is formed by electrolysis, a reaction type chromate-free treatment in which a film is formed by utilizing a reaction with the material and then the excess treatment liquid is washed away, and an application type chromate-free treatment in which a film is formed by applying a treatment liquid to an object to be coated and drying the treatment liquid without washing with water. Any treatment may be adopted.

[0105] Further, an organic resin film made of a single layer or two or more layers may be formed on the film immediately above the plating layer. The organic resin is not limited to a specific type, and examples thereof include polyester resins, polyurethane resins, epoxy resins, acrylic resins, polyolefin resins, and modified products of these resins. Here, the modified product refers to a resin obtained by causing a reactive functional group included in the structures of these resins to react with another compound (a monomer, a crosslinking agent, or the like) having a functional group capable of reacting with the functional group in the structure thereof.

[0106] As such an organic resin, one or more types of organic resins (unmodified organic resins) may be mixed and used, or one or more types of organic resins obtained by modifying, in the presence of at least one type of organic resin, at least one type of other organic resin may be mixed and used. The organic resin film may contain any coloring pigment or antirust pigment. Also, water-based organic resins, which are dissolved or dispersed in water, may be used.<Corrosion resistance evaluation>

[0107] The corrosion resistance of the plating layer can be evaluated by an accelerated corrosion test such as JASO. Specifically, the number of cycles (hours) until red rust occurs is compared. When the cycle is longer until red rust occurs, it is evaluated that corrosion resistance is good. When the cycle is shorter, it is evaluated that corrosion resistance is poor. Since the cycle until red rust occurs also varies depending on the adhesion amount of the plating layer, the plated steel materials to be compared preferably have a uniform adhesion amount.<Workability evaluation>

[0108] The workability of the plating layer can be evaluated by performing bending and measuring the number of cracks in the plating layer at the worked portion. The smaller the number of cracks in the plating layer, the better the workability. When there is no crack in the plating layer, wear of the plating layer due to sacrificial corrosion protection is suppressed, so that the corrosion resistance of the worked portion becomes high as same as the corrosion resistance of the flat portion.Examples

[0109] An original sheet of the plated steel material was cut out in a size of 180 mm × 100 mm from a cold-rolled steel sheet having a thickness of 0.8 mm. The original sheets were SS400 (general steel). A batch type hot-dip plating simulator (manufactured by RHESCA Co., Ltd.) was used. A K thermocouple was attached to a part of the steel sheet, and the sheet surface was sufficiently reduced by annealing at 800°C in a reducing atmosphere of N 2 containing 5% of H 2 . The steel sheet was immersed in a plating bath for 3 seconds and then pulled up, and the plating thickness was adjusted to be 20 µm (± 1 µm) by N 2 gas wiping. The plating had an equal thickness on the front surface and the back surface. After the steel material was pulled up from the plating bath, plated steel materials were manufactured under various cooling conditions of the following A to E.

[0110] Condition A: After the steel material was pulled up from the plating bath, the average cooling rate between the bath temperature and 380°C was 30 °C / sec, the average cooling rate between 380°C and 300°C was 5 °C / sec, and the average cooling rate between 300°C and 150°C was 15 °C / sec. Natural cooling was performed at 150°C or lower.

[0111] Condition B (comparative condition): After the steel material was pulled up from the plating bath, the average cooling rate between the bath temperature and 150°C was 20 °C / sec. Natural cooling was performed at 150°C or lower.

[0112] Condition C (comparative condition): After the steel material was pulled up from the plating bath, the average cooling rate between the bath temperature and 150°C was 2 °C / sec. Natural cooling was performed at 150°C or lower.

[0113] Condition D (comparative condition): After the steel material was pulled up from the plating bath, the average cooling rate between the bath temperature and 150°C was 60 °C / sec. Natural cooling was performed at 150°C or lower.

[0114] Condition E (comparative condition): After the steel material was pulled up from the plating bath, the average cooling rate between the bath temperature and 380°C was 30 °C / sec, the average cooling rate between 380°C and 300°C was 1 °C / sec, and the average cooling rate between 300°C and 150°C was 15 °C / sec. Natural cooling was performed at 150°C or lower.

[0115] The average chemical composition of the plating layer was measured as follows. The plating layer was peeled off and dissolved with an acid containing an inhibitor that suppresses corrosion of the base metal (steel material) to obtain an acid solution. Next, the obtained acid solution was measured by ICP emission spectrometry or ICP-MS to determine the average chemical composition of the plating layer. The results are shown in Tables 1A to 1F.

[0116] In the method for measuring the area fraction of the phases and microstructures (MgZn 2 phase, Al phase, Al-Zn phase [Al / Zn / MgZn 2 ternary eutectic structure], remainder in microstructure) in the plating layer, as described above, the cross section in the thickness direction of the plating layer perpendicular to the surface of the steel material was exposed, and the metallographic structure thereof was confirmed in a visual field at a magnification of 500 to 5000 times. Specifically, the metallographic structure was observed in a visual field of 25000 µm 2< in total, thereby determining the area fraction of the phases or microstructures constituting the metallographic structure of the plating layer. In order to confirm each phase, the composition of the phase was confirmed at pinpoint in the EDS analysis, and phases having substantially equivalent components were read from element mapping to specify the phase. Phases having substantially equivalent components were discriminated by element mapping.

[0117] For the area percentage of the Al phase having a circle equivalent diameter of 20 µm or less, in the EDS analysis on the observed visual field of 25000 µm 2< , the composition of the phase was confirmed at pinpoint, and phases having substantially equivalent components were read from element mapping to specify the Al phase. Next, the Al phase in the observed visual field was extracted by image processing, each crystal area was measured, and the equivalent circle diameter of each crystal was calculated. Then, the Al phase having a circle equivalent diameter of 20 µm or less was extracted, and the total area thereof was determined. Then, the area fraction (%) of the Al phase having a circle equivalent diameter of 20 µm or less based on the total area of the Al phase in the observed visual field was determined.

[0118] Further, an X-ray diffraction pattern of the surface of the plating layer was measured under the conditions of an X-ray output of 50 kV and 300 mA using a Cu-Kα ray, from which I(200) Al / {(I(111) Al + I(220) Al + I(200) Al + I(311) Al } defined in the formula (1) was determined. The measurement method was as follows. First, the surface of the plating layer was mechanically polished and chemically polished as necessary to bring the surface of the plating layer into a mirror surface state. Next, X-ray diffraction measurement was performed using an X-ray diffractometer (manufactured by Rigaku Corporation (model number RINT-TTR III) under the conditions of X-ray output: 50 kV and 300 mA; copper target; goniometer TTR (horizontal goniometer); slit width of Kβ filter: 0.05 mm; longitudinal limiting slit width: 2 mm; light receiving slit width: 8 mm; and light receiving slit 2: open, and under the measurement conditions of scan speed: 5 deg. / min; step width: 0.01 deg; and scan axis: 2θ (5 to 90°). Then, the diffraction intensity of the (200) of Al (maximum intensity in the range of 44.74° ± 0.20°), the diffraction intensity of the (111) of Al (maximum intensity in the range of 38.47° ± 0.20°), the diffraction intensity of the (220) of Al (maximum intensity in the range of 65.13° ± 0.20°), and the diffraction intensity of the (311) of Al (maximum intensity in the range of 78.23° ± 0.20°) were measured, respectively. The diffraction intensity was an intensity excluding the background intensity. From the obtained diffraction intensity, I 200 Al / I 111 Al + I 220 Al + I 200 Al + I 311 Al was determined. The results are shown in Tables 2A and 2B.(Corrosion resistance evaluation)

[0119] The test material was cut out into 50 × 100 mm, the end surface was not painted and sealed, and a combined cyclic test was performed in accordance with JASO M609 and M610 to evaluate corrosion resistance. Specifically, performed was a salting-drying-wetting repeating test in which salt water spraying, drying, and wetting were repeated. In the salting-drying-wetting repeating test, the test material was sprayed with a 5% NaCl aqueous solution (35°C for 2 hours), dried (relative humidity 30%, temperature 60°C for 4 hours), and wetted (relative humidity 95%, temperature 50°C for 2 hours), which was one cycle; and the test material was washed with water and dried every time the cycle was finished, and then the surface of the test material was observed and the area fraction of red rust was calculated. The area fraction of red rust was calculated as follows: the surface of the test material after the salting-drying-wetting repeating test was photographed; the photo was binarized by image analysis; the area per 1 pixel was calculated; and then the number of pixels at the rusted portion was counted. The area fraction of red rust was calculated by the following formula.

[0120] When the area fraction of red rust was 5% or more, it was determined that red rust was generated. Corrosion resistance was evaluated as follows. "B" was defined as unacceptable, and "A" to "S" were defined as acceptable. The results are shown in Tables 3A and 3B. B: Red rust was generated in less than 200 cycles. A: Red rust was generated in 200 cycles. AA: Red rust was generated in more than 200 to less than 350 cycles. AAA: Red rust was generated in 350 or more and less than 500 cycles. S: Red rust was not generated in 500 cycles. (Workability evaluation)

[0121] The test material was cut into a size of 30 mm (C direction) × 100 mm (L direction), and subjected to 5t180° bending. That is, when the test material was bent, 5 sheets as thick as the test material were sandwiched and 180° bending was performed. Thereafter, the number of cracks in the range of 30 mm × 1.6 mm at the top of the bent portion was measured with a stereoscopic microscope at a magnification of 40, and determined as follows. The results are shown in Table 3. B: The number of cracks: 30 or more A: The number of cracks: 20 or more and less than 30. AA: The number of cracks: 10 or more and less than 20 AAA: The number of cracks: 5 or more and less than 10 S: The number of cracks: less than 5.

[0122] As shown in Tables 1A to 3B, in No. 3 to 43, 53, and 54 (Examples), each of which was according to the present invention, the chemical composition and the metallographic structure of the plating layer were appropriately controlled, and both corrosion resistance and workability were excellent. The Mg 2 Zn 11 phase was not contained.

[0123] In Comparative Example No. 1, the Al amount and the Mg amount of the hot-dip plating layer were insufficient, and the content of Ti and Zr was 0%. I(200) Al / (I(111) Al + I(220) Al + I(200) Al + I(311) Al } was less than 0.40. Therefore, in No. 1, both corrosion resistance and workability were insufficient.

[0124] In Comparative Example No. 2, the Al amount of the hot-dip plating layer was insufficient, and the content of Ti and Zr was 0%. I(200) Al / {(I(111) Al + I(220) Al + I(200) Al + I(311) Al } was less than 0.40. Therefore, in No. 2, workability was insufficient.

[0125] In Comparative Example No. 44, the Al amount and the Mg amount in the hot-dip plating layer were excessively large. Therefore, in No. 44, both corrosion resistance and workability were insufficient.

[0126] In Comparative Example No. 45, the Al amount in the hot-dip plating layer was excessively large. No. 45 had insufficient corrosion resistance.

[0127] In Comparative Example No. 46, the content of Ti and Zr was 0% in the hot-dip plating layer. I(200) Al / {(I(111) Al + I(220) Al + I(200) Al + I(311) Al } was less than 0.40. Therefore, in No. 46, workability was insufficient.

[0128] In Comparative Example No. 47, the Ca amount in the hot-dip plating layer was excessively large. In addition, the manufacturing conditions were outside the range of the preferable conditions. In No. 47, both corrosion resistance and workability were insufficient.

[0129] In Comparative Examples No. 48, 49, and 50, the manufacturing conditions were outside the range of the preferable conditions. I(200) Al / {(I(111) Al + I(220) Al + I(200) Al + I(311) Al } was less than 0.40. Therefore, in No. 48, 49, and 50, workability deteriorated.

[0130] In Comparative Example No. 51, the Zr amount in the hot-dip plating layer was excessively large. Therefore, in No. 51, corrosion resistance was insufficient.

[0131] In Comparative Example No. 52, the Ti amount in the hot-dip plating layer was excessively large. Therefore, in No. 52, corrosion resistance was insufficient. [Table 1A]No.ClassificationBath temperature (°C)Manufacturing method classificationAverage chemical composition of plating layer (mass%) balance: impuritiesMain elementTiZrTi + ZrZn + Mg + AlZnAlMg1Comparative Example500A99.692.65.02.00002Comparative Example500A99.786.77.55.50003Example500A99.284.010.05.20.100.14Example500A99.183.610.05.50.050.0010.0515Example500A99.283.810.05.40.0200.026Example500A99.183.110.15.90.00100.0017Example550A98.081.910.16.00.020.020.048Example550A98.282.010.26.000.050.059Example500A99.178.714.95.50.100.110Example500A98.177.614.95.60.20.10.311Example500A98.477.514.96.00.010.20.2112Example500A98.277.215.06.00.10.30.413Example500A98.477.415.06.00.020.050.0714Example500A98.976.115.07.80.00500.00515Example500A98.975.815.18.000.0050.00516Example500A99.073.119.96.00.0100.0117Example500A98.972.820.06.100.10.118Example500A98.572.420.06.10.300.319Example550A98.170.220.07.90.30.050.3520Example550A97.769.720.08.00.0010.0010.00221Example550A98.570.420.18.00.050.010.0622Example500A98.667.824.95.90.0200.0223Example500A98.367.424.96.00.010.010.0224Example500A97.764.725.08.00.40.10.525Example500A97.664.525.08.10.0020.010.01226Example550A99.364.325.010.00.0100.01Underlined portions indicate that those are outside the scope of the present invention. [Table 1B] No.ClassificationBath temperature (°C)Manufacturing method classificationAverage chemical composition of plating layer (mass%) balance: impuritiesMain elementTiZrTi + ZrZn + Mg + AlZnAlMg27Example550A97.262.125.010.10.010.40.4128Example550A95.759.829.96.000.010.0129Example550A98.062.030.06.00.10.010.1130Example550A96.760.630.06.10.050.20.2531Example500A97.759.730.08.00.200.232Example500A99.060.930.18.000.020.0233Example550A96.256.130.110.00.0020.010.01234Example550A98.357.434.96.00.070.020.0935Example550A98.257.234.96.10.0500.0536Example550A94.751.935.07.800.050.0537Example550A95.850.835.010.00.020.10.1238Example550A98.751.235.012.50.0010.0050.00639Example600A97.552.239.85.501.01.040Example600A96.851.139.95.80.20.50.741Example600A97.151.239.96.00.10.30.442Example550A97.050.040.07.000.0010.00143Example550A97.550.540.07.01.001.044Comparative Example600A98.440.445.013.000045Comparative Example600A99.248.645.15.50.0100.0146Comparative Example550A99.183.210.05.900047Comparative Example500B95.579.510.06.00.0500.0548Comparative Example500C98.177.115.06.00.0050.0010.00649Comparative Example550D96.174.215.16.80.100.150Comparative Example600E98.971.920.07.000.010.0151Comparative Example550A97.561.530.06.001.21.252Comparative Example550A96.853.835.08.01.201.253Example550A98.271.320.06.90.500.554Example550A97.560.530.07.00.50.20.7 Underlined portions indicate that those are outside the scope of the present invention. [Table 1C] No.ClassificationAverage chemical composition of plating layer (mass%) balance: impuritiesElement group AElement group BElement group CSiCaYLaCeSrSnBiInBP1Comparative Example000000000002Comparative Example000000000003Example0.1000000000004Example00.1000000.050.050.05005Example00.1000000.0500.05006Example00.1000000.100000.017Example00.2000000.2000008Example00.400000.100.4000009Example0.20000000000010Example0.200.3000000.50000011Example0.200.300000000.250012Example0.200.30000000.2500.05013Example0.200.3000000.50000014Example00.5000000000015Example00.2000000000016Example0.30000000000017Example0.300.2000000000018Example0.300.2000000.10000019Example00.6000000000020Example0.200.2000000.50000.10021Example00.3000000.10000022Example0.30000000.100.10000.00523Example0.500.4000000000024Example0.200.2000000.80000025Example0.200.5000001.00000026Example00.10000000000 [Table 1D] No.ClassificationAverage chemical composition of plating layer (mass%) balance: impuritiesElement group AElement group BElement group CSiCaYLaCeSrSnBiInBP27Example0.100.100.010001.50000028Example0.2000.200.10002.50000029Example0.400.5000000000030Example0.6000.4000000.8000031Example0.80000.1000.200000032Example0000000000033Example0.201.5000.010.010000.800.05034Example0.100000000.4000035Example0.50000000000036Example3.000.2000.200.200000.5000.00537Example2.00000.400.40000.100.100038Example00.2000000000039Example000000.200000040Example000000.400.100.200.100041Example1.200.0500000000042Example1.200.5000000000043Example00.3000000000044Comparative Example0.20000000000045Comparative Example0000000000046Comparative Example0000.10000000047Comparative Example03.50000.2000000048Comparative Example0.200.200000.500000049Comparative Example2.00000001.00000050Comparative Example0.100.1000000000051Comparative Example0.100.1000000000052Comparative Example0.100.2000000.50000053Example0.200.200000000.050.12054Example0.400.2000000.10000.120 Underlined portions indicate that those are outside the scope of the present invention. [Table 1E] No.ClassificationAverage chemical composition of plating layer (mass%) balance: impuritiesElement group DElement group ECrVNiCoNbCuMnMoWAgLiNaBaKFeSbPb1Comparative Example000000000000000.30.0102Comparative Example000000000000000.3003Example000.10000000000000.5004Example000.10000000000000.50.0205Example00.100000000000000.5006Example0.1000.10000000000000.5007Example0.2000.80000000000000.500.018Example000.200000000.1000000.5009Example000000000000000.60010Example000000000000000.60011Example0.010000000000.010000.60012Example000000000000000.60013Example000000000000000.50014Example000000000000000.50015Example000000.10000000000.500.2016Example00.100000000000000.50017Example000000000000000.50018Example000000000.05000000.50019Example000000.35000000.01000.50020Example0.200.100000000000000.50.40021Example000000.05000000000.500.4022Example0000.1000000000000.50.20023Example0000.2000000000000.50024Example00.010000000000000.50025Example00.05000000.100000000.50026Example000000000000000.500 [Table 1F] No.ClassificationAverage chemical composition of plating layer (mass%) balance: impuritiesElement group DElement group ECrVNiCoNbCuMnMoWAgLiNaBaKFeSbPb27Example0000000.100000000.010.50028Example0000000.2000000000.90.05029Example000000000000001.00030Example00.2000000000000.1001.00031Example000000000000001.00032Example000000000000001.00033Example00.200000000000001.00034Example000000000000001.10035Example00000.100000000001.10036Example0.0500000000000001.10037Example000000000000001.10038Example000000000000001.10039Example00000.100000000001.20040Example0.200000.2000000.0500001.20041Example000000000000001.20042Example000000000000001.20043Example0000001000000001.20044Comparative Example000000000000001.30045Comparative Example000000000000000.80046Comparative Example000000000000000.80047Comparative Example000000000000000.80048Comparative Example00.200000000000000.80049Comparative Example000000000000000.80050Comparative Example0.0500000000000000.800.0551Comparative Example0000000.1000000001.00.05052Comparative Example000000.050000.0500001.10053Example000000000000000.70054Example000000000000001.000 [Table 2A] No.ClassificationPlating layer structureMgZn 2 phaseAl primary crystalArea fraction of Al primary crystal having a grain size of 20 µm or lessX-ray intensity ratioTernary eutectic structure (area%)Balance (area%)(area%)Al-Zn phase (area%)Al phase (area%)Total(%)I (200) / (I (111) + I (220) + I (200) + I (311))1Comparative Example510010300.108052Comparative Example2010010300.106553Example1515520600.456054Example25101020400.405055Example25101020500.405056Example30101020400.404557Example30101020500.404558Example3010515500.405059Example20201030500.4045510Example20201030600.5045511Example30151530600.4535512Example30151530700.5035513Example30151530500.4035514Example40101525400.4030515Example40101525400.4030516Example35152035400.4025517Example35152035500.4025518Example35152035500.5025519Example45102535600.5015520Example45102535500.4015521Example45102535500.4015522Example35153045500.4515523Example35153045500.4515524Example40153045600.6010525Example40153045400.4510526Example45153045400.4555 Underlined portions indicate that those are outside the scope of the present invention. [Table 2B] No.ClassificationPlating layer structureMgZn 2 phaseAl primary crystalArea fraction of Al primary crystal having a grain size of 20 µm or lessX-ray intensity ratioTernary eutectic structure (area%)Balance (area%)(area%)Al-Zn phase (area%)Al phase (area%)Total(%)I (200) / (I (111) + I (220) + I (200) + I (311))27Example45153045600.555528Example35104050400.4510529Example35104050500.4510530Example35104050600.5510531Example4554045600.555532Example4554045500.455533Example4554045500.455534Example35105060500.500535Example35105060500.500536Example4055055500.500537Example4554550500.500538Example5054045400.600539Example25106070700.650540Example30105565700.650541Example30105565600.650542Example30105565400.550543Example30105565700.650544Comparative Example5553540300.400545Comparative Example2057075400.550546Comparative Example20101020300.3055547Comparative Example1551520200.40551048Comparative Example30102030100.2535549Comparative Example30151530500.3035550Comparative Example40152035500.1520551Comparative Example35104050600.7010552Comparative Example4055055600.700553Example40152540900.6515554Example40550551000.7005 Underlined portions indicate that those are outside the scope of the present invention. [Table 3A] No.ClassificationPerformanceCorrosion resistanceWorkability1Comparative ExampleBB2Comparative ExampleAB3ExampleAAAAA4ExampleSA5ExampleSAA6ExampleAAAA7ExampleSAA8ExampleSAA9ExampleAAAA10ExampleAAAS11ExampleSAAA12ExampleSS13ExampleSAAA14ExampleSA15ExampleSA16ExampleAAAAA17ExampleAAAAAA18ExampleSS19ExampleSAAA20ExampleSAAA21ExampleSAA22ExampleAAAAAA23ExampleAAAAAA24ExampleSS25ExampleSAA26ExampleAAAA [Table 3B] No.ClassificationPerformanceCorrosion resistanceWorkability27ExampleSS28ExampleAAAAA29ExampleAAAAA30ExampleAAAS31ExampleAAAS32ExampleAAAAA33ExampleSAAA34ExampleAAAS35ExampleAAS36ExampleAAAS37ExampleSS38ExampleAAAAA39ExampleAAAA40ExampleAAAAA41ExampleAAS42ExampleAAAAA43ExampleAAAAA44Comparative ExampleBB45Comparative ExampleBAA46Comparative ExampleAAB47Comparative ExampleBB48Comparative ExampleAAAB49Comparative ExampleSB50Comparative ExampleAAAB51Comparative ExampleBS52Comparative ExampleBS53ExampleSS54ExampleAAAS INDUSTRIAL APPLICABILITY

[0132] The present invention is industrially applicable in that it is possible to provide a plated steel material excellent in corrosion resistance and also excellent in the workability of the plating layer thereof.REFERENCE SIGNS LIST

[0133] 1Plated steel material 11Steel material 12Plating layer

Claims

1. A plated steel material comprising: a steel material; and a plating layer on the steel material, wherein the plating layer includes, as an average chemical composition, in terms of mass%, 10.0 to 40.0% of Al, 5.0 to 12.5% of Mg, 0 to 1.0% of Ti, 0 to 1.0% of Zr, 0 to 5.00% of Si, 0 to 3.00% of Ca, 0 to 0.50% of Y, 0 to 0.50% of La, 0 to 0.50% of Ce, 0 to 0.50% of Sr, 0 to 3.00% of Sn, 0 to 1.00% of Bi, 0 to 1.00% of In, 0 to 1.00% of B, 0 to 0.50% of P, 0 to 0.25% of Cr, 0 to 0.25% of V, 0 to 1.0% of Ni, 0 to 0.25% of Co, 0 to 0.25% of Nb, 0 to 1.0% of Cu, 0 to 0.25% of Mn, 0 to 0.25% of Mo, 0 to 0.25% of W, 0 to 1.00% of Ag, 0 to 0.50% of Li, 0 to 0.05% of Na, 0 to 0.25% of Ba, 0 to 0.05% of K, 0 to 5.0% of Fe, 0 to 0.50% of Sb, 0 to 0.50% of Pb, and a balance including 50.0% or more of Zn and impurities; the plating layer includes Ti and Zr in a total amount of 0.001 % or more; and the plating layer has a diffraction intensity satisfying a formula (1) below, the diffraction intensity being obtained from an X-ray diffraction measurement result: I 200 Al / I 111 Al + I 220 Al + I 200 Al + I 311 Al ≥ 0.40 wherein, in the formula (1), I(200)Al is a diffraction intensity of (200) of Al, I(111)Al is a diffraction intensity of (111) of Al, I(220)Al is a diffraction intensity of (220) of Al, and I(311)Al is a diffraction intensity of (311) of Al.

2. The plated steel material according to claim 1, wherein the plating layer includes Ti and Zr in a total amount of 0.020% or more.

3. The plated steel material according to claim 1 or 2, wherein a total area of an Al phase having a circle equivalent diameter of 20 µm or less is included in a ratio of 50% or more based on a total area of an Al phase in a cross section in a thickness direction of the plating layer.

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