fused steel

Abstract

The molten steel of this case has the following chemical composition by mass%: Al: greater than 10.0% and less than 60.0%, Mg: 4.0~15.0%, Si: 3.5%~8.0%, and the remainder is Zn and impurities. In the elemental distribution profile of qualitative analysis performed by GDS method from the surface of the coating towards the steel, the thickness of the region from the surface of the coating to the depth position where the maximum strength of Fe is equivalent to 5% of the Fe strength is detected is defined as Tg. At this time, the average Si value from the surface of the coating to Tg / 3 is defined as Si(surf), the average Si value from the surface of the coating to the range of Tg / 3 to 2Tg / 3 is defined as Si(centre), and the average Si value from the surface of the coating to the range of 2Tg / 3 to Tg is defined as Si(deep). At this time, the following formula (1) will be satisfied: Si(surf) < Si(deep) < Si(centre)...(1).

Description

Hot-dip coated steel Field of the Invention The present invention relates to a hot-dip coated steel. This case claims priority based on Japanese Patent Application No. 2023-125776 filed on August 1, 2023, and incorporates its content herein by reference. Background of the Invention When using steel for a long time, it is advisable to apply some rust prevention treatment to the steel that can withstand corrosion. As a low-cost means of rust prevention for steel, the hot-dip Zn coating method has been used in various fields such as civil engineering, construction, and the automotive field that require rust prevention of steel. The corrosion prevention means provided by the coating layer is generally determined by the inherent corrosion resistance of the coating layer and the coating layer thickness. For example, Patent Document 1 describes that a coated steel plate is manufactured by continuously immersing a steel plate in a hot-dip coating bath, that is, by the so-called continuous hot-dip coating method. After that, the coated steel plate is processed into a part shape, thereby manufacturing a part. In recent years, various studies have been carried out to improve the performance of coated steel plates. For example, Patent Documents 1 and 2 describe a Zn-Al-Mg-based coated steel (steel plate) as a coated steel with high corrosion resistance. In these Zn-Al-Mg-based coated steels, attempts are made to improve properties such as corrosion resistance by controlling the structure of the coating layer, adding elements to the coating layer, or actively forming corrosion products. [Prior Art Documents] [Patent Documents] [Patent Document 1] International Publication No. 2018 / 139619 [Patent Document 2] International Publication No. 2019 / 230894 Summary of the Invention Problems to be Solved by the Invention In the conventional Zn-Al-Mg-based coated steels described in Patent Documents 1 and 2, there has been insufficient study on the morphology of intermetallic compounds in the coating layer except for the main part. Therefore, under severe processing conditions, problems such as a decrease in workability such as peeling (fragmentation) of the coating layer sometimes occur due to intermetallic compounds. In addition, in the conventional Zn-Al-Mg-based coated steels, the hardness of the coating layer is insufficient, and it is sometimes difficult to stably ensure good damage resistance. The problem to be solved by one embodiment of the present invention is to provide a hot-dip coated steel with sufficient coating hardness and excellent workability and excellent corrosion resistance. Means for Solving the Problems To solve the above problems, each aspect of the present invention adopts the following configuration. [1] The hot-dip coated steel material according to one aspect of the present invention has: a steel material and a coating layer disposed on the surface of the steel material; the coating layer has the following chemical composition by mass%: containing: Al: greater than 10.0% and 60.0% or less, Mg: 4.0% or more and 15.0% or less, Si: 3.5% or more and 8.0% or less; and further containing: Sn: 0% or more and 0.7% or less, Sr: 0% or more and 1.5% or less, Bi: 0% or more and 0.3% or less, In: 0% or more and 0.3% or less, Ca: 0% or more and 0.6% or less, Y: 0% or more and 0.3% or less, La: 0% or more and 0.3% or less, Ce: 0% or more and 0.3% or less, Li: 0% or more and 0.3% or less, Ni: 0% or more and 1.0% or less, Cu: 0% or more and 1.0% or less, Ag: 0% or more and 0.25% or less, Sb: 0% or more and 0.25% or less, Pb: 0% or more and 0.25% or less, B: 0% or more and 0.5% or less, P: 0% or more and 0.5% or less, Ti: 0% or more and 0.25% 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, Mn: 0% or more and 0.25% or less, Zr: 0% or more and 0.25% or less, W: 0% or more and 0.25% or less, Fe: 0% or more and 5.0% or less, and the balance is Zn and impurities; the coating layer contains Mg 2Si intermetallic compound; in the elemental distribution profile obtained by glow discharge optical emission spectrometry from the surface of the aforementioned plating layer towards the aforementioned steel material, the thickness of the region from the surface of the aforementioned plating layer to the depth position where the Fe intensity equivalent to 5% of the maximum intensity for Fe is detected is defined as Tg. At this time, the average value of the Si qualitative analysis value from the surface of the aforementioned plating layer to Tg / 3 is defined as Si(surf), the average value of the Si qualitative analysis value in the range from Tg / 3 to 2Tg / 3 with the surface of the aforementioned plating layer as the starting point is defined as Si(centre), and the average value of the Si qualitative analysis value in the range from 2Tg / 3 to Tg with the surface of the aforementioned plating layer as the starting point is defined as Si(deep). At this time, the following formula (1) is satisfied: Si(surf) < Si(deep) < Si(centre)…(1). [2] For the molten-plated steel material described in [1] above, in the X-ray diffraction pattern of the surface of the aforementioned plating layer measured under the conditions of using Cu-Kα rays and an X-ray output of 50 kV and 300 mA, the following formula (2) can also be satisfied: {I(26.19°) + I(44.6°)} / {2 × I(12.5°)} > 2.0…(2) In formula (2), I(n°) is the X-ray diffraction intensity at the diffraction angle n°, and n is the diffraction angle (2θ) shown in formula (2). Advantageous Effects of Invention According to an embodiment of the present invention, it is possible to provide a molten-plated steel material having sufficient plating hardness and excellent workability and excellent corrosion resistance at the same time. Embodiment of the Present Invention Modes for Carrying Out the Invention Hereinafter, a molten-plated steel material according to an embodiment of the present invention will be described. In addition, in this specification, unless otherwise specified, the “%” indication of the content of each element in the chemical composition of the plating layer means “mass %”. Also, the numerical range indicated by “~” means: a range including the numerical values described before and after “~” as the lower limit value and the upper limit value. In addition, the numerical range when the numerical values described before and after “~” are marked with “greater than” or “less than” means: a range not including these numerical values as the lower limit value or the upper limit value. First, the relationship between the intermetallic compound formed in the Zn-Al-Mg-based plating layer and the workability of the plated steel material was examined. The examination results will be described below. Generally, when an intermetallic compound having a covalent bond is contained in the plating layer, it becomes a hard particle, and thus the overall hardness of the plating layer increases. Also, since the intermetallic compound is also excellent in insulation, high corrosion resistance is exhibited by containing the intermetallic compound in the plating layer. On the other hand, when the intermetallic compound is excessively contained in the plating layer, the entire plating layer becomes hard, and sometimes the plastic deformation ability of the plating layer decreases. If the entire plating layer becomes hard, when the plated steel material is formed using it as a raw material, sometimes the plating layer becomes liable to be damaged and plating layer peeling such as pulverization occurs. Therefore, containing a large amount of intermetallic compound in the plating layer is not good in terms of practicality. Also, in the plating layer, especially on the surface and interface of the plating layer, if a continuous and layered intermetallic compound is formed, sometimes peeling occurs during bending processing, for example, or interface peeling is caused at the interface between the plating layer and the base material due to differences in corrosion rates during corrosion. Then, there is a pursuit for a plating layer which has the hardness and high corrosion resistance of the conventional desired level, and has good workability and does not cause peeling or the like. Here, in order to improve the hardness and corrosion resistance of the plating layer, there is a technique of making the plating layer contain Ca. When a large amount of Ca is contained in the plating layer, it forms an intermetallic compound with Zn, Al, etc. in the plating layer. The melting point of this Ca-containing intermetallic compound is very high during the solidification process of Zn-Al-Mg-based molten plating. Therefore, regarding Ca in the plating layer, large Ca-containing intermetallic compounds are formed in the initial stage after the steel material is lifted from the plating bath, and they grow in the plating layer. In the normal molten plating process, the surface of the plating layer is greatly cooled by the external air, so the solidification of the plating layer starts from the surface. Also in the Ca-containing bath, due to the same mechanism, Ca-containing intermetallic compounds are precipitated from parts with low free energy and stability such as the surface or interface of the plating layer. As a result, the Ca-containing intermetallic compounds are particularly likely to aggregate on the surface of the plating layer, and they grow thick and sometimes the Ca-containing intermetallic compounds are connected in layers. In the case of a plating layer in which the Ca-containing intermetallic compounds are connected in layers, during forming processing, the Ca-containing intermetallic compounds may undergo brittle fracture, resulting in the peeling of the plating layer from the surface of the plating layer, that is, the so-called "pulverization phenomenon" occurs. Accordingly, it is difficult to simultaneously improve the hardness, workability, and corrosion resistance in a plating layer containing a high concentration of Ca. Then, after the inventors of the present case examined elements that can exhibit the same effects as Ca, they obtained the insight that Si is very effective. Specifically, the insight obtained is that although Si forms Mg-Si-based intermetallic compounds, compared with the Ca-containing intermetallic compounds, the Mg-Si-based intermetallic compounds have the property of being difficult to aggregate at the interface between the plating layer and the base material. That is, by making the plating layer contain Si, the same effects as Ca can be exerted, and at the same time, the formed Mg-Si-based intermetallic compounds can be aggregated at the center of the plating layer in the thickness direction. Therefore, the workability can be improved more than before. [Hot-dip galvanized steel sheet] Hereinafter, the hot-dip galvanized steel sheet of the present embodiment will be described in detail. The hot-dip galvanized steel sheet of the present embodiment has: a steel sheet and a plating layer disposed on the surface of the steel sheet; the average chemical composition of the plating layer contains, by mass%: Al: greater than 10.0% and 60.0% or less, Mg: 4.0% or more and 15.0% or less, Si: 3.5% or more and 8.0% or less; and further includes: Sn: 0% or more and 0.7% or less, Sr: 0% or more and 1.50% or less, Bi: 0% or more and 0.3% or less, In: 0% or more and 0.3% or less, Ca: 0% or more and 0.6% or less, Y: 0% or more and 0.3% or less, La: 0% or more and 0.3% or less, Ce: 0% or more and 0.3% or less, Li: 0% or more and 0.3% or less, Ni: 0% or more and 1.0% or less, Cu: 0% or more and 1.0% or less, Ag: 0% or more and 0.25% or less, Sb: 0% or more and 0.25% or less, Pb: 0% or more and 0.25% or less, B: 0% or more and 0.5% or less, P: 0% or more and 0.5% or less, Ti: 0% or more and 0.25% 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, Mn: 0% or more and 0.25% or less, Zr: 0% or more and 0.25% or less, W: 0% or more and 0.25% or less, Fe: 0% or more and 5.0% or less, and the balance is Zn and impurities. In addition, the plating layer in the hot-dip galvanized steel sheet of the present embodiment contains Mg 2 Si intermetallic compound; in the elemental distribution profile obtained by qualitative analysis using glow discharge optical emission spectrometry from the surface of the plating layer towards the steel sheet, the thickness of the region from the surface of the plating layer to the depth position where the Fe intensity equivalent to 5% of the maximum intensity for Fe is detected is defined as Tg. At this time, the average value of the Si qualitative analysis value from the surface of the plating layer to Tg / 3 is defined as Si(surf), the average value of the Si qualitative analysis value in the range of Tg / 3 to 2Tg / 3 starting from the surface of the plating layer is defined as Si(centre), and the average value of the Si qualitative analysis value in the range of 2Tg / 3 to Tg starting from the surface of the plating layer is defined as Si(deep). At this time, the following formula (1) is satisfied. Si(surf) < Si(deep) < Si(centre)…(1) (Steel material) First, the steel material (mother plate) to be plated is described. The steel material is mainly, for example, a steel plate, but its size is not particularly limited. The steel plate only needs to be applicable to the normal hot-dip galvanizing process. Specifically, a steel plate applicable to a step of dipping in molten metal and solidifying it, such as in a continuous galvanizing line (CGL), is perfectly suitable here. The steel plate size can be, for example, a plate thickness of 10 mm or less and a plate width of 2000 mm or less, but the steel plate size is not limited to this. The material of the steel material is not particularly limited. The steel material can be applicable to, for example: general steel, aluminum-deoxidized steel (Al killed steel), extra-low carbon steel, high-carbon steel, various high-tensile steels, locally high-alloy steels (steels containing corrosion-resistant strengthening elements such as Ni and Cr, etc.), steel for bolts, steel wire rods for bridge steel cables, and various other steel plates and steel materials. More specifically, the steel material can be applicable to, for example: hot-rolled steel plates specified in JIS G 3131 (2018), cold-rolled steel plates specified in JIS G 3141 (2017), those contained in hot-rolled steel materials for general structural use corresponding to so-called SS materials, so-called general steel covered by the hot-rolled steel plates shown in JIS G 3193 (2019), pre-plated steels thinly plated with various metals as described in JIS H 8641 (2021), JIS G 3302 (2019), 3303 (2017), 3313 (2017), 3314 (2019), 3315 (2017), 3317 (2019), and 3321 (2019), etc., hot-rolled steel materials for building structures described in JIS G 3136 (2012), aluminum-deoxidized steel (Al killed steel) described in JIS G 3126 (2015), extra-low carbon steel, high-carbon steel, various high-tensile steels described in JIS G 3113 (2018), 3134 (2018), and 3135 (2018), and locally high-alloy steels (steels containing corrosion-resistant strengthening elements such as Ni and Cr, etc.). (Plating layer) Next, the plating layer provided on the steel material is described. The plating layer of this embodiment includes a Zn-Al-Mg alloy layer. The Zn-Al-Mg alloy layer contains a Zn phase, an Al phase, and a MgZn 2 phase. The plating layer of this embodiment also contains Mg 2 Si intermetallic compound. The plating layer of this embodiment may sometimes further contain other intermetallic compounds. When alloying elements such as Al and Mg are contained in the Zn phase, the corrosion resistance is improved. Therefore, for a plating layer containing such a Zn phase, even if it is a thin film (for example, about half the thickness of a normal Zn plating layer), it can exhibit the same corrosion resistance as a normal Zn plating layer. Similarly, for the plating layer of this embodiment, even when formed as a thin film, it can still ensure corrosion resistance equal to or higher than that of a conventional Zn plating layer. MgZn 2 Phase The plating layer of this embodiment contains MgZn 2 phase. A certain amount of MgZn is contained in the plating layer 2 phase, thereby enabling the corrosion resistance in a water-wet environment to be further enhanced. Zn phase (Al-Zn phase, Zn-Al phase) The Zn phase mainly exists in the form of a ternary eutectic structure (Zn / Al / MgZn 2 ternary eutectic structure). Also, when the plating layer contains a large amount of Al, since Al and Zn are mixed in a solid state to form an Al-Zn phase, the Zn phase may sometimes dissolve in the Al phase. On the other hand, Al may sometimes dissolve in the Zn phase to form a Zn-Al phase (the Al concentration in the phase is about 20%). The phase composed of Zn and Al is highly workable. Al phase The Al phase exists in the form of Al primary crystals in the plating layer in a块状 form. During the solidification process of the plating layer, the Al phase dissolves various elements, especially Zn, into its phase. Since the plating layer of this embodiment has a high Al content, the Al phase becomes supersaturated with elements such as Zn during the solidification process. During the solidification process, the Al phase forms a dendritic crystal structure that spreads into a tree shape in the plating layer to form the backbone of the plating layer. The Al phase is soft and highly workable, and thus exhibits a cracking prevention effect: preventing the progress of cracks that have occurred and reducing the fatal defects of the plating layer. Mg 2 Mg-Si intermetallic compound The plating layer of this embodiment contains Mg 2 Si intermetallic compound. Mg 2 Si intermetallic compound is an intermetallic compound that can be observed with a clear boundary and in an island shape in the solidification structure of a plating layer containing Si. It is considered that Zn, Al, and other additive elements are not dissolved in the Mg 2 Si intermetallic compound, or even if there is dissolution, it is extremely微量. Mg 2The Si intermetallic compound can be clearly distinguished from other phases when observed under a microscope in the plating layer. Mg 2 The Si intermetallic compound is formed in the plating layer by making the plating layer contain Si. Generally, the intermetallic compounds formed in the plating layer have their atoms bonded complexly to each other, and thus have the effect of improving corrosion resistance and hardness. On the other hand, if the intermetallic compounds are formed continuously and layer by layer on the plating surface and interface, there may be cases of agglomeration and peeling during bending processing, and surface peeling and / or interface peeling may occur due to differences in corrosion rates during corrosion. It is currently known that Ca is an effective element for improving the corrosion resistance and hardness of the plating layer. However, as described above, the Ca-containing intermetallic compound is a compound that easily forms layers and especially easily aggregates at the interface. The reason is that it is easy to form an intermetallic compound based on CaZn 4 and the CaZn 4 is formed when Ca is excessively contained in the Zn-Al-Mg-based plating layer. In contrast, the obtained insight is that Si has a tendency to improve the corrosion resistance and hardness of the plating layer in much the same way as Ca, especially Mg 2 The Si intermetallic compound has a tendency to be less likely to aggregate at the interface than the Ca-containing intermetallic compound. Also, the more the intermetallic compound aggregates towards the center of the plating layer, the less likely it is to be crushed even under severe processing conditions. By making the plating layer contain Mg 2 Si intermetallic compound in such a way as to satisfy the following respective formulas, the hardness of the plating layer can be further improved, and at the same time, the corrosion resistance can be improved and good workability can be ensured. Mg 2 The existence of intermetallic compounds such as the Mg Si intermetallic compound can be confirmed by the GDS method (glow discharge optical emission spectrometry). Next, a method for analyzing the composition in the depth direction inside the plating layer in the plating layer of the present embodiment will be described. The compositional analysis by GDS is carried out from the surface of the plating layer towards the steel along the depth direction until the Fe concentration reaches 100% (reaching the base iron). Accordingly, the analysis range for the depth direction analysis by GDS is the range from the surface of the plating layer until it reaches a part of the Zn-Al-Mg plating layer, the Al-Fe alloy layer, and the steel. After the GDS analysis, the profile sputtering depth is measured using "surfcom130A" manufactured by Tokyo Seimitsu Co., Ltd. By performing compositional analysis through GDS, the elemental distribution profile in the depth direction of the plating layer can be obtained. In the elemental distribution profile, when the total amount of the measured elements is set to 100%, the content distribution in the depth direction of each element is shown. In this embodiment, in the elemental distribution profile obtained by qualitative analysis from the surface of the plating layer towards the steel by GDS, the thickness of the region from the surface of the plating layer until the depth position where the Fe intensity corresponding to 5% of the maximum intensity for Fe is detected is defined as Tg. At this time, the average value of the Si qualitative analysis value from the surface of the plating layer to Tg / 3 is defined as Si(surf), the average value of the Si qualitative analysis value in the range from Tg / 3 to 2Tg / 3 with the surface of the plating layer as the starting point is defined as Si(centre), and the average value of the Si qualitative analysis value in the range from 2Tg / 3 to Tg with the surface of the plating layer as the starting point is defined as Si(deep). At this time, the following formula (1) is satisfied. In addition, Si(surf), Si(centre), and Si(deep) are obtained by performing qualitative analysis by GDS 10 times and calculating the average of the qualitative analysis values in the obtained elemental distribution profile. The qualitative analysis is carried out at non-overlapping positions on the surface of the plating layer. Si(surf) < Si(deep) < Si(centre)…(1) In such a manner that the above (1) is satisfied, Mg 2 Si intermetallic compounds aggregate in the central part in the thickness direction of the plating layer (specifically, the aforementioned region), whereby the workability can be improved, and even under severe processing conditions, pulverization can be avoided. That is, by satisfying formula (1), it is possible to achieve an increase in the hardness of the plating layer and an increase in corrosion resistance, and as a result, a plated steel material with high hardness, good workability, and corrosion resistance can be obtained. It is considered that if there is an insulator such as Mg 2 Si intermetallic compounds at positions where the electric potential is likely to change significantly, such as the central part in the thickness direction of the plating layer or the boundary between the plating layer / Fe, the situation of promoting corrosion is suppressed and the corrosion resistance is improved. In addition, Mg 2Si intermetallic compounds have the effect of improving corrosion resistance and hardness. On the other hand, if a large amount of Mg 2 Si intermetallic compounds are formed on the surface and interface of the plating layer, then during processing, this Mg 2 Si intermetallic compound may sometimes peel off. Also, during corrosion, due to the difference in corrosion rates, there may be peeling on the surface and / or interface of the Mg 2 Si intermetallic compound, which may damage the processability and corrosion resistance. Regarding the reduction of processability and corrosion resistance, the Mg 2 Si intermetallic compound formed on the surface of the plating layer has a greater impact. Therefore, in this embodiment, Si(surf) is made lower than Si(deep). That is, the amount of Si in the region from the surface of the plating layer to Tg / 3 is made lower than the amount of Si in the range from 2Tg / 3 to Tg. Thereby, during processing or corrosion, peeling caused by the Mg 2 Si intermetallic compound can be suppressed, and the processability and corrosion resistance can be further improved. In addition, in this embodiment, in the elemental distribution profile obtained by qualitative analysis using the GDS method from the surface of the plating layer toward the steel material, the region up to the depth position where the Fe intensity equivalent to 5% of the maximum Fe intensity is detected satisfies the above formula (1). This region is roughly the same as the region where the Zn-Al-Mg alloy layer exists. Figure 1 shows an example of the result of depth-direction analysis of the plating layer of this embodiment using GDS. The chart shown in Figure 1 is an elemental distribution profile. In this embodiment, the region defined by the above formula (1) is defined as: when analyzing in the depth direction from the surface of the plating layer, from the surface of the plating layer to the position of 5% of the maximum Fe intensity. For example, for the analysis result shown in Figure 1, since the maximum Fe intensity is 53 V, in the region up to the position of 5% of its intensity, that is, the position where the Fe intensity reaches 2.7 V, the above formula (1) is defined. Next, the index of the Mg 2 Si intermetallic compound obtained by X-ray diffraction is described. In the X-ray diffraction pattern of the surface of the plating layer measured under the conditions of using Cu-Kα rays and an X-ray output of 50 kV and 300 mA for the plating layer of this embodiment, when the diffraction intensity of the Mg 2 Si intermetallic compound is defined as I(26.19°) and I(44.6°), and the background intensity is defined as I(12.5°), the following formula (2) is satisfied. {I(26.19°) + I(44.6°)} / {2 × I(12.5°)} > 2.0...(2) In the formula (2), I(n°) is the X-ray diffraction intensity at the diffraction angle of n°, and n is the diffraction angle (2θ) shown in the formula (2). Figure 2 shows an example of the X-ray diffraction pattern in the coating layer of the present embodiment. As shown in Figure 2, peaks of Mg 2 Si intermetallic compounds appear near 26.19° and near 44.6°. That is, I(26.19°) and I(44.6°) in the formula (2) respectively represent the X-ray diffraction intensities of Mg 2 Si intermetallic compounds at the diffraction angles of 26.19° and 44.6°. In the present embodiment, when the background intensity is defined as I(12.5°), the above formula (2) is satisfied, whereby an intermetallic compound excellent in corrosion resistance and hardness is formed in the coating layer. As a result, high hardness and corrosion resistance can be exhibited while maintaining the plastic deformation ability of the coating surface and interface. The coating layer of the present embodiment may also contain an Al-Fe-based interface alloy layer (Al-Fe-based interface alloy layer) containing Al and Fe. The average thickness of the Al-Fe-based interface alloy layer is less than 5 μm. The Al-Fe-based interface alloy layer is an interface alloy layer located between the steel material and the Zn-Al-Mg-based alloy layer and contacts the surface of the steel material. That is, the coating layer of the present embodiment may be a single-layer structure composed of a Zn-Al-Mg-based alloy layer or a laminated structure including a Zn-Al-Mg-based alloy layer and an Al-Fe-based interface alloy layer. Although the Al-Fe-based interface alloy layer does not have a significant impact on corrosion resistance, it has an impact on the coating adhesion and workability (presence or absence of cracks) of the hot-dip coated steel material during processing. In particular, the Al-Fe-based interface alloy layer sometimes affects the pulverization resistance, which indicates the degree of peeling of the coating layer during processing. Generally, the thinner the thickness of the Al-Fe-based interface alloy layer, the more the starting points of cracks in the coating layer during processing can be reduced and the pulverization resistance can be improved more. Therefore, for hot-dip coated steel materials that can be highly processed when used as components, etc., the thickness of the Al-Fe-based interface alloy layer should be as thin as possible. Specifically, the thickness of the intermetallic compound constituting the Al-Fe-based interface alloy layer is set to be less than 5 μm. This thickness should be set to 2 μm or less, preferably 1 μm or less, more preferably 0.5 μm or less. It may also be 0.3 μm or less. Thereby, the occurrence of cracks during processing can be suppressed and the pulverization resistance can be improved more. Furthermore, the ratio of the thickness of the Al-Fe interface alloy layer to the thickness of the coating layer is less than 10% on average, preferably less than 5%. An Al-Fe-based interfacial alloy layer is formed on the surface of the steel material, specifically between the steel material and the Zn-Al-Mg-based alloy layer. The Al-Fe-based interfacial alloy layer is a layer mainly composed of an Al 5 Fe 2 phase. The Al-Fe-based interfacial alloy layer is formed due to the mutual atomic diffusion of the base iron (steel plate) and the plating bath. When the continuous melting plating method is used as the manufacturing method, the Al-Fe-based interfacial alloy layer is likely to be formed in the plating layer containing the Al element. In the present embodiment, since the plating bath contains Al above a certain concentration, Al 5 Fe 2 phase forms the most. However, since atomic diffusion takes time, the Fe concentration in the Al-Fe-based interfacial alloy layer is not uniform, and sometimes the Fe concentration becomes higher in the part close to the base iron. Therefore, the Al-Fe-based interfacial alloy layer sometimes contains a small amount of AlFe phase, Al 3 Fe phase, Al 5 Fe 2 phases, etc., locally. Also, since the plating bath contains a certain concentration of Zn, the Al-Fe-based interfacial alloy layer sometimes contains a small amount of Zn as well. In the present embodiment, sometimes a part of Si is brought into the Al-Fe-based interfacial alloy layer to form an Al-Fe-Si intermetallic compound phase. As for the distinguishable Al-Fe-Si intermetallic compound phases, there is an AlFeSi phase. Regarding the isomers of the AlFeSi phase, there are an α phase, a β phase, a q1 phase, a q2 phase, etc. Therefore, in the Al-Fe-based interfacial alloy layer, sometimes these AlFeSi phases, etc., are detected. The Al-Fe-based interfacial alloy layer containing these AlFeSi phases, etc., is also called an Al-Fe-Si alloy layer. Next, the average chemical composition of the plating layer is described. When the plating layer is a single-layer structure of a Zn-Al-Mg-based alloy layer, the average chemical composition of the entire plating layer is the average chemical composition of the Zn-Al-Mg-based alloy layer. Also, when the plating layer is a laminated structure composed of an Al-Fe-based interfacial alloy layer and a Zn-Al-Mg-based alloy layer, it is the combined average chemical composition of the Al-Fe-based interfacial alloy layer and the Zn-Al-Mg-based alloy layer. In the plating layer of the present embodiment, the thickness of the Al-Fe-based interfacial alloy layer should be 10% or less relative to the overall thickness of the plating layer. Thus, when the thickness of the Al-Fe-based interfacial alloy layer is relatively thin compared to the overall plating layer, the Fe concentration in the plating layer will mostly be within 5%. Al: greater than 10.0% and 60.0% or less. Al is an element that constitutes the main body of the plating layer. If the Al content is 10.0% or less, sometimes a sufficient amount of Zn-Al phase may not be ensured. Therefore, the Al content is greater than 10.0%. On the other hand, if the Al content is greater than 60.0%, sometimes the corrosion resistance may decrease. Therefore, the upper limit of the Al content is 60.0% or less. The lower limit of the Al content should be 15.0% or more. Also, the upper limit of the Al content should be 45.0% or less, and more preferably 30.0% or less. Mg: 4.0% or more and 15.0% or less. Mg is an element that constitutes the main body of the plating layer, the same as Zn. Mg is an important element for improving the corrosion resistance in the plated steel sheet of the present embodiment. Compared with the case without Mg, when the Mg content in the plating layer is less than 4.0%, the effect of improving the corrosion resistance is not obvious. Accordingly, the Mg content is set to 4.0% or more. On the other hand, in the Zn-Al-Mg plating bath, if Mg is added in excess, a violent oxidation reaction will occur on the bath surface of the plating bath and plating cannot be stably performed. Therefore, in order to stably perform plating to ensure good manufacturability, the Mg content in the plating layer is set to 15% or less. Si: 3.5% or more and 8.0% or less. Si bonds with Mg to form an intermetallic compound composed of a certain Mg 2 Si composition. Also, Si inhibits the excessive Al-Fe reaction, thereby suppressing the formation of the Al-Fe-based interfacial alloy layer. If the Si content is less than 3.5%, sometimes the amount of Mg 2 Si generated will decrease, the hardness of the plating layer will become lower, and the corrosion resistance will also decrease. On the other hand, if the Si content is greater than 8.0%, sometimes the amount of Mg 2 Si generated will become excessive, the plating layer will undergo brittle fracture, and the plating layer will agglomerate and peel off from the plating surface, resulting in a pulverization phenomenon. As a result, the corrosion resistance may sometimes also decrease. Therefore, the Si content is set to 3.5% or more and 8.0% or less. Sr: 0% or more and 1.5% or less. Sr forms covalent bonds with Zn, Al, Si, etc. to form an intermetallic compound with excellent corrosion resistance and hardness. On the other hand, when the Sr content is greater than 1.5%, excessive Sr-based intermetallic compounds are generated in the plating layer, causing the entire plating layer to become hard. As a result, when forming a processed product using the plated steel material as a raw material, the plating layer is sometimes easily damaged and plating layer peeling such as pulverization occurs. Therefore, the Sr content is set to 0.03% or more and 1.5% or less. Sn: 0% or more and 0.7% or less. Bi: 0% or more and 0.3% or less. In: 0% or more and 0.3% or less. The inclusion of each of the elements Sn, Bi, and In in the plating layer promotes the softening of the plating layer. Since Sn, Bi, and In are elements that can be contained optionally, their respective contents are set to 0% or more. When Sn is contained, it tends to form Mg in the plating layer. 9 Sn 5 Bi also forms Mg. 3 Bi 2 In also forms Mg. 3 In, etc. Since these elements are softer than the MgZn 2 phase and have good workability, the inclusion of them in the plating layer can significantly improve the workability. Also, since these elements exhibit electrochemical properties with a very low potential, they have a high anti-corrosion effect. By containing at least one of Sn, Bi, and In within the above ranges, the effect of improving the corrosion resistance of the processed part can be obtained. Ca: 0% or more and 0.6% or less. Ca is an element that helps to improve the hardness and corrosion resistance of the plating layer. On the other hand, when a large amount of Ca is contained in the plating layer, Zn and / or Al in the plating layer form intermetallic compounds. The Ca-containing intermetallic compounds formed in this way are particularly likely to aggregate on the surface of the plating layer. Depending on the situation, the aggregated Ca-containing intermetallic compounds sometimes grow thick and the Ca-containing intermetallic compounds are connected in a layer. If the Ca-containing intermetallic compounds in the plating layer are connected in a layer, the Ca-containing intermetallic compounds will undergo brittle fracture during forming processing, and the plating layer will peel off from the surface of the plating layer, resulting in a possible reduction in workability. Therefore, the Ca content is set to 0.6% or less. Y: 0% to 0.3% La: 0% to 0.3% Ce: 0% to 0.3% Li: 0% to 0.3% Ni: 0% to 1.0% Cu: 0% to 1.0% Ag: 0% to 0.25% Sb: 0% to 0.25% Pb: 0% to 0.25% B: 0% to 0.5% P: 0% to 0.5% Ti: 0% to 0 .25% 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 Mn: 0% or more and 0.25% or less Zr: 0% or more and 0.25% or less W: 0% or more and 0.25% or less Y, La, Ce, Li, Ni, Cu, Ag, Sb, Pb, B, P, Ti, Co, V, Nb, Mn, Zr, and W all form intermetallic compounds with Si, Zn, and Al. However, when the content of these elements is within the above range, it will not affect the initial corrosion of the plating layer. On the other hand, when these elements are contained in excess, a potential difference will be generated in the plating layer, and a large amount of initial white rust may occur. Therefore, if they are to be contained, they can be contained within the above range. Fe: 0% or more and 5.0% or less Since the melt-coated steel material of this embodiment is manufactured by a continuous melt-coating method, Fe sometimes diffuses from the coating material to the coating layer during manufacturing. As mentioned above, in this embodiment, although the Al concentration of the coating layer is high and an Al-Fe-based interface alloy layer is sometimes formed, its thickness is thin. As a result, although the coating layer sometimes contains up to 5.0% Fe, if the Fe concentration is suppressed to below 5.0%, it will not affect the frequency of turtle cracks in the coating layer. Therefore, the Fe content is set to 0~5.0%. The Fe content may also be greater than 0%. Remaining part: Zn and impurity remaining part preferably contain Zn. Since the hot-dip plated steel material of this embodiment is a Zn-based plated steel material with high versatility, the element constituting the main phase of the plated layer is Zn. Impurities are components contained in the raw materials or mixed in during the manufacturing process, and are components that are not intentionally contained. For example, due to atomic diffusion between the steel material (base iron) and the plating bath, components other than Fe may be mixed into the plating layer in trace amounts as impurities. In addition, 3N purity metals are usually used to produce plating alloys, so the total impurity concentration can be set to about 0.03% or less. For the identification of the average chemical composition of the plating layer, an acid containing an inhibitor that can suppress the corrosion of the base iron (steel) is used, and the plating layer is peeled and dissolved by the acid to obtain an acid solution. Regarding the components insoluble in the acid, the acid solution is filtered, and the resulting residue is liquefied by alkali dissolution treatment. Then, the obtained acid solution and the solution obtained by alkali dissolution treatment are measured by ICP emission spectrometry or ICP-MS method, whereby the chemical composition can be obtained. Regarding the type of acid, there is no particular limitation as long as it can dissolve the plating layer. By measuring the area and weight before and after peeling in advance, the plating adhesion amount (g / m 2 ) can also be obtained simultaneously. [Manufacturing method of hot-dip plated steel] Next, the manufacturing method of the hot-dip plated steel of this embodiment will be described. The manufacturing method of the plated steel of this embodiment is not particularly limited. Here, regarding the method of forming the Si-containing plating layer as described above, it is considered that the method of simply directly adding Si to the Zn-Al-Mg plating bath for plating can be used. However, in this method, Mg 2 Si intermetallic compounds are likely to form on the surface and in the vicinity of the plating layer rather than in the central part of the plating layer. Therefore, as an example of a suitable manufacturing method for manufacturing the hot-dip plated steel of this embodiment, a method of supplying Si from a Si-containing pre-plating layer provided on a plating mother board to the plating layer will be described below. In addition, in this specification, the method of first forming a predetermined pre-plating layer on the plating mother board and then applying a Zn-Al-Mg hot-dip plating is referred to as the "two-stage plating method". First, an Al-Si pre-plating layer is formed in advance on a plating mother board such as a cold-rolled / hot-rolled steel plate. The pre-plating means can be hot-dip plating, electroplating, displacement plating, or evaporation plating, etc. In addition, these pre-plating layers can also be alloyed by heating. In addition, when the pre-plating performed on the mother board is carried out by hot-dip plating, it can be carried out, for example, under the conditions of an Al-8 to 10% Si bath or the like that is usually used to form an aluminum plating, without particular stipulation. Next, the plating mother board is heated to 450 to 600 °C, preferably to a temperature similar to the temperature of the plating bath described later. This heating can also serve as the annealing of the mother board (hereinafter, this heating may sometimes be referred to as pre-annealing). By heating the steel plate before dipping it into the plating bath described later, the temperature variation of the plating bath can be reduced. The mother board on which the pre-plating layer has been formed and heated is immersed in a Zn-Al-Mg plating bath that has been adjusted to obtain the desired plating composition, and then lifted, whereby the pre-plating layer is brought into the Zn-Al-Mg alloy layer to form the final plating layer. The plating bath temperature is preferably 480 to 550 °C. Furthermore, in order to incorporate the pre-plated layer into the Zn-Al-Mg alloy layer to obtain a single-layer plated layer, the immersion time of the mother plate in the plating bath should be ensured for a certain period of time or more. Specifically, the immersion time should be between 3 and 10 seconds. In order to fully incorporate the pre-plated layer into the Zn-Al-Mg alloy layer, the immersion time should be set to 4 seconds or more. In addition, if the immersion time is too long, the alloy layer at the interface between the plating and the steel plate will become a thick film, which may cause the plating to peel off. Therefore, the immersion time should be 8 seconds or less. Furthermore, in this embodiment, temperature control should be performed when lifting the plating mother plate. That is, by appropriately controlling the cooling conditions after immersion, Si will be contained in the plating layer to form the desired Mg 2 Si intermetallic compound. Specifically, in order to fully form Mg 2 Si intermetallic compound, the average cooling rate in the temperature range of 550 to 450 °C should be set to 25 °C / second or less. When the average cooling rate in the temperature range of 550 to 450 °C is greater than 25 °C / second, Si will be uniformly dispersed in the thickness direction of the plating layer, and sometimes the desired plating layer may not be obtained. Regarding the cooling conditions in the temperature region other than the temperature region of 550 to 450 °C, since they do not affect the formation of intermetallic compounds, etc., they are not particularly limited. In this way, by appropriately controlling the cooling conditions after the plating mother plate is lifted from the bath, the formation of Mg 2 Si intermetallic compound on the surface and interface of the plating layer can be more effectively suppressed, and Mg 2 Si intermetallic compound can be appropriately dispersed near the center of the plating layer. As a result, while maintaining the plastic deformation ability of the plating surface and interface, high plating hardness, workability, and corrosion resistance can be exhibited. Furthermore, if a steel plate with an Al-Si pre-plated layer formed is used as the plating substrate, Mg 2 Si intermetallic compound can be more concentrated near the center and interface of the plating layer rather than on the plating surface. As a result, the plating layer desired in this embodiment can be formed. Next, the performance evaluation method of the molten-plated steel is described. (Bending workability) Regarding the bending workability of the plated steel in this embodiment, it can be evaluated by measuring the amount of crushing (peeling amount) during the reverse folding after 0R to 5R - 60 degrees - V bending. Specifically, after forming by pressing with a 2R - 60 - degree - V - shaped mold, further reverse folding processing is performed with a flat mold. For the part that was the valley part after V - shaped processing, a cellophane tape with a pressing width of 24 mm is pressed and then peeled off, and the part with a cellophane tape length of 90 mm is judged by the naked eye. The evaluation criteria are as described below. <Evaluation Criteria> A: No peeling part is generated. B: The peeling part is partially peeled off in a dot - like manner (less than 5% of the processed area). C: There is a linearly peeled part in the peeling part (5% to less than 10% of the processed area). D: There is a linearly peeled part in the peeling part (10% to less than 20% of the processed area). E: The peeling part is almost completely peeled off (20% or more of the processed area). (Corrosion Resistance) A flat - part test piece with a thickness of 0.8 mm is made, and a salt - water spray composite cyclic corrosion test (CCT, JASO - M609 - 91) is carried out, and the red - rust area ratio generated is measured. The number of cycles is set to 600 cycles. The evaluation criteria are set as described below. <Evaluation Criteria> A: No red rust is generated. B: Red - rust area ratio: less than 10%. C: Red - rust area ratio: 10% or more and less than 20%. D: Red - rust area ratio: 20% or more. (Hardness) The hardness obtained by Vickers test (Vickers hardness) is used as an evaluation index for the damage resistance of the plating layer. Specifically, the Vickers hardness of the plating - layer surface is measured with a load of 10 gf. Regarding the Vickers hardness, 10 points of Vickers hardness are measured in a cross - section covering the thickness direction of the plating layer, and the average of them is defined. After forming the plating layer, various chemical conversion treatments or coating treatments can also be carried out. The molten - plated steel material of this embodiment can also form a film on the plating layer. The film can be formed in one layer or two or more layers. Examples of the type of film directly above the plating layer include chromate film, phosphate film, and chromium - free chromate film. The formation of these films can be carried out by known methods such as chromate treatment, phosphate treatment, and chromium - free chromate treatment. Regarding chromate treatment, there are the following treatments: electrolytic chromate treatment for forming a chromate film through electrolysis, reaction - type chromate treatment for forming a film by reacting with the material and then rinsing the remaining treatment liquid, and coating - type chromate treatment for coating the treatment liquid on the object to be coated and drying without water washing to form a film. Any of these treatments can be adopted. Examples of electrolytic chromate treatment include electrolytic chromate treatment using the following components: chromic acid, silica sol, resin (phosphoric acid, acrylic resin, vinyl ester resin, vinyl acetate - acrylic emulsion, carboxylated styrene - butadiene latex, diisopropanolamine - modified epoxy resin, etc.), and hard silica. Phosphate treatment can be exemplified by, for example, zinc phosphate treatment, zinc calcium phosphate treatment, and manganese phosphate treatment. Chromate-free treatment is particularly suitable because it has no environmental burden. For chromate-free treatment, there are the following treatments: electrolytic chromate-free treatment that forms a chromate-free film through electrolysis, reactive chromate-free treatment that forms a film by reacting with the material and then rinses the remaining treatment solution, and coating-type chromate-free treatment that coats the treatment solution on the object to be coated and forms a film without water washing and then drying. Any of these treatments can be adopted. In addition, above the film directly above the plating layer, there may also be one or two or more organic resin films. The organic resin is not limited to a specific type, and examples include polyester resin, polyurethane resin, epoxy resin, acrylic resin, polyolefin resin, or modified products of these resins. Here, the so-called modified product refers to a resin obtained by reacting a reactive functional group contained in the structure of these resins with other compounds (such as monomers or crosslinking agents), and the other compounds contain functional groups that can react with the functional group in the structure. Regarding such an organic resin, one or two or more organic resins (unmodified) can be mixed, or one or two or more of the following organic resins can be mixed and used: those obtained by modifying at least one other organic resin in the presence of at least one organic resin. Also, the organic resin film may contain any coloring pigment and rust-preventing pigment. Materials dissolved or dispersed in water and made into an aqueous system can also be used. [Examples] Next, the examples of the present invention will be described. However, the conditions in the examples are a set of conditional examples used to confirm the feasibility and effects of the present invention, and the present invention is not limited to this set of conditional examples. As long as it does not deviate from the gist of the present invention and can achieve the purpose of the present invention, the present invention can adopt various conditions. First, a cold-rolled steel sheet (SPCC) with a size of 100 mm × 200 mm and a plate thickness of 0.8 mm was prepared as a plating mother board. For this cold-rolled steel sheet, first, an Al-Si plating bath (bath temperature: 650 °C) was used to form an Al-Si pre-plating layer on the steel sheet surface as described in Tables 1A and 1B. In addition, in the "Manufacturing Method" column of Tables 1A and 1B, "two-stage plating" indicates the application of the aforementioned two-stage plating method. "Sendzimir" in Tables 1A and 1B indicates the method applied, which is to perform reduction annealing on the cold-rolled steel sheet surface and then plating without performing pre-plating. After forming an Al-Si pre-plating layer on the plating mother board to produce a plating substrate, at 400 °C, H 2 (25%)-N 2 In a gas environment, the plating substrate was heated for 0.5 to 3.0 minutes. For the above-described pre-annealed plating substrate, melt plating was carried out using a melt plating simulator. First, an alloy having the plating bath compositions shown in Tables 1A and 1B was prepared by a vacuum melting method, and the plating bath was built in a completely oxygen / nitrogen-free replacement gas environment (O 2 concentration less than 5 ppm). The remainder of the plating bath compositions in Tables 1A and 1B is substantially Zn. Next, a point (the center of the back surface of the evaluation surface) of the plating substrate was spot welded to attach a K thermocouple, and the temperature history until the plating solidification was completed was grasped. Next, the plating substrate was heated to a predetermined temperature in an H 2 (25%)-N 2 gas environment. The plating bath temperature was set as shown in Tables 1A and 1B, and the plating substrate was immersed in the plating bath at an immersion speed of 500 mm / second, and the plating substrate was immersed in the bath for the immersion times shown in Tables 1A and 1B. After that, the plating substrate was lifted from the plating bath at a speed of 500 mm / second. After lifting, immediately, the average plating thickness Tp was adjusted to 40 μm with a wiping gas, and then N with a controlled flow rate was blown in an oxygen / nitrogen-free replacement gas environment 2 gas, and cooling was carried out at an average cooling rate shown in Table 1 in the temperature range of 550 to 450°C. 2 Through the above steps, a plated steel sheet was obtained. In addition, the plating layer thickness (μm) shown in Tables 2A and 2B is the thickness including the interfacial alloy layer, and was measured from the cross-section of the plating layer using an electron microscope. Next, samples for evaluation were cut out from various plated steel sheets. The samples for GDS analysis and for SEM observation were cut at a 30 mm square position on the opposite side of the position of the thermocouple. Samples (100×50 mm) for various property evaluations were taken from the central part in the plane direction of the plating layer. Regarding the evaluation of the various cut-out samples, a bending test, Vickers hardness measurement, and corrosion test SST were carried out. In addition, although the composition of Fe in the plating layer is not shown in the table, it is all in the range of 0 to 5%. Regarding the evaluation results, the composition of the plating layer, the GDS analysis results, the XRD measurement results, etc., are shown in Tables 2A and 2B. The remainder of the plating layer composition in Tables 2A and 2B is substantially Zn. In addition, the underlines in each table indicate: outside the scope of the present invention, suitable manufacturing conditions, or poor characteristic values. ​In the example of No. 52, the immersion time of the plating substrate in the plating bath was short, so the pre-plated layer could not be sufficiently introduced into the Zn-Al-Mg alloy layer, and as a result, a plating layer with a single-layer structure could not be obtained. In the example of No. 53, the bath temperature of the plating bath was low, so the pre-plated layer could not be sufficiently introduced into the Zn-Al-Mg alloy layer, and as a result, a plating layer with a single-layer structure could not be obtained. In the example of No. 54, the immersion time of the plating substrate in the plating bath was long, so the reaction between the plating bath and the plating mother board (base steel plate) proceeded excessively. Specifically, in the cross-section of the plating layer observed by an electron microscope, an interfacial alloy layer with a thickness of about 5 μm was observed. Also, in the results of GDS analysis for No. 54, the aggregation of Si towards the central part in the thickness direction of the plating layer could not be confirmed either. In the example of No. 55, the bath temperature of the plating bath was high, so the alloying between the plating bath and the plating mother board (base steel plate) proceeded excessively. Specifically, in the cross-section of the plating layer observed by an electron microscope, an interfacial alloy layer with an average thickness of about 5 μm was observed. Also, in the results of GDS analysis for No. 55, the aggregation of Si towards the central part in the thickness direction of the plating layer could not be confirmed either. [Table 1A] [Table 1B] [Table 2A] [Table 2B] Industrial Applicability According to the above aspects of the present invention, a hot-dip plated steel material with excellent plating hardness, corrosion resistance, and workability can be obtained. Accordingly, the obtained hot-dip plated steel material has high industrial applicability because it is suitable for applications in the automotive field, building materials field, etc. (None) Figure 1 is a chart showing an example of an element distribution profile and is a chart showing the following results: the results of GDS analysis performed on the plating layer of the hot-dip plated steel material according to the embodiment of the present invention. Figure 2 shows an example of an X-ray diffraction pattern in the plating layer according to the embodiment of the present invention.

Claims

1. A molten-coated steel material, comprising: a steel material, and a coating layer disposed on the surface of the steel material; the coating layer having the following chemical composition by mass%: containing: Al: greater than 10.0% and less than 60.0%, Mg: 4.0% and less than 15.0%, Si: 3.5% and less than 8.0%; and further comprising: Sn: 0% and less than 0.7%, Sr: 0% and less than 1.5%, Bi: 0% and less than 0.3%, In: 0% and less than 0.3%, Ca: 0% and less than 0.6%, Y: 0% and less than 0.3%, La: 0% and less than 0.3%, Ce: 0% and less than 0.3%, Li: 0% and less than 0.3%, Ni: 0% and less than 1.0%, Cu: 0% and less than 1.0%, Ag: 0% and less than 0.25%. Sb: 0% or more and 0.25% or less, Pb: 0% or more and 0.25% or less, B: 0% or more and 0.5% or less, P: 0% or more and 0.5% or less, Ti: 0% or more and 0.25% 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, Mn: 0% or more and 0.25% or less, Zr: 0% or more and 0.25% or less, W: 0% or more and 0.25% or less, Fe: 0% or more and 5.0% or less, with the remainder being Zn and impurities; the aforementioned coating contains Mg2Si intermetallic compounds; In the elemental distribution profile obtained by qualitative analysis using glow discharge luminescence analysis from the surface of the aforementioned plating layer toward the aforementioned steel, the thickness of the region from the surface of the aforementioned plating layer to the depth position where the maximum Fe strength is equivalent to 5% of the Fe strength is detected is defined as Tg. At this time, the average value of the qualitative analysis of Si from the surface of the aforementioned plating layer to Tg / 3 is defined as Si(surf), the average value of the qualitative analysis of Si from the surface of the aforementioned plating layer in the range of Tg / 3 to 2Tg / 3 is defined as Si(centre), and the average value of the qualitative analysis of Si from the surface of the aforementioned plating layer in the range of 2Tg / 3 to Tg is defined as Si(deep). At this time, the following formula (1) will be satisfied: Si(surf)<Si(deep)<Si(centre)…(1).

2. As in request item 1, the fused-coated steel, wherein, The X-ray diffraction pattern of the aforementioned coating surface measured using Cu-Kα line with X-ray output of 50kV and 300mA will satisfy the following formula (2): {I(26.19°)+I(44.6°)} / {2×I(12.5°)}>2.0…(2) In formula (2), I(n°) is the X-ray diffraction intensity at a diffraction angle of n°, and n is the diffraction angle (2θ) shown in formula (2).

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