Hot-dip plated steel sheet

Abstract

A hot dipped steel sheet wherein a plating layer comprises Al in an amount of greater than 30.0% but not more than 50.0%, Mg in an amount of greater than 5.0% but not more than 15.0%, Si in an amount of greater than 0.5% but not more than 1.0% when the Al is greater than 30.0% but less than 35.0% and in an amount of 0.03-1.0% when the Al is 35.0-50%, and Fe in an amount of 0-5.0%, with the remainder being Zn and impurities. In an X-ray diffraction pattern of the surface of the plating layer, I1 determined from the X-ray diffraction peak of MgZn2, Al, and Zn is not more than 0.10, and I2 determined from the X-ray diffraction peak of Al2O5Si is not less than 1.05.

Description

Hot-dip galvanized steel sheet

[0001] This application claims priority to Japanese Patent Application No. 2022-024939, filed on February 21, 2022, the contents of which are incorporated herein by reference.

[0002] Plated steel products are classified into post-plated products and pre-plated products depending on the manufacturing method. Post-plated products are manufactured by processing a steel sheet into a steel material of a predetermined shape, and then immersing the steel material in a hot-dip galvanizing bath (dip galvanizing method). On the other hand, pre-plated products are manufactured by continuously immersing a steel sheet in a hot-dip galvanizing bath to form a hot-dip plated steel sheet, and then processing the hot-dip plated steel sheet into a predetermined shape. JIS H 8641:2007 specifies the type, symbol, plating quality, appearance, and coating weight for post-plated products. For example, a coating with the symbol HDZ35 has a coating weight of 350 g / m ２ The coating weight of the HDZ55 plating is 550 g / m ２ That is said to be the case.

[0003] Such plated steel is used in a variety of applications, including underwater applications where the corrosive environment is particularly severe. Examples of applications for such plated steel include steel water channels and drainage gutters. According to the website "About Zinc Plating" of the Japan Hot Dip Galvanizing Association, the corrosion rate of zinc in water is 30 to 100 g / m. ２ This means that even for post-plated products with a relatively thick plating thickness equivalent to HDZ35-55, the plating layer will reach the end of its life in as little as 3-5 years.

[0004] Therefore, for applications in underwater environments or applications where water exposure is likely, a thick coating is required, and for such applications, post-plated products manufactured by the hot-dip dipping method are often used. On the other hand, pre-plated products are made from hot-dip galvanized steel sheets or zinc alloy-plated steel sheets manufactured by steel manufacturers, but the coating thickness of these plated steel sheets is about one-third of the coating thickness of post-plated products, which is extremely disadvantageous in terms of durability in underwater environments or environments where water exposure is likely.

[0005] The present inventors have been studying the application of pre-plated products as plated steel materials to be used in underwater environments or environments where water exposure occurs. For example, they have developed zinc-based plated steel sheets as shown in Patent Documents 1 to 3. As a result, corrosion resistance in underwater and water-wet applications has been ensured, but there is room for further improvement. If corrosion resistance in underwater and water-wet environments can be further improved, it is expected that pre-plated products will be more widely adopted as plated steel materials to be used in ponds, rivers, seashores, etc.

[0006] International Publication No. WO 2018 / 139619 International Publication No. WO 2018 / 139620 International Publication No. WO 2019 / 221193

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a hot-dip galvanized steel sheet that can exhibit high corrosion resistance in water or in a constantly wet environment where water wetting may occur.

[0008] In order to solve the above problems, the present invention employs the following configuration. [1] A hot-dip galvanized steel sheet having a coating layer on a steel sheet surface, wherein the coating layer has an average chemical composition, in mass%, of Al: more than 30.0% and not more than 50.0%, Mg: more than 5.0% and not more than 15.0%, Sn: 0% or more and not more than 0.70%, Bi: 0% or more and not more than 0.30%, In: 0% or more and not more than 0.30%, Ca: 0.03% or more and not more than 0.60%, Y: 0% or more and not more than 0.30%, La: 0% or more and not more than 0.30%, Ce: 0% or more and not more than 0.30%, Si: more than 0.5% and not more than 1.0% when Al is more than 30.0% and less than 35.0%, and 0.03% or more and not more than 1.0% when Al is 35.0% or more and not more than 50.0%, Cr: 0% or more and not more than 0.25%, Ti: 0% or more, 0.25% or less, Ni: 0% or more, 1.0% 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, Cu: 0% or more, 0.25% or less, Mn: 0% or more, 0.25% or less, Fe: 0% or more, 5.0% or less, Sr: 0% or more, 0.5% or less, Sb: 0% or more, 0.5% or less, Pb: 0% or more, 0.5% or less, B: 0% or more, 0.5% or less, Li: 0% or more, 0.5% or less, Zr: 0% or more, 0.5% or less, Mo: 0% or more, 0.5% or less, W : 0% or more, 0.5% or less, Ag: 0% or more, 0.5% or less, P the balance consisting of Zn and impurities; the total amount ΣA of Sn, Bi and In is 0% or more and 0.70% or less; the total amount ΣB of Ca, Y, La and Ce is 0.03% or more and 0.60% or less; the total amount ΣC of Cr, Ti, Ni, Co, V, Nb, Cu and Mn is 0% or more and 1.00% or less; the total amount ΣD of Sr, Sb, Pb, B, Li, Zr, Mo, W, Ag and P is 0% or more and 0.5% or less; and the following formulas (1) to (3) are satisfied: In an X-ray diffraction pattern of the surface of the plating layer measured using Cu-Kα rays under conditions of an X-ray output of 50 kV and 300 mA, Zn, Al and MgZn are not present. ２ I obtained from the X-ray diffraction peak １ is defined by formula (A-1), formula (A-2) is satisfied, and Al ２ O５ I obtained from the X-ray diffraction peak of Si ２ A hot-dip galvanized steel sheet that satisfies the following formula (B-2) when the above formula (B-1) is defined as Sn≦Si (1), 15≦Mg / Si (2), and 1.0≦Si / Ca≦5.0 (3). In the formulas (1) to (3), Sn, Si, Mg, and Ca are the contents (mass%) of each element in the plating layer, and Imax (k to m°) in formulas (A-1) and (B-1) is the maximum value of the X-ray diffraction intensity between diffraction angles k and m°, Imax (n°) is the X-ray diffraction intensity at a diffraction angle n°, and k, m, and n are the diffraction angles shown in formulas (A-1) and (B-1), respectively. [2] In the X-ray diffraction pattern of the plating layer surface measured using Cu-Kα radiation under conditions of an X-ray output of 50 kV and 300 mA, MgZn ２ I obtained from the X-ray diffraction peak ３ The hot-dip galvanized steel sheet according to [1], wherein when defined by formula (C-1), formula (C-2) is satisfied. Here, Imax (k to m°) in formula (C-1) is the maximum value of the X-ray diffraction intensity between diffraction angles k and m°, and k and m are the diffraction angles shown in formula (C-1).

[0009] According to the present invention, it is possible to provide a hot-dip galvanized steel sheet that can exhibit high corrosion resistance in water (in simulated acid rain or salt water such as seawater) or in a constantly wet environment where water exposure may occur. In the following description, "in simulated acid rain" may refer to water with a relatively low salt concentration, and "seawater (salt water)" may refer to water with a relatively high salt concentration.

[0010] FIG. 1 is a schematic diagram illustrating formula (B-1).

[0011] The present inventors have conducted extensive research to improve the corrosion resistance of a hot-dip galvanized steel sheet provided with a plating layer containing Al, Mg, and Zn and produced by a continuous hot-dip galvanizing method in a constantly water-wet environment.

[0012] When a coating layer contains Zn, a Zn phase may be formed in the structure of the coating layer. The Zn phase is susceptible to corrosion in water, and corrosion will continue until the Zn phase disappears, so this phase must not be the main phase of the coating layer. Various intermetallic compound phases are found in coating layers containing Al, Mg, and Zn. In the present invention, the chemical composition is adjusted, and the amount of Al in particular is increased, in order to limit the amount of Zn phase.

[0013] When the amount of Al is increased, a large amount of Al phase is formed in the structure of the plating layer. In water with a relatively low salt concentration, such as soft water, hard water, or acid rain, the Al phase has excellent corrosion resistance, so Al may be contained. The reason why the Al phase has excellent water resistance is that Al is deposited on the surface of the Al. ２ O ３ This is thought to be due to the formation of an alumina coating such as the one shown in Figure 1. However, when the amount of Al is low, the effect of this coating is insufficient, so the surface must be covered with an oxide that is stable in water. To achieve this, it is effective to add Si, which is also stable as an oxide, to the plating layer, and the inclusion of an Al-Si-O compound ensures corrosion resistance in water.

[0014] On the other hand, since Al is easily corroded in seawater containing salt, the Al content must be limited. In order to improve corrosion resistance to saltwater while keeping the Al content high, it is preferable to increase the proportion of compounds with complex crystal structures such as intermetallic compounds. For example, MgZn ２ However, it is preferable to include a large amount of MgZn phase. ２ When a large amount of phase is contained, MgZn of a specific plane orientation such as that contained in a ternary eutectic structure is used. ２ Reduce the amount of coarse grain MgZn ２ It is necessary to grow the phase large. MgZn, which exists in the ternary eutectic together with Zn phase, Al phase, etc. ２ Many of the phases are susceptible to corrosion. This is due to the active coupling reaction with the surrounding structure and the specific MgZn ２ The reason is thought to be that the orientation of the MgZn phase exists in this ternary eutectic structure. ２By limiting the phase, it is possible to achieve extremely high corrosion resistance even in salt water.

[0015] On the other hand, if a coating bath containing Al, Mg, and Zn contains a large amount of Al, when a steel sheet is immersed in the coating bath, the iron contained in the steel sheet reacts with the Al in the coating bath to produce an Fe-Al compound, which forms an interfacial alloy layer between the coating layer and the steel sheet. If the interfacial alloy layer is formed too thick, the coating layer becomes relatively thin, and sufficient corrosion resistance cannot be obtained. In addition, the adhesion of the coating layer decreases. Therefore, in order to produce a hot-dip coated steel sheet according to the present invention, it is necessary to devise a way to minimize the formation of the interfacial alloy layer.

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

[0017] A hot-dip galvanized steel sheet according to an embodiment of the present invention is a hot-dip galvanized steel sheet having a coating layer on a steel sheet surface, and the coating layer has an average chemical composition, in mass %, of Al: more than 30.0% and not more than 50.0%, Mg: more than 5.0% and not more than 15.0%, Sn: 0% or more and not more than 0.70%, Bi: 0% or more and not more than 0.3%, In: 0% or more and not more than 0.3%, Ca: 0.03% or more and not more than 0.60%, Y: 0% or more and not more than 0.3%, La: 0% or more and not more than 0.3%, Ce: 0% or more and not more than 0.3%, Si : when Al is more than 30.0% and less than 35.0%, it is more than 0.5% and 1.0% or less; when Al is 35.0% or more and less than 50.0%, it is 0.03% or more and 1.0% or less; Cr: 0% or more and 0.25% or less; Ti: 0% or more and 0.25% or less; Ni: 0% or more and 1.0% or less; Co: 0% or more and 0.25% or less; V: 0% or more and 0.25% or less; Nb: 0% or more and 0.25% or less; Cu: 0% or more and 0.25% or less; Mn: 0% or more and 0.25% or less; Fe: 0% or more and 5.0% or more Sr: 0% or more and 0.5% or less, Sb: 0% or more and 0.5% or less, Pb: 0% or more and 0.5% or less, B: 0% or more and 0.5% or less, Li: 0% or more and 0.5% or less, Zr: 0% or more and 0.5% or less, Mo: 0% or more and 0.5% or less, W: 0% or more and 0.5% or less, Ag: 0% or more and 0.5% or less, P: 0% or more and 0.5% or less, the balance being Zn and impurities, and the total amount ΣA of Sn, Bi and In is 0% or more and 0.70% or less, and the total amount ΣA of Ca, Y, La and The total amount ΣB of Ce is 0.03% or more and 0.60% or less, the total amount ΣC of Cr, Ti, Ni, Co, V, Nb, Cu and Mn is 0% or more and 1.00% or less, the total amount ΣD of Sr, Sb, Pb, B, Li, Zr, Mo, W, Ag and P is 0% or more and 0.5% or less, and the following formulas (1) to (3) are satisfied. In the X-ray diffraction pattern of the plating layer surface measured using Cu-Kα rays under conditions of an X-ray output of 50 kV and 300 mA, ２ I obtained from the X-ray diffraction peak １ is defined by formula (A-1), formula (A-2) is satisfied, and Al ２ O ５ I obtained from the X-ray diffraction peak of Si ２ is defined by formula (B-1), formula (B-2) is satisfied.

[0018]

[0019] In formulas (1) to (3), Sn, Si, Mg, and Ca are the contents (mass%) of each element in the plating layer, Imax (k to m°) in formulas (A-1) and (B-1) is the maximum value of the X-ray diffraction intensity between diffraction angles k and m°, Imax (n°) is the X-ray diffraction intensity at a diffraction angle n°, and k, m, and n are the diffraction angles shown in formulas (A-1) and (B-1), respectively.

[0020] In the following description, the "%" used to indicate the content of each element in the chemical composition means "mass %." A numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. When "greater than" or "less than" is added to the numerical values ​​before and after "to," the numerical range does not include these numerical values ​​as the lower or upper limit.

[0021] Furthermore, "corrosion resistance" refers to the corrosion resistance of the plating layer itself. Because a Zn-based plating layer has a sacrificial corrosion protection effect on steel materials, the plating layer corrodes and turns into white rust before the steel material corrodes, and after the white rusted plating layer disappears, the steel material corrodes and turns into red rust, which is the corrosion process of plated steel sheets.

[0022] The steel sheets to be plated are explained below. The steel sheets are mainly in the form of plates, but there are no particular restrictions on their size. These are plates produced by a normal hot-dip galvanizing process, such as continuous hot-dip galvanizing lines (CGLs), where the steel is immersed in molten metal and solidified. By processing (including welding) and combining these plates, they can be processed into a variety of products, and it is possible to manufacture steel structural members (pre-plated products) with excellent corrosion resistance.

[0023] There are no particular limitations on the material of the base sheet of the steel sheet. 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 (steels containing elements that strengthen corrosion resistance, such as Ni and Cr). Furthermore, there are no particular limitations on the conditions for the steel sheet, such as the manufacturing method (blast furnace material, electric furnace material) and the manufacturing method (hot rolling method, pickling method, cold rolling method, etc.).

[0024] Next, the plating layer will be described. The plating layer according to this embodiment includes a Zn-Al-Mg alloy layer. Adding alloying elements such as Al and Mg to Zn improves corrosion resistance, so a thin film, for example, about half the thickness of a typical Zn plating layer, can provide equivalent corrosion resistance. Similarly, the present invention also ensures corrosion resistance equivalent to or greater than that of a Zn plating layer with a thin film. The plating layer may also include an Al-Fe alloy layer.

[0025] The Zn—Al—Mg alloy layer is made of a Zn—Al—Mg alloy, which means a ternary alloy containing Zn, Al, and Mg.

[0026] The Al--Fe alloy layer is an interface alloy layer between the steel material and the Zn--Al--Mg alloy layer.

[0027] That is, the plating layer may have a single-layer structure of a Zn—Al—Mg alloy layer, or a laminate structure including a Zn—Al—Mg alloy layer and an Al—Fe alloy layer. In the case of a laminate structure, the Zn—Al—Mg alloy layer is preferably a layer that forms the surface of the plating layer.

[0028] As will be described later, when a hot-dip galvanized steel sheet or hot-dip zinc alloy-plated steel sheet manufactured by CGL is used as the base sheet for plating, traces of the interface alloy layer formed when the steel sheet was immersed remain. On the other hand, when an electrogalvanized steel sheet or the like is used as the base sheet for plating, traces of the interface alloy layer and the like almost disappear, and the Al-Fe alloy layer and the like may hardly be visible. Furthermore, when a Ni pre-plated steel sheet or a steel sheet containing Sn, Cr, or the like is used as the base sheet for plating, these metals may be mixed into the interface alloy layer.

[0029] The Al-Fe alloy layer bonds the steel material and the Zn-Al-Mg alloy layer. The thickness of the interfacial alloy layer can be controlled in any way by controlling the plating bath temperature, plating bath immersion time, line speed, and wiping pressure during the production of the plated steel material. Typically, in hot-dip plated steel sheet manufacturing methods centered on the Sendzimir process, the Zn-Al-Mg alloy layer constitutes the majority of the plating layer, and the thickness of the Al-Fe alloy layer is sufficiently small, so that it has little effect on the corrosion resistance of the plating layer. Furthermore, since it is formed near the interface, it has almost no effect on the corrosion resistance in the initial stage of corrosion or the appearance of the plating layer. Therefore, even when a steel sheet that has been plated once using CGL or the like is used and then immersed again in the plating bath of the present invention, the thickness of the interfacial alloy layer is often sufficiently small, making it difficult to identify any traces of the interfacial alloy layer.

[0030] The Al-Fe alloy layer is formed on the surface of the steel sheet (specifically, between the steel sheet and the Zn-Al-Mg alloy layer), and has an Al structure. ５ Fe ２ The Al-Fe alloy layer is formed by mutual atomic diffusion between the base steel (steel sheet) and the coating bath. When a continuous hot-dip coating method is used as the manufacturing method, an Al-Fe alloy layer is likely to be formed in a coating layer containing Al element. In the present invention, since the coating bath contains Al at a certain concentration or more, the Al-Fe alloy layer is easily formed. ５ Fe ２ However, atomic diffusion takes time, and the Fe concentration is high in some areas near the base steel. Therefore, the Al-Fe alloy layer is partially composed of AlFe phase, Al ３ Fe phase, Al ５ Fe ２ In addition, since the plating bath also contains a certain concentration of Zn, the Al-Fe alloy layer also contains a small amount of Zn and / or Si, which tends to accumulate at the interface.

[0031] In the present invention, the plating layer contains Si. Si is particularly likely to be incorporated into an Al-Fe alloy layer, and may form an Al-Fe-Si intermetallic compound phase. The intermetallic compound phase that can be identified is 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 alloy layer. An Al-Fe alloy layer containing these AlFeSi phases is also referred to as an Al-Fe-Si alloy layer.

[0032] Furthermore, when a steel sheet with a pre-plated layer is used as the base sheet for plating, elements such as Ni, Sn, and Cr that constituted the pre-plated layer may remain in the form of a layer in the interface alloy layer. Elements with particularly high melting points tend to remain in the form of a layer in the interface alloy layer, and may be mixed into the Al-Fe alloy layer or may exist as intermetallic compounds containing these elements. Low-melting-point metals such as Sn do not leave traces easily, and may not be identified.

[0033] The thickness of the entire plating layer depends on the plating conditions, and therefore there are no particular limitations on the upper and lower limits of the thickness of the entire plating layer. For example, in a typical hot-dip plating method, the thickness of the entire plating layer is related to the viscosity and specific gravity of the plating bath. Furthermore, the coating weight is adjusted by the drawing speed of the steel sheet (base sheet for plating) and the strength of wiping. The maximum thickness of the plating layer formed by a typical hot-dip plating method is often 100 μm or less in continuous hot-dip plating and 200 μm or less in batch-type plating.

[0034] Preferably, an oxide film of the constituent elements of the plating layer is formed on the outermost surface of the plating layer, with a thickness of less than 1 μm. Typically, elements contained in the plating layer bond with oxygen on the plating layer surface, resulting in the presence of a thin oxide film in which bonds such as Zn—O, Mg—O, Al—O, Si—O, and Ca—O, or Mg—Al—O and Al—Si—O, etc., are confirmed by surface analysis such as XPS (X-ray spectroscopy). Elements that are relatively easily oxidized tend to be present on the plating surface. These oxides are useful for ensuring high corrosion resistance in water, but because they are extremely thin, less than 1 μm, it is difficult to accurately confirm their function using an electron microscope or the like. In the present invention, their presence is confirmed by X-ray diffraction measurement, as described below.

[0035] Next, the average chemical composition of the plating layer will be described. When the plating layer has a single-layer structure of a 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 laminated structure of an Al—Fe alloy layer and a Zn—Al—Mg alloy layer, the average chemical composition is the combined average chemical composition of the Al—Fe alloy layer and the Zn—Al—Mg alloy layer.

[0036] Typically, in continuous hot-dip galvanizing processes, the chemical composition of the Zn—Al—Mg alloy layer is almost identical to that of the coating bath because the reaction for forming the coating layer is almost always completed within the coating bath. Furthermore, in continuous hot-dip galvanizing processes, the Al—Fe alloy layer is instantly formed and grows immediately after immersion in the coating bath. The reaction for forming the Al—Fe alloy layer is already completed within the coating bath, and its thickness is often sufficiently smaller than that of the Zn—Al—Mg alloy layer. Therefore, unless special heat treatment such as a thermal alloying treatment is performed after coating, the average chemical composition of the entire coating layer is substantially identical to that of the Zn—Al—Mg alloy layer, and components such as the Al—Fe alloy layer can be ignored.

[0037] Al: more than 30.0% and 50.0% or less. Al is an element that mainly constitutes the coating layer. In Zn-Al-Mg coatings, it mainly forms an Al phase in the coating layer. If the Al content is 30.0% or less, a Zn phase and a ternary eutectic structure (Zn phase, Al phase, MgZn phase) are formed during the solidification process of the coating layer. ２ Zn / Al / MgZn containing phase ２ The Zn phase and the MgZn contained in the ternary eutectic structure are formed. ２ The Al content is set to more than 30.0% to prevent the formation of a Zn phase or a ternary eutectic structure. On the other hand, if the Al content exceeds 50.0%, the melting point of the coating bath increases, which activates the growth of the Al-Fe alloy layer, resulting in the inclusion of a large amount of Fe in the coating layer and impairing the performance of the coating layer. Therefore, the Al content is set to 50.0% or less.

[0038] Mg: More than 5.0% and 15.0% or less Like Zn, Mg is an element that mainly constitutes the plating layer. A lack of Mg tends to reduce corrosion resistance in salty water, so the Mg content is set to more than 5.0%. On the other hand, if the Mg content exceeds 15.0%, there is a problem with the soundness of the plating layer, and it is difficult to ensure corrosion resistance in water (simulated acid rain and seawater (salt water)). Therefore, the Mg content is set to 15.0% or less.

[0039] Element group A Sn: 0% or more and 0.70% or less Bi: 0% or more and 0.30% or less In: 0% or more and 0.30% or less Total amount of Sn, Bi, and In ΣA: 0% or more and 0.70% or less Each element in element group A (Sn, Bi, In) can be optionally contained, so the content of each is set to 0% or more. When Sn is contained, Mg ９ Sn ５ Bi tends to form Mg ３ Bi ２ , In is Mg ３ In and the like are also formed. This tends to improve corrosion resistance in saltwater. The inclusion of these elements in small amounts has little effect on corrosion resistance in water (simulated acid rain and seawater (saltwater)), but excessive inclusion drastically deteriorates corrosion resistance in simulated acid rain and saltwater, so it is necessary to limit the upper limit of their content. Since all elements have similar effects, they must be managed by their total amount as element group A. The total of element group A must be 0.70% or less.

[0040] Element group B Ca: 0.03% to 0.60% Y: 0% to 0.30% La: 0% to 0.30% Ce: 0% to 0.30% Total amount ΣB of Ca, Y, La, and Ce: 0.03% or more, 0.60% or less In order to ensure corrosion resistance in water (simulated acid rain and seawater (salt water)), it is necessary to form Al-Ca-Si compounds near the interface between the coating layer and the steel sheet. Ca in particular tends to bond with Si, and Al-Ca-Si compounds are likely to be formed when the component range of 1≦Si / ΣB≦5 is satisfied. When the Ca content is high, in addition to Al-Ca-Si compounds, Al ２．１５ Zn １．８５These compounds have high corrosion resistance in simulated acid rain and salt water, and are particularly formed around the interfacial alloy layer near the base steel by bonding with Si. This is thought to ensure coating adhesion and contribute to corrosion protection of the base steel near the interface in water. Note that adjusting the formation of these compounds near the interface is closely related to the manufacturing method disclosed in this invention. For these reasons, the Ca content is set to 0.03% to 0.60%.

[0041] Elements that play a role similar to Ca include Y, La, and Ce. These elements are optional elements and tend to substitute for Ca when included. However, if Ca is not included, sufficient performance may not be achieved even if Y, La, and Ce are included. When Y, La, and Ce are each included in a range of 0.30% or less, they form mutual substitution compounds with each other and function similarly to Ca in water (simulated acid rain and seawater (saltwater)). However, if the Y, La, and Ce contents each exceed 0.30%, corrosion resistance in water (simulated acid rain and seawater (saltwater)) is significantly deteriorated. Therefore, the contents of Y, La, and Ce are each set to 0.30% or less.

[0042] Furthermore, if the total amount of elements in element group B becomes excessive, the corrosion resistance in water (simulated acid rain and seawater (salt water)) deteriorates, so the total amount ΣB of Ca, Y, La and Ce is set to 0.03% or more and 0.60% or less.

[0043] Si: When Al is greater than 30.0% and less than 35.0%, Si is greater than 0.5% and less than 1.0%. When Al is 35.0% or more and less than 50.0%, Si is 0.03% or more and less than 1.0%. Si is an element necessary for forming intermetallic compounds in the coating layer. In coating baths with an Al content of 35.0% or more and less than 50.0%, the coating bath temperature often exceeds 500°C. Immersing a steel sheet in a coating bath at this temperature range tends to cause excessive Al-Fe alloying reactions, increasing the Fe concentration in the coating layer and deteriorating corrosion resistance in water. Therefore, when Al is 35.0% or more, the Si content must be 0.03% or more. The inclusion of Si in the coating layer forms Al-Ca-Si compounds, suppressing excessive Al-Fe reactions. As mentioned above, the formation of Al-Ca-Si compounds is closely related to the manufacturing method disclosed in the present invention. These compounds and the like accumulate near the interface between the plating layer and the steel sheet, suppressing Fe diffusion and enabling the plating layer to form an appropriate structure in accordance with the solidification process.

[0044] On the other hand, when the Al content is greater than 30.0% and less than 35.0%, the Al content is relatively low, and corrosion resistance in water is likely to be insufficient. In this case, if the Si content is greater than 0.5%, Al-Si-O oxides are formed on the surface of the coating layer, ensuring corrosion resistance in water. Therefore, when the Al content is greater than 30.0% and less than 35.0%, the Si content is set to greater than 0.5%. Note that, to form Al-Si-O oxides, the coating layer must be formed in an atmosphere with an oxygen concentration equal to or greater than a certain level.

[0045] In addition, Si is an element that bonds very easily with Ca, and examples thereof include CaAlSi and Al ２ CaSi ２ , Ca ２ Al ４ Si ３ , Ca ２ Al ３ Si ４ However, excessive Si impairs the corrosion resistance of the coating layer in water. Therefore, the Si content is set to 1.0% or less.

[0046] Element Group C Cr: 0% or more, 0.25% or less Ti: 0% or more, 0.25% or less Ni: 0% or more, 1.0% 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 Cu: 0% or more, 0.25% or less Mn: 0% or more, 0.25% or less Total amount ΣC of Cr, Ti, Ni, Co, V, Nb, Cu, and Mn: 0% or more, 1.00% or less The elements of element group C are metal elements that can be contained in the plating layer and may be contained. These metal elements tend to substitute for Al, Zn, etc. in the plating layer, shifting the potential of the plating layer to the noble side, and when contained within this concentration range, corrosion resistance in water (particularly in simulated acid rain) tends to be improved. Excessive content of these elements forms intermetallic compounds composed of these elements, which deteriorates corrosion resistance in water. Therefore, the content of Cr, Ti, Co, V, Nb, Cu, and Mn is each limited to 0.25% or less. The content of Ni is limited to 1.0% or less. The total content of elements in element group C is limited to 0 to 1.00%.

[0047] Fe: 0% or more, 5.0% or less The hot-dip galvanized steel sheet of this embodiment is manufactured by a continuous hot-dip galvanizing method, so Fe may diffuse from the original plate to the coating layer during manufacturing. The coating layer may contain up to 5.0% Fe, but no change in corrosion resistance due to the inclusion of this element has been confirmed. Therefore, the Fe content is set to 0 to 5.0%.

[0048] Element Group D Sr: 0% or more, 0.5% or less Sb: 0% or more, 0.5% or less Pb: 0% or more, 0.5% or less B: 0% or more, 0.5% or less Li: 0% or more, 0.5% or less Zr: 0% or more, 0.5% or less Mo: 0% or more, 0.5% or less W: 0% or more, 0.5% or less Ag: 0% or more, 0.5% or less P: 0% or more, 0.5% or less The total amount ΣD of Sr, Sb, Pb, B, Li, Zr, Mo, W, Ag, and P is 0% or more, 0.5% or less Elements of element group D may be contained in the plating layer. These elements have the same effects as the elements of element group C described above, and are relatively easier to contain than elements of element group C. Therefore, the content of each element of element group D is set to 0 to 0.5%. The total amount of elements in element group D is set to 0 to 0.5%.

[0049] The balance is preferably Zn and impurities. The balance is preferably Zn. The hot-dip galvanized steel sheet of this embodiment is a highly versatile Zn-based plated steel sheet, and by including a certain amount or more of Zn for the purpose of ensuring sacrificial corrosion protection, it is possible to impart appropriate sacrificial corrosion protection to the steel sheet. With regard to corrosion resistance in water with a low salt concentration, a high Al content is preferable, but in water with a relatively high salt content, such as seawater, a high Al content is preferable in order to ensure corrosion resistance. ２ It is necessary to ensure corrosion resistance by including Zn-Mg based intermetallic compounds such as the above. In order to ensure the necessary amount of Zn-Mg based intermetallic compounds, the remainder is Zn.

[0050] 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.

[0051] Furthermore, the plating layer according to this embodiment must satisfy the following formulas (1) to (3). In formulas (1) to (3), Sn, Si, Mg, and Ca represent the content (mass %) of each element in the plating layer. Sn≦Si (1) 15≦Mg / Si (2) 1.0≦Si / Ca≦5.0 (3)

[0052] Sn≦Si The Si content must be equal to or greater than the Sn content. If the Si content is less than the Sn content, excess Fe will diffuse from the steel sheet into the coating layer, making it difficult to form the desired intermetallic compound.

[0053] 15≦Mg / Si Furthermore, the Si content must satisfy the condition 15≦Mg / Si. This improves corrosion resistance in water (simulated acid rain and seawater (salt water)). If the Si content relative to the Mg content becomes high and the Mg / Si ratio becomes less than 15, the plating layer will contain Mg. ２ If a large amount of Si is formed, the corrosion resistance in water (simulated acid rain and seawater (salt water)) cannot be fully exhibited. Preferably, the Mg / Si ratio satisfies 20≦Mg / Si. When the Mg / Si ratio is 20 or more, the corrosion resistance in salt water is further improved.

[0054] 1.0≦Si / Ca≦5.0 Si and Ca easily bond with each other and form compounds. Y, La, or Ce also easily bond with Si. If the Si / Ca ratio is less than 1.0, a large amount of Ca-Al-Zn compounds is formed, making it difficult for Al-Ca-Si compounds to form near the interface between the coating layer and the steel sheet, resulting in a significant loss of corrosion resistance in water. If the Si / Ca ratio exceeds 5.0, the effect of containing Ca in the coating layer is reduced, and Mg ２ If a large amount of Si is formed, Al-Ca-Si compounds are not formed, and corrosion resistance in water is significantly impaired. Therefore, this index is introduced as a control index. If 1.0≦Si / Ca≦5.0 is satisfied, corrosion resistance in salt water is improved. More preferably, 1.0≦Si / Ca≦4.0 is satisfied. This allows Mg ２ By suppressing the amount of Si, a sufficient amount of Al-X-Si is formed, and corrosion resistance in water can be sufficiently ensured. More preferably, the ratio 1.0≦Si / Ca≦3.0 is satisfied. This further improves corrosion resistance in salt water.

[0055] To identify the average chemical composition of the plating layer, the plating layer is stripped and dissolved using an acid containing an inhibitor that suppresses corrosion of the base steel (steel material) to obtain an acid solution. The resulting acid solution is then measured using ICP atomic emission spectroscopy or ICP-MS to obtain the chemical composition. There are no particular restrictions on the type of acid, as long as it is an acid that can dissolve the plating layer. By measuring the area and weight before and after stripping, the plating adhesion amount (g / m ２ ) can also be obtained at the same time.

[0056] Next, the intermetallic compounds contained in the plating layer will be described. Since the plating layer of this embodiment is a Zn-Al-Mg alloy plating, the plating layer contains a Zn phase, an Al phase, an MgZn phase, and the like. ２ Corrosion resistance varies depending on the content of each phase, but by controlling the plating structure, such as by including intermetallic compounds, corrosion resistance can be ensured in underwater environments (simulated acid rain and seawater (saltwater)).

[0057] Zn phase Zn phase exists in the coating layer and has a ternary eutectic structure (Zn / Al / MgZn２ The Zn phase is mainly present as a ternary eutectic structure. There are also Zn phases that are not included in the ternary eutectic structure. The Zn phase and the ternary eutectic structure containing the Zn phase have low corrosion resistance in water (simulated acid rain and seawater (salt water)) and disappear within a short period of time when immersed in water, so it is necessary to prevent the inclusion of the Zn phase. In the present invention, the presence or absence of the Zn phase is strictly limited, and the Zn contained in the plating layer is dissolved in the Al phase or is mixed with the MgZn phase. ２ The phase is an intermetallic compound, which ensures corrosion resistance of the plating layer in water (simulated acid rain and seawater (saltwater)).

[0058] Al phase The Al phase exists in the plating layer in the form of clumps as primary Al crystals. The plating layer of the present invention contains a certain amount of Zn, but the Al phase existing in the form of clumps contains up to about 35% Zn. Therefore, strictly speaking, the primary Al crystals are Al-Zn phases. The Al-Zn phase is a collection of extremely fine crystal grains, and when confirmed by crystal size, it is a structure in which fine crystal grains of several nm to about 3 μm are aggregated. It may be confirmed as a structure containing fine Al phases and Zn phases by X-ray diffraction, TEM, etc., and in the present invention, such a fine structure is also referred to as the Al phase. The Al phase, which may contain up to about 35% Zn, is present on the surface as Al ２ O ３ A stable oxide film such as Al is formed, and the underwater corrosion resistance is particularly high in water (simulated acid rain). It is estimated that an Al concentration of over 35% is required for this oxide film. On the other hand, in water containing salt, Al ２ O ３ cannot exist stably, and corrosion resistance deteriorates drastically.

[0059] MgZn ２ Phase MgZn ２ The phase exists in the plating layer, and MgZn ２ It exists as a blocky phase, and also as an Al-MgZn phase together with the Al phase. ２ Dendrite-like structures formed when solidified on the eutectic line, and ternary eutectic structures (Zn / Al / MgZn ２ A certain amount of MgZn is contained as fine crystal grains in the ternary eutectic structure. ２The MgZn phase has good corrosion resistance in water, and is highly resistant to corrosion in both simulated acid rain and salt water. ２ The corrosion resistance of the phase is dependent on the grain size, and the MgZn contained in the ternary eutectic structure ２ These tend to corrode easily due to coupling reactions. MgZn contained in the ternary eutectic structure ２ shows a diffraction peak of the (102) plane in X-ray diffraction measurement. Therefore, MgZn showing the orientation of the (102) plane ２ Reducing the phase tends to improve corrosion resistance in water (simulated acid rain and seawater (saltwater)).

[0060] As described above, the inventors attempted to improve the plating layer to ensure corrosion resistance in water (simulated acid rain and seawater (saltwater)). As a result, they discovered that the formation of specific intermetallic compounds ensures corrosion resistance in water. X-ray diffraction is preferably used to determine the presence of specific intermetallic compounds in a plating layer. This detection method provides average information on the plating layer compared to SEM observation, TEM observation, etc., and has less selectivity for the measurement location (field of view), making it excellent for quantification. Furthermore, by specifying the measurement conditions, if a specific intermetallic compound is present, diffraction peak intensities are obtained at the same angle (2θ) at a fixed rate, making it easy to infer the internal structure of the plating layer.

[0061] The conditions for obtaining the X-ray diffraction image are as follows.

[0062] X-ray diffraction using Cu as the target X-ray source is the most convenient method, as it can obtain average information about the constituent phases of the plating layer. As an example of measurement conditions, the X-ray conditions are a voltage of 50 kV and a current of 300 mA. There are no particular limitations on the X-ray diffraction device, but for example, a horizontal sample-type high-power X-ray diffraction device RINT-TTR III manufactured by Rigaku Corporation can be used.

[0063] The substances to be measured in the X-ray diffraction measurement are explained below. The substances to be measured are Zn, Al, MgZn, etc. ２ , Al ２ O ５ It is Si.

[0064] Zn Zn is a substance designated by the database number (ICDD-JCPDS Powder Diffraction Database) 00-004-0831. Within the plating composition range of this embodiment, there is one angle that is convenient for detecting Zn. That is, the diffraction angle 2θ is 36.30° ((002) plane).

[0065] Al In the plating composition range of this embodiment, there is one angle that is convenient for detecting Al, namely, the diffraction angle 2θ is 38.47° ((111) plane).

[0066] MgZn ２ Within the plating composition range of this embodiment, there is one angle that is convenient for detecting this intermetallic compound, namely, the diffraction angle 2θ of 19.67° ((100) plane).

[0067] Al ２ O ５ SiAl ２ O ５ Si is a substance designated by the database number (ICDD-JCPDS Powder Diffraction Database) 01-075-4827. Within the composition range of the plating layer of this embodiment, the diffraction angle suitable for detecting this intermetallic compound is 16.18° (110 plane) in 2θ.

[0068] The diffraction peaks at the above diffraction angles are convenient for quantification and determination of the content because they do not overlap with the diffraction peaks of the main crystalline structure of the plating layer. In other words, if diffraction peaks with diffraction intensities exceeding a certain amount are obtained at these diffraction angles, it can be said that the target substance is definitely contained.

[0069] In the X-ray diffraction pattern of the plating layer surface obtained by X-ray diffraction (X-ray output 50 kV, 300 mA) using a Cu target on the plating layer surface, Zn, Al and MgZn ２ I obtained from the X-ray diffraction peak １ is defined by formula (A-1). In this case, in order to ensure the corrosion resistance of the hot-dip galvanized steel sheet in water (simulated acid rain and seawater (salt water)), formula (A-2) must be satisfied.

[0070]

[0071] In formula (A-1), Imax (k to m°) is the maximum value of the X-ray diffraction intensity between diffraction angles k and m°, and k and m are the diffraction angles shown in formula (A-1).

[0072] That is, Imax (36.00 to 36.60°) in formula (A-1) is the maximum value of the X-ray diffraction intensity between the diffraction angles of 36.00 to 36.60°, and corresponds to the diffraction intensity of the (002) plane of Zn. Imax (38.00 to 39.00°) is the maximum value of the X-ray diffraction intensity between the diffraction angles of 38.00 to 39.00°, and corresponds to the diffraction intensity of the (111) plane of Al. Imax (19.20 to 20.00°) is the maximum value of the X-ray diffraction intensity between the diffraction angles of 19.20 to 20.00°, and corresponds to the diffraction intensity of the (111) plane of Al. ２ This corresponds to the diffraction intensity of the (100) plane.

[0073] Therefore, I defined by formula (A-1) １ is Zn, Al and MgZn ２ represents the ratio of the diffraction intensity of Zn to the total diffraction intensity of I １ The smaller the value, the less the Zn phase in the coating layer. １ is set to 0.10 or less. This makes it possible to ensure corrosion resistance in water. That is, a low ratio of Zn phase in the plating layer leads to improved corrosion resistance in water, and makes it possible to maintain the plating layer in water. １ The lower limit of does not need to be particularly limited, but may be 0 or more.

[0074] Next, when Al is more than 30.0% and less than 35.0%, the Al concentration in the plating layer is relatively low, and the Al content is low enough to maintain corrosion resistance in water (especially simulated acid rain). ２ O ３ On the other hand, when the Al content is more than 30.0% and less than 35.0%, the Si content is more than 0.5% and not more than 1.0%, but within the composition range of Al and Si, the Al content exhibits high corrosion resistance in water. ２ O ５The silicon can be obtained as an oxide film of the plating layer. Even if the amount of aluminum is 35.0% or more, this oxide film is formed, and corrosion resistance in simulated acid rain tends to improve. ２ O ５ I obtained from the X-ray diffraction peak of Si ２ When is defined by formula (B-1), formula (B-2) must be satisfied.

[0075]

[0076] Here, Imax (k to m°) in formula (B-1) is the maximum value of the X-ray diffraction intensity between diffraction angles k and m°, Imax (n°) is the X-ray diffraction intensity at a diffraction angle n°, and k, m, and n are the diffraction angles shown in formula (A-1) and formula (B-1), respectively.

[0077] Imax (15.60° to 16.60°) in formula (B-1) is the maximum value of the X-ray diffraction intensity in the diffraction angle range of 15.60° to 16.60°, and Al ２ O ５ I(15.60°) and I(16.60°) are the X-ray diffraction intensities at diffraction angles of 15.60° and 16.60°, respectively, and correspond to the diffraction intensity of the (110) plane of Si. ２ O ５ This corresponds to the background intensity of the diffraction peak of the Si (110) plane.

[0078] The molecule of formula (B-1) (Imax (15.60 to 16.60°)) is Al ２ O ５ This is the intensity corresponding to the diffraction peak of Si at 2θ = 16.18° ((110) plane), and is the maximum diffraction intensity of the diffraction peak including the background intensity. Because the diffraction angle of the (110) plane may deviate from 16.18° due to measurement errors in X-ray diffraction, the maximum value between 15.60 and 16.60° is obtained.

[0079] The denominator of formula (B-1) is the background intensity at a diffraction angle of 16.18°, calculated from the diffraction intensities at 15.60° and 16.60°. That is, as shown in FIG. 1, a straight line is drawn connecting the diffraction line at 15.60° and the diffraction line at 16.60°. This straight line serves as the baseline of the diffraction peak. Next, I(15.60°) - I(16.60°) is calculated. In addition, the ratio (0.58 / 1.00 = 0.58) of the difference between the diffraction angles of 15.60° and 16.60° (1.00°) to the difference between the diffraction angles of 15.60° and 16.18° (0.58°) is calculated. Then, the background intensity at a diffraction angle of 16.18° is calculated using the formula given in the denominator of formula (B-1) above.

[0080] By setting the formula (B-1) as described above, even if measurement errors or background fluctuations occur due to differences in measurement conditions, Al ２ O ５ It becomes possible to measure the intensity of the Si diffraction peak at 2θ=16.18° (110) with high precision.

[0081] As shown in formula (B-2), I ２ When the value of I is 1.05 or more, corrosion resistance in water (especially simulated acid rain) can be ensured. ２ Although a larger value is preferable, no clear effect can be confirmed when Al is more than 30.0% and less than 35.0%.

[0082] When the Al concentration is 35.0% or more, the corrosion resistance in salt water is I ２ There is a tendency for improvement in the range of I = 1.05 to 20. ２ I ２ It is more preferable that I is 3 to 20. The higher the Si concentration, the larger the value tends to be. ２ The lower limit of does not need to be particularly limited, but may be 0 or more, or may be more than 0.

[0083] To satisfy formulas (A-2) and (B-2), the chemical composition of the plating layer must fall within the range of the present invention, and the plating production method, heat treatment, and atmosphere control must be appropriate in the production method.

[0084] Next, in the composition range of the plating layer of this embodiment, MgZn ２ The phase crystallizes out. MgZn ２ The MgZn phase is inherently highly corrosion resistant in water, but when it is surrounded by fine Al and Zn phases, the coupling reaction between these phases accelerates corrosion. ２ The MgZn phase has a lower corrosion potential than the Zn phase. ２ The phase dissolves quickly in water. ２ The phase is MgZn contained in the ternary eutectic structure in the plating layer. ２ Therefore, in this embodiment, the MgZn phase contained in the ternary eutectic structure ２ It is preferable to reduce the number of phases, and therefore the number of ternary eutectic structures.

[0085] The MgZn contained in this ternary eutectic structure ２ There is one diffraction angle that is convenient for detecting the phase by X-ray diffraction. ２ The phase has a strong diffraction intensity in the (102) plane. That is, the diffraction peak appearing in the diffraction intensity in the (102) plane at a diffraction angle 2θ of 28.73° does not overlap with the diffraction peak of the main crystal structure of the plating layer, making it convenient for quantification and determination of the content. In other words, if diffraction peaks with diffraction intensities exceeding a certain amount are obtained at these diffraction angles, it can be said that the target phase is certainly contained.

[0086] MgZn showing crystal orientation other than the (102) plane ２ The phase is a coarse MgZn phase that covers the Al phase by peritectic reaction. ２ phase or coarse MgZn precipitated by other than the ternary eutectic reaction ２ These MgZn alloys, which have excellent corrosion resistance in water, ２ The phase exhibits diffraction intensities at the above-mentioned diffraction angle 2θ of 19.67° ((100) plane), as well as 20.78° ((002) plane) and 22.26° ((101) plane). The diffraction peaks that appear at these diffraction angles do not overlap with the diffraction peaks of the main crystal structure of the plating layer, making them convenient for quantification and determination of the content.

[0087] MgZn contained in the plating layer ２ Therefore, in the hot-dip coated steel sheet of this embodiment, in the X-ray diffraction pattern of the coating layer surface measured using Cu-Kα radiation under conditions of an X-ray output of 50 kV and 300 mA, MgZn ２ I obtained from the X-ray diffraction peak ３ is defined by formula (C-1), it is preferable that formula (C-2) is satisfied.

[0088]

[0089] Here, Imax (k to m°) in formula (C-1) is the maximum value of the X-ray diffraction intensity between diffraction angles k and m°, and k and m are the diffraction angles shown in formula (C-1).

[0090] That is, Imax (28.52 to 28.92°) in formula (C-1) is the maximum value of the X-ray diffraction intensity between the diffraction angles of 28.52 to 28.92°, and MgZn ２ This corresponds to the diffraction intensity of the (102) plane of MgZn. ２ is the MgZn contained in the ternary eutectic structure ２ Imax (19.20 to 20.00°) is the maximum value of the X-ray diffraction intensity between the diffraction angles of 19.20 and 20.00°, and corresponds to the MgZn phase. ２ Imax (20.58 to 20.98°) is the maximum value of the X-ray diffraction intensity between the diffraction angles of 20.58 and 20.98°, and corresponds to the diffraction intensity of the (100) plane of MgZn. ２ Imax (22.06 to 22.45°) is the maximum value of the X-ray diffraction intensity between the diffraction angles of 22.06 to 22.45°, and corresponds to the diffraction intensity of the (002) plane of MgZn. ２ This corresponds to the diffraction intensity of the (101) plane.

[0091] Therefore, I defined by formula (C-1) ３ is the MgZn contained in the plating layer ２ The sum of the diffraction intensities of MgZn contained in the ternary eutectic structure ２represents the ratio of the diffraction intensities of the phases, and I ３ The smaller the value, the more MgZn is contained in the ternary eutectic structure. ２ This means that there is little ternary eutectic structure. ３ This makes it possible to obtain a ternary eutectic structure of MgZn. ２ The phase is almost completely eliminated, and corrosion resistance in simulated acid rain and salt water is further improved. ３ The lower limit of I does not need to be particularly limited, but it may be 0 or more. ３ In order to control this, it is advisable to control the immersion time in the plating bath in the two-stage plating method.

[0092] The plated steel sheet of this embodiment includes a steel sheet and a plating layer formed on the surface of the steel sheet. Typically, Zn-Al-Mg-based plating is formed by metal deposition and solidification reaction. The easiest means for forming the plating layer is to form the plating layer on the steel sheet surface by hot-dip galvanizing, and this can be done by the Sendzimir method, the flux method, two-stage plating method, or the like.

[0093] In this embodiment, a manufacturing method equivalent to a two-stage plating method is preferred in order to appropriately control the morphology of the interface alloy layer. The reason why a two-stage plating method is preferably adopted is as follows. A plating bath containing more than 30.0% Al typically requires a bath temperature of 520°C or higher in order to melt the plating bath and perform hot-dip plating. When using such a plating bath, a Sendzimir method or the like tends to rapidly react between the reduced Fe surface and the plating bath, resulting in the growth of a thick Al-Fe alloy layer. The hot-dip plated steel sheet of this embodiment may be used as a material for pre-plated products, but such a thick interface alloy layer can cause various problems, such as peeling of the plating layer during processing of the hot-dip plated steel sheet and early development of Fe rust during corrosion. Therefore, the manufacturing method of this embodiment employs a manufacturing method equivalent to a two-stage plating method, and it is necessary to use a plating base sheet capable of suppressing the reaction between the Fe surface and the plating bath. In order to ensure the performance of the plating layer produced as the product of the present invention, the plating thickness of the plating base sheet must be at least 10 μm or more, and more preferably 20 μm or more. In this case, the interfacial alloy layer needs to be less than 10% of the entire plating layer, and more preferably less than 1 μm. In addition, the thickness of the plating layer is more preferably 80 μm or less from the viewpoint of preventing plating appearance defects such as sagging patterns.

[0094] In cases where the Sendzimir method is unavoidable, it is acceptable to use a plating bath containing more than 35.0% Al. However, the original sheet to be plated must be a plated steel sheet that is difficult to dissolve in Fe and has a barrier coating effect that suppresses the reaction between the plating bath and Fe, and a Ni or Cr pre-plating layer of 0.7 g / m per side is required. ２The steel sheet to which the above-described coatings have been applied must be used as the base sheet. Ni and Cr act as a barrier against Fe diffusion. However, even in this case, the formation of an Al-Ca-Si alloy layer, which should be included in the coating layer of this embodiment, tends to be suppressed, and the solidification of the coating layer is barely suppressed to a minimum, barely allowing for proper coating solidification. Furthermore, Al-Si-O oxide is required to ensure corrosion resistance in water. While this ensures corrosion resistance in simulated acid rain, corrosion resistance in saltwater tends to be inferior. This phenomenon is thought to be due to the fact that even if the coating layer thickness can be manufactured within the desired range, the thickness of the interfacial alloy layer is around 10% or more, making it impossible to achieve the desired performance.

[0095] A preferred method for producing a hot-dip galvanized steel sheet according to this embodiment is described below. The method for producing a hot-dip galvanized steel sheet according to this embodiment uses a continuous hot-dip galvanizing process in which a base steel sheet is continuously immersed in a hot-dip galvanizing bath and then withdrawn. However, as described above, the hot-dip galvanizing bath used in this embodiment has a high Al content, resulting in a relatively high bath temperature. If a steel sheet is directly immersed in the hot-dip galvanizing bath as a base steel sheet, the reaction between the bath and the steel substrate becomes active. This results in a large amount of Fe diffusing into the coating layer, resulting in the formation of a thick interfacial alloy layer made of an Fe-Al alloy, and significantly reducing the adhesion of the coating layer. Therefore, in this embodiment, a galvanized steel sheet or a pre-galvanized steel sheet on which a coating layer of a predetermined amount or more has been formed is used as the base steel sheet. This suppresses the reaction between the coating bath and the steel substrate, enabling the interfacial alloy layer to be thin.

[0096] The zinc-plated steel sheet used as the base sheet for plating has a coating weight of at least 40 g / m2 on one side. ２ More than 100 g / m ２or more is preferable. This means that, in terms of the thickness of the plating layer, the intended thickness is approximately 10 μm or more, more preferably approximately 21 μm or more. There are no restrictions on the method for producing the plating layer of the base sheet for plating, and either hot-dip plating or electroplating may be used. It is necessary that the interfacial alloy layer of the base sheet for plating is less than 1 μm and that the plating layer is mainly composed of Zn, but for example, the plating layer may contain 1% or less of Al. It is not preferable to use a plated steel sheet with an interfacial alloy layer formed from the beginning as a base sheet, as this changes the reaction. In other words, the interfacial alloy layer formed at the time of manufacturing the base sheet for plating remains as an interfacial alloy layer even after two-stage plating, so this alloy layer must be strictly limited, preferably less than 1 μm, and it is essential that it be less than 10% of the total thickness of the plating layer.

[0097] Furthermore, the base sheet for the galvanized steel sheet may be a Zn-Al-Mg-plated steel sheet whose plating layer contains elements contained in the plating layer of the present invention, such as Al and Mg. Even in such a Zn-Al-Mg-plated steel sheet, the thickness of the interface alloy layer must be less than 1 μm. In addition, in hot-dip zinc / zinc-based alloy-plated steel sheets generally produced on a continuous hot-dip plating line, the thickness of the interface alloy layer rarely exceeds 1 μm due to the immersion time. Therefore, it is more preferable to use a hot-dip galvanized steel sheet / zinc-based alloy-plated steel sheet as the base sheet for plating.

[0098] When a galvanized steel sheet is immersed in a hot-dip galvanizing bath, the coating layer on the steel sheet is easily replaced by the metallic elements in the hot-dip galvanizing bath, and a coating layer consisting of the components of the coating bath is formed while suppressing the reaction between the coating bath and the base steel. A galvanized steel sheet has a coating layer mainly composed of zinc on a steel sheet, and in the case of a hot-dip galvanized steel sheet, there is an interfacial alloy layer between the coating layer and the steel sheet.

[0099] In addition, examples of pre-plated steel sheets used as base sheets for plating include pre-plated steel sheets pre-coated with a plating layer of Zn, Ni, Cr, Sn, or an alloy-based combination of these elements, with a plating thickness of 30 μm or less. When the pre-plated steel sheet is immersed in a hot-dip plating bath, the pre-plated layer easily replaces the metal elements in the hot-dip plating bath, forming a plating layer composed of the components of the plating bath while suppressing reaction between the plating bath and the base steel. The constituent elements of the pre-plated layer, such as Sn, Ni, and Cr, react with Al and Si in the plating bath and act as a barrier layer that suppresses the diffusion of Fe. Furthermore, it is also possible to eliminate unplated areas (areas where the plating metal is repelled by an oxide film, etc.) caused by components contained in the plating bath.

[0100] Furthermore, there is no problem in using a low-temperature plated Sn-plated steel sheet or an electroplated Zn-Ni steel sheet as the base sheet for plating.

[0101] In the manufacturing method of this embodiment, the above-mentioned base sheet for plating is immersed in a hot-dip plating bath and then removed. The composition of the plating layer can be controlled by the composition of the plating bath to be prepared. The plating bath is prepared by mixing predetermined amounts of pure metals to prepare an alloy of the plating bath components, for example, by a melting method in an inert atmosphere.

[0102] By immersing the base sheet in a plating bath maintained at a predetermined concentration, a plating layer with almost the same components as the plating bath is formed. The immersion time may be changed depending on the plating coating weight used on the base sheet. The immersion time (seconds) is determined based on the plating coating weight per side (g / m ２ ) is M, it is preferable that the time is in the range of M / 30 (seconds) or more and M / 10 (seconds) or less.

[0103] Furthermore, in order to satisfy the above formula (C-2), it is preferable that the immersion time (seconds) is set in the range of M / 15 (seconds) or more and M / 10 (seconds) or less.

[0104] Furthermore, the temperature of the plated original sheet during immersion does not need to be raised to match the temperature of the plating bath, and can be room temperature (for example, 50°C or less). However, in the case of Zn-based plating, there is no problem even if the temperature is raised up to a maximum of about 600°C (a temperature at which the surface plating layer does not melt).

[0105] Immediately after immersion in the plating bath, the various plating layers formed on the original sheet are exposed to the plating bath at 500°C or higher and instantly dissolved. On the other hand, the temperature of the base steel of the plated steel sheet does not rise sufficiently, so the reaction between Fe and the plating bath tends to be suppressed, and the diffusion of Fe into the plating layer and the formation of Fe-induced intermetallic compounds are significantly suppressed. By immersing for a short period of time, the plating layer on the original sheet is replaced by a hot-dip plating layer before the Fe diffuses, and the sheet is then pulled out as is.

[0106] When forming an Al—Si—O oxide on the coating layer immediately after pulling up from the coating bath, the atmosphere must be an air environment (oxygen concentration of 2000 ppm or more). Also, immediately after pulling up, the coating thickness can be controlled by wiping. Furthermore, during the series of coating solidification reactions, it is preferable to control the steel sheet temperature so that it does not exceed 500°C. This is because, if this temperature is exceeded, Fe will rapidly diffuse into the coating bath.

[0107] The series of production methods can be carried out in an air environment. When the Al content in the plating bath exceeds 35.0%, production can also be carried out in an inert atmosphere such as a nitrogen atmosphere, but in this case, an Al—Si—O oxide film will not be formed.

[0108] There are no particular restrictions on cooling the plating layer. ２ It may be cooled and solidified by spraying gas or mist or the like.

[0109] After plating, various chemical conversion treatments and painting treatments may be performed. Taking advantage of the uneven pattern on the plated surface, it is also possible to apply a plating layer of Cr, Ni, Au, etc., and then paint it to impart a design. Furthermore, to further improve corrosion resistance, touch-up paint for repair, thermal spraying treatment, etc. may be performed on welded parts, processed parts, etc.

[0110] The hot-dip galvanized steel sheet of this embodiment may have a coating formed on the plating layer. One or more coating layers may be formed. Examples of the coating directly on the plating layer include a chromate coating, a phosphate coating, and a chromate-free coating. The chromate treatment, phosphate treatment, and chromate-free treatment for forming these coatings can be performed by known methods.

[0111] Chromate treatments include electrolytic chromate treatments that form a chromate film by electrolysis, reactive chromate treatments that form a film by utilizing a reaction with the material and then wash away excess treatment solution, and paint-on chromate treatments that apply a treatment solution to the substrate and dry it without rinsing with water to form a film. Any of these treatments may be used.

[0112] Examples of electrolytic chromate treatments include electrolytic chromate treatments using chromic acid, silica sol, resins (phosphoric acid, acrylic resins, vinyl ester resins, vinyl acetate acrylic emulsions, carboxylated styrene butadiene latex, diisopropanolamine-modified epoxy resins, etc.), and hard silica.

[0113] Examples of the phosphate treatment include zinc phosphate treatment, zinc calcium phosphate treatment, and manganese phosphate treatment.

[0114] 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.

[0115] 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 thereof include polyester resins, polyurethane resins, epoxy resins, acrylic resins, polyolefin resins, and modified versions of these resins. Here, the term "modified version" refers to a resin obtained by reacting a reactive functional group contained in the structure of these resins with another compound (such as a monomer or a crosslinking agent) containing a functional group capable of reacting with the functional group.

[0116] Such organic resins may be a mixture of one or more unmodified organic resins, 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 coating may also contain any coloring pigment or anti-rust pigment. These organic resins may also be used in aqueous solutions prepared by dissolving or dispersing them in water.

[0117] In this embodiment, the corrosion resistance in acid rainwater and the corrosion resistance in salt water are measured and evaluated as follows: When the corrosion resistance in acid rainwater and the corrosion resistance in salt water are both evaluated as "E", the product is deemed to have failed, and when the evaluation is otherwise, the product is deemed to have passed.

[0118] (Corrosion resistance in acid rain) The corrosion resistance in acid rain is evaluated by a simulated acid rain corrosion resistance test. This test is a test that simulates a situation in which acid rain flows into the atmosphere. As the simulated acid rain, NaCl, HNO 3 and the like are added to ion-exchanged water. ３ , H ２ SO ４ and the pH was adjusted with NaOH to obtain Cl － : 10 ppm, NO ３－ : 20 ppm, SO ４ ２－Test water adjusted to 40 ppm and pH 5.0 ± 0.2 is prepared. 60 L of test water is placed in a cubic container with sides of 50 cm. A plated steel test piece is attached to the tip of a stainless steel shaft (φ25 mm) using a jig and bolts. The test piece is a 130 mm diameter disk. A hole is drilled in the center of the disk, and the tip of the stainless steel shaft is fitted into this hole to secure the test piece. The test piece is immersed in the test water and rotated at high speed so that the peripheral speed of the test piece is 2.2 m / s. The area where the test piece comes into contact with the jig is insulated with tape seals or similar. The pH is constantly monitored, and if it deviates from the pH 5.0 ± 0.2 range, the pH is returned to 5.0 with dilute hydrochloric acid or NaOH aqueous solution. The water temperature is maintained between 23 and 25°C. The test solution is replaced every 250 hours. After 1000 hours, the test piece was taken out and immersed in a 30% aqueous solution of chromic acid (VI) for 15 minutes. The weight difference before and after immersion was measured, and the corrosion weight loss (g / m ２ The end faces of the test piece are left open, and the central hole is not evaluated. The evaluation criteria are as follows:

[0119] Corrosion weight loss: 5g / m ２ Less than: Corrosion resistance in simulated acid rain "A" Corrosion weight loss 5-10g / m ２ Less than: Corrosion resistance in simulated acid rain "B" Corrosion weight loss 10-20g / m ２ Less than: Corrosion resistance in simulated acid rain "C" Corrosion weight loss 20-30g / m ２ Less than: Corrosion resistance in simulated acid rain "D" Corrosion weight loss 30g / m ２ Above: Corrosion resistance in simulated acid rain "E"

[0120] (Corrosion Resistance in Salt Water) Corrosion resistance in salt water is evaluated by a corrosion resistance test in a salt water solution. This test is performed in the same manner as the simulated acid rain corrosion resistance test, except that the test water is a 5% NaCl aqueous solution. After 1000 hours, the specimen is immersed in a 30% chromic acid (VI) aqueous solution for 15 minutes, and the corrosion weight loss before and after immersion is determined. The evaluation criteria are as follows:

[0121] Corrosion weight loss: 15g / m ２ Less than: Corrosion resistance "S" in salt water Corrosion loss 15-20g / m ２ Less than: Corrosion resistance "A" in salt water Corrosion loss 20-30g / m ２Less than: Corrosion resistance in salt water "B" Corrosion weight loss 30-40g / m ２ Less than: Corrosion resistance "C" in salt water Corrosion loss 40-50g / m ２ Less than: Corrosion resistance "D" in salt water Corrosion loss 50g / m ２ Above: Corrosion resistance in salt water "E"

[0122] The plated steel sheets shown in Tables 2A to 5C were manufactured and their performance evaluated. Pure metals were mixed to prepare each plating bath. After the bath was prepared, Fe powder was added to the plating alloy components to prevent an increase in the Fe concentration during testing.

[0123] The manufacturing conditions were as shown in Table 1 below. The unit of the plating weight on one side of the base sheet is g / m. ２ The heating temperature of the steel sheet before immersion in the plating bath was set to room temperature to 800°C. The room temperature was 50°C or less. The immersion time was set to 2 to 15 seconds.

[0124]

[0125] Manufacturing methods A, A1, and A2: The base sheet for plating was a cold-rolled steel sheet, a Ni-preplated steel sheet, or a Cr-preplated steel sheet. The thickness of the interface alloy layer of the preplated steel sheet was less than 1 μm. The manufacturing method used was the CGL Sendzimir method. That is, before immersion in the plating bath, the base sheet for plating was subjected to H ２ The steel sheet was heated for 60 seconds at a predetermined temperature in a 5% nitrogen atmosphere (oxygen concentration 20 ppm or less, dew point -40°C) to perform surface reduction. ２ The plate was cooled with gas and immersed in a plating bath. After being pulled out, the plate was adjusted by wiping to a thickness of 20 μm per side, and cooled in the atmosphere at an average cooling rate of 10°C / sec. The plating coating weight was also 20 μm per side in Manufacturing Methods B to L.

[0126] Manufacturing methods B, B1, and B2: These manufacturing methods were the same as the manufacturing methods A, A1, and A2 described above, up to the point of immersion in the coating bath. After being removed from the coating bath, the steel sheet was covered with a sealing box and cooled in a nitrogen atmosphere with an oxygen concentration of less than 2000 ppm.

[0127] Manufacturing methods C, D, and E: A hot-dip galvanized steel sheet produced by the CGL Sendzimir process was used as the base sheet for plating. Details are as shown in Table 1. The thickness of the interface alloy layer of the hot-dip galvanized steel sheet was less than 1 μm, which was less than 10% of the thickness of the entire plating layer. The base sheet for plating was immersed in the plating bath without heating. The plating bath was maintained so that the temperature of the plating bath did not change before and after immersion. Regarding the treatment after pulling up, Manufacturing methods C and E were the same as Manufacturing methods A to A2, and Manufacturing method D was the same as Manufacturing methods B to B2.

[0128] Manufacturing methods F, G, and H: A hot-dip Zn—Al—Mg alloy-plated steel sheet produced by the CGL Sendzimir process was used as the base sheet for plating. Details are as shown in Table 1. The thickness of the interface alloy layer of the hot-dip Zn—Al—Mg alloy-plated steel sheet was less than 1 μm, which was less than 10% of the thickness of the entire plating layer. The plating process was as shown in Table 1.

[0129] Manufacturing methods I, J, K, and L: Plated steel sheets shown in Table 1 were used as base sheets for plating. The thickness of the interface alloy layer of these plated steel sheets was less than 1 μm, which was less than 10% of the thickness of the entire plating layer. The plating process was as shown in Table 1.

[0130] The plating bath temperature was 550°C for plating baths with an Al content of less than 35.0%, and 600°C for plating baths with an Al content of 35.0% or more.

[0131] The X-ray intensity was measured as follows. The hot-dip plated steel sheet after plating was cut into 20 mm square pieces, and measurements were performed using a high-angle X-ray diffractometer manufactured by Rigaku Corporation (model number RINT-TTR III) with an X-ray output of 50 kV, 300 mA, a copper (Cu) target, a TTR goniometer (horizontal goniometer), a Kβ filter slit width of 0.05 mm, a longitudinal limiting slit width of 2 mm, a receiving slit width of 8 mm, and receiving slit 2 open, under the measurement conditions of a scan speed of 5 deg. / min, a step width of 0.01 deg, and a scan axis 2θ (5 to 90°), to obtain the cps intensity at each angle.

[0132] The corrosion resistance in simulated acid rainwater and saltwater was measured and evaluated as follows, and the results are shown in the table.

[0133] (Corrosion resistance in acid rain) The corrosion resistance in acid rain was evaluated by a simulated acid rain corrosion resistance test. This test was conducted under the assumption that acid rain from the atmosphere flows into the building. The simulated acid rain was prepared by adding NaCl, HNO3, and HCl to ion-exchanged water. ３ , H ２ SO ４ and the pH was adjusted with NaOH to obtain Cl － : 10 ppm, NO ３－ : 20 ppm, SO ４ ２－ Test water adjusted to 40 ppm and pH 5.0±0.2 was prepared. 60 L of test water was placed in a cubic container with sides measuring 50 cm. A plated steel test specimen was attached to the tip of a stainless steel shaft (φ25 mm) using a jig and bolts. The test specimen was a 130 mm diameter disk. A hole was drilled in the center of the disk, and the tip of the stainless steel shaft was fitted into this hole to secure the specimen in place. The test specimen was immersed in the test water and rotated at high speed so that the peripheral speed of the test specimen was 2.2 m / s. The contact area between the test specimen and the jig was insulated with tape seals or other insulation. The pH was constantly monitored, and if it deviated from the pH 5.0±0.2 range, it was returned to pH 5.0 with dilute hydrochloric acid or NaOH aqueous solution. The water temperature was maintained between 23 and 25°C. The test solution was replaced every 250 hours. After 1000 hours, the test piece was taken out and immersed in a 30% aqueous solution of chromic acid (VI) for 15 minutes. The weight difference before and after immersion was measured, and the corrosion weight loss (g / m ２ ) was determined. The end faces of the test pieces were left open, and the central hole was not evaluated. The evaluation criteria were as follows: "E" was considered a failure.

[0134] Corrosion weight loss: 5g / m ２ Less than: Corrosion resistance in simulated acid rain "A" Corrosion weight loss 5-10g / m ２ Less than: Corrosion resistance in simulated acid rain "B" Corrosion weight loss 10-20g / m ２ Less than: Corrosion resistance in simulated acid rain "C" Corrosion weight loss 20-30g / m ２ Less than: Corrosion resistance in simulated acid rain "D" Corrosion weight loss 30g / m ２ Above: Corrosion resistance in simulated acid rain "E"

[0135] (Corrosion Resistance in Salt Water) The corrosion resistance in salt water was evaluated by a corrosion resistance test in a salt water solution. This test was carried out in the same manner as the simulated acid rain corrosion resistance test, except that the test water was a 5% NaCl aqueous solution. After 1000 hours had passed, the specimens were immersed in a 30% chromic acid (VI) aqueous solution for 15 minutes, and the corrosion weight loss before and after immersion was determined. The evaluation criteria were as follows: "E" was considered a failure.

[0136] Corrosion weight loss: 15g / m ２ Less than: Corrosion resistance "S" in salt water Corrosion loss 15-20g / m ２ Less than: Corrosion resistance "A" in salt water Corrosion loss 20-30g / m ２ Less than: Corrosion resistance in salt water "B" Corrosion weight loss 30-40g / m ２ Less than: Corrosion resistance "C" in salt water Corrosion loss 40-50g / m ２ Less than: Corrosion resistance "D" in salt water Corrosion loss 50g / m ２ Above: Corrosion resistance in salt water "E"

[0137] Nos. 1 and 44 had an Al content outside the range of the present invention, so １ This was outside the scope of the invention, resulting in reduced corrosion resistance in water.

[0138] Nos. 54, 66, 69, and 73 had Si contents outside the range of the present invention, and therefore were １ This was outside the scope of the invention, resulting in reduced corrosion resistance in water.

[0139] Nos. 5 to 11, 14, 28 to 32, 35, 115 to 119, and 122 were produced under conditions outside the preferred range. １ or I ２ This was outside the scope of the invention, and the corrosion resistance in water was reduced.

[0140] Nos. 45 and 50 had Mg contents outside the range of the present invention, so １ This was outside the scope of the invention, resulting in reduced corrosion resistance in water.

[0141] Nos. 51 to 53 are not included in the range of the present invention because the elements in element group A are outside the range of the present invention. １ This was outside the scope of the invention, resulting in reduced corrosion resistance in water.

[0142] Nos. 55, 56, 58, 60, 62, 64, and 65 are not included in the range of the present invention because the elements in element group B are outside the range of the present invention. １ This was outside the scope of the invention, resulting in reduced corrosion resistance in water.

[0143] Nos. 77, 79, 81, 83, 85, 87, 89, 91, 93, and 95 are not included in the scope of the present invention because the elements in element group C are outside the scope of the present invention. １ This was outside the scope of the invention, resulting in reduced corrosion resistance in water.

[0144] In No. 97, the Fe content was outside the range of the present invention, so I １ This was outside the scope of the invention, resulting in reduced corrosion resistance in water.

[0145] Nos. 99, 101, 103, 105, 107, 109, 111, 128, 130, 132, and 135 are not included in the scope of the present invention because the elements in element group D are outside the scope of the present invention. １ This was outside the scope of the invention, resulting in reduced corrosion resistance in water.

[0146] No. 137 does not satisfy the condition Si≦Sn, so I １ Since the Si / Ca ratio of No. 139 was outside the range of the present invention, the corrosion resistance in water was reduced. １ This was outside the scope of the invention, resulting in reduced corrosion resistance in water.

[0147] On the other hand, the hot-dip plated steel sheets other than those mentioned above were excellent in corrosion resistance in water.

[0148]

[0149]

[0150]

[0151]

[0152]

[0153]

[0154]

[0155]

[0156]

[0157]

[0158]

[0159]

[0160] According to the present invention, it is possible to provide a hot-dip galvanized steel sheet that can exhibit high corrosion resistance in water (in simulated acid rain or salt water such as seawater) or in a constantly wet environment where water wetting may occur, and therefore the present invention has high industrial applicability.

Claims

1. A hot-dip galvanized steel sheet having a coating layer on the steel sheet surface, wherein the average chemical composition of the coating layer is, in mass%, Al: more than 30.0% and not more than 50.0%, Mg: more than 5.0% and not more than 15.0%, Sn: 0% or more and not more than 0.70%, Bi: 0% or more and not more than 0.30%, In: 0% or more and not more than 0.30%, Ca: 0.03% or more and not more than 0.60%, Y: 0% or more and not more than 0.30%, La: 0% or more and not more than 0.30%, Ce: 0% or more and not more than 0.30%, Si: more than 0.5% and not more than 1.0% when Al is more than 30.0% and less than 35.0%, and 0.03% or more and not more than 1.0% when Al is 35.0% or more and not more than 50.0%, Cr: 0% or more and not more than 0.25%, Ti: 0% or more, 0.25% or less, Ni: 0% or more, 1.0% 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, Cu: 0% or more, 0.25% or less, Mn: 0% or more, 0.25% or less, Fe: 0% or more, 5.0% or less, Sr: 0% or more, 0.5% or less, Sb: 0% or more, 0.5% or less, Pb: 0% or more, 0.5% or less, B: 0% or more, 0.5% or less, Li: 0% or more, 0.5% or less, Zr: 0% or more, 0.5% or less, Mo: 0% or more, 0.5% or less, W : 0% or more, 0.5% or less, Ag: 0% or more, 0.5% or less, P the balance consisting of Zn and impurities; the total amount ΣA of Sn, Bi and In is 0% or more and 0.70% or less; the total amount ΣB of Ca, Y, La and Ce is 0.03% or more and 0.60% or less; the total amount ΣC of Cr, Ti, Ni, Co, V, Nb, Cu and Mn is 0% or more and 1.00% or less; the total amount ΣD of Sr, Sb, Pb, B, Li, Zr, Mo, W, Ag and P is 0% or more and 0.5% or less; and the following formulas (1) to (3) are satisfied: In an X-ray diffraction pattern of the surface of the plating layer measured using Cu-Kα rays under conditions of an X-ray output of 50 kV and 300 mA, Zn, Al and MgZn are not present. ２ I obtained from the X-ray diffraction peak １ is defined by formula (A-1), formula (A-2) is satisfied, and Al ２ O ５ I obtained from the X-ray diffraction peak of Si ２ A hot-dip galvanized steel sheet that satisfies the following formula (B-2) when the above formula (B-1) is defined as Sn≦Si (1), 15≦Mg / Si (2), and 1.0≦Si / Ca≦5.0 (3). In formulas (1) to (3), Sn, Si, Mg, and Ca are the contents (mass%) of each element in the plating layer, Imax (k to m°) in formulas (A-1) and (B-1) is the maximum value of the X-ray diffraction intensity between diffraction angles k and m°, Imax (n°) is the X-ray diffraction intensity at a diffraction angle n°, and k, m, and n are the diffraction angles shown in formulas (A-1) and (B-1), respectively.

2. In the X-ray diffraction pattern of the surface of the plating layer measured using Cu-Kα rays under conditions of an X-ray output of 50 kV and 300 mA, MgZn ２ I obtained from the X-ray diffraction peak ３ The hot-dip plated steel sheet according to claim 1, wherein when is defined by formula (C-1), formula (C-2) is satisfied. Here, Imax (k to m°) in formula (C-1) is the maximum value of the X-ray diffraction intensity between diffraction angles k and m°, and k and m are the diffraction angles shown in formula (C-1).

Images