EP4756065A1

EP4756065A1 - Hot-dip plated steel material

Info

Publication number: EP4756065A1
Application number: EP24849249.8A
Authority: EP
Inventors: Shinya Furukawa; Kohei Tokuda; Yasuto Goto
Original assignee: Nippon Steel Corp
Current assignee: Nippon Steel Corp
Priority date: 2023-08-01
Filing date: 2024-08-01
Publication date: 2026-06-10
Also published as: AU2024318267A1; CN121511324A; KR20260028115A; TW202507025A; JPWO2025028604A1; WO2025028604A1; JP7653049B1

Abstract

In this hot-dip plated steel material, the plated layer has a chemical composition including, in terms of mass%, more than 10.0% and 60.0% or less of Al, 4.0% or more and 15.0% or less of Mg, 3.5% or more and 8.0% or less of Si, and a remainder of Zn and impurities, and in a case where, in an elemental distribution profile obtained by a qualitative analysis using a GDS method in a direction from a surface of the plated layer toward the steel material, a thickness of a region from a surface of the plated layer to a depth position where an Fe intensity corresponding to 5% with respect to the maximum intensity of Fe is detected is denoted by Tg, the average value of Si from the surface of the plated layer to Tg/3 is denoted by Si (surf), the average value of Si in a range of Tg/3 to 2 Tg/3 starting from the surface of the plated layer is denoted by Si (centre), and the average value of Si in a range of 2 Tg/3 to Tg starting from the surface of the plated layer is denoted by Si (deep), Expression (1) is satisfied.

Si (surf) < Si (deep) < Si (centre)

Description

TECHNICAL FIELD

The present invention relates to a hot-dip plated steel material.
Priority is claimed on Japanese Patent Application No. 2023-125776, filed August 1, 2023 , the content of which is incorporated herein by reference.

BACKGROUND ART

In a case where a steel material is used for a long period of time, it is preferable to apply some kind of antirust treatment to resist corrosion of the steel material. A hot-dip Zn plating method is used in various fields where antirust for steel materials is required, such as the fields of civil engineering, construction, and automobiles, as a means for inexpensive antirust of steel materials.
An anticorrosion means provided by a plated layer is generally determined by inherent corrosion resistance of the plated layer and thickness of the plated layer. For example, Patent Document 1 describes that a plated steel sheet is manufactured by a so-called continuous hot-dip plating method in which a steel sheet is continuously immersed in a hot-dip plating bath. Thereafter, the plated steel sheet is processed into a component shape to manufacture a component.
In recent years, various examinations have been made to improve performance of a plated steel sheet.
For example, Patent Documents 1 and 2 describe Zn-Al-Mg-based plated steel materials (steel sheets) as plated steel materials having high corrosion resistance. In these Zn-Al-Mg-based plated steel materials, performance such as corrosion resistance is improved by controlling the microstructure of the plated layer, adding an element to the plated layer, or positively forming a corrosion product.

Citation List

Patent Documents

Patent Document 1: PCT International Publication No. WO 2018/139619
Patent Document 2: PCT International Publication No. WO 2019/230894

SUMMARY OF INVENTION

Technical Problem

In the conventional Zn-Al-Mg-based plated steel materials as described in Patent Documents 1 and 2, the form of intermetallic compounds in the plated layer has not been sufficiently examined except for the main form. Therefore, under severe working conditions, problems such as deterioration in workability such as peeling (powdering) of the plated layer may also occur due to the intermetallic compounds. Furthermore, in the conventional Zn-Al-Mg-based plated steel material, hardness of the plated layer is insufficient, and it may be difficult to stably ensure good defect resistance.
An object of an embodiment of the present invention is to provide a hot-dip plated steel material capable of achieving all of sufficient plating hardness, excellent workability, and excellent corrosion resistance.

Solution to Problem

In order to solve the above-described problem, aspects of the present invention adopt the following configurations.

[1] A hot-dip plated steel material according to an aspect of the present invention includes a steel material, and a plated layer disposed on a surface of the steel material, wherein
- the plated layer has a chemical composition including, in terms of mass%,
- more than 10.0% and 60.0% or less of Al,
- 4.0% or more and 15.0% or less of Mg, and
- 3.5% or more and 8.0% or less of Si, and
- further including
- 0% or more and 0.7% or less of Sn,
- 0% or more and 1.5% or less of Sr,
- 0% or more and 0.3% or less of Bi,
- 0% or more and 0.3% or less of In,
- 0% or more and 0.6% or less of Ca,
- 0% or more and 0.3% or less of Y,
- 0% or more and 0.3% or less of La,
- 0% or more and 0.3% or less of Ce,
- 0% or more and 0.3% or less of Li,
- 0% or more and 1.0% or less of Ni,
- 0% or more and 1.0% or less of Cu,
- 0% or more and 0.25% or less of Ag,
- 0% or more and 0.25% or less of Sb,
- 0% or more and 0.25% or less of Pb,
- 0% or more and 0.5% or less of B,
- 0% or more and 0.5% or less of P,
- 0% or more and 0.25% or less of Ti,
- 0% or more and 0.25% or less of Co,
- 0% or more and 0.25% or less of V,
- 0% or more and 0.25% or less of Nb,
- 0% or more and 0.25% or less of Mn,
- 0% or more and 0.25% or less of Zr,
- 0% or more and 0.25% or less of W,
- 0% or more and 5.0% or less of Fe, and
- a remainder of Zn and impurities,
- the plated layer contains a Mg₂Si intermetallic compound, and
- in a case where, in an elemental distribution profile obtained by a qualitative analysis using glow discharge optical emission spectrometry in a direction from a surface of the plated layer toward the steel material, a thickness of a region from a surface of the plated layer to a depth position where an Fe intensity corresponding to 5% with respect to the maximum intensity of Fe is detected is denoted by Tg, the average value of a qualitative analysis value of Si from the surface of the plated layer to Tg/3 is denoted by Si (surf), the average value of a qualitative analysis value of Si in a range of Tg/3 to 2 Tg/3 starting from the surface of the plated layer is denoted by Si (centre), and the average value of a qualitative analysis value of Si in a range of 2 Tg/3 to Tg starting from the surface of the plated layer is denoted by Si (deep), Expression (1) is satisfied, $Si (surf) < Si (deep) < Si (centre)$
[2] The hot-dip plated steel material according to [1], wherein in an X-ray diffraction pattern of the surface of the plated layer measured by using Cu-Kα radiation under conditions of 50 kV and 300 mA X-ray output, Expression (2) may be satisfied, $\{I (26.19 °) + I (44.6 °)\} / \{2 \times I (12.5 °)\} > 2.0$ in Expression (2), I (n°) is an X-ray diffraction intensity at a diffraction angle n°, and n is a diffraction angle (20) indicated in Expression (2).

Advantageous Effects of Invention

According to an embodiment of the present invention, it is possible to provide a hot-dip plated steel material capable of achieving all of sufficient plating hardness, excellent workability, and excellent corrosion resistance.

BRIEF DESCRIPTION OF DRAWINGS

[FIG. 1] A diagram representing a result of GDS analysis performed on a plated layer of a hot-dip plated steel material according to an embodiment of the present invention, and a graph illustrating an example of an elemental distribution profile.
[FIG. 2] An example representing an X-ray diffraction pattern in a plated layer according to an embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a hot-dip plated steel material according to an embodiment of the present invention will be described.
Note that, in the present specification, the "%" indication of the amount of each element in a chemical composition of a plated layer means "mass%" unless otherwise specified.
In addition, a numerical range represented by "to" means a range including the numerical values described before and after "to" as the lower limit and the upper limit. Note that a numerical range in which "more than" or "less than" is attached to the numerical values described before and after "to" means a range not including these numerical values as the lower limit or the upper limit.
First, a relationship between an intermetallic compound formed in a Zn-Al-Mg-based plated layer and workability of a plated steel material was examined. Hereinafter, examination results will be described below.
In general, in a case where an intermetallic compound having a covalent bond is contained in the plated layer, hard particles are formed, so that the hardness of the entire plated layer increases. In addition, since the intermetallic compound is also excellent in insulation properties, containment of the intermetallic compound in the plated layer results in high corrosion resistance.
On the other hand, in a case where the intermetallic compound is excessively contained in the plated layer, the hardness of the entire plated layer may increase, leading to deterioration in plastic deformability of the plated layer. In addition, in a case where the hardness of the entire plated layer increases, the plated layer is easily broken during forming working of a plated steel material used as a material, and peeling of the plated layer such as powdering may occur. Therefore, it is practically not preferable to contain a large amount of the intermetallic compound in the plated layer.
In addition, in a case where the intermetallic compound is continuously formed in a layered manner particularly on the surface and the interface of the plated layer among the plated layers, for example, peeling may occur during bending, or interface peeling may occur at the interface between the plated layer and the base metal due to a difference in corrosion rate during corrosion. Therefore, conventionally, there has been a demand for a plated layer having a desired level of hardness and high corrosion resistance and having good workability without occurrence of peeling or the like.
Here, there is a technique in which Ca is contained in the plated layer in order to improve the hardness and corrosion resistance of the plated layer. In a case where a large amount of Ca is contained in the plated layer, an intermetallic compound is formed with Zn, Al, or the like in the plated layer. The melting point of this Ca-containing intermetallic compound is very high in the solidification process of Zn-Al-Mg-based hot-dip plating. Therefore, Ca in the plated layer becomes a large Ca-containing intermetallic compound at the initial stage after the steel material is pulled up from the plating bath, and grows in the plated layer.
In a general hot-dip plating process, the surface of the plated layer is significantly cooled by the outside air, so that solidification of the plated layer proceeds from the surface. Also in the bath containing Ca, precipitation of the Ca-containing intermetallic compound is initiated from a low and stable free energy portion such as a surface or an interface of the plated layer by a similar mechanism. As a result, the Ca-containing intermetallic compound is likely to accumulate particularly on the surface of the plated layer, and the Ca-containing intermetallic compound may coarsely grow to be continuous in layers.
In a case of a plated layer in which Ca-containing intermetallic compounds are continuous in layers, there is a possibility that a so-called "powdering phenomenon" occurs, in which the Ca-containing intermetallic compounds are brittlely fractured during forming working, and the plated layer is peeled off from the plated layer surface. Therefore, in the plated layer containing Ca at a high concentration, it has been difficult to improve all of hardness, workability, and corrosion resistance.
Therefore, the present inventors examined an element capable of exerting the same effect as Ca, and found that Si is effective. Specifically, it has been found that Si forms a Mg-Si-based intermetallic compound, but the Mg-Si-based intermetallic compound has a property of being less likely to accumulate at the interface between the plated layer and the base metal as compared with the Ca-containing intermetallic compound. That is, by containing Si in the plated layer, it is possible to accumulate the Mg-Si-based intermetallic compound formed at the central part in the thickness direction of the plated layer while exerting substantially the same effect as Ca, and thus, it is possible to further enhance the workability as compared with the conventional plated layer.

[Hot-Dip Plated Steel Material]

Hereinafter, a hot-dip plated steel material according to the present embodiment will be described.
The hot-dip plated steel material of the present embodiment includes a steel material, and a plated layer disposed on a surface of the steel material, wherein the average chemical composition of the plated layer includes, in terms of mass%,

more than 10.0% and 60.0% or less of Al,
4.0% or more and 15.0% or less of Mg, and
3.5% or more and 8.0% or less of Si, and
further including
0% or more and 0.7% or less of Sn,
0% or more and 1.50% or less of Sr,
0% or more and 0.3% or less of Bi,
0% or more and 0.3% or less of In,
0% or more and 0.6% or less of Ca,
0% or more and 0.3% or less of Y,
0% or more and 0.3% or less of La,
0% or more and 0.3% or less of Ce,
0% or more and 0.3% or less of Li,
0% or more and 1.0% or less of Ni,
0% or more and 1.0% or less of Cu,
0% or more and 0.25% or less of Ag,
0% or more and 0.25% or less of Sb,
0% or more and 0.25% or less of Pb,
0% or more and 0.5% or less of B,
0% or more and 0.5% or less of P,
0% or more and 0.25% or less of Ti,
0% or more and 0.25% or less of Co,
0% or more and 0.25% or less of V,
0% or more and 0.25% or less of Nb,
0% or more and 0.25% or less of Mn,
0% or more and 0.25% or less of Zr,
0% or more and 0.25% or less of W,
0% or more and 5.0% or less of Fe, and
a remainder of Zn and impurities.

In addition, the plated layer in the hot-dip plated steel material of the present embodiment contains a Mg₂Si intermetallic compound, and
in a case where, in an elemental distribution profile obtained by a qualitative analysis using glow discharge optical emission spectrometry in a direction from a surface of the plated layer toward the steel material, a thickness of a region from a surface of the plated layer to a depth position where an Fe intensity corresponding to 5% with respect to the maximum intensity of Fe is detected is denoted by Tg, the average value of a qualitative analysis value of Si from the surface of the plated layer to Tg/3 is denoted by Si (surf), the average value of a qualitative analysis value of Si in a range of Tg/3 to 2 Tg/3 starting from the surface of the plated layer is denoted by Si (centre), and the average value of a qualitative analysis value of Si in a range of 2 Tg/3 to Tg starting from the surface of the plated layer is denoted by Si (deep), Expression (1) is satisfied,
$Si (surf) < Si (deep) < Si (centre)$

(Steel Material)

First, a steel material (base steel sheet) to be plated will be described.
The steel material is, for example, mainly a steel sheet, but its size is not particularly limited. The steel sheet may be a steel sheet applicable to a general hot-dip galvanizing step. Specifically, steel sheets applicable in a step of solidification by immersion in molten metal, such as a continuous hot-dip galvanizing line (CGL), apply to this. As the size of the steel sheet, for example, a steel sheet having a sheet thickness of 10 mm or less and a sheet width of 2000 mm or less can be applied, but the size of the steel sheet is not limited thereto.
The composition of the steel material is not particularly limited. As the steel material, for example, various steel sheets and steel materials such as a general steel, an Al-killed steel, an ultra low carbon steel, a high carbon steel, various high tensile strength steels, some high alloy steels (for example, steels containing corrosion resistance-enhancing elements such as Ni and Cr), a bolt steel, and a steel wire rod for bridge cable can be applied. More specifically, as the steel material, for example, a hot-rolled steel sheet defined in JIS G 3131 (2018) and a cold-rolled steel sheet defined in JIS G 3141 (2017), a steel material included in a rolled steel material for general structural use corresponding to a so-called SS material, a so-called general steel included in a hot-rolled steel sheet defined in JIS G 3193 (2019), pre-plated steels in which various metals are thinly plated described in JIS H 8641 (2021), JIS G 3302 (2019), JIS G 3303 (2017), JIS G 3313 (2017), JIS G 3314 (2019), JIS G 3315 (2017), JIS G 3317 (2019), JIS G 3321 (2019), and the like, a rolled steel material for structural use in buildings described in JIS G 3136 (2012), Al-killed steel described in JIS G 3126 (2015), ultra low carbon steel, high carbon steel, various high tensile strength steels described in JIS G 3113 (2018), JIS G 3134 (2018), and JIS G 3135 (2018), and some high alloy steels (for example, steels containing corrosion resistance-enhancing elements such as Ni and Cr) are applicable.

(Plated Layer)

Next, the plated layer provided on the steel material will be described.
The plated layer according to the present embodiment includes a Zn-Al-Mg-based alloy layer. The Zn-Al-Mg-based alloy layer contains a Zn phase, an Al phase, and a MgZn₂ phase. In addition, the plated layer of the present embodiment contains a Mg₂Si intermetallic compound. Furthermore, the plated layer of the present embodiment may contain other intermetallic compounds.
In a case where an alloying element such as Al or Mg is contained in the Zn phase, corrosion resistance is improved. Therefore, such a plated layer containing the Zn phase can exhibit corrosion resistance equivalent to that of a conventional Zn-plated layer even though the plated layer is formed as a thin film (for example, a thickness of about a half of the conventional Zn-plated layer). Similarly, even in a case where the plated layer of the present embodiment is formed as a thin film, corrosion resistance equal to or higher than that of the conventional Zn-plated layer is ensured.

MgZn₂ Phase

The plated layer according to the present embodiment contains a MgZn₂ phase. When a certain amount of the MgZn₂ phase is contained in the plated layer, corrosion resistance in an environment with water exposure can be further improved.

Zn Phase (Al-Zn Phase and Zn-Al Phase)

A Zn phase is mainly present as a ternary eutectic structure (Zn/Al/MgZn₂ ternary eutectic structure). In addition, in a case where the plated layer contains a large amount of Al, Zn in the Zn phase and Al may be mixed with each other in the solid state, whereby an Al-Zn phase is formed, and Zn may also form as a solid solution in the Al phase. On the other hand, Al may form as a solid solution in the Zn phase to form a Zn-Al phase (the Al concentration in the phase is up to about 20%). The phase containing Zn and Al is extremely rich in workability.

Al Phase

An Al phase is present in a massive form as an Al primary phase in the plated layer. The Al phase forms a solid solution with various elements, particularly Zn, in its phase during the solidification process of the plated layer. Since the plated layer of the present embodiment has a high Al content, the Al phase contains an element such as Zn in a supersaturated manner in the solidification process. In the solidification process, the Al phase forms a dendrite microstructure spreading in a dendritic shape in the plated layer and forms a frame of the plated layer. Since the Al phase is soft and rich in workability, the Al phase plays a role of inhibiting the propagation of cracks that have occurred and reducing critical defects in the plated layer.

Mg₂Si Intermetallic Compound

The plated layer according to the present embodiment contains a Mg₂Si intermetallic compound. The Mg₂Si intermetallic compound is an intermetallic compound observed in an island shape with a clear boundary in the solidified microstructure of the plated layer containing Si. It is considered that Zn, Al, or another additive element is not formed as a solid solution in the Mg₂Si intermetallic compound, or even if it is formed as a solid solution, the amount of thereof is extremely small. The Mg₂Si intermetallic compound can be clearly distinguished from other phases in the plated layer by microscopic observation. The Mg₂Si intermetallic compound is formed in the plated layer by containing Si in the plated layer.
The intermetallic compound formed in the plated layer generally serves to enhance corrosion resistance and hardness due to the intricate bonding of individual atoms. On the other hand, in a case where the intermetallic compound is continuously formed in a layered manner on the plated surface and the interface, cohesive peeling may occur during bending, and surface peeling and/or interface peeling may occur due to a difference in corrosion rate during corrosion.
Here, Ca is known as an element effective for improving corrosion resistance and hardness of the plated layer. However, as described above, the Ca-containing intermetallic compound is a compound that is likely to be formed in a layered manner, and is particularly likely to accumulate at the interface. This is because an intermetallic compound based on CaZn₄ tends to be formed easily in a case where Ca is excessively contained in the Zn-Al-Mg-based plated layer. On the other hand, it has been found that Si tends to improve the corrosion resistance and hardness of the plated layer almost similarly to Ca, and particularly, the Mg₂Si intermetallic compound tends to be less likely to accumulate at the interface as compared with the Ca-containing intermetallic compound.
In addition, as the intermetallic compound accumulates in the central part of the plated layer, powdering is less likely to occur even under severe working conditions. By containing the Mg₂Si intermetallic compound in the plated layer so as to satisfy each expression described later, the hardness of the plated layer can be further increased, the corrosion resistance is improved, and good workability can be ensured.
The presence of intermetallic compounds such as the Mg₂Si intermetallic compound can be confirmed by glow discharge optical emission spectrometry (GDS).
Next, an analysis method for components in the plated layer in the depth direction in the plated layer according to the present embodiment will be described.
As the analysis method for components in the plated layer in the depth direction, glow discharge optical emission spectrometry (GDS) with a glow discharge optical emission spectrometer may be used. In the present embodiment, LECO Japan 850A is used as the glow discharge optical emission spectrometer, but the measurement apparatus is not limited thereto. In addition, in a case of performing analysis in the depth direction, it is preferable to perform the analysis while performing Ar sputtering, the analysis conditions include an argon pressure of 0.27 MPa, an output power of 30 W, an output voltage of 1000 V, and a discharge region in a circular region having a diameter of 4 mm.
The component analysis by GDS is performed from the surface of the plated layer toward the steel material along the depth direction until the Fe concentration reaches 100% (reaches the base metal). Therefore, the analysis range of the depth direction analysis by GDS is a range reaching from the surface of the plated layer to the Zn-Al-Mg plated layer, the Al-Fe alloy layer, and part of the steel material. After the GDS analysis, the sputtering depth of the cross section is measured using "surfcom 130A" manufactured by Tokyo Seimitsu Co. Ltd. The elemental distribution profile of the plated layer in the depth direction is obtained by the component analysis by GDS. In the elemental distribution profile, in a case where the total amount of the detected elements is 100%, the distribution of the amount of each element in the depth direction is illustrated.
In the present embodiment, in a case where, in an elemental distribution profile obtained by a qualitative analysis using GDS in a direction from a surface of the plated layer toward the steel material, a thickness of a region from a surface of the plated layer to a depth position where an Fe intensity corresponding to 5% with respect to the maximum intensity of Fe is detected is denoted by Tg, the average value of a qualitative analysis value of Si from the surface of the plated layer to Tg/3 is denoted by Si (surf), the average value of a qualitative analysis value of Si in a range of Tg/3 to 2 Tg/3 starting from the surface of the plated layer is denoted by Si (centre), and the average value of a qualitative analysis value of Si in a range of 2 Tg/3 to Tg starting from the surface of the plated layer is denoted by Si (deep), Expression (1) is satisfied. Note that Si (surf), Si (centre), and Si (deep) are obtained by performing qualitative analysis by GDS 10 times and obtaining the average of qualitative analysis values in the obtained elemental distribution profile. The qualitative analysis is performed at positions not overlapping each other on the surface of the plated layer. $Si (surf) < Si (deep) < Si (centre)$
By accumulating the Mg₂Si intermetallic compound at the central part in the thickness direction of the plated layer (specifically, the above-described region) to satisfy the above Expression (1), workability can be improved, and powdering can be avoided even under severe working conditions. That is, by satisfying Expression (1), it is possible to realize an increase in hardness and improvement in corrosion resistance of the plated layer, and as a result, it is possible to obtain a plated steel material that is hard and has good workability and corrosion resistance. It is considered that in a case where an insulator such as the Mg₂Si intermetallic compound is present in a portion where the potential is likely to greatly change, such as the central part in the thickness direction of the plated layer or the boundary portion of the plated layer/Fe, corrosion promotion is suppressed and corrosion resistance is improved.
Note that the Mg₂Si intermetallic compound has an action of increasing corrosion resistance and hardness. On the other hand, in a case where a large amount of Mg₂Si intermetallic compound is formed on the surface and the interface of the plated layer, the Mg₂Si intermetallic compound may be peeled off during processing. In addition, due to a difference in corrosion rate during corrosion, surface peeling and/or interface peeling of the Mg₂Si intermetallic compound may occur, and workability and corrosion resistance may be impaired. The Mg₂Si intermetallic compound formed on the surface of the plated layer has a larger influence on deterioration in workability and corrosion resistance. Therefore, in the present embodiment, Si (surf) is made smaller than Si (deep). That is, by making the amount of Si in a region from the surface of the plated layer to Tg/3 smaller than the amount of Si in a range from 2 Tg/3 to Tg, peeling derived from the Mg₂Si intermetallic compound during processing or corrosion can be suppressed, and workability and corrosion resistance can be further improved.
Note that, in the present embodiment, in an elemental distribution profile obtained by a qualitative analysis using the GDS method in a direction from a surface of the plated layer toward the steel material, the above Expression (1) is satisfied in a region to a depth position where an Fe intensity corresponding to 5% with respect to the maximum intensity of Fe is detected. The region is generally the same as an existing region of the Zn-Al-Mg-based alloy layer.
FIG. 1 illustrates an example of a depth direction analysis result by GDS in the plated layer according to the present embodiment. The graph illustrated in FIG. 1 is an elemental distribution profile. In the present embodiment, the region defining the above Expression (1) is a region from the surface of the plated layer to a position of 5% of the maximum intensity of Fe when analyzed in the depth direction from the surface of the plated layer. For example, in a case of the analysis result as illustrated in FIG. 1, since the maximum intensity of Fe is 53 V, the above Expression (1) is defined in a region to a position where the intensity is 5%, that is, a position where the Fe intensity is 2.7 V.
Next, an index of the Mg₂Si intermetallic compound by X-ray diffraction will be described.
In the plated layer according to the present embodiment, in a case where a diffraction intensity of the Mg₂Si intermetallic compound is I (26.19°) and I (44.6°) and an intensity of the background is I (12.5°) in an X-ray diffraction pattern of the surface of the plated layer measured by using Cu-Kα radiation under conditions of 50 kV and 300 mA X-ray output, Expression (2) is satisfied, $\{I (26.19 °) + I (44.6 °)\} / \{2 \times I (12.5 °)\} > 2.0$
Here, in Expression (2), I (n°) is an X-ray diffraction intensity at a diffraction angle n°, and n is a diffraction angle (2θ) indicated in Expression (2).
FIG. 2 illustrates an example representing an X-ray diffraction pattern in the plated layer according to the present embodiment. As illustrated in FIG. 2, the peaks of the Mg₂Si intermetallic compound appear in the vicinity of 26.19° and in the vicinity of 44.6°. That is, I (26.19°) and I (44.6°) in Expression (2) represent the X-ray diffraction intensities of the Mg₂Si intermetallic compound at diffraction angles of 26.19° and 44.6°, respectively. In the present embodiment, in a case where the intensity of the background is I (12.5°), an intermetallic compound excellent in corrosion resistance and hardness is formed in the plated layer by satisfying the above Expression (2). As a result, high hardness and corrosion resistance can be exhibited while maintaining the plastic deformability of the plated surface and the interface.
The plated layer of the present embodiment may include an interfacial alloy layer containing Al and Fe (Al-Fe-based interfacial alloy layer). The average thickness of the Al-Fe-based interfacial alloy layer is less than 5 µm. The Al-Fe-based interfacial alloy layer is an interfacial alloy layer between the steel material and the Zn-Al-Mg-based alloy layer, and is in contact with a surface of the steel material. That is, the plated layer according to the present embodiment may have a single-layer structure including the Zn-Al-Mg-based alloy layer or a stacked layer structure including the Zn-Al-Mg-based alloy layer and the Al-Fe-based interfacial alloy layer.
The Al-Fe-based interfacial alloy layer does not have a large influence on corrosion resistance, but has an influence on adhesion and workability (presence or absence of cracks) of the plated layer during processing of the hot-dip plated steel material. In particular, the Al-Fe-based interfacial alloy layer may affect powdering resistance indicating the degree of peeling of the plated layer during processing. Usually, an Al-Fe-based interfacial alloy layer having a thin thickness can reduce the number of crack initiation sites in the plated layer during processing, thereby further improving powdering resistance. Therefore, it is preferable that the thickness of the Al-Fe-based interfacial alloy layer is as thin as possible in a hot-dip plated steel material that may be subjected to high processing when used as a member or the like. Specifically, the thickness of an intermetallic compound constituting the Al-Fe-based interfacial alloy layer is less than 5 µm. The thickness is preferably 2 µm or less, more preferably 1 µm or less, and still more preferably 0.5 µm or less. The thickness may be 0.3 µm or less. As a result, the occurrence of cracks during processing can be suppressed, and the powdering resistance can be further improved. Furthermore, a ratio of the thickness of the Al-Fe interfacial alloy layer to the thickness of the plated layer is less than 10% on average, more preferably less than 5%.
The Al-Fe-based interfacial alloy layer is formed on a 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 in which an Al₅Fe₂ phase is the main phase as the microstructure. The Al-Fe-based interfacial alloy layer is formed by mutual atomic diffusion between the base metal (steel sheet) and the plating bath. In a case where a continuous hot-dip plating method is used as a procedure, the Al-Fe-based interfacial alloy layer is easily formed in the plated layer containing an Al element. In the present embodiment, since a certain concentration or more of Al is contained in the plating bath, the Al₅Fe₂ phase is formed most in the Al-Fe-based interfacial alloy layer. However, since it takes time to diffuse atoms, the Fe concentration in the Al-Fe-based interfacial alloy layer is not uniform, and the Fe concentration may be high in a portion close to the base metal. Therefore, a small amount of an AlFe phase, an Al₃Fe phase, an Al₅Fe₂ phase, or the like may be partially contained in the Al-Fe-based interfacial alloy layer. In addition, since a certain concentration of Zn is also contained in the plating bath, a small amount of Zn may also be contained in the Al-Fe-based interfacial alloy layer.
Note that, in the plated layer according to the present embodiment, part of Si may be incorporated into the Al-Fe-based interfacial alloy layer to form an Al-Fe-Si intermetallic compound phase. One of the identified Al-Fe-Si intermetallic compound phases is an AlFeSi phase. Examples of the isomer of the AlFeSi phase include an α phase, a β phase, a q1 phase, and a q2 phase. Therefore, these AlFeSi phases and the like may be detected in the Al-Fe-based interfacial alloy layer. The Al-Fe-based interfacial alloy layer containing these AlFeSi phases and the like is also referred to as an Al-Fe-Si alloy layer.
Next, the average chemical composition of the plated layer will be described. In a case where the plated layer has a single-layer structure of the Zn-Al-Mg-based alloy layer, the average chemical composition of the entire plated layer is the average chemical composition of the Zn-Al-Mg-based alloy layer. In addition, in a case where the plated layer has a stacked layer structure including the Al-Fe-based interfacial alloy layer and the Zn-Al-Mg-based alloy layer, the average chemical composition of the entire plated layer is the total average chemical composition of the Al-Fe-based interfacial alloy layer and the Zn-Al-Mg-based alloy layer.
In the plated layer of the present embodiment, the thickness of the Al-Fe-based interfacial alloy layer is preferably 10% or less with respect to the thickness of the entire plated layer. In a case where the thickness of the Al-Fe-based interfacial alloy layer is sufficiently small with respect to the entire plated layer as described above, the Fe concentration of the plated layer is often 5% or less.

Al: more than 10.0% and 60.0% or less

Al is an element mainly constituting the plated layer. In a case where the Al content is 10.0% or less, a sufficient amount of a Zn-Al phase may not be ensured. Therefore, the Al content is more than 10.0%. On the other hand, in a case where the Al content is more than 60.0%, corrosion resistance may be deteriorated. 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. The upper limit of the Al content is preferably 45.0% or less, and more preferably 30.0% or less.

Mg: 4.0% or more and 15.0% or less

Similarly to Zn, Mg is an element mainly constituting the plated layer. Mg is an important element for improving corrosion resistance in the plated steel sheet according to the present embodiment. In a case where the Mg content in the plated layer is less than 4.0%, the effect of improving corrosion resistance is not clearly observed as compared with the case where Mg is not contained. Therefore, the Mg content is 4.0% or more. On the other hand, in a case where Mg is excessively added in the Zn-Al-Mg-based plating bath, a rapid oxidation reaction occurs on a bath surface of the plating bath, and plating cannot be stably performed. Therefore, in order to stably perform plating and ensure good manufacturability, the Mg content in the plated layer is 15% or less.

Si: 3.5% or more and 8.0% or less

Si bonds with Mg to form an intermetallic compound having a composition of Mg₂Si. In addition, Si suppresses an excessive Al-Fe reaction, thereby suppressing the formation of an Al-Fe-based interfacial alloy layer.
In a case where the Si content is less than 3.5%, the production amount of Mg₂Si may decrease, the hardness of the plated layer may decrease, and corrosion resistance may also be deteriorated. On the other hand, in a case where the Si content is more than 8.0%, the production amount of Mg₂Si in the plated layer is too large, the plated layer may be brittlely fractured, the plated layer may be cohesively peeled off from the plated surface, a powdering phenomenon may occur, and as a result, corrosion resistance may also be deteriorated. Thus, the Si content is 3.5% or more and 8.0% or less.

Sr: 0% or more and 1.5% or less

Sr forms a covalent bond with Zn, Al, Si, or the like, and forms an intermetallic compound excellent in corrosion resistance and hardness. On the other hand, in a case where the Sr content exceeds 1.5%, a Sr-based intermetallic compound is excessively generated in the plated layer, and the hardness of the entire plated layer increases. As a result, the plated layer is easily broken during forming working of a plated steel material used as a material, and peeling of the plated layer such as powdering may occur. Thus, the Sr content is 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

Each element of Sn, Bi, and In is an element that promotes softening of the plated layer when contained in the plated layer. Since Sn, Bi, and In are elements that can be optionally contained, each content is 0% or more. When Sn is contained, Mg₉Sn₅ tends to be formed in the plated layer. Bi forms Mg₃Bi₂, and In forms Mg₃In, for example. These elements are softer than the MgZn₂ phase and have good workability, so that containment of these elements in the plated layer clearly improves workability. In addition, these elements also exhibit a very low electrochemical property, and thus provide a high anticorrosion effect. By containing at least one of Sn, Bi, and In within the above-described range, the effect of improving worked portion corrosion resistance can be obtained.

Ca: 0% or more and 0.6% or less

Ca is an element that contributes to improvement in hardness and corrosion resistance of the plated layer. On the other hand, in a case where a large amount of Ca is contained in the plated layer, an intermetallic compound is formed with Zn and/or Al in the plated layer. The Ca-containing intermetallic compound formed in this way is likely to accumulate particularly on the surface of the plated layer, and in some cases, the accumulated Ca-containing intermetallic compounds may coarsely grow, and the Ca-containing intermetallic compounds may be continuous in layers. In a case of a plated layer in which the Ca-containing intermetallic compounds are continuous in layers, there is a possibility that the Ca-containing intermetallic compounds are brittlely fractured during forming working, and the plated layer is peeled off from the surface of the plated layer, and as a result, workability is deteriorated. Therefore, the Ca content is 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

Y, La, Ce, Li, Ni, Cu, Ag, Sb, Pb, B, P, Ti, Co, V, Nb, Mn, Zr, and W all form an intermetallic compound with Si, Zn, Al, or the like. However, in a case where the contents of these elements are within the above-described range, the elements do not affect the initial corrosion of the plated layer. On the other hand, in a case where these elements are excessively contained, a potential difference may be generated in the plated layer, and a large amount of initial white rust may be formed. Therefore, in a case where these elements are contained, the contents thereof may be within the above-described range.

Fe: 0% or more and 5.0% or less

Since the hot-dip plated steel material of the present embodiment is manufactured by a continuous hot-dip plating method, Fe may be diffused into the plated layer from the plating raw material during manufacturing. As described above, in the present embodiment, the Al concentration of the plated layer is high, and the Al-Fe-based interfacial alloy layer may be formed, but the thickness thereof is thin. As a result, Fe may be contained in the plated layer up to 5.0%, but Fe does not affect the frequency of occurrence of cracks and the like in the plated layer as long as the Fe concentration is limited to 5.0% or less. Therefore, the Fe content is 0 to 5.0%. The Fe content may be more than 0%.

Remainder: Zn and impurities

The remainder preferably contains Zn. Since the hot-dip plated steel material of the present embodiment is a highly versatile Zn-based plated steel material, the element constituting the main phase of the plated layer is Zn.
The impurity refers to a component that is contained in the raw material or mixed in the manufacturing step and not intentionally contained. For example, in the plated layer, a small amount of component other than Fe may be mixed as the impurity due to mutual atomic diffusion between the steel material (base metal) and the plating bath. In addition, since a metal having a purity of 3 N is usually used for manufacturing a plating alloy, the concentration of impurities may be approximately 0.03% or less in total.
In order to identify the average chemical composition of the plated layer, an acid solution is obtained in which the plated layer is peeled off and dissolved with an acid containing an inhibitor that suppresses corrosion of the base metal (steel material). For the component insoluble in the acid, the acid solution is filtered, and the obtained residue is liquefied by alkali melting treatment. Next, the obtained acid solution and the solution obtained by alkali melting treatment are measured by ICP emission spectrometry or ICP-MS to obtain the chemical composition. The type of the acid is not particularly limited as long as the acid can dissolve the plated layer. In a case where the area and weight before and after peeling are measured, a plating adhesion amount (g/m²) can also be obtained at the same time.

[Method for Manufacturing Hot-Dip Plated Steel Material]

Next, a method for manufacturing the hot-dip plated steel material of the present embodiment will be described.
In the plated steel material according to the present embodiment, the procedure is not particularly limited.
Therefore, as a method for forming the Si-containing plated layer as described above, a method for plating by directly adding Si to a Zn-Al-Mg-based plating bath is conceivable. However, in this method, the Mg₂Si intermetallic compound tends to be formed easily not at the central part of the plated layer but at the surface and the vicinity thereof. Therefore, as an example of a suitable procedure for manufacturing the hot-dip plated steel material of the present embodiment, a method for supplying Si from a Si-containing pre-plated layer provided on a plating base steel sheet to a plated layer will be described below as an example. Note that, in the present specification, as described above, a method for forming a predetermined pre-plated layer in advance on the plating base steel sheet and then sequentially performing Zn-Al-Mg-based hot-dip plating is referred to as a "two-stage plating method".
First, an Al-Si pre-plated layer is formed in advance on a plating base steel sheet such as a cold-rolled or hot-rolled steel sheet. The pre-plating means may be hot-dip plating, electro plating, substitution plating, vapor deposition, or the like. Furthermore, these pre-plated layers may be heated and alloyed.
Note that in a case where the pre-plating on the base steel sheet is performed by hot-dip plating, the pre-plating may be performed under conditions for forming normal aluminum plating, such as an Al-8 to 10% Si bath, and there is no particular limitation.
Next, the plating base steel sheet is heated to 450 to 600°C, and is preferably heated to the same temperature as the temperature of the plating bath described later. The heating may also serve as annealing of the base steel sheet (hereinafter, the heating may be referred to as pre-annealing). By heating the steel sheet before immersion in the plating bath described later, temperature fluctuation of the plating bath can be reduced.
The base steel sheet on which the pre-plated layer is formed and heated is immersed in a Zn-Al-Mg plating bath adjusted to obtain a desired plating composition, and then pulled up, whereby the pre-plated layer is incorporated into the Zn-Al-Mg-based alloy layer, and a final plated layer can be formed. The plating bath temperature is preferably 480 to 550°C.
In addition, in order to incorporate the pre-plated layer into the Zn-Al-Mg-based alloy layer to obtain a plated layer having a single-layer structure, it is preferable to ensure a certain or more immersion time of the base steel sheet in the plating bath. Specifically, the immersion time is preferably 3 to 10 seconds. In order to sufficiently incorporate the pre-plated layer into the Zn-Al-Mg-based alloy layer, the immersion time is preferably 4 seconds or more. Note that if the immersion time is excessively long, the alloy layer at the interface between the plating and the steel sheet may be thickened, resulting in plating peeling. Therefore, the immersion time is preferably 8 seconds or less.
In addition, in the present embodiment, temperature control is preferably performed when the plating base steel sheet is pulled up. That is, by performing appropriate cooling condition control after immersion, Si is contained in the plated layer. Therefore, a desired Mg₂Si intermetallic compound can be formed.
Specifically, in order to sufficiently form the Mg₂Si intermetallic compound, the average cooling rate in a temperature range of 550 to 450°C is preferably 25°C/sec or less. In a case where the average cooling rate in a temperature range of 550 to 450°C is more than 25°C/sec, Si is uniformly dispersed in the thickness direction of the plated layer, and a desired plated layer may not be obtained.
The cooling conditions in the temperature range other than the temperature range of 550 to 450°C are not particularly limited because they do not affect the formation of the intermetallic compound, and the like.
As described above, by appropriately controlling the cooling conditions after the plating base steel sheet is pulled up from the bath, the formation of the Mg₂Si intermetallic compound on the surface and interface of the plated layer can be further suppressed, and the Mg₂Si intermetallic compound can be appropriately dispersed in the vicinity of the central part of the plated layer. As a result, high plating hardness, workability, and corrosion resistance can be exhibited while maintaining the plastic deformability of the plated surface and the interface.
In addition, in a case where a steel sheet on which an Al-Si pre-plated layer is formed is used as the plating substrate, the Mg₂Si intermetallic compound can be more aggregated not on the plated surface but at the central part of the plated layer and in the vicinity of the interface. As a result, a desired plated layer of the present embodiment can be formed.
Next, a method for evaluating performance of the hot-dip plated steel material will be described.

(Bending Workability)

Bending workability of the plated steel material of the present embodiment can be evaluated by measuring the powdering amount (peeling amount) after 0 R to 5 R-60 degree-V-bending, and then unbending.
Specifically, after forming with a 2 R-60 degree-V-shaped die press, the plated steel material is further subjected to unbending using a flat sheet die. After the V-shaped processing, a cellophane tape having a width of 24 mm is pressed against the former bend bottom and pulled off, and a portion having a length of 90 mm of the cellophane tape is visually determined.
Here, the evaluation criteria are as follows.

A: There are no peeled portions.
B: There are some peeled portions in the form of spots (accounting for less than 5% with respect to the processed area).
C: There are line-shaped peeled portions (accounting for 5% to less than 10% of the processed area).
D: There are line-shaped peeled portions (accounting for 10% to less than 20% of the processed area).
E: Peeled portions are almost entirely peeled off (accounting for 20% or more of the processed area).

(Corrosion Resistance)

A flat portion test piece having a thickness of 0.8 mm is prepared, a salt spray composite cycle corrosion test (CCT, JASO-M609-91) is performed, and an area fraction of generated red rust is measured. The number of cycles is 600.
The evaluation criteria are as follows.

A: Red rust is not generated.
B: Red rust area fraction of less than 10%.
C: Red rust area fraction of 10% or more and less than 20%.
D: Red rust area fraction of 20% or more.

(Hardness)

As an evaluation index of the defect resistance of the plated layer, hardness (Vickers hardness) by the Vickers test is adopted. Specifically, the Vickers hardness of the surface of the plated layer is measured under a load of 10 gf. For the Vickers hardness, the Vickers hardness is measured at 10 points in a cross section including the thickness direction of the plated layer, and the average thereof is taken.
After the plated layer is formed, various chemical conversion treatments and coating treatments may be performed.
In the hot-dip plated steel material of the present embodiment, a film may be formed on the plated layer. A film having a single layer or two or more layers may be formed. Examples of the type of the film immediately above the plated layer include a chromate film, a phosphate film, and a chromate-free film. A chromate treatment, a phosphating treatment, and a chromate-free treatment for forming these films can be performed by known methods.
The chromate treatment includes an electrolytic chromate treatment in which a chromate film is formed by electrolysis, a reaction type chromate treatment in which a film is formed by utilizing a reaction with the material and then the excess treatment liquid is washed away, and an application type chromate treatment in which a film is formed by applying a treatment liquid to an object to be coated and drying the treatment liquid without washing with water. Any treatment may be adopted.
Examples of the electrolytic chromate treatment include an electrolytic chromate treatment using chromic acid, a silica sol, a resin (phosphoric acid, an acrylic resin, a vinyl ester resin, a vinyl acetate acrylic emulsion, a carboxylated styrene-butadiene latex, a diisopropanolamine-modified epoxy resin, and the like), and hard silica.
Examples of the phosphating treatment include a zinc phosphate treatment, a zinc calcium phosphate treatment, and a manganese phosphate treatment.
The chromate-free treatment, which does not impose a burden on the environment, is particularly suitable. The chromate-free treatment includes an electrolytic chromate-free treatment in which a chromate-free film is formed by electrolysis, a reaction type chromate-free treatment in which a film is formed by utilizing a reaction with the material and then the excess treatment liquid is washed away, and an application type chromate-free treatment in which a film is formed by applying a treatment liquid to an object to be coated and drying the treatment liquid without washing with water. Any treatment may be adopted.
Further, an organic resin film made of a single layer or two or more layers may be formed on the film immediately above the plated layer. The organic resin is not limited to a specific type, and examples thereof include polyester resins, polyurethane resins, epoxy resins, acrylic resins, polyolefin resins, and modified products of these resins. Here, the modified product refers to a resin obtained by causing a reactive functional group included in the structures of these resins to react with another compound (a monomer, a crosslinking agent, or the like) having a functional group capable of reacting with the reactive functional group in the structure thereof.
As such an organic resin, one or two or more types of organic resins (unmodified organic resins) may be mixed and used, or one or two or more types of organic resins obtained by modifying, in the presence of at least one type of organic resin, at least one type of another organic resin may be mixed and used. The organic resin film may contain any coloring pigment or antirust pigment. Also, water-based organic resins that are dissolved or dispersed in water can be used.

Examples

Next, Examples of the present invention will be described, but conditions in Examples are examples of conditions adopted to confirm feasibility and an effect of the present invention, and the present invention is not limited to these examples of conditions. The present invention may adopt various conditions as long as an object of the present invention is achieved without departing from the gist of the present invention.
First, a cold-rolled steel sheet (SPCC) having a size of 100 mm × 200 mm and a sheet thickness of 0.8 mm was prepared as a plating base steel sheet. For this cold-rolled steel sheet, first, an Al-Si pre-plated layer as described in Tables 1A and 1B was formed on the sheet surface using an Al-Si-based plating bath (bath temperature: 650°C). Note that the term "Two-stage plating" in the "Procedure" column in Tables 1A and 1B indicates that the above-described two-stage plating method was applied. "Sendzimir" 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 without performing pre-plating.
An Al-Si pre-plated layer was formed on the plating base steel sheet to manufacture a plated substrate, and then the plated substrate was heated at 400°C in a H₂ (25%)-N₂ atmosphere for 0.5 to 3.0 minutes.
The plated substrate after the pre-annealing described above was hot-dip plated in a hot-dip plating simulator.
First, alloys having plating bath components shown in Tables 1A and 1B were prepared by a vacuum dissolution method, and a plating bath was formed in a completely oxygen-free and nitrogen-substituted atmosphere (O₂ concentration: less than 5 ppm). The remainder of the plating bath components in Tables 1A and 1B is substantially Zn.
Next, one point (the center rear surface of the evaluation surface) of the plated substrate was bonded to a K thermocouple by spot welding, and the temperature history until the completion of plating solidification was grasped. Subsequently, the plated substrate was heated to a predetermined temperature in a H₂ (25%)-N₂ atmosphere. The plating bath temperature was as shown in Tables 1A and 1B, the plated substrate was immersed in the plating bath at an immersion rate of 500 mm/sec, and the plated substrate was immersed in the bath for the immersion time shown in Tables 1A and 1B. Thereafter, the plated substrate was pulled up from the plating bath at a rate of 500 mm/sec.
Immediately after the pulling up, the average plating thickness Tp was adjusted to 40 µm with N₂ wiping gas, and N₂ gas whose flow rate was controlled in an oxygen-free and nitrogen-substituted atmosphere was then blown, and the temperature range of 550 to 450°C was cooled at an average cooling rate shown in Table 1.
A plated steel sheet was obtained by the above-described steps. Note that the thickness (µm) of the plated layer shown in Tables 2A and 2B is a thickness including the interfacial alloy layer, and was measured from the cross section of the plated layer using an electron microscope.
Next, samples for evaluation were cut out from the various plated steel sheets. Each sample for GDS analysis and SEM observation was cut out at a 30 mm square position on the opposite side to the thermocouple position. Samples (100 × 50 mm) for evaluation of various characteristics were collected from the center portion in the planar direction of the plated layer.
As the evaluation of the various samples that have been cut out, a bending test, Vickers hardness measurement, and a corrosion test SST were performed. Note that, among the compositions of the plated layer, the composition of Fe was not described in the tables, but was in a range of 0 to 5%.
Tables 2A and 2B show the evaluation results, the compositions of the plated layer, the GDS analysis results, and the XRD measurement results. The remainder of the composition of the plated layer in Tables 2A and 2B is substantially Zn. Note that the underline in each table indicates that the numerical value is out of the range of the present invention or out of the preferable manufacturing conditions, or the characteristic value is not preferable.
In the example of No. 52, since the immersion time of the plated substrate in the plating bath was short, the pre-plated layer could not be sufficiently incorporated into the Zn-Al-Mg-based alloy layer, and as a result, a plated layer having a single-layer structure could not be obtained.
In the example of No. 53, since the bath temperature of the plating bath was low, the pre-plated layer could not be sufficiently incorporated into the Zn-Al-Mg-based alloy layer, and as a result, a plated layer having a single-layer structure could not be obtained.
In the example of No. 54, since the immersion time of the plated substrate in the plating bath was long, the reaction between the plating bath and the plating base steel sheet (base steel sheet) excessively proceeded. Specifically, an interfacial alloy layer having a thickness of about 5 µm was observed in a cross-sectional view of the plated layer by an electron microscope. In addition, as a result of analysis by GDS in No. 54, accumulation of Si in the center portion in the thickness direction of the plated layer was not observed.

In the example of No. 55, since the bath temperature of the plating bath was high, alloying of the plating bath and the plating base steel sheet (base steel sheet) excessively proceeded. Specifically, an interfacial alloy layer having an average thickness of about 5 µm was observed in a cross-sectional view of the plated layer by an electron microscope. In addition, as a result of analysis by GDS in No. 55, accumulation of Si in the center portion in the thickness direction of the plated layer was not observed.

[Table 1A]

No.	Classification	Manufacturing method
		Procedure	Bath temperature	Average cooling rate	Pre-plated layer		Immersion time	Plating bath component (mass%)
			Bath temperature	Average cooling rate	Composition	Adhesion amount	Immersion time	Plating bath component (mass%)
			(°C)	(°C/sec)	Composition	(g/m²)	(sec)	Al	Mg	Ca	Si	Others
1	Example	Two-stage plating	550	10	Al-8% Si	96	3	17.3	8.9	0.0	0.0
2	Example	Two-stage plating	550	10	Al-8% Si	138	5	6.7	13.3	0.0	0.0
3	Example	Two-stage plating	550	10	Al-12% Si	147	4	2.0	14.0	0.0	0.0
4	Example	Two-stage plating	550	10	Al-14% Si	55	4	4.7	6.7	0.0	0.0
5	Example	Two-stage plating	550	20	Al-14% Si	55	4	11.3	6.7	0.0	0.0
6	Example	Two-stage plating	550	10	Al-14% Si	55	5	24.7	6.7	0.0	0.0
7	Example	Two-stage plating	550	10	Al-14% Si	55	5	38.0	6.7	0.0	0.0
8	Example	Two-stage plating	550	25	Al-14% Si	55	5	51.3	6.7	0.0	0.0
9	Example	Two-stage plating	550	10	Al-8% Si	96	10	17.3	12.4	0.0	0.0
10	Example	Two-stage plating	550	10	Al-8% Si	96	10	17.3	17.8	0.0	0.0
11	Example	Two-stage plating	550	20	Al-8% Si	96	10	17.3	23.1	0.0	0.0
12	Example	Two-stage plating	550	10	Al-8% Si	96	5	17.3	8.9	0.0	0.0	La, Ce = 0.089
13	Example	Two-stage plating	550	10	Al-8% Si	138	5	6.7	13.3	0.0	0.0	La, Ce = 0.133
14	Example	Two-stage plating	550	15	Al-12% Si	147	5	2.0	14.0	0.0	0.0	La, Ce = 0.150
15	Example	Two-stage plating	550	23	Al-8% Si	96	5	17.3	8.9	0.0	0.0	Y = 0.089
16	Example	Two-stage plating	550	10	Al-8% Si	138	5	6.7	13.3	0.0	0.0	Y = 0.133
17	Example	Two-stage plating	550	10	Al-12% Si	147	3	4.0	15.0	0.0	0.0	Y=0.150
18	Example	Two-stage plating	550	10	Al-8% Si	96	5	17.3	8.9	0.0	0.0	Sn = 0.178
19	Example	Two-stage plating	550	23	Al-8% Si	138	5	6.7	13.3	0.0	0.0	Sn = 0.178
20	Example	Two-stage plating	550	10	Al-12% Si	147	8	2.0	14.0	0.0	0.0	Sn = 0.178
21	Example	Two-stage plating	550	10	Al-8% Si	96	5	17.3	8.9	0.4	0.0
22	Example	Two-stage plating	550	10	Al-8% Si	138	5	6.7	13.3	0.5	0.0
23	Example	Two-stage plating	550	10	Al-12% Si	147	5	4.0	15.0	0.6	0.0
24	Comparative Example	Two-stage plating	550	10	Al-8% Si	28	5	21.1	6.9	0.0	0.0
25	Comparative Example	Two-stage plating	550	10	Al-8% Si	55	5	9.3	8.0	0.0	0.0
26	Comparative Example	Two-stage plating	550	10	Al-10% Si	66	5	4.3	8.6	0.0	0.0
27	Comparative Example	Two-stage plating	550	10	Al-14% Si	141	5	13.2	16.8	0.0	0.0
28	Comparative Example	Two-stage plating	550	10	Al-8% Si	96	5	8.4	5.3	0.0	0.0
29	Comparative Example	Two-stage plating	550	10	Al-8% Si	96	5	8.4	28.4	0.0	0.0
30	Comparative Example	Two-stage plating	550	10	Al-20% Si	39	5	9.0	6.0	0.0	3.5
31	Comparative Example	Two-stage plating	550	10	Al-8% Si	96	5	44.0	10.7	0.0	0.0
32	Comparative Example	Sendzimir	550	10	No pre-plating	-	5	11.0	5.0	0.0	3.5
33	Comparative Example	Sendzimir	550	10	No pre-plating	-	5	30.0	5.0	1.0	0.0

[Table 1B]

No.	Classification	Manufacturing method
		Procedure	Bath temperature	Average cooling rate	Pre-plated layer		Immersion time	Plating bath component (mass%)
			Bath temperature	Average cooling rate	Composition	Adhesion amount	Immersion time	Plating bath component (mass%)
			(°C)	(°C/sec)	Composition	(g/m²)	(sec)	Al	Mg	Ca	Si	Others
34	Example	Two-stage plating	550	10	Al-8% Si	96	5	17.3	8.9	0.0	0.0	Sr = 0.181
35	Example	Two-stage plating	550	10	Al-8% Si	138	5	6.7	13.3	0.0	0.0	Bi = 0.192
36	Example	Two-stage plating	550	10	Al-12% Si	147	5	2.0	14.0	0.0	0.0	In = 0.121
37	Example	Two-stage plating	550	10	Al-8% Si	96	5	17.3	8.9	0.0	0.0	Li = 0.093
38	Example	Two-stage plating	550	10	Al-8% Si	138	5	6.7	13.3	0.0	0.0	Ni = 0.156
39	Example	Two-stage plating	550	10	Al-12% Si	147	5	2.0	14.0	0.0	0.0	Cu=0.202
40	Example	Two-stage plating	550	10	Al-8% Si	96	5	17.3	8.9	0.0	0.0	Ag = 0.150
41	Example	Two-stage plating	550	10	Al-8% Si	138	5	6.7	13.3	0.0	0.0	Sb = 0.132
42	Example	Two-stage plating	550	10	Al-12% Si	147	5	2.0	14.0	0.0	0.0	Pb = 0.103
43	Example	Two-stage plating	550	10	Al-8% Si	96	5	17.3	8.9	0.0	0.0	B = 0.105
44	Example	Two-stage plating	550	10	Al-8% Si	138	5	6.7	13.3	0.0	0.0	P = 0.092
45	Example	Two-stage plating	550	10	Al-12% Si	147	5	2.0	14.0	0.0	0.0	Ti = 0.092
46	Example	Two-stage plating	550	10	Al-8% Si	96	5	17.3	8.9	0.0	0.0	Co = 0.100
47	Example	Two-stage plating	550	10	Al-8% Si	138	5	6.7	13.3	0.0	0.0	V = 0.104
48	Example	Two-stage plating	550	10	Al-12% Si	147	5	2.0	14.0	0.0	0.0	Nb = 0.105
49	Example	Two-stage plating	550	10	Al-8% Si	96	5	17.3	8.9	0.0	0.0	Mn = 0.105
50	Example	Two-stage plating	550	10	Al-8% Si	138	5	6.7	13.3	0.0	0.0	Zr = 0.097
51	Example	Two-stage plating	550	10	Al-12% Si	147	5	2.0	14.0	0.0	0.0	W = 0.095
52	Comparative Example	Two-stage plating	550	10	Al-8% Si	96	1	17.3	8.9	0.0	0.0
53	Comparative Example	Two-stage plating	400	-	Al-12% Si	147	10	2.0	14.0	0.0	0.0
54	Comparative Example	Two-stage plating	550	10	Al-8% Si	96	12	17.3	8.9	0.0	0.0
55	Comparative Example	Two-stage plating	600	10	Al-8% Si	96	3	17.3	8.9	0.0	0.0

[Table 2A]

No.	Classification	Plated layer						GDS (average optional intensity V)			XRD	Hardness	Bending workability	Planar corrosion resistance
		Thickness Tp	Chemical composition (mass%): remainder Zn					GDS (average optional intensity V)			XRD	Hardness
		Thickness Tp	Al	Mg	Ca	Si	Others (Other than Fe)	Si (surf)	Si (centre)	Si (deep)	Left hand side of Expression (2)	(Hv)
		(µm)	Al	Mg	Ca	Si	Others (Other than Fe)	Si (surf)	Si (centre)	Si (deep)	Left hand side of Expression (2)	(Hv)
1	Example	40	50.1	5.1	0	3.5		0.09	0.25	0.21	3.1	300	A	B
2	Example	40	59.8	5.3	0	5.0		0.18	0.45	0.38	3.8	310	A	A
3	Example	40	51.3	5.2	0	8.0		0.42	0.88	0.66	4.3	320	B	A
4	Example	40	25.2	4.8	0	3.5		0.09	0.25	0.21	3.2	300	A	B
5	Example	40	31.5	4.9	0	3.5		0.09	0.25	0.21	3.2	300	A	B
6	Example	40	42.1	5.0	0	3.5		0.09	0.25	0.21	3.2	300	A	B
7	Example	40	49.7	4.9	0	3.5		0.09	0.25	0.21	3.2	300	A	B
8	Example	40	59.8	5.0	0	3.5		0.09	0.25	0.21	3.2	300	A	B
9	Example	40	51.2	7.3	0	3.5		0.09	0.25	0.21	3.5	310	B	B
10	Example	40	50.5	10.6	0	3.5		0.09	0.25	0.21	3.9	320	B	B
11	Example	40	52.4	12.8	0	3.5		0.09	0.25	0.21	4.2	330	B	B
12	Example	40	51.1	5.2	0	3.5	La, Ce = 0.05	0.09	0.25	0.21	3.2	300	A	A
13	Example	40	59.7	5.1	0	5.0	La, Ce = 0.05	0.18	0.45	0.38	3.8	310	A	A
14	Example	40	49.6	5.1	0	8.0	La, Ce = 0.05	0.42	0.88	0.66	4.3	320	A	A
15	Example	40	50.3	4.9	0	3.5	Y = 0.05	0.09	0.25	0.21	3.2	300	A	A
16	Example	40	58.9	5.0	0	5.0	Y = 0.05	0.18	0.45	0.38	3.8	310	A	A
17	Example	40	59.6	5.1	0	8.0	Y = 0.05	0.42	0.88	0.66	4.3	320	B	A
18	Example	40	50.3	5.0	0	3.5	Sn = 0.1	0.09	0.25	0.21	3.2	300	A	A
19	Example	40	59.8	5.2	0	5.0	Sn = 0.1	0.18	0.45	0.38	3.8	310	A	A
20	Example	40	60.0	5.1	0	8.0	Sn = 0.1	0.42	0.88	0.66	4.3	320	B	A
21	Example	40	50.1	5.0	0.2	3.5		0.09	0.25	0.21	3.2	300	A	A
22	Example	40	59.9	5.2	0.2	5.0		0.18	0.45	0.38	3.8	310	A	A
23	Example	40	58.7	5.3	0.2	8.0		0.42	0.88	0.66	4.3	320	B	A
24	Comparative Example	40	31.3	6.0	0	1.0		0.03	0.07	0.06	1.2	270	B	C
25	Comparative Example	40	30.8	6.2	0	2.0		0.05	0.15	0.12	1.5	280	B	C
26	Comparative Example	40	31.2	6.2	0	3.0		0.09	0.23	0.21	2.0	290	B	C
27	Comparative Example	40	59.7	6.4	0	9.0		0.50	0.68	0.55	4.0	340	E	C
28	Comparative Example	40	44.9	3.0	0	3.5		0.09	0.25	0.21	1.8	280	A	C
29	Comparative Example	40	45.1	16.0	0	3.5		0.09	0.25	0.21	3.2	350	E	C
30	Comparative Example	40	9.1	6.1	0	3.5		0.09	0.25	0.21	3.2	300	A	D
31	Comparative Example	40	64.8	6.4	0	3.5		0.09	0.25	0.21	3.2	300	A	D
32	Comparative Example	40	11.2	5.2	0	3.5		0.25	0.09	0.21	3.2	300	D	B
33	Comparative Example	40	30.4	5.1	1.0	0.0		0.00	0.00	0.00	-	300	D	B

[Table 2B]

No.	Classification	Plated layer						GDS (average optional intensity V)			XRD	Hardness	Bending workability	Planar corrosion resistance
		Thickness Tp	Chemical composition (mass%): remainder Zn					GDS (average optional intensity V)			XRD	Hardness
		Thickness Tp	Al	Mg	Ca	Si	Others (Other than Fe)	Si (surf)	Si (centre)	Si (deep)	Left hand side of Expression (2)	(Hv)
		(µm)	Al	Mg	Ca	Si	Others (Other than Fe)	Si (surf)	Si (centre)	Si (deep)	Left hand side of Expression (2)	(Hv)
34	Example	40	51.1	5.2	0	3.5	Sr = 0.1	0.10	0.27	0.21	3.2	300	A	A
35	Example	40	59.7	5.1	0	5.0	Bi = 0.05	0.19	0.45	0.38	3.8	310	A	A
36	Example	40	49.6	5.1	0	8.0	In = 0.05	0.19	0.89	0.67	4.3	320	A	A
37	Example	40	51.1	5.2	0	3.5	Li = 0.05	0.09	0.25	0.20	3.2	300	A	A
38	Example	40	59.7	5.1	0	5.0	Ni = 0.1	0.17	0.45	0.38	3.8	310	A	A
39	Example	40	49.6	5.1	0	8.0	Cu = 0.1	0.41	0.87	0.64	4.3	320	A	A
40	Example	40	51.1	5.2	0	3.5	Ag = 0.05	0.09	0.25	0.20	3.2	300	A	A
41	Example	40	59.7	5.1	0	5.0	Sb = 0.05	0.18	0.45	0.38	3.8	310	A	A
42	Example	40	49.6	5.1	0	8.0	Pb = 0.05	0.42	0.87	0.65	4.3	320	A	A
43	Example	40	51.1	5.2	0	3.5	B = 0.05	0.09	0.25	0.20	3.2	300	A	A
44	Example	40	59.7	5.1	0	5.0	P = 0.05	0.18	0.45	0.38	3.8	310	A	A
45	Example	40	49.6	5.1	0	8.0	Ti = 0.05	0.42	0.87	0.65	4.3	320	A	A
46	Example	40	51.1	5.2	0	3.5	Co = 0.05	0.09	0.25	0.20	3.2	300	A	A
47	Example	40	59.7	5.1	0	5.0	V = 0.05	0.18	0.45	0.38	3.8	310	A	A
48	Example	40	49.6	5.1	0	8.0	Nb = 0.05	0.42	0.88	0.65	4.3	320	A	A
49	Example	40	51.1	5.2	0	3.5	Mn = 0.05	0.09	0.25	0.20	3.2	300	A	A
50	Example	40	59.7	5.1	0	5.0	Zr = 0.05	0.18	0.45	0.38	3.8	310	A	A
51	Example	40	49.6	5.1	0	8.0	W = 0.05	0.42	0.87	0.65	4.3	320	A	A
52	Comparative Example	40	-	-	-	-		0.00	0.00	0.51	-	240	E	D
53	Comparative Example	40	-	-	-	-		0.00	0.00	0.51	-	240	E	D
54	Comparative Example	40	51.1	5.2 Example	0	3.5		0.09	0.18	0.21	-	310	E	C
55	Comparative Example	40	51.1	5.2	0	3.5		0.09	0.20	0.21	-	310	E	C

INDUSTRIAL APPLICABILITY

According to the above aspect of the present invention, a hot-dip plated steel material excellent in plating 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 and building materials, and thus has high industrial applicability.

Claims

A hot-dip plated steel material comprising:
a steel material; and

a plated layer disposed on a surface of the steel material, wherein

the plated layer has a chemical composition including, in terms of mass%,

more than 10.0% and 60.0% or less of Al,

4.0% or more and 15.0% or less of Mg, and

3.5% or more and 8.0% or less of Si, and

further including

0% or more and 0.7% or less of Sn,

0% or more and 1.5% or less of Sr,

0% or more and 0.3% or less of Bi,

0% or more and 0.3% or less of In,

0% or more and 0.6% or less of Ca,

0% or more and 0.3% or less of Y,

0% or more and 0.3% or less of La,

0% or more and 0.3% or less of Ce,

0% or more and 0.3% or less of Li,

0% or more and 1.0% or less of Ni,

0% or more and 1.0% or less of Cu,

0% or more and 0.25% or less of Ag,

0% or more and 0.25% or less of Sb,

0% or more and 0.25% or less of Pb,

0% or more and 0.5% or less of B,

0% or more and 0.5% or less of P,

0% or more and 0.25% or less of Ti,

0% or more and 0.25% or less of Co,

0% or more and 0.25% or less of V,

0% or more and 0.25% or less of Nb,

0% or more and 0.25% or less of Mn,

0% or more and 0.25% or less of Zr,

0% or more and 0.25% or less of W,

0% or more and 5.0% or less of Fe, and

a remainder of Zn and impurities,

the plated layer contains a Mg₂Si intermetallic compound, and

in a case where, in an elemental distribution profile obtained by a qualitative analysis using glow discharge optical emission spectrometry in a direction from a surface of the plated layer toward the steel material, a thickness of a region from a surface of the plated layer to a depth position where an Fe intensity corresponding to 5% with respect to a maximum intensity of Fe is detected is denoted by Tg, an average value of a qualitative analysis value of Si from the surface of the plated layer to Tg/3 is denoted by Si (surf), an average value of a qualitative analysis value of Si in a range of Tg/3 to 2 Tg/3 starting from the surface of the plated layer is denoted by Si (centre), and an average value of a qualitative analysis value of Si in a range of 2 Tg/3 to Tg starting from the surface of the plated layer is denoted by Si (deep), Expression (1) is satisfied, $Si (surf) < Si (deep) < Si (centre)$
The hot-dip plated steel material according to claim 1, wherein in an X-ray diffraction pattern of the surface of the plated layer measured by using Cu-Kα radiation under conditions of 50 kV and 300 mA X-ray output, Expression (2) is satisfied, $\{I (26.19 °) + I (44.6 °)\} / \{2 \times I (12.5 °)\} > 2.0$ in Expression (2), I (n°) is an X-ray diffraction intensity at a diffraction angle n°, and n is a diffraction angle (20) indicated in Expression (2).