Hot-dip plated steel material

Abstract

Provided is a hot-dip plated steel material, wherein a plating layer has a chemical composition containing, in mass%, more than 10.0% but not more than 60.0% of Al, 4.0-15.0% of Mg, and 3.5-8.0% of Si, with the remainder comprising Zn and impurities. In an element distribution profile obtained by qualitative analysis performed from the plating layer surface toward the steel material with a GDS method, formula (1) below is satisfied, where Si(surf) is an average value of Si from the plating layer surface to Tg / 3, Si(centre) is an average value of Si in a range from Tg / 3 to 2Tg / 3 starting from the plating layer surface, Si(deep) is an average value of Si in a range from 2Tg / 3 to Tg starting from the plating layer surface, and Tg is a thickness of a region from the plating layer surface to a depth position at which Fe strength equivalent to 5% with respect to the maximum strength of Fe is detected. (1): Si(surf)<Si(deep)<Si(centre)

Description

Hot-dip galvanized steel

[0001] This application claims priority to Japanese Patent Application No. 2023-125776, filed on August 1, 2023, the contents of which are incorporated herein by reference.

[0002] When steel materials are used for a long period of time, it is preferable to apply some kind of rust prevention treatment to the steel materials to make them resistant to corrosion. Hot-dip Zn plating is used as a means of inexpensively preventing rust on steel materials in various fields where rust prevention of steel materials is required, such as civil engineering, construction, and automotive fields.

[0003] The corrosion protection measures by the plating layer are roughly determined by the inherent corrosion resistance of the plating layer and the thickness of the plating layer. For example, Patent Document 1 describes the production of a plated steel sheet by a so-called continuous hot-dip plating method in which a steel sheet is continuously immersed in a hot-dip plating bath. The plated steel sheet is then processed into the shape of the part, thereby producing the part.

[0004] In recent years, various studies have been conducted to improve the performance of plated steel sheets.

[0005] For example, Patent Documents 1 and 2 describe Zn—Al—Mg-based plated steel materials (steel sheets) as plated steel materials with high corrosion resistance. In these Zn—Al—Mg-based plated steel materials, improvements in performance such as corrosion resistance have been achieved by controlling the structure of the plated layer, adding elements to the plated layer, or actively forming corrosion products.

[0006] International Publication No. WO 2018 / 139619 International Publication No. WO 2019 / 230894

[0007] In conventional Zn-Al-Mg plated steel materials such as those described in Patent Documents 1 and 2, the morphology of intermetallic compounds in the plating layer has not been fully investigated, except for major ones. As a result, under severe processing conditions, problems such as reduced workability, such as peeling (powdering) of the plating layer, have sometimes occurred due to the intermetallic compounds. Furthermore, in conventional Zn-Al-Mg plated steel materials, the hardness of the plating layer has sometimes been insufficient, making it difficult to stably ensure good scratch resistance.

[0008] An object of one embodiment of the present invention is to provide a hot-dip plated steel material that can simultaneously achieve sufficient plating hardness, excellent workability, and excellent corrosion resistance.

[0009] In order to solve the above problems, each aspect of the present invention employs the following configuration. [1] A hot-dip galvanized steel material according to one aspect of the present invention comprises a steel material and a coating layer disposed on a surface of the steel material, wherein the coating layer contains, in mass%, Al: more than 10.0% and not more than 60.0%, Mg: 4.0% or more and 15.0% or less, Si: 3.5% or more and 8.0% or less, and further contains 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, The plating layer has a chemical composition containing 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, the balance being Zn and impurities, and the plating layer contains Mg ２The plating layer contains a Si intermetallic compound, and in an element distribution profile obtained by qualitatively analyzing the plating layer from the surface toward the steel material by glow discharge optical emission spectrometry, when the thickness of a region from the surface of the plating layer to a depth position at which an Fe intensity equivalent to 5% of the maximum Fe intensity is detected is defined as Tg, the average value of the qualitative analysis values ​​of Si from the surface of the plating layer to Tg / 3 is defined as Si(surf), the average value of the qualitative analysis values ​​of Si in the range from Tg / 3 to 2Tg / 3 starting from the surface of the plating layer is defined as Si(centre), and the average value of the qualitative analysis values ​​of Si in the range from 2Tg / 3 to Tg starting from the surface of the plating layer is defined as Si(deep), the following formula (1) is satisfied: Si(surf)<Si(deep)<Si(centre) ... (1) [2] The hot-dip plated steel material described in [1] above may have an X-ray diffraction pattern of the surface of the plating layer measured using Cu-Kα rays at an X-ray output of 50 kV and 300 mA, which satisfies 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 n°, and n is the diffraction angle (2θ) shown in formula (2).

[0010] According to one embodiment of the present invention, it is possible to provide a hot-dip plated steel material that can simultaneously achieve sufficient plating hardness, excellent workability, and excellent corrosion resistance.

[0011] 1 is a graph showing an example of an element distribution profile obtained by GDS analysis of a coating layer of a hot-dip galvanized steel material according to an embodiment of the present invention, and shows an example of an X-ray diffraction pattern of the coating layer according to an embodiment of the present invention.

[0012] Hereinafter, a hot-dip plated steel material according to one embodiment of the present invention will be described. In this specification, the "%" used to indicate the content of each element in the chemical composition of the plating layer means "mass %" unless otherwise specified. Furthermore, a numerical range expressed using "to" means a range that includes the numerical values ​​written before and after "to" as the lower and upper limits. Furthermore, when "greater than" or "less than" is added to the numerical values ​​written before and after "to", the numerical range does not include these numerical values ​​as the lower or upper limit.

[0013] First, we investigated the relationship between the intermetallic compounds formed in the Zn-Al-Mg based plating layer and the workability of the plated steel material. The results of this investigation are explained below.

[0014] Generally, when a plating layer contains intermetallic compounds with covalent bonds, they become hard particles, increasing the hardness of the entire plating layer. In addition, since intermetallic compounds also have excellent insulating properties, their inclusion in the plating layer leads to high corrosion resistance.

[0015] On the other hand, if an excessive amount of intermetallic compounds is contained in the plating layer, the entire plating layer becomes hard, which may reduce the plastic deformability of the plating layer. Furthermore, if the entire plating layer becomes hard, the plating layer becomes more susceptible to breakage when the plated steel material is subjected to forming processing, which may cause peeling of the plating layer, such as powdering. Therefore, it is not practically preferable to contain a large amount of intermetallic compounds in the plating layer.

[0016] Furthermore, when intermetallic compounds are formed continuously and in layers, particularly on the surface and interface of a plating layer, peeling may occur during bending, or interfacial peeling may occur at the interface between the plating layer and the base material due to differences in corrosion rate during corrosion. Therefore, there has been a demand for a plating layer that has a desired level of hardness and high corrosion resistance, and good workability that does not cause peeling or the like.

[0017] Here, there is a technique for incorporating Ca into a coating layer to improve the hardness and corrosion resistance of the coating layer. When a large amount of Ca is incorporated into the coating layer, an intermetallic compound is formed with Zn, Al, and the like in the coating layer. The melting point of this Ca-containing intermetallic compound is very high during the solidification process of Zn-Al-Mg hot-dip coating. Therefore, Ca in the coating layer becomes a large Ca-containing intermetallic compound in the early stages after the steel material is pulled out of the coating bath, and grows in the coating layer.

[0018] In a typical hot-dip coating process, the surface of the coating layer is significantly cooled by the outside air, so solidification of the coating layer proceeds from the surface. In a Ca-containing bath, precipitation of Ca-containing intermetallic compounds begins in stable areas with low free energy, such as the surface or interface of the coating layer, due to a similar mechanism. As a result, Ca-containing intermetallic compounds tend to accumulate, particularly on the surface of the coating layer, and may grow coarsely, resulting in the formation of a layered structure of Ca-containing intermetallic compounds.

[0019] In the case of a plating layer in which Ca-containing intermetallic compounds are connected in layers, there is a risk of the Ca-containing intermetallic compounds undergoing brittle fracture during forming, resulting in peeling of the plating layer from the surface of the plating layer, a phenomenon known as "powdering." Therefore, it has been difficult to improve all of the hardness, workability, and corrosion resistance of a plating layer containing a high concentration of Ca.

[0020] Therefore, the present inventors investigated elements that can exert the same effect as Ca and found that Si is effective. Specifically, they found that Si forms Mg-Si intermetallic compounds, but that these Mg-Si intermetallic compounds are less likely to accumulate at the interface between the plating layer and the base material than Ca-containing intermetallic compounds. In other words, by including Si in the plating layer, it is possible to exert substantially the same effect as Ca, while allowing the formed Mg-Si intermetallic compounds to accumulate in the center of the plating layer in the thickness direction, thereby improving workability compared to conventional methods.

[0021] [Hot-dip plated steel material] Hereinafter, the hot-dip plated steel material according to this embodiment will be described in detail. The hot-dip plated steel material of this embodiment is a hot-dip plated steel material having a steel material and a coating layer disposed on a surface of the steel material, and the coating layer has an average chemical composition, in mass%, of Al: more than 10.0% and not more than 60.0%, Mg: 4.0% or more and 15.0% or less, Si: 3.5% or more and 8.0% or less, and further contains 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, 1.0% or less, Ag: 0% or more, 0.25% or less, Sb: 0% or more, 0.25% or less, Pb: 0% or more, 0.25% or less, B: 0% or more, 0.5% or less, P: 0% or more, 0.5% or less, Ti: 0% or more, 0.25% or less, Co: 0% or more, 0.25% or less, V: 0% or more, 0.25% or less, Nb: 0% or more, 0.25% or less, Mn: 0% or more, 0.25% or less, Zr: 0% or more, 0.25% or less, W: 0% or more, 0.25% or less, Fe: 0% or more, 5.0% or less, the remainder contains Zn and impurities.

[0022] In addition, the coating layer of the hot-dip coated steel material of this embodiment contains Mg ２ In an element distribution profile obtained by qualitatively analyzing a coating layer containing a Si intermetallic compound from the surface of the coating layer toward the steel material by glow discharge optical emission spectrometry, the following formula (1) is satisfied when Tg is the thickness of a region from the surface of the coating layer to a depth position at which an Fe intensity equivalent to 5% of the maximum Fe intensity is detected, Si(surf) is the average value of the qualitative analysis values ​​of Si from the surface of the coating layer to Tg / 3, Si(centre) is the average value of the qualitative analysis values ​​of Si in the range from Tg / 3 to 2Tg / 3 starting from the surface of the coating layer, and Si(deep) is the average value of the qualitative analysis values ​​of Si in the range from 2Tg / 3 to Tg starting from the surface of the coating layer.

[0023] Si(surf)<Si(deep)<Si(centre)…(1)

[0024] (Steel Material) First, the steel material (original sheet) to be plated will be described. The steel material is, for example, mainly a steel plate, but its size is not particularly limited. The steel plate may be any steel plate that can be applied to a normal hot-dip galvanizing process. Specifically, this applies to steel plates that can be applied to a process in which the steel plate is immersed in molten metal and solidified, such as a continuous hot-dip galvanizing line (CGL). The size of the steel plate that can be applied is, for example, a plate thickness of 10 mm or less and a plate width of 2000 mm or less, but the size of the steel plate is not limited to this.

[0025] The quality of the steel material is not particularly limited, and various steel plates and steel materials such as general steel, Al-killed steel, ultra-low carbon steel, high carbon steel, various high-tensile steels, some high alloy steels (steels containing elements for strengthening corrosion resistance such as Ni and Cr), steel for bolts, and steel wire rods for bridge cables can be used. More specifically, the steel material may be, for example, a hot-rolled steel plate defined in JIS G 3131 (2018), a cold-rolled steel plate defined in JIS G 3141 (2017), a material included in the general structural rolled steel material corresponding to the so-called SS material, a so-called general steel included in the hot-rolled steel plate defined in JIS G 3193 (2019), a pre-plated steel thinly plated with various metals described in JIS H 8641 (2021), JIS G 3302 (2019), 3303 (2017), 3313 (2017), 3314 (2019), 3315 (2017), 3317 (2019), and 3321 (2019), a rolled steel material for building structures described in JIS G 3136 (2012), a pre-plated steel thinly plated with various metals described in JIS G Applicable steels include Al-killed steels, ultra-low carbon steels, and high carbon steels described in JIS G 3126 (2015), various high-tensile steels described in JIS G 3113 (2018), 3134 (2018), and 3135 (2018), and some high alloy steels (steels containing elements that strengthen corrosion resistance, such as Ni and Cr, etc.).

[0026] (Plating layer) Next, the plating layer provided on the steel material will be described. The plating layer according to this embodiment includes a Zn—Al—Mg alloy layer. The Zn—Al—Mg alloy layer contains a Zn phase, an Al phase, an MgZn phase, and a Zn—Al—Mg alloy phase. ２ The plating layer of this embodiment contains Mg ２The plating layer of this embodiment may contain other intermetallic compounds.

[0027] When alloying elements such as Al and Mg are contained in the Zn phase, corrosion resistance is improved. Therefore, in the case of a plating layer containing such a Zn phase, even a thin film (for example, about half the thickness of a normal Zn plating layer) can exhibit corrosion resistance equivalent to that of a normal Zn plating layer. Similarly, even when the plating layer of this embodiment is thin, corrosion resistance equivalent to or greater than that of a conventional Zn plating layer is ensured.

[0028] MgZn ２ The plating layer according to this embodiment includes MgZn ２ phase is included. ２ By including a certain amount of this phase in the plating layer, corrosion resistance in a water-soaked environment can be further improved.

[0029] Zn phase (Al-Zn phase, Zn-Al phase) The Zn phase is mainly a ternary eutectic structure (Zn / Al / MgZn ２ In addition, when the plating layer contains a large amount of Al, the Zn phase may dissolve in the Al phase, as Al and Zn mix together in the solid state to form an Al-Zn phase. On the other hand, Al may dissolve in the Zn phase to form a Zn-Al phase (with an Al concentration of up to about 20%). A phase composed of Zn and Al is highly workable.

[0030] Al Phase The Al phase exists in the coating layer in the form of clumps of primary Al crystals. The Al phase dissolves various elements, particularly Zn, within the phase during the solidification process of the coating layer. Because the coating 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 dendrite structure that spreads in a tree-like manner within the coating layer, forming the skeleton of the coating layer. Because the Al phase is soft and highly workable, it serves to hinder the propagation of cracks that occur and reduce fatal defects in the coating layer.

[0031] Mg ２ The plating layer according to this embodiment contains an Si intermetallic compound. ２Contains Si intermetallic compounds. Mg ２ The Si intermetallic compound is an intermetallic compound observed as an island with clear boundaries in the solidification structure of the Si-containing coating layer. ２ It is believed that Zn, Al, and other additive elements are not dissolved in the Si intermetallic compound, or even if they are dissolved, the amount is extremely small. ２ The Si intermetallic compounds can be clearly distinguished from other phases in the plating layer under a microscope. ２ The Si intermetallic compound is formed in the plating layer when the plating layer contains Si.

[0032] Intermetallic compounds formed in a plating layer generally have the effect of increasing corrosion resistance and hardness due to the complex bonding of individual atoms. However, if intermetallic compounds are formed in a continuous layer on the plating surface and interface, they may aggregate and peel off during bending, and during corrosion, the difference in corrosion rate may cause surface and / or interfacial peeling.

[0033] Here, Ca is known as an element effective in improving the corrosion resistance and hardness of the plating layer. However, as mentioned above, Ca-containing intermetallic compounds are easily formed in layers, and are particularly prone to accumulating at the interface. This is due to the CaZn formation that occurs when an excessive amount of Ca is contained in the Zn-Al-Mg based plating layer. ４ On the other hand, Si tends to improve the corrosion resistance and hardness of the plating layer in a manner similar to that of Ca, and Mg ２ It was found that Si intermetallic compounds tend to accumulate less at the interface than Ca-containing intermetallic compounds. In addition, the more the intermetallic compounds accumulate in the center of the plating layer, the less likely powdering occurs even under severe processing conditions. ２ By including the Si intermetallic compound, the hardness of the plating layer can be further increased, the corrosion resistance can be improved, and good workability can be ensured.

[0034] Mg ２ The presence of intermetallic compounds such as Si intermetallic compounds can be confirmed by GDS (glow discharge optical emission spectroscopy).

[0035] Next, a method for analyzing components in the depth direction inside the plating layer according to this embodiment will be described.

[0036] The method for analyzing the components in the depth direction inside the plating layer is preferably glow discharge optical emission spectroscopy (GDS) using a glow discharge optical emission spectrometer. In this embodiment, a LECO Japan 850A glow discharge optical emission spectrometer is used, but the measuring device is not limited to this. Furthermore, when performing depth direction analysis, it is preferable to perform the analysis while performing Ar sputtering, and the analysis conditions are as follows: argon pressure: 0.27 MPa, output power: 30 W, output voltage: 1000 V, discharge area: within a circular area with a diameter of 4 mm.

[0037] Elemental analysis using GDS is performed from the surface of the plating layer in the depth direction toward the steel material until the Fe concentration reaches 100% (reaching the base steel). Therefore, the analysis range of depth direction analysis using GDS is the range from the surface of the plating layer to the Zn-Al-Mg plating layer, the Al-Fe alloy layer, and a portion of the steel material. After GDS analysis, the sputter depth of the cross section is measured using a "surfcom130A" manufactured by Tokyo Seimitsu Co., Ltd. Elemental analysis using GDS provides an elemental distribution profile in the depth direction of the plating layer. The elemental distribution profile shows the distribution of the content of each element in the depth direction when the total amount of detected elements is set to 100%.

[0038] In this embodiment, in an element distribution profile obtained by qualitatively analyzing the surface of the coating layer toward the steel material using GDS, if Tg is the thickness of the region from the surface of the coating layer to a depth position where an Fe intensity equivalent to 5% of the maximum Fe intensity is detected, the average Si qualitative analysis value from the surface of the coating layer to Tg / 3 is defined as Si(surf), the average Si qualitative analysis value in the range from Tg / 3 to 2Tg / 3 starting from the surface of the coating layer is defined as Si(center), and the average Si qualitative analysis value in the range from 2Tg / 3 to Tg starting from the surface of the coating layer is defined as Si(deep), the following formula (1) is satisfied. Note that Si(surf), Si(center), and Si(deep) are obtained by performing qualitative analysis using GDS 10 times and averaging the qualitative analysis values ​​in the obtained element distribution profile. The qualitative analyses are performed at positions on the surface of the coating layer that do not overlap each other.

[0039] Si(surf)<Si(deep)<Si(centre)…(1)

[0040] To satisfy the above (1), Mg ２ Accumulating Si intermetallic compounds in the thickness direction center of the plating layer (specifically, the aforementioned region) improves workability and prevents powdering even under severe processing conditions. In other words, satisfying formula (1) increases the hardness and corrosion resistance of the plating layer, resulting in a plated steel product that is hard, has good workability, and exhibits good corrosion resistance. By accumulating Mg intermetallic compounds in the thickness direction center of the plating layer and the boundary between the plating layer and Fe, where the potential is likely to change significantly, ２ It is believed that the presence of an insulating material such as a Si intermetallic compound inhibits the promotion of corrosion and improves corrosion resistance.

[0041] In addition, Mg ２ The Si intermetallic compound has the effect of increasing corrosion resistance and hardness. On the other hand, a large amount of Mg is present on the surface and interface of the plating layer. ２ When the Si intermetallic compound is formed, this Mg ２ The Si intermetallic compound may peel off. Also, due to the difference in corrosion rate, Mg ２This can cause surface and / or interface peeling of the Si intermetallic compound, which can impair workability and corrosion resistance. ２ Therefore, in this embodiment, the amount of Si(surf) is made smaller than the amount of Si(deep). That is, by making the amount of Si in the region from the surface of the plating layer to Tg / 3 smaller than the amount of Si in the range from 2Tg / 3 to Tg, the amount of Mg during processing and corrosion can be reduced. ２ It is possible to suppress peeling caused by Si intermetallic compounds, and to further improve workability and corrosion resistance.

[0042] In this embodiment, in an element distribution profile obtained by qualitatively analyzing the surface of the coating layer toward the steel material by the GDS method, the above formula (1) is satisfied in a region up to a depth position where an Fe intensity equivalent to 5% of the maximum Fe intensity is detected. This region is generally the same as the region where the Zn-Al-Mg alloy layer exists.

[0043] FIG. 1 shows an example of the results of depth profile analysis by GDS of the plating layer according to this embodiment. The graph shown in FIG. 1 is an element distribution profile. In this embodiment, the region that defines the above formula (1) is defined as a region from the surface of the plating layer to a position that is 5% of the maximum Fe intensity, when analyzed in the depth direction from the surface of the plating layer. For example, in the analysis results shown in FIG. 1, the maximum Fe intensity is 53 V, so the above formula (1) is defined in the region up to the position of 5% of that intensity, i.e., the position where the Fe intensity is 2.7 V.

[0044] Next, Mg ２ The index of the Si intermetallic compound by X-ray diffraction will be explained.

[0045] The plating layer of this embodiment is characterized in that, 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, Mg ２ When the diffraction intensities of the Si intermetallic compound are I (26.19°) and I (44.6°) and the background intensity is I (12.5°), the following formula (2) is satisfied.

[0046] {I(26.19°)+I(44.6°)} / {2×I(12.5°)}>2.0 (2) In equation (2), I(n°) is the X-ray diffraction intensity at a diffraction angle of n°, and n is the diffraction angle (2θ) shown in equation (2).

[0047] FIG. 2 shows an example of an X-ray diffraction pattern of the plating layer according to this embodiment. As shown in FIG. ２ The peaks of the Si intermetallic compound appear at around 26.19° and 44.6°. That is, I(26.19°) and I(44.6°) in formula (2) represent the peaks of Mg at diffraction angles of 26.19° and 44.6°, respectively. ２ This shows the X-ray diffraction intensity of the Si intermetallic compound. In this embodiment, when the background intensity is I (12.5°), by satisfying the above formula (2), an intermetallic compound with excellent corrosion resistance and hardness is formed in the plating layer. As a result, high hardness and corrosion resistance can be achieved while maintaining the plastic deformability of the plating surface and interface.

[0048] The plating layer of this embodiment may include an interface alloy layer containing Al and Fe (Al-Fe-based interface alloy layer). 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 between the steel material and the Zn-Al-Mg-based alloy layer, and is in contact with the surface of the steel material. In other words, the plating layer of this embodiment may have a single-layer structure composed of a Zn-Al-Mg-based alloy layer, or may have a laminated structure including a Zn-Al-Mg-based alloy layer and an Al-Fe-based interface alloy layer.

[0049] Although the Al-Fe-based interface alloy layer does not significantly affect corrosion resistance, it does affect the adhesion of the plating layer and workability (presence or absence of cracks) during processing of hot-dip galvanized steel. In particular, the Al-Fe-based interface alloy layer may affect powdering resistance, which indicates the degree of peeling of the plating layer during processing. Typically, a thinner Al-Fe-based interface alloy layer reduces the number of crack initiation points in the plating layer during processing, thereby further improving powdering resistance. Therefore, in hot-dip galvanized steel materials that may be subjected to high processing when used as components, etc., it is preferable that the thickness of the Al-Fe-based interface alloy layer be as thin as possible. Specifically, the thickness of the intermetallic compound constituting the Al-Fe-based interface alloy layer is less than 5 μm. This thickness is preferably 2 μm or less, more preferably 1 μm or less, and even more preferably 0.5 μm or less. It may even be 0.3 μm or less. This suppresses cracking during processing and further improves powdering resistance. Furthermore, the ratio of the thickness of the Al-Fe interfacial alloy layer to the thickness of the plating layer is less than 10% on average, and more preferably less than 5%.

[0050] The Al-Fe interfacial alloy layer is formed on the surface of the steel material, specifically, between the steel material and the Zn-Al-Mg alloy layer. ５ Fe ２ The Al-Fe interfacial 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 interfacial alloy layer is likely to be formed in a coating layer containing Al element. In this embodiment, since the coating bath contains Al at a certain concentration or more, the Al-Fe interfacial alloy layer contains Al. ５ Fe ２ However, because atomic diffusion takes time, the Fe concentration in the Al-Fe system interface alloy layer is not uniform, and the Fe concentration may be higher in the area closer to the base steel. Therefore, the Al-Fe system interface alloy layer is partially composed of an AlFe phase, an Al ３ Fe phase, Al ５ Fe ２In addition, since the plating bath also contains a certain concentration of Zn, the Al-Fe-based interface alloy layer may also contain a small amount of Zn.

[0051] In the plating layer according to this embodiment, some of the Si may be incorporated into the Al-Fe-based interfacial alloy layer to form an Al-Fe-Si intermetallic compound phase. The Al-Fe-Si intermetallic compound phase that can be identified is the AlFeSi phase. Phases such as the α phase, β phase, q1 phase, and q2 phase exist as isomers of the AlFeSi phase. Therefore, these AlFeSi phases may be detected in the Al-Fe-based interfacial alloy layer. An Al-Fe-based interfacial alloy layer containing these AlFeSi phases is also referred to as an Al-Fe-Si alloy layer.

[0052] 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 multilayer structure composed of an Al-Fe interfacial alloy layer and a Zn-Al-Mg alloy layer, the average chemical composition is the combined average chemical composition of the Al-Fe interfacial alloy layer and the Zn-Al-Mg alloy layer.

[0053] In the plating layer of this embodiment, the thickness of the Al-Fe-based interface alloy layer is preferably 10% or less of the total thickness of the plating layer. When the thickness of the Al-Fe-based interface alloy layer is sufficiently small relative to the total thickness of the plating layer, the Fe concentration of the plating layer is often 5% or less.

[0054] Al: More than 10.0% and 60.0% or less Al is an element that mainly constitutes the coating layer. If the Al content is 10.0% or less, a sufficient amount of Zn-Al phase may not be secured. Therefore, the Al content is more than 10.0%. On the other hand, if the Al content exceeds 60.0%, corrosion resistance may decrease. Therefore, the upper limit of the Al content is 60.0% or less. The lower limit of the Al content is preferably 15.0% or more. Furthermore, the upper limit of the Al content is preferably 45.0% or less, more preferably 30.0% or less.

[0055] Mg: 4.0% or more, 15.0% or less Like Zn, Mg is an element that mainly constitutes the coating layer. In the coated steel sheet according to this embodiment, Mg is an important element for improving corrosion resistance. If the Mg content in the coating layer is less than 4.0%, the effect of improving corrosion resistance is not as clear as when no Mg is contained. Therefore, the Mg content is set to 4.0% or more. On the other hand, if excessive Mg is added to a Zn-Al-Mg-based coating bath, a rapid oxidation reaction occurs at the surface of the coating bath, making stable coating impossible. Therefore, to ensure stable coating and good manufacturability, the Mg content in the coating layer is set to 15% or less.

[0056] Si: 3.5% or more and 8.0% or less Si combines with Mg to form Mg ２ Si forms an intermetallic compound having a composition of Mg. Si also suppresses excessive Al-Fe reaction, thereby suppressing the formation of an Al-Fe-based interface alloy layer. When the Si content is less than 3.5%, Mg ２ The amount of Si produced decreases, which may result in a decrease in the hardness of the coating layer and a decrease in corrosion resistance. On the other hand, if the Si content exceeds 8.0%, the Mg content in the coating layer may decrease. ２ If the amount of Si generated becomes too large, the plating layer may undergo brittle fracture, and the plating layer may aggregate and peel from the plating surface, causing a powdering phenomenon, which may result in a decrease in corrosion resistance. Therefore, the Si content is set to 3.5% or more and 8.0% or less.

[0057] Sr: 0% or more, 1.5% or less Sr forms covalent bonds with Zn, Al, Si, etc. to form intermetallic compounds that have excellent corrosion resistance and hardness. On the other hand, if the Sr content exceeds 1.5%, Sr-based intermetallic compounds are excessively formed in the plating layer, making the entire plating layer hard. As a result, when the plated steel material is used for forming, the plating layer is easily damaged, and peeling of the plating layer, such as powdering, may occur. Therefore, the Sr content is set to 0.03% or more, 1.5% or less.

[0058] Sn: 0% or more, 0.7% or less Bi: 0% or more, 0.3% or less In: 0% or more, 0.3% or less Each of Sn, Bi, and In is an element that promotes softening of the plating layer when contained in the plating layer. Since Sn, Bi, and In are elements that can be contained arbitrarily, 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 other elements are also formed. ２ Sn, Bi, and In are elements that are softer than the tin phase and have good workability, and their inclusion in the plating layer clearly improves workability. Furthermore, these elements exhibit very base electrochemical properties, so they have a high corrosion prevention effect. By incorporating at least one of Sn, Bi, and In within the above ranges, the corrosion resistance of the processed part can be improved.

[0059] Ca: 0% or more, 0.6% or less. Ca is an element that contributes to improving the hardness and corrosion resistance of the plating layer. On the other hand, if a large amount of Ca is contained in the plating layer, an intermetallic compound is formed with Zn and / or Al in the plating layer. The Ca-containing intermetallic compounds formed in this manner tend to accumulate, particularly on the plating layer surface. In some cases, the accumulated Ca-containing intermetallic compounds may grow coarsely and form layers of Ca-containing intermetallic compounds. In the case of a plating layer in which Ca-containing intermetallic compounds are connected in layers, the Ca-containing intermetallic compounds may undergo brittle fracture during forming, causing the plating layer to peel off from the plating layer surface, resulting in reduced workability. Therefore, the Ca content is set to 0.6% or less.

[0060] Y: 0% or more, 0.3% or less La: 0% or more, 0.3% or less Ce: 0% or more, 0.3% or less Li: 0% or more, 0.3% or less Ni: 0% or more, 1.0% or less Cu: 0% or more, 1.0% or less Ag: 0% or more, 0.25% or less Sb: 0% or more, 0.25% or less Pb: 0% or more, 0.25% or less B: 0% or more, 0.5% or less P: 0% or more, 0.5% or less Ti: 0% or more, 0.25% or less Co: 0% or more, 0.25% or less V: 0% or more, 0.25% or less Nb: 0% or more, 0.25% or less Mn: 0% or more, 0.25% or less Zr: 0% or more, 0.25% or less W: 0% or more, 0.25% or less 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, Al, etc. However, when the contents of these elements are within the above ranges, they do not affect the initial corrosion of the plating layer. On the other hand, if these elements are contained in excess, a potential difference may occur in the plating layer, causing a large amount of initial white rust to occur. Therefore, when these elements are contained, it is advisable to keep them within the above ranges.

[0061] Fe: 0% or more, 5.0% or less. The hot-dip plated steel material of this embodiment is produced by a continuous hot-dip plating method, so Fe may diffuse from the base material to be plated into the plated layer during production. As described above, in this embodiment, the Al concentration of the plated layer is high, and an Al-Fe-based interfacial alloy layer may be formed, but its thickness is thin. As a result, the plated layer may contain up to 5.0% Fe, but as long as the Fe concentration is limited to 5.0% or less, there is no effect on the frequency of cracks in the plated layer, etc. Therefore, the Fe content is set to 0 to 5.0%. The Fe content may be greater than 0%.

[0062] The balance is preferably Zn and impurities. The balance preferably contains Zn. Since the hot-dip plated steel material of this embodiment is a highly versatile Zn-based plated steel material, the element constituting the main phase of the plated layer is Zn.

[0063] Impurities refer to components contained in raw materials or components mixed in during the manufacturing process, but not intentionally included. For example, trace amounts of components other than Fe may be mixed into the plating layer as impurities due to atomic diffusion between the steel material (base steel) and the plating bath. Furthermore, since metals with 3N purity are typically used to manufacture plating alloys, the total concentration of impurities may be approximately 0.03% or less.

[0064] To identify the average chemical composition of the plating layer, an acid solution is obtained by stripping and dissolving the plating layer with an acid containing an inhibitor that suppresses corrosion of the base steel (steel material). The acid solution is filtered to remove the insoluble matter, and the resulting residue is liquefied by alkali fusion treatment. The resulting acid solution and the solution obtained by alkali fusion treatment are 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.

[0065] [Method of manufacturing hot-dip plated steel material] Next, a method of manufacturing hot-dip plated steel material according to this embodiment will be described. The plated steel material according to this embodiment is not particularly limited in its manufacturing method. Therefore, a simple method of forming the Si-containing plating layer as described above is to add Si directly to a Zn-Al-Mg-based plating bath to form a plating layer. However, this method tends to deposit Mg on the surface and its vicinity, rather than at the center of the plating layer. ２ Si intermetallic compounds are likely to be formed. Therefore, as an example of a suitable manufacturing method for producing the hot-dip plated steel material of this embodiment, a method of supplying Si to the plated layer from a Si-containing pre-plated layer provided on the base sheet for plating will be described below. In this specification, this method of forming a predetermined pre-plated layer on the base sheet for plating in advance and then applying Zn-Al-Mg-based hot-dip plating in this order is referred to as a "two-stage plating method."

[0066] First, an Al-Si pre-plating layer is formed on a base sheet for plating, such as a cold-rolled or hot-rolled steel sheet. The pre-plating method may be hot-dip plating, electroplating, displacement plating, vapor deposition, or the like. Furthermore, these pre-plating layers may be heated and alloyed.

[0067] When pre-plating on the base sheet is performed by hot dip plating, the pre-plating may be performed under conditions for forming a normal aluminum plating, such as an Al-8 to 10% Si bath, and there are no particular restrictions.

[0068] Next, the original sheet to be plated is heated to 450 to 600°C, preferably to a temperature similar to the temperature of the plating bath described below. This heating may also serve as annealing of the original sheet (hereinafter, this heating may be referred to as pre-annealing). Heating the steel sheet before immersion in the plating bath described below can reduce temperature fluctuations in the plating bath.

[0069] The heated base sheet with the pre-plated layer formed thereon is immersed in a Zn—Al—Mg plating bath adjusted to obtain the desired plating composition, and then pulled out, whereby the pre-plated layer is incorporated into the Zn—Al—Mg alloy layer to form the final plating layer. The plating bath temperature is preferably 480 to 550°C.

[0070] Furthermore, in order to incorporate the pre-plating layer into the Zn-Al-Mg alloy layer and obtain a plating layer with a single-layer structure, it is preferable to ensure that the base sheet is immersed in the plating bath for a certain period of time or more. Specifically, the immersion time is preferably between 3 and 10 seconds. In order to sufficiently incorporate the pre-plating layer into the Zn-Al-Mg alloy layer, the immersion time is preferably 4 seconds or more. However, if the immersion time is excessively long, the alloy layer at the interface between the plating and the steel sheet may become thick, which may result in plating peeling. Therefore, the immersion time is preferably 8 seconds or less.

[0071] In this embodiment, it is preferable to control the temperature when the original plate is pulled up. That is, by controlling the cooling conditions appropriately after immersion, Si is contained in the plating layer, and the desired Mg ２ Si intermetallic compounds can be formed.

[0072] Specifically, Mg ２In order to sufficiently form Si intermetallic compounds, it is preferable to set the average cooling rate to 25°C / sec or less in the temperature range of 550 to 450°C. If the average cooling rate in the temperature range of 550 to 450°C exceeds 25°C / sec, Si will be dispersed uniformly in the thickness direction of the plating layer, and the desired plating layer may not be obtained.

[0073] Cooling conditions in a temperature range outside the range of 550 to 450° C. are not particularly limited, as they do not affect the formation of intermetallic compounds.

[0074] In this way, by appropriately controlling the cooling conditions after the plating base sheet is pulled out of the bath, Mg ２ The formation of Si intermetallic compounds on the surface and interface of the plating layer is further suppressed, and Mg ２ The Si intermetallic compounds can be dispersed appropriately, which results in high plating hardness, workability, and corrosion resistance while maintaining the plastic deformability of the plating surface and interface.

[0075] In addition, when a steel sheet with an Al-Si pre-plated layer is used as the plating substrate, Mg is deposited not on the plating surface but in the center and near the interface of the plating layer. ２ The Si intermetallic compounds can be more aggregated, and as a result, the desired plating layer of this embodiment can be formed.

[0076] Next, a method for evaluating the performance of hot-dip galvanized steel materials will be described.

[0077] (Bending Workability) The bending workability of the plated steel material of this embodiment can be evaluated by measuring the amount of powdering (amount of peeling) when bending the material 0R to 5R at 60 degrees in a V-shape and then unbending it.

[0078] Specifically, the sheet is molded using a 2R-60°V-shaped die press, and then bent back into a flat plate using a flat die. After V-shaping, a 24 mm wide cellophane tape is pressed against the valley and pulled away, and a 90 mm long section of the cellophane tape is visually evaluated. The evaluation criteria are as follows:

[0079] <Evaluation criteria> A: No peeling occurred. B: Partially peeled off in spots (less than 5% of the processed area). C: Linear peeling occurred (5 to less than 10% of the processed area). D: Linear peeling occurred (10 to less than 20% of the processed area). E: Almost all peeled off (20% or more of the processed area).

[0080] (Corrosion Resistance) A 0.8 mm thick flat test piece was prepared and subjected to a salt spray combined cycle corrosion test (CCT, JASO-M609-91) to measure the area ratio of red rust that developed. The number of cycles was 600. The evaluation criteria were as follows:

[0081] <Evaluation Criteria> A: No red rust occurred. B: Red rust area ratio: less than 10%. C: Red rust area ratio: 10% or more but less than 20%. D: Red rust area ratio: 20% or more.

[0082] (Hardness) The hardness measured by the Vickers test (Vickers hardness) is used as an evaluation index for the scratch resistance of the plating layer. Specifically, the Vickers hardness of the plating layer surface is measured under a load of 10 gf. The Vickers hardness is measured at 10 points on a cross section including the thickness direction of the plating layer, and the average of these measurements is used.

[0083] After the plating layer is formed, various chemical conversion treatments and painting treatments may be carried out.

[0084] In the hot-dip plated steel material of this embodiment, a coating may be formed on the plating layer. One or more layers of the coating may be formed. Examples of the type of coating directly on the plating layer include a chromate coating, a phosphate coating, and a chromate-free coating. These coatings can be formed by known methods such as chromate treatment, phosphate treatment, and chromate-free treatment.

[0085] 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.

[0086] 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.

[0087] Examples of the phosphate treatment include zinc phosphate treatment, zinc calcium phosphate treatment, and manganese phosphate treatment.

[0088] 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.

[0089] 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.

[0090] 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 film may also contain any coloring pigment or anti-rust pigment. Water-based organic resins obtained by dissolving or dispersing them in water may also be used.

[0091] Next, examples of the present invention will be described, but the conditions in the examples are merely examples adopted to confirm the feasibility and effects of the present invention, and the present invention is not limited to these examples. Various conditions can be adopted in the present invention as long as they do not deviate from the gist of the present invention and the object of the present invention is achieved.

[0092] First, a cold-rolled steel sheet (SPCC) measuring 100 mm x 200 mm and having a thickness of 0.8 mm was prepared as the base sheet for plating. An Al-Si pre-plating layer as shown in Tables 1A and 1B was formed on the surface of this cold-rolled steel sheet using an Al-Si-based plating bath (bath temperature: 650°C). Note that "two-stage plating" in the "Manufacturing Method" column in Tables 1A and 1B indicates that the above-mentioned two-stage plating method was applied. "Sendzimer" in Tables 1A and 1B indicates that a method was applied in which the surface of the cold-rolled steel sheet was subjected to reduction annealing and plating without pre-plating.

[0093] After forming an Al-Si pre-plating layer on the base sheet to produce a plating substrate, the plating substrate was heated at 400°C under H ２ (25%)-N ２ The mixture was heated in an atmosphere for 0.5 to 3.0 minutes.

[0094] The pre-annealed plated substrate was subjected to hot-dip plating using a hot-dip plating simulator.

[0095] First, alloys having the plating bath components shown in Tables 1A and 1B were prepared by vacuum melting, and the alloys were placed in a completely oxygen-free, nitrogen-substituted atmosphere (O ２ The plating bath was prepared in a state where the zinc concentration was less than 5 ppm. The balance of the plating bath components in Tables 1A and 1B was essentially Zn. Next, one point on the plating substrate (the backside of the center of the evaluation surface) was spot-welded to a K thermocouple, and the temperature history until the plating solidification was completed was determined. Subsequently, the plating substrate was ２ (25%)-N ２ The plating bath temperature was set as shown in Tables 1A and 1B, and the substrate was immersed in the plating bath at an immersion speed of 500 mm / sec for the immersion time shown in Tables 1A and 1B. Thereafter, the substrate was withdrawn from the plating bath at a speed of 500 mm / sec.

[0096] Immediately after the lift, N ２ The wiping gas was adjusted so that the average plating thickness Tp was 40 μm, and then the N ２ Gas was blown onto the material to cool it in the temperature range of 550 to 450°C at the average cooling rate shown in Table 1.

[0097] The thicknesses (μm) of the plating layers shown in Tables 2A and 2B include the thickness of the interfacial alloy layer, and were measured from the cross section of the plating layer using an electron microscope.

[0098] Next, evaluation samples were cut out from each of the plated steel sheets. Samples for GDS analysis and SEM observation were cut out at 30 mm square positions on the opposite side of the thermocouple position. Samples (100 × 50 mm) for evaluating various properties were taken from the center of the plated layer in the planar direction.

[0099] The cut samples were evaluated by bending tests, Vickers hardness measurements, and corrosion tests (SST). The Fe content of the plating layer is not shown in the table, but it was in the range of 0 to 5%.

[0100] The evaluation results, plating layer compositions, GDS analysis results, XRD measurement results, etc. are shown in Tables 2A and 2B. The remainder of the plating layer compositions in Tables 2A and 2B is essentially Zn. Note that underlines in each table indicate that the results are outside the scope of the present invention, that the preferred manufacturing conditions are not met, or that the characteristic values ​​are unfavorable.

[0101] In the example of No. 52, the immersion time of the substrate for plating in the plating bath was short, so the pre-plating layer could not be sufficiently incorporated into the Zn-Al-Mg alloy layer, and as a result, a plating layer with a single layer structure could not be obtained.

[0102] In the example of No. 53, the bath temperature of the plating bath was low, so the pre-plating layer could not be sufficiently incorporated into the Zn-Al-Mg alloy layer, and as a result, a plating layer with a single-layer structure could not be obtained.

[0103] In the case of Example No. 54, the substrate for plating was immersed in the plating bath for a long time, which resulted in excessive reaction between the plating bath and the base steel sheet. Specifically, an interfacial alloy layer approximately 5 μm thick was observed in a cross-sectional view of the plating layer using an electron microscope. Furthermore, the results of GDS analysis of Example No. 54 did not reveal any accumulation of Si in the center of the plating layer in the thickness direction.

[0104] In Example No. 55, the high bath temperature of the coating bath caused excessive alloying between the coating bath and the base steel sheet. Specifically, an interfacial alloy layer with an average thickness of approximately 5 μm was observed in a cross-section of the coating layer using an electron microscope. Furthermore, the results of GDS analysis of Example No. 55 showed no accumulation of Si in the center of the coating layer in the thickness direction.

[0105]

[0106]

[0107]

[0108]

[0109] According to the above-described aspects of the present invention, a hot-dip plated steel material having excellent coating hardness, corrosion resistance, and workability can be obtained. Therefore, the obtained hot-dip plated steel material can be suitably applied to the fields of automobiles, building materials, etc., and therefore has high industrial applicability.

Claims

1. A hot-dip plated steel material having a steel material and a plating layer disposed on a surface of the steel material, the plating layer containing, by mass%, Al: more than 10.0% and not more than 60.0%, Mg: 4.0% or more and not more than 15.0%, Si: 3.5% or more and not more than 8.0%, and further containing Sn: 0% or more and not more than 0.7%, Sr: 0% or more and not more than 1.5%, Bi: 0% or more and not more than 0.3%, In: 0% or more and not more than 0.3%, Ca: 0% or more and not more than 0.6%, 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%, Li: 0% or more and not more than 0.3%, Ni: 0% or more and not more than 1.0%, Cu: 0% or more and not more than 1.0%, a chemical composition including Ag: 0% or more, 0.25% or less, Sb: 0% or more, 0.25% or less, Pb: 0% or more, 0.25% or less, B: 0% or more, 0.5% or less, P: 0% or more, 0.5% or less, Ti: 0% or more, 0.25% or less, Co: 0% or more, 0.25% or less, V: 0% or more, 0.25% or less, Nb: 0% or more, 0.25% or less, Mn: 0% or more, 0.25% or less, Zr: 0% or more, 0.25% or less, W: 0% or more, 0.25% or less, Fe: 0% or more, 5.0% or less, the balance being Zn and impurities, and the plating layer is ２ A hot-dip plated steel material containing a Si intermetallic compound, and in an element distribution profile obtained by qualitatively analyzing the surface of the plated layer toward the steel material by glow discharge optical emission spectrometry, the thickness of a region from the surface of the plated layer to a depth position at which an Fe intensity equivalent to 5% of the maximum Fe intensity is detected is defined as Tg, the average value of the qualitative analysis value of Si from the surface of the plated layer to Tg / 3 is defined as Si(surf), the average value of the qualitative analysis value of Si in the range from Tg / 3 to 2Tg / 3 starting from the surface of the plated layer is defined as Si(centre), and the average value of the qualitative analysis value of Si in the range from 2Tg / 3 to Tg starting from the surface of the plated layer is defined as Si(deep), which satisfies the following formula (1): Si(surf)<Si(deep)<Si(centre) ... (1) 2. The hot-dip plated steel product according to claim 1, wherein an X-ray diffraction pattern of the surface of the plating layer measured using Cu-Kα radiation at an X-ray output of 50 kV and 300 mA satisfies 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 n°, and n is the diffraction angle (2θ) shown in formula (2).

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