Plated steel sheet

Abstract

The purpose of the present invention is to provide a plated steel sheet capable of further improving hydrogen release properties while maintaining corrosion resistance after coating. This plated steel sheet has, on the surface of a steel sheet, a plating layer having a chemical composition containing, in mass%, 0.50-5.00% of Al, 0.50-3.00% of Mg, 0.01-15.00% of Fe, and optionally containing one or more elements selected from the group consisting of element group A, element group B, element group C, element group D, element group E, element group F, and element group G, with the remainder being Zn and impurities, in a surface structure in a plan view of the plating layer, the average area ratio of an [alpha]-precipitated [eta] phase, which is a metallographic structure in which the [alpha] phase is precipitated in the [eta]-parent phase, is 5-95%, and when a 130 [mu] m * 100 [mu] m region of the surface of the plating layer is observed by an electron microscope, the total length of cracks present in the region is 50 [mu] m or more.

Description

Technical Field

[0001] The present invention relates to a plated steel sheet. Background Art

[0002] In recent years, the demand for high-strength steel sheets has increased in the automotive and / or building material fields due to the need for lightweighting. In addition to various processing steps such as stamping and / or bending to achieve the desired shape, high-strength steel sheets are often also required to exhibit high corrosion resistance. Therefore, high-strength steel sheets are required to combine strength, workability, and corrosion resistance. To achieve high corrosion resistance, the use of various plated steel sheets using high-strength steel sheets as the base plate is increasing.

[0003] It is known that when high-strength steel sheets are used as base plates for plating, hydrogen embrittlement is likely to occur due to the inevitable intrusion of hydrogen into the steel during the plating line. In particular, hot-dip Zn-Al-Mg-based plated steel sheets can sometimes experience hydrogen embrittlement even when using relatively low-strength steel sheets such as 590 MPa grade as base plates for plating. Therefore, various countermeasures against hydrogen embrittlement have been proposed.

[0004] For example, Patent Document 1 below proposes a technique in which strain is applied to a hot-dip Zn—Al—Mg-based steel sheet to introduce cracks into the coating layer, and then the plated steel sheet is baked to reduce the hydrogen concentration in the steel.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2018-204065 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] The present inventors studied the technique proposed in Patent Document 1 and found that it is important to strike a balance between achieving the desired amount of cracks required to facilitate hydrogen desorption and the reduction in ductility of the steel sheet caused by excessive crack introduction. To achieve this trade-off, Patent Document 1 found that it is necessary to control the amount of cracks introduced by paying attention to the strain imparted during crack introduction, and that there is room for improvement from the perspective of hydrogen desorption.

[0010] The present invention has been made in view of the above-mentioned viewpoints, and an object of the present invention is to provide a plated steel sheet that can maintain corrosion resistance after coating and further improve hydrogen desorption properties.

[0011] Solutions for solving problems

[0012] The present inventors focused on the relatively hard coating structure of the Zn-Al-Mg coating disclosed in Patent Document 1. Based on this, the present inventors came to the conclusion that if a structure that serves as a starting point for crack initiation could be introduced into the coating, a more appropriate number of cracks could be efficiently generated without excessively controlling the application of strain, further improving hydrogen desorption properties.

[0013] The gist of the present invention completed based on this concept is as follows.

[0014] (1) A plated steel sheet having a plated layer on its surface, the plated layer having the following chemical composition: containing, in mass %, 0.50 to 5.00% Al, 0.50 to 3.00% Mg, and 0.01 to 15.00% Fe, and selectively containing one or more elements selected from the group consisting of the following element group A, element group B, element group C, element group D, element group E, element group F, and element group G, with the remainder being Zn and impurities, wherein, in a surface structure when the surface of the plated layer is viewed from above, an average area ratio of a precipitated η phase in a metallographic structure obtained by precipitation of an α phase in an η matrix phase is 5 to 95%, and when a 130 μm×100 μm area on the surface of the plated layer is observed by an electron microscope, the total length of cracks existing in the area is 50 μm or more.

[0015] [Element Group A]: One or two elements selected from the group consisting of Si: more than 0% and 2.00% or less and Ca: more than 0% and 2.00% or less

[0016] [Element Group B]: One or more elements selected from the group consisting of Sb: more than 0% and 0.5000% or less, Pb: more than 0% and 0.5000% or less, and Sr: more than 0% and 0.5000% or less

[0017] [Element Group C]: One or more elements selected from the group consisting of Cu: more than 0% and 1.0000%, Ti: more than 0% and 1.0000%, Cr: more than 0% and 1.0000%, Nb: more than 0% and 1.0000%, Ni: more than 0% and 1.0000%, Mn: more than 0% and 1.0000%, Mo: more than 0% and 1.0000%, Co: more than 0% and 1.0000%, and V: more than 0% and 1.0000%.

[0018] [Element Group D]: One or more elements selected from the group consisting of Sn: more than 0% and 1.0000% or less, In: more than 0% and 1.0000% or less, and Bi: more than 0% and 1.0000% or less

[0019] [Element Group E]: One or more elements selected from the group consisting of Zr: more than 0% and 1.0000% or less, Ag: more than 0% and 1.0000% or less, and Li: more than 0% and 1.0000% or less

[0020] [Element Group F]: one or more elements selected from the group consisting of La: more than 0% and 0.5000% or less, Ce: more than 0% and 0.5000% or less, and Y: more than 0% and 0.5000% or less

[0021] [Element Group G]: B: more than 0% and 0.5000% or less

[0022] (2) The plated steel sheet according to (1), which has a chemical composition containing the aforementioned element group A.

[0023] (3) The plated steel sheet according to (1), which has a chemical composition containing the element group B.

[0024] (4) The plated steel sheet according to (1), which has a chemical composition containing the aforementioned element group C.

[0025] (5) The plated steel sheet according to (1), which has a chemical composition containing the element group D.

[0026] (6) The plated steel sheet according to (1), which has a chemical composition containing the element group E.

[0027] (7) The plated steel sheet according to (1), which has a chemical composition containing the aforementioned element group F.

[0028] (8) The plated steel sheet according to (1), which has a chemical composition containing the element group G.

[0029] (9) The plated steel sheet according to any one of (1) to (8), wherein the plated layer contains 1.00 to 5.00 mass% of Al and 1.00 to 3.00 mass% of Mg.

[0030] (10) The plated steel sheet according to (1), wherein the tensile strength of the steel sheet is 980 MPa or more.

[0031] (11) The plated steel sheet according to (1), wherein the tensile strength of the steel sheet is 1180 MPa or more.

[0032] (12) The plated steel sheet according to (1), wherein the average area ratio of the α-precipitated η phase is 5 to 70%.

[0033] (13) The plated steel sheet according to (1), wherein the average area ratio of the α-precipitated η phase is 5 to 40%.

[0034] Effects of the Invention

[0035] As described above, according to the present invention, in a Zn—Al—Mg-based plated steel sheet, the hydrogen desorption property can be further improved while maintaining the corrosion resistance after coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1A It is an explanatory diagram schematically showing the structure of a plated steel sheet according to an embodiment of the present invention.

[0037] Figure 1B It is an explanatory diagram schematically showing the structure of the plated steel sheet according to this embodiment.

[0038] Figure 2 It is a schematic diagram for explaining the plating layer of the plated steel sheet in this embodiment.

[0039] Figure 3 It is a schematic diagram for explaining the plating layer of the plated steel sheet in this embodiment. DETAILED DESCRIPTION

[0040] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that in this specification and the accompanying drawings, components having substantially the same functional configuration are denoted by the same reference numerals to omit repeated description.

[0041] (Regarding plated steel sheets)

[0042] First, refer to Figure 1A and Figure 1B The overall structure of the plated steel sheet according to the embodiment of the present invention will be described. Figure 1A and Figure 1B It is an explanatory diagram schematically showing an example of a plated steel sheet according to the present embodiment.

[0043] like Figure 1A As shown schematically, the plated steel sheet 1 of this embodiment includes a steel sheet 11 as a base material and a plated layer 13 located at least partially on the surface of the steel sheet 11. Figure 1A The surface existing on one side of the steel plate 11 as shown may also be Figure 1B It is schematically shown as existing on the surfaces of both sides of the steel plate 11.

[0044] <About Steel Plate 11>

[0045] The size, composition, structure, and mechanical properties of the steel plate 11 used as the base material of the plated steel sheet 1 of this embodiment are not particularly limited. For example, various steel plates can be used depending on the mechanical strength (e.g., tensile strength) required of the plated steel sheet 1. As an example of such a steel plate 11, there are steel materials specified in the Japanese Industrial Standards (JIS), such as carbon steel, alloy steel, and high-tensile steel used for general structural and / or mechanical structural purposes. Specific examples of such steel materials include cold-rolled steel, hot-rolled steel, hot-rolled steel sheets for automotive structures, hot-rolled high-tensile steel sheets for automotive processing, cold-rolled steel sheets for automotive structures, cold-rolled high-tensile steel sheets for automotive processing, and high-tensile steel materials commonly referred to as hot stamping materials that are quenched during hot working. The composition of such steel materials is not particularly limited, and in addition to Fe and C, they may also contain one or more of Si, Mn, S, P, Al, N, Cr, Mo, Ni, Cu, Ca, Mg, Ce, Hf, La, Zr, and Sb. In order to obtain the required material strength and formability, one or more of these optional added elements may be appropriately selected, and the content may be appropriately adjusted.

[0046] Among the high-strength steels described above, for example, high-strength steel with a tensile strength of 980 MPa or higher (so-called 980 MPa-grade or higher high-strength steel) is more preferred because it can further improve the robustness of the manufactured article. The tensile strength of the steel plate 11 can be measured using a known method. For example, a test piece specified in JIS Z 2241:2011 can be prepared from a portion of the steel plate whose tensile strength is to be measured, and the tensile strength of the obtained test piece can be measured using the specified method.

[0047] The thickness of the steel sheet 11 is not particularly limited and may be appropriately set according to the mechanical strength required of the plated steel sheet 1 .

[0048] About Plating 13

[0049] like Figure 1A and Figure 1B As schematically shown, the plating layer 13 is provided on the surface of the steel plate 11, and more preferably, is provided on the entire surface of the steel plate 11. Hereinafter, first, the chemical composition of the plating layer 13 will be described in detail.

[0050] ◇About the chemical composition of coating 13

[0051] According to one embodiment, the chemical composition of the plating layer 13 of the present embodiment has a chemical composition containing, by mass%, Al: 0.50-5.00%, Mg: 0.50-3.00%, Fe: 0.01-15.00%, and the balance being Zn and impurities.

[0052] According to another embodiment, the chemical composition of the plating layer 13 of this embodiment has the following chemical composition: Al: 0.50-5.00%, Mg: 0.50-3.00%, Fe: 0.01-15.00%, and one or more elements selected from the group consisting of the following element groups: A, B, C, D, E, F, and G, with the balance being Zn and impurities. Specifically, in the chemical composition of the plating layer 13 of this embodiment, the contents of Al, Mg, and Fe are within the above-described ranges, the total content of Al, Mg, Fe, and elements A through G is less than 100% by mass, and the balance is Zn and impurities.

[0053] [Element Group A]: One or two elements selected from the group consisting of Si: more than 0% and 2.00% or less and Ca: more than 0% and 2.00% or less

[0054] [Element Group B]: One or more elements selected from the group consisting of Sb: more than 0% and 0.5000% or less, Pb: more than 0% and 0.5000% or less, and Sr: more than 0% and 0.5000% or less

[0055] [Element Group C]: One or more elements selected from the group consisting of Cu: more than 0% and 1.0000%, Ti: more than 0% and 1.0000%, Cr: more than 0% and 1.0000%, Nb: more than 0% and 1.0000%, Ni: more than 0% and 1.0000%, Mn: more than 0% and 1.0000%, Mo: more than 0% and 1.0000%, Co: more than 0% and 1.0000%, and V: more than 0% and 1.0000%.

[0056] [Element Group D]: One or more elements selected from the group consisting of Sn: more than 0% and 1.0000% or less, In: more than 0% and 1.0000% or less, and Bi: more than 0% and 1.0000% or less

[0057] [Element Group E]: One or more elements selected from the group consisting of Zr: more than 0% and 1.0000% or less, Ag: more than 0% and 1.0000% or less, and Li: more than 0% and 1.0000% or less

[0058] [Element Group F]: one or more elements selected from the group consisting of La: more than 0% and 0.5000% or less, Ce: more than 0% and 0.5000% or less, and Y: more than 0% and 0.5000% or less

[0059] [Element Group G]: B: more than 0% and 0.5000% or less

[0060] Thus, the coating 13 of this embodiment is a coating having the following chemical composition: in terms of mass %, it contains Al: 0.50-5.00%, Mg: 0.50-3.00%, Fe: 0.01-15.00%, and selectively contains one or more selected from the group consisting of element group A, element group B, element group C, element group D, element group E, element group F and element group G, with the remainder being Zn and impurities.

[0061] [Al: 0.50-5.00 mass %]

[0062] Al is an essential element for forming the main phase (Zn-Al-Mg alloy phase) of the coating 13 of this embodiment. As a plated steel sheet, Al must contain a certain amount or more to ensure the corrosion resistance of the portion that becomes the weld heat affected zone after welding and the corrosion resistance of the portion that becomes the non-weld portion. If the Al content in the coating 13 is less than 0.50 mass%, the corrosion resistance of the portions that become the weld heat affected zone and the non-weld portion cannot be ensured. Therefore, in the coating 13 of this embodiment, the Al content is 0.50 mass% or more. The Al content is preferably 1.00 mass% or more, and more preferably 1.50 mass% or more. By setting the Al content within the above range, the corrosion resistance of the plated steel sheet 1 can be ensured.

[0063] On the other hand, when the Al content in the coating 13 exceeds 5.00% by mass, the solidification behavior of the coating from the liquid phase to the solid phase changes, making it difficult to crystallize the η phase, and forming a dendritic structure mainly composed of Al. If a dendritic structure mainly composed of Al is formed, it will promote corrosion in the surrounding area, so the corrosion resistance of the coated steel sheet 1 cannot be ensured. In addition, due to the lack of η phase, the interface between the η phase and the eutectic structure, which is the source of cracking, is reduced, which also becomes a cause of insufficient cracking during processing. Therefore, in the coating 13 of this embodiment, the Al content is 5.00% by mass or less. The Al content is preferably 4.00% by mass or less, and more preferably 3.00% by mass or less.

[0064] [Mg: 0.50-3.00 mass %]

[0065] Mg is an element necessary for constituting the main phase (Zn-Al-Mg alloy phase) of the coating 13 of the present embodiment. As a plated steel sheet, it is necessary to contain a certain amount or more to ensure the corrosion resistance of the portion that becomes the weld heat affected zone and the corrosion resistance of the portion that becomes the non-weld portion. Therefore, in the coating 13 of the present embodiment, the Mg content is 0.50% by mass or more. The Mg content is preferably 1.50% by mass or more, and more preferably 2.00% by mass or more. By making the Mg content within the above range, the corrosion resistance of the plated steel sheet 1 can be ensured. When the Mg content exceeds 3.00%, it is difficult to precipitate the α phase from the η phase. The η phase in which Al is dissolved is hard, so deformation cannot be concentrated in the η phase during processing, which is the reason for the reduction in the number of cracks. Therefore, the upper limit of the Mg content is 3.00%.

[0066] On the other hand, if the Mg content in the coating 13 is less than 0.50 mass%, the corrosion resistance improvement effect achieved by the modification of corrosion products is insufficient, and thus the corrosion resistance of the plated steel sheet 1 cannot be ensured. Furthermore, if the Mg content is insufficient, the entire coating 13 becomes soft, and deformation during processing cannot be concentrated in the η phase, resulting in a decrease in the number of cracks. Therefore, in the coating 13 of this embodiment, the Mg content is 0.50 mass% or more. The Mg content is preferably 1.50 mass% or more, and more preferably 2.00 mass% or more. By setting the Mg content within the above range, the corrosion resistance of the plated steel sheet 1 can be ensured.

[0067] [Fe: 0.01 to 15.00 mass%]

[0068] Elements that constitute the steel sheet may sometimes be incorporated into the coating 13 from the steel sheet 11, which serves as the base material. In particular, in hot-dip coating, elements that constitute the steel sheet 11 are easily incorporated into the coating 13 due to interdiffusion of elements caused by a solid-liquid reaction between the steel sheet 11 and the coating 13. This incorporation of elements causes the coating 13 to contain a certain amount of Fe, typically at a content of 0.01% by mass or greater. Promoting this interdiffusion improves the adhesion between the steel sheet 11 and the coating 13. From the perspective of improving the adhesion between the steel sheet 11 and the coating 13, the Fe content in the coating 13 is preferably at least 0.20% by mass.

[0069] Furthermore, Fe may be intentionally added to the plating bath used to produce the coating 13, within a range that does not impair the effects of the present invention. However, if the Fe content in the coating 13 is 15.00 mass % or greater, a high-melting-point intermetallic compound of Fe and Al forms in the coating bath. This high-melting-point intermetallic compound adheres to the coating as scum, significantly reducing the appearance quality, which is not preferable. From this perspective, the Fe content in the coating bath is adjusted to 15.00 mass % or less. The Fe content in the coating 13 is more preferably 10.00 mass % or less.

[0070] In the plating layer 13 , the balance of the above-mentioned Al, Mg, and Fe is Zn and impurities.

[0071] Zn is an essential element for constituting the main phase (Zn-Al-Mg alloy phase) of the coating 13 of this embodiment and is an important element for improving the corrosion resistance of the plated steel sheet. Furthermore, by containing the aforementioned Al, Mg, and Fe within the aforementioned ranges and also containing Zn, the corrosion resistance of the plated steel sheet can be ensured.

[0072] Next, element groups A to E that may be included in the chemical composition of the plating layer 13 according to another aspect of the present embodiment will be described in detail.

[0073] It should be noted that in the coating 13 of this embodiment, when containing at least one element belonging to the following element group B to element group E, it is preferred that the coating 13 contain at least one element belonging to the following element group B to element group E within the following content range and with a total content of 5.0000 mass % or less.

[0074] By setting the total content of elements belonging to element groups B to E to 5.0000 mass % or less, the effects exhibited by the addition of each element, as described in detail below, can be achieved without mutually impairing each other. The total content of elements belonging to element groups B to E is preferably 1.0000 mass % or less, and more preferably 0.2000 mass % or less.

[0075] ◇Element Group A

[0076] In another aspect of the plating layer 13 of this embodiment, the element group A that can be contained in the plating layer 13 will be described. At least one element of the element group A described below is an element that can be contained in the plating layer 13 in place of a portion of the balance Zn.

[0077] [Element Group A]: One or two elements selected from the group consisting of Si: more than 0% and 2.00% or less and Ca: more than 0% and 2.00% or less

[0078] [Si: 0-2.00 mass %]

[0079] The coating 13 of this embodiment may not contain Si, so the lower limit of the Si content is 0% by mass. On the other hand, Si is an element that can suppress the excessive growth of the Fe-Al intermetallic compound phase formed at the interface between the coating and the steel sheet, thereby further improving the adhesion between the coating and the steel sheet. When Si is contained in the coating 13, in order to suppress the excessive growth of the Fe-Al intermetallic compound phase, the Si content is preferably 0.05% by mass or more, and more preferably 0.10% by mass or more.

[0080] On the other hand, if the Si content exceeds 2.00% by mass, Si and Mg excessively form a high-melting-point intermetallic compound phase, which may hinder the formation of an Al-Mg oxide film that has a Zn evaporation-inhibiting effect, making it difficult to suppress Zn evaporation during welding of the plated steel sheet. Therefore, the Si content in the coating 13 is preferably 2.00% by mass. In addition, if the Si content in the plating bath used to produce the coating 13 is too high, the viscosity of the coating bath may increase beyond necessity, resulting in a decrease in plating workability. Therefore, from the perspective of plating workability, the Si content in the coating bath is adjusted so that the Si content in the coating 13 is preferably 1.00% by mass or less, and more preferably 0.50% by mass or less.

[0081] [Ca: 0-2.00 mass %]

[0082] The coating 13 of this embodiment may not contain Ca, so the lower limit of the Ca content is 0% by mass. On the other hand, if Ca is contained in the coating 13, it forms an intermetallic compound phase with Al and Zn. Furthermore, if Si is contained in the coating 13 along with Ca, Ca and Si form an intermetallic compound phase. These intermetallic compound phases have a high melting point and a stable structure, thus suppressing liquid metal embrittlement cracking (LME) during welding of the plated steel sheet. When Ca is contained in the coating 13, the effect of suppressing LME during welding is achieved by setting the Ca content to 0.01% by mass or more. The Ca content in the coating 13 is more preferably 0.05% by mass or more.

[0083] On the other hand, if the Ca content in the coating 13 exceeds 2.00 mass%, the corrosion resistance of the plated steel sheet may be reduced. From this viewpoint, the Ca content in the coating 13 is 2.00 mass% or less. The Ca content in the coating 13 is preferably 1.50 mass% or less, and more preferably 1.00 mass% or less.

[0084] ◇Element Group B

[0085] Next, in another aspect of the plating layer 13 of this embodiment, the element group B that can be contained in the plating layer 13 will be described. At least one element of the element group B described below is an element that can be contained in the plating layer 13 in place of a portion of the balance Zn.

[0086] [Element Group B]: One or more elements selected from the group consisting of Sb: more than 0% and 0.5000% or less, Pb: more than 0% and 0.5000% or less, and Sr: more than 0% and 0.5000% or less

[0087] [Sb: 0 to 0.5000 mass %]

[0088] [Pb: 0 to 0.5000 mass %]

[0089] [Sr: 0 to 0.5000 mass %]

[0090] It is also possible to consider the case where the coating 13 of the present embodiment does not contain Sb, Pb, and Sr, so the lower limit of the content of these elements is 0% by mass. On the other hand, if at least any one of Sb, Pb, and Sr is contained in the coating 13, zinc flowers are formed on the surface of the coating 13, and it is possible to achieve an improvement in metallic luster. Therefore, from the viewpoint of improving the design of the coated steel sheet, it is preferred that at least any one of Sb, Pb, and Sr is contained in the coating 13. This design improvement effect is manifested when the content of at least any one of Sb, Pb, and Sr is 0.0500% by mass or more. Therefore, when at least any one of Sb, Pb, and Sr is contained in the coating 13, the content of these elements is each independently preferably 0.0500% by mass or more.

[0091] On the other hand, when forming the coating 13 in which any one of the contents of Sb, Pb, and Sr exceeds 0.5000 mass%, the amount of scum generated in the coating bath used to form the coating 13 increases, and it is impossible to produce a plated steel sheet with good coating properties. Therefore, the contents of Sb, Pb, and Sr in the coating 13 are each independently 0.5000 mass% or less. The contents of Sb, Pb, and Sr are each independently preferably 0.2000 mass% or less.

[0092] ◇Element Group C

[0093] Next, in another aspect of the plating layer 13 of this embodiment, the element group C that can be contained in the plating layer 13 will be described. At least one element of the element group C described below is an element that can be contained in the plating layer 13 in place of a portion of the balance Zn.

[0094] [Element Group C]: One or more elements selected from the group consisting of Cu: more than 0% and 1.0000%, Ti: more than 0% and 1.0000%, Cr: more than 0% and 1.0000%, Nb: more than 0% and 1.0000%, Ni: more than 0% and 1.0000%, Mn: more than 0% and 1.0000%, Mo: more than 0% and 1.0000%, Co: more than 0% and 1.0000%, and V: more than 0% and 1.0000%.

[0095] [Cu: 0 to 1.0000 mass %]

[0096] [Ti: 0 to 1.0000 mass%]

[0097] [Cr: 0 to 1.0000 mass %]

[0098] [Nb: 0 to 1.0000 mass %]

[0099] [Ni: 0 to 1.0000 mass %]

[0100] [Mn: 0 to 1.0000 mass %]

[0101] [Co: 0 to 1.0000 mass %]

[0102] [V: 0 to 1.0000 mass %]

[0103] The coating 13 of this embodiment may not contain Cu, Ti, Cr, Nb, Ni, Mn, Co, or V, so the lower limit of the content of these elements is 0% by mass. On the other hand, if at least one of Cu, Ti, Cr, Nb, Ni, Mn, Co, and V is contained in the coating 13, these elements will be incorporated into the Al-Fe alloy phase generated by welding when the plated steel sheets are welded, thereby improving the corrosion resistance of the resulting weld. This effect of improving the corrosion resistance of the weld is achieved when the content of at least one of Cu, Ti, Cr, Nb, Ni, Mn, Co, and V in the coating 13 is 0.0050% by mass or more. Therefore, when at least one of Cu, Ti, Cr, Nb, Ni, Mn, Co, and V is contained in the coating 13, the content of each of these elements is preferably 0.0050% by mass or more.

[0104] On the other hand, when forming the coating 13 in which the content of any of Cu, Ti, Cr, Nb, Ni, Mn, Co, and V exceeds 1.0000 mass%, these elements form various intermetallic compound phases in the plating bath used to form the coating 13, resulting in increased viscosity of the plating bath and an inability to produce a plated steel sheet with good plating properties. Therefore, the content of Cu, Ti, Cr, Nb, Ni, Mn, Co, and V in the coating 13 is each independently 1.0000 mass% or less. The content of Cu, Ti, Cr, Nb, Ni, Mn, Co, and V is each independently 0.2000 mass% or less.

[0105] [Mo: 0 to 1.0000 mass %]

[0106] The coating 13 of this embodiment may not contain Mo, so the lower limit of the Mo content is 0 mass%. On the other hand, if Mo is included in the coating 13, the corrosion resistance can be further improved. This effect of improving corrosion resistance is apparent when the Mo content is 0.0100 mass% or more. Therefore, when Mo is included, its content is preferably 0.0100 mass% or more.

[0107] On the other hand, if the plating layer 13 is formed with a Mo content exceeding 1.0000 mass%, this will cause a large amount of scum to be generated in the plating bath used, which is not preferable. Therefore, the Mo content is 1.0000 mass% or less. The Mo content is preferably 0.0500 mass% or less.

[0108] ◇Element Group D

[0109] Next, in another aspect of the plating layer 13 of the present embodiment, the element group D that can be contained in the plating layer 13 will be described. The elements of the element group D described below are elements that can be contained in the plating layer 13 in place of a portion of the balance Zn.

[0110] [Element Group D]: One or more elements selected from the group consisting of Sn: more than 0% and 1.0000% or less, In: more than 0% and 1.0000% or less, and Bi: more than 0% and 1.0000% or less

[0111] [Sn: 0 to 1.0000 mass %]

[0112] [In: 0 to 1.0000 mass %]

[0113] [Bi: 0 to 1.0000 mass %]

[0114] It is also possible to consider the case where the coating 13 of this embodiment does not contain Sn, In, or Bi, so the lower limit of the Sn content is 0% by mass. On the other hand, the coating 13 containing Sn, In, and Bi is an element that increases the Mg dissolution rate when placed in a corrosive environment. If the Mg dissolution rate increases, Mg ions are supplied to the exposed portion of the steel plate 11, improving corrosion resistance. From this viewpoint, when containing Sn, In, and Bi, it is preferred that the contents of Sn, In, and Bi are each independently set to 0.0050% by mass or more. On the other hand, adding excessive amounts of Sn, In, and Bi will excessively promote the Mg dissolution rate, and the corrosion resistance of the plated steel sheet may be reduced. If any of the contents of Sn, In, and Bi exceeds 1.0000% by mass, the increase in the Mg dissolution rate becomes significant, so the contents of Sn, In, and Bi are each independently 1.0000% by mass or less. The contents of Sn, In, and Bi are each independently preferably 0.2000% by mass or less.

[0115] ◇Element Group E

[0116] Next, in another aspect of the plating layer 13 of this embodiment, the element group E that can be contained in the plating layer 13 will be described. At least one element of the element group E described below is an element that can be contained in the plating layer 13 in place of a portion of the balance Zn.

[0117] [Element Group E]: One or more elements selected from the group consisting of Zr: more than 0% and 1.0000% or less, Ag: more than 0% and 1.0000% or less, and Li: more than 0% and 1.0000% or less

[0118] [Zr: 0 to 1.0000 mass %]

[0119] [Ag: 0 to 1.0000 mass %]

[0120] [Li: 0 to 1.0000 mass %]

[0121] It is also possible to consider the case where the coating 13 of the present embodiment does not contain Zr, Ag, and Li, so the lower limit of the content of these elements is 0 mass%. On the other hand, if at least any one of Zr, Ag, and Li is contained in the coating 13, the plating workability can be improved. The effect of improving the plating property is manifested when the content of at least any one of Zr, Ag, and Li in the coating 13 becomes 0.0100 mass% or more. Therefore, when containing at least any one of Zr, Ag, and Li, the content of these elements is preferably 0.0100 mass% or more, each independently.

[0122] On the other hand, when forming the plating layer 13 in which the content of any one of Zr, Ag, and Li exceeds 1.0000 mass%, a large amount of scum is likely to be generated in the plating bath used to form the plating layer 13. Therefore, the content of at least one of Zr, Ag, and Li is each independently 1.0000 mass% or less. The content of at least one of Zr, Ag, and Li is each independently preferably 0.1000 mass% or less.

[0123] ◇Element Group F

[0124] Next, in another aspect of the plating layer 13 of this embodiment, the element group F that can be contained in the plating layer 13 will be described. At least one element of the element group F described below is an element that can be contained in the plating layer 13 in place of a portion of the balance Zn.

[0125] [Element Group F]: one or more elements selected from the group consisting of La: more than 0% and 0.5000% or less, Ce: more than 0% and 0.5000% or less, and Y: more than 0% and 0.5000% or less

[0126] [La: 0 to 0.5000 mass %]

[0127] [Ce: 0 to 0.5000 mass %]

[0128] [Y: 0 to 0.5000 mass %]

[0129] It is also possible to consider the case where the coating 13 of the present embodiment does not contain La, Ce, and Y. Therefore, the lower limit of the content of these elements is 0% by mass. On the other hand, La, Ce, and Y are elements that show an effect roughly equivalent to that of Ca, further suppressing the formation of pores during welding. This is because the atomic radius of each element is close to that of Ca. If the coating 13 contains these elements, substitution is performed at the Ca position. Therefore, these elements are detected in the same position as Ca in EDS. In addition, when these elements become oxides after welding of the plated steel sheet, the oxides of these elements are also detected at the same position as CaO.

[0130] The effect of suppressing pore formation during welding is achieved by setting the content of each of these elements independently to 0.0100 mass% or greater. Therefore, when at least one of Zr, Ag, and Li is contained, the content of each of these elements is preferably independently 0.0100 mass% or greater. The content of La, Ce, and Y in the plating layer 13 is more preferably independently 0.0500 mass% or greater.

[0131] On the other hand, if the La, Ce, and Y contents in the plating bath used to produce the coating layer 13 are excessive, the viscosity of the plating bath may increase beyond necessity, resulting in reduced plating workability. Therefore, from the perspective of plating workability, the La, Ce, and Y contents in the plating bath are adjusted so that each of the La, Ce, and Y contents is independently 0.5000 mass% or less. The La, Ce, and Y contents are each independently preferably 0.1000 mass% or less.

[0132] ◇Element Group G

[0133] Next, in another aspect of the plating layer 13 of the present embodiment, the element group G that can be contained in the plating layer 13 will be described. The elements of the element group G shown below are elements that can be contained in the plating layer 13 in place of a portion of the balance Zn.

[0134] [Element Group G]: B: more than 0% and 0.5000% or less

[0135] [B: 0 to 0.5000 mass %]

[0136] The coating 13 of this embodiment may not contain B, so the lower limit of its content is 0 mass%. On the other hand, B, when contained in the coating 13, has the effect of suppressing LME. This is presumably because B, when contained in the coating 13, combines with at least one of Zn, Al, Mg, and Ca to form various intermetallic compound phases. Furthermore, it is believed that the presence of B in the coating 13 allows B to diffuse from the coating 13 into the steel sheet 11, suppressing LME in the steel sheet 11 through grain boundary strengthening. Furthermore, it is presumed that the melting points of the various intermetallic compounds formed by B are extremely high, thus also contributing to the suppression of Zn evaporation during welding. These improvements are achieved when B is present in an amount of 0.0500 mass% or more. Therefore, when B is present, the B content is preferably 0.0500 mass% or more.

[0137] On the other hand, if the coating bath contains excessive amounts of B in order to include B in the coating layer 13, the coating melting point will rise sharply, the coating workability will decrease, and it will be impossible to produce a coated steel sheet with excellent coating properties. This decrease in coating workability becomes significant when the B content exceeds 0.50 mass%, so the B content is 0.5000 mass% or less. The B content is preferably 0.1000 mass% or less.

[0138] [Measurement method of chemical composition]

[0139] The chemical composition of the above-mentioned coating 13 can be measured using inductively coupled plasma atomic emission spectrometry (ICP-AES, Inductively Coupled Plasma Atomic Emission Spectrometry) or inductively coupled plasma mass spectrometry (ICP-MS, Inductively Coupled Plasma Mass Spectrometry). It should be noted that when analyzing chemical compositions up to 0.1% by mass, ICP-AES is used, and when analyzing trace amounts of chemical compositions less than 0.1% by mass, ICP-MS is used. The coated steel sheet is immersed in a 10% HCl aqueous solution to which an inhibitor is added for about 1 minute, the coating portion is peeled off, and a solution in which the coating is dissolved is prepared. The obtained solution is analyzed by ICP-AES or ICP-MS to obtain the overall average chemical composition of the coating.

[0140] ◇About the adhesion amount of plating layer 13

[0141] There is no particular limitation on the coating weight of the coating layer 13 described above. For example, it is preferably 15 to 250 g / m2 per side of the steel plate. 2By setting the coating amount of the plating layer 13 within the above-mentioned range, the plated steel sheet 1 of the present embodiment can exhibit sufficient corrosion resistance.

[0142] It should be noted that the adhesion amount of the coating 13 is measured as follows. First, a sample with a size of 30 mm × 30 mm when viewed from above is cut out from the coated steel plate, and the mass of the sample is measured in advance. It should be noted that when the sample is cut out, the entire thickness direction is cut out. A sealing tape is affixed to one side of the sample to prevent the coating on this side from dissolving in the next step. On this basis, the sample is immersed in a 10% HCl aqueous solution to which an inhibitor is added, the coating is pickled and peeled, and the mass of the sample after pickling is measured. Based on the change in the mass of the sample before and after pickling, the adhesion amount of the coating 13 on each side can be determined.

[0143] ◇About the metallographic structure of coating 13

[0144] Next, the metallographic structure of the plating layer 13 having the chemical composition described above will be described.

[0145] The coating 13 of this embodiment has the chemical composition described above. Furthermore, the coating 13 is formed by the manufacturing method described in detail below and contains metallic phases and / or intermetallic compound phases such as an α phase, an η-Zn phase, a MgZn2 phase, an η / α / MgZn2 ternary eutectic phase, and an η / MgZn2 binary eutectic phase. Furthermore, depending on the elements that the coating 13 may contain, in addition to the aforementioned phases, the coating 13 may also contain intermetallic compounds such as an Al-Si-Ca phase, an Al-Si-Ca-Fe phase, a Mg2Si phase, and a Mg2Sn phase. The coating 13 of this embodiment exhibits excellent corrosion resistance due to its metallographic structure as described above.

[0146] Furthermore, in the coating 13 of this embodiment, a portion of the aforementioned α phase and η-Zn phase exists in a specific state as described in detail below, functioning as a starting point for crack generation. Thus, in the coating 13 of this embodiment, a more appropriate amount of cracks can be efficiently generated without excessively focusing on controlling the application of strain, further improving the hydrogen desorption properties of the plated steel sheet 1.

[0147] Here, what kind of phase the coating 13 of the present embodiment has can be determined by observing the surface of the coating 13 using a scanning electron microscope (SEM). That is, by observing the solidification structure of the surface of the coating 13 by SEM, it is possible to determine what kind of phase it has based on the point analysis results based on SEM-EPMA (Electron Probe MicroAnalyzer) and the morphology of the crystalline phase in the reflected electron image in the observation field. At this time, before SEM observation, pre-treatment such as grinding may not be performed. However, in the case of imparting a chemical conversion coating, grinding may be performed to remove the chemical conversion coating. In the case of grinding, grinding is performed in such a way that more than 80% of the thickness of the coating remains, and after the surface becomes a mirror-finished state, SEM observation is performed to form the surface structure.

[0148] Next, refer to Figure 2 and Figure 3 The specific state in which a portion of the α phase and the η-Zn phase are present in the plating layer 13 of this embodiment will be described in detail. Figure 2 and Figure 3 This is a schematic diagram for explaining the α-precipitated η phase included in the coating layer 13 of the plated steel sheet 1 according to the present embodiment.

[0149] Focusing on the surface normal direction ( Figure 2 The surface of the plating layer 13 of this embodiment is observed on the positive Z-axis side) Figure 2 The XY plane in the figure.

[0150] When this observation was performed, in the coating layer 13 of the plated steel sheet 1 of the present embodiment, the surface structure thereof had the α-precipitated η phase ( Figure 2 101 in the figure), with an average area ratio of 5 to 95%. Furthermore, the remainder of the α-precipitated η phase 101 forms a hard structure 103 composed of a MgZn2 phase, an η / α / MgZn2 ternary eutectic phase, an η / MgZn2 binary eutectic phase, and the like. It should be noted that the coating 13 of this embodiment contains 0.50% by mass or more of Mg as a chemical composition of the coating, and therefore, the hard structure 103 described above is inevitably formed by this chemical composition.

[0151] like Figure 3As schematically shown, the α-precipitated η phase 101 is a metallurgical structure in which Al supersaturated solid solution in a matrix composed of an η-Zn phase (hereinafter referred to as "η matrix phase 113") precipitates as α phase 111, resulting in softening. When focusing on the backscattered electron image during SEM observation, the α phase 111 appears as a black substance, while the η matrix phase 113 appears as a white substance. Therefore, when SEM observation based on the backscattered electron image is performed, the α-precipitated η phase 101 is recognized as a structure with black particles dispersed within a white phase.

[0152] The presence of such α-precipitated η phase 101 in the hard structure 103 causes uneven hardness in the plating layer 13. If strain accompanying processing is applied to the plating layer 13 under the condition that a relatively soft metal structure exists in the hard metal structure, the applied strain will be concentrated on the α-precipitated η phase 101 which is the soft metal structure. As a result, in the plating layer 13 of this embodiment, as shown in FIG. Figure 2 As schematically shown, cracks 105 are generated starting from the α-precipitated η phase 101 .

[0153] The present inventors have verified that, if the end of a crack 105 generated in the hard structure 103 is located within the range of the coating 13 deposition amount described above, most of the hydrogen will reach the interface between the coating 13 and the steel sheet 11. In the plated steel sheet 1 of this embodiment, hydrogen present in the steel sheet 11 is released to the outside (i.e., the external air) via such cracks 105. Furthermore, even if the crack 105 does not reach the interface between the coating 13 and the steel sheet 11, hydrogen in the steel that reaches the end of the crack 105 will subsequently be released to the outside along the crack 105.

[0154] Furthermore, in the surface structure of the coating 13 of this embodiment, as described above, the average area ratio of the α-precipitated η phase 101 is within the range of 5 to 95%. By ensuring that the average area ratio of the α-precipitated η phase 101 is within this range, cracks 105 can be introduced into the coating 13 at an appropriate amount, even within the range of strain imparted when, for example, the coated steel sheet is processed into various shapes. As a result, the coated steel sheet 1 of this embodiment can maintain corrosion resistance while further improving hydrogen desorption properties.

[0155] When the average area ratio is less than 5%, the amount of α-precipitated η phase 101 present is too small, so an appropriate number of cracks 105 cannot be introduced, and the hydrogen desorption properties of the plated steel sheet 1 cannot be improved. By setting the average area ratio to 5% or more, the corrosion resistance can be maintained while improving the hydrogen desorption properties of the plated steel sheet 1. The average area ratio of the α-precipitated η phase 101 is preferably 8% or more, and more preferably 15% or more.

[0156] On the other hand, when the average area ratio of the α-precipitated η phase 101 exceeds 95%, the soft α-precipitated η phase occupies the majority of the coating, resulting in ductility in the coating as a whole. The α-precipitated η phase no longer functions as a crack initiation site, which is not preferred. By setting the average area ratio of the α-precipitated η phase 101 to 95% or less, corrosion resistance can be maintained, and by allowing the α-precipitated η phase 101 to function as a crack initiation site in the coating, the hydrogen desorption properties of the plated steel sheet 1 can be improved. The average area ratio of the α-precipitated η phase 101 is preferably 70% or less, more preferably 40% or less, and even more preferably 30% or less.

[0157] ◇Calculation method of the average area ratio of the α-precipitated η phase 101 in the coating layer 13

[0158] Here, the above-mentioned average area ratio is measured as follows.

[0159] Specifically, an elemental map was obtained by observing an arbitrary position on the surface of the coating 13 using SEM and SEM-EPMA. The obtained elemental map was binarized using the binarization function of a commercially available image analysis application, and the region corresponding to the α-precipitated η phase 101 was determined, and its area ratio was calculated.

[0160] More specifically, an area of ​​120 μm×100 μm in plan view at an arbitrary position on the surface of the plating layer 13 was observed by SEM (equivalent to a magnification of approximately 1000 times), and point analysis was performed by SEM-EPMA.

[0161] Specifically, the acceleration voltage was 15.0 kV, the irradiation current was 4.999×10 -8 A. Irradiation time: 50 milliseconds. Observe the aforementioned 120 μm × 100 μm area at a magnification of 1000. Under these conditions, obtain a reflected electron image of the desired area and, using the contrast of the reflected electron image, perform point analysis on three points for each metallographic structure.

[0162] In this analysis, a phase that satisfies the following conditions: Al: 20-99 atomic %, Zn: 0.5-80 atomic %, Mg: 0-5 atomic %, and a total of Al and Zn content of 70 atomic % or greater can be identified as an α phase. Furthermore, a phase with a Zn content of 98 atomic % or greater and a total content of other elements of 2 atomic % or less can be identified as an η-Zn phase.

[0163] It should be noted that the phase in which the content of Mg and Zn is respectively greater than 10 atomic % and the total content of Mg and Zn is greater than 85 atomic % is judged to be a hard structure 103 composed of MgZn2 phase, η / α / MgZn2 ternary eutectic phase, η / MgZn2 binary eutectic phase, etc.

[0164] The η-Zn phase does not contain Mg, while a hard structure 103 containing Mg exists around the η-Zn phase. Therefore, by focusing on the distribution of the Mg element, a contour line can be determined that represents the boundary between the metallographic structure containing Mg and the metallographic structure not containing Mg. The metallographic structure not containing Mg surrounded by this contour line can be identified as the η-Zn phase. A person skilled in the art can easily distinguish the η-Zn phase from the surrounding hard structure 103 through visual identification.

[0165] Determine the outline of the η-Zn phase within the field of view during SEM observation as described above and manually draw this outline using various image analysis applications (e.g., ImageJ). Binarizing the image within the image analysis application makes it easy to determine whether black precipitates corresponding to the α phase are present within the η-Zn phase. For this purpose, the binarization threshold can be set to, for example, 200 in the Brightness / Contrast setting.

[0166] Next, for the η-Zn phase identified as described above, it is determined whether there is an α phase inside it. As described above, when observing using a reflected electron image, the α phase is visually identified as a black precipitate (i.e., black particles), while the η-Zn phase is visually identified as a white parent phase. Therefore, the α precipitated η phase 101 focused on in this embodiment is as follows: Figure 3 As shown schematically, a phase in which black particles are dispersed in a white matrix is ​​observed. Figure 3 In FIG, the outline shown by the dotted line corresponds to the outline of the η-Zn phase described above.

[0167] Therefore, by observing the reflected electron image as described above, the phase in which the black particles are dispersed in the white matrix is ​​determined, and then point analysis based on SEM-EPMA is performed. Focusing on one of the phases in which the black particles are dispersed in the white matrix, as shown in FIG. Figure 3 As shown schematically, a spot analysis using SEM-EPMA was performed on an arbitrary 5 μm x 5 μm area encompassing both the black particles and the white matrix phase. The results of the spot analysis indicate that regions with a Zn content of 90 atomic % or greater and an Al content of 0.05 to 10.00 atomic % can be identified as the α phase 111 within the η matrix phase 113. In this case, any black phase surrounding the region identified as the α phase can be uniformly identified as the α phase.

[0168] By the method as described above, it is possible to determine the region of the α-precipitated η phase 101 in the region of 120 μm × 100 μm when viewed from above at any position on the surface of the coating 13. On this basis, various image analysis applications (such as ImageJ, etc.) are used to calculate the area ratio of the determined region. Specifically, on the basis of calculating the area of ​​the region equivalent to the α-precipitated η phase 101 by the image analysis application, the area of ​​the obtained α-precipitated η phase 101 is divided by the area of ​​the entire visual field, thereby obtaining the area ratio of the α-precipitated η phase 101 in the visual field of interest.

[0169] The above-described measurement / calculation process is performed at five arbitrary locations, and the average of the five obtained area ratios is calculated. The average thus obtained average is defined as the average area ratio of the α-precipitated η phase 101 .

[0170] It should be noted that, when focusing on a plated steel sheet 1 that has been processed into a product by welding and / or bonding, the above-described observation can be performed on an arbitrary 120 μm × 100 μm area, for example, at least 50 mm away from the end of the product, the weld heat-affected zone, or the bonding site, and a flat portion that has not been processed. Furthermore, if various coatings exist on the surface of the coating layer 13, the existing coatings can be removed using a coating stripper.

[0171] ◇The length of the crack 105 in the coating 13

[0172] Here, focusing on an area that is, for example, more than 50 mm away from the end of the plated steel sheet 1, at any position on the surface of the coating 13 of the present embodiment, when an area having a size of 130 μm × 100 μm when viewed from above is observed using an electron microscope (more specifically, SEM), the total length of the cracks 105 present in the above-mentioned area is more than 50 μm.

[0173] The plated steel sheet 1 of this embodiment exhibits excellent hydrogen desorption properties by setting the total length of the cracks 105 present in the above region to 50 μm or more. The total length of the cracks 105 present in the above region is preferably 150 μm or more, more preferably 500 μm or more.

[0174] On the other hand, the larger the total length of the cracks 105, the better. There is no particular upper limit, but in practice, it is approximately 1000 μm. It should be noted that even when the total length of the cracks 105 increases, the Mg contained in the coating layer 13 exhibits corrosion resistance, thereby maintaining the corrosion resistance of the plated steel sheet 1.

[0175] Here, to measure the sum of the lengths of the cracks 105, SEM observation can be performed in the same manner as for observing the metallographic structure of the plating layer 13. For this observation, focus on an arbitrary area measuring 130 μm x 100 μm and, using a length measurement application program attached to the SEM, measure the sum of the lengths of the cracks 105 present in that area. Perform the above-described measurement process at five arbitrary locations, and calculate the average of the five measured values. This average value is defined as the sum of the lengths of the cracks 105 in the 130 μm x 100 μm area.

[0176] Above, refer to Figures 1A to 3 The plated steel sheet 1 of the present embodiment has been described in detail. The plated steel sheet 1 of the present embodiment described above can be suitably used as a material for automotive chassis parts, for example.

[0177] The plated steel sheet 1 of this embodiment may further include one or more layers of various coatings on the plated layer 13. Examples of such coatings include chromate coatings, phosphate coatings, chromate-free coatings, and organic resin coatings.

[0178] (Regarding the method for producing a plated steel sheet)

[0179] Next, an example of the method for producing the plated steel sheet described above will be described.

[0180] The plated steel sheet 1 of the present embodiment is manufactured by forming the plated layer 13 on the surface of the steel sheet 11 using the steel sheet 11 as a base material, and then applying strain to the steel sheet 11 having the plated layer 13 formed thereon by various methods.

[0181] Here, the coating 13 can be formed by methods other than hot dipping, such as spraying, cold spraying, sputtering, vapor deposition, and electroplating. However, hot dipping is most preferred in terms of cost in order to form a coating having a thickness generally used in automobiles and the like.

[0182] The plated steel sheet (steel sheet 11 having the coating layer 13) obtained by the above method is subjected to a specific heat treatment process described below. As a result, an α-precipitated η phase 101 is formed in the coating layer 13. Then, by applying strain to the plated steel sheet that has undergone the heat treatment process using various methods, cracks 105 are generated starting from the α-precipitated η phase 101, thereby obtaining the plated steel sheet 1 of this embodiment.

[0183] Hereinafter, an example of a method for producing the plated steel sheet 1 according to the present embodiment using a hot-dip coating method will be described in detail.

[0184] In the manufacturing process of the plated steel sheet 1 , first, a steel sheet 11 serving as a base material is rolled to a desired thickness by the Sendzimir method, and then wound into a coil and placed in a hot-dip coating line.

[0185] In a hot-dip coating line, steel sheets are continuously threaded onto a strip while being unwound from a coil. The steel sheets are then subjected to a heat reduction treatment at 800°C in an N2-5% H2 atmosphere, in an annealing facility installed in the line, under a low-oxidation environment (e.g., an oxygen concentration of 20 ppm or less). The steel sheets are then air-cooled with N2 gas to a temperature of approximately +20°C above the subsequent coating bath temperature, and then immersed in the coating bath.

[0186] Here, a molten plating alloy having the above-mentioned chemical composition is prepared in a plating bath, and the bath temperature of the plating bath is equal to or higher than the melting point of the plating alloy (eg, approximately 400 to 500° C.).

[0187] When preparing the material for the plating alloy, it is preferable to use pure metals (purity 99% or higher) as the alloying material. First, the alloying metals are mixed in predetermined amounts to form the composition of the aforementioned plating layer. The alloy is then completely melted in a high-frequency induction furnace and / or an arc furnace under vacuum or inert gas substitution to form the alloy. This alloy, mixed with the predetermined composition (the aforementioned plating layer composition), is then melted in the atmosphere, and the resulting melt is used as the plating bath.

[0188] It should be noted that, in the production of the above-mentioned plating alloy, there is no particular restriction on using pure metals, and existing Zn alloys, Mg alloys, and Al alloys can also be melted and used. In this case, there is no problem as long as a predetermined composition alloy with few impurities is used.

[0189] After immersing the steel sheet in the above-described plating bath, it is pulled out at a predetermined speed. At this time, the coating deposition amount is controlled, for example, by using N2 wiping gas, so that the formed coating layer 13 has the desired thickness. Regarding conditions other than the bath temperature, general plating operating conditions can be applied, and no special equipment and / or conditions are required.

[0190] Next, the molten plating alloy on the steel sheet is subjected to the following first and second cooling steps, thereby forming the molten plating alloy into a plating layer 13 and generating an α-precipitated η phase 101 in the plating layer 13. The first and second cooling steps are described in detail below.

[0191] The first cooling process is a cooling process performed when the temperature of the plating alloy is below the bath temperature and above 240°C. In this first cooling process, the plated steel sheet in the temperature range described above is rapidly cooled at an average cooling rate of 15.0°C / second or more. Here, when the average cooling rate is less than 15.0°C / second, the concentration of Al dissolved in the η phase decreases, and the driving force for the subsequent precipitation of the α phase in the η phase is insufficient, resulting in difficulty in forming the α-precipitated η phase. It should be noted that when hot-dip plating is used in the plating process, the first cooling process is performed just after the steel sheet comes out of the plating bath. As a result, Al is dissolved in the solidifying η-Zn phase.

[0192] Here, the average cooling rate is preferably 25.0° C. / second or higher. The upper limit of the average cooling rate is not particularly specified, but approximately 90.0° C. / second is a practical upper limit, for example.

[0193] Then, when the temperature of the plating alloy (plating) is within the range of less than 240°C and more than 70°C, a second cooling process is implemented. In this second cooling process, the plated steel sheet in the temperature range described above is slowly cooled at an average cooling rate of less than 1.0°C / second. Here, when the average cooling rate exceeds 1.0°C / second, the time for the α phase to precipitate from the η phase cannot be ensured, and the formation of the α precipitation η phase becomes difficult. As a result, Al dissolved in the η-Zn phase in the first cooling process precipitates as the α phase, thereby softening the η-Zn phase to become the α precipitation η phase 101, and a hard structure 103 exists around the α precipitation η phase 101. Here, the above-mentioned average cooling rate is preferably less than 0.5°C / second.

[0194] As described above, by undergoing two cooling steps of rapid cooling in a temperature range below the bath temperature and above 240°C and slow cooling in a temperature range below 240°C and above 70°C, the α-precipitated η phase 101 can be formed in the coating layer 13 at a desired average area ratio.

[0195] Note that there is no particular limitation on the cooling state from 70° C. to room temperature, and cooling to room temperature may be performed by various methods.

[0196] Here, the interval from the end of the first cooling step to the start of the second cooling step is preferably within 3 seconds, and the second cooling step is preferably started immediately after the end of the first cooling step. If the interval from the end of the first cooling step to the start of the second cooling step exceeds 3 seconds, an undesirable cooling process occurs, and the desired α-precipitated η phase 101 cannot be generated.

[0197] It should be noted that, without performing either the first cooling step or the second cooling step as described above, the desired α-precipitated η phase 101 cannot be achieved. By performing both the first cooling step and the second cooling step as described above, the α-precipitated η phase 101 can be generated in the coating layer 13 at a desired average area ratio, and a soft structure can be appropriately introduced into the coating layer 13.

[0198] Furthermore, if an alloying heat treatment step (e.g., a heat treatment step involving heating to a sheet temperature of approximately 480 to 550°C) is performed after the second cooling step, which is often performed in the production of alloyed hot-dip galvannealed steel sheets, the state of the α-precipitated η phase 101 controlled by the first and second cooling steps collapses, and as a result, the hydrogen desorption properties targeted in this embodiment cannot be achieved. From this perspective, it is important not to perform a heat treatment step after the second cooling step.

[0199] Here, in the cooling process described above, generally known methods such as N2 gas cooling, spray cooling, immersion, etc. can be applied. In addition, the cooling gas can also use a gas with a high heat removal effect such as He gas or hydrogen gas in addition to N2 gas.

[0200] It should be noted that as a method for measuring the temperature of the coating, for example, a contact thermocouple (K-type) can be used. By installing a contact thermocouple on the steel plate that becomes the base material, the average temperature of the entire coating can be monitored at all times. In addition, if various speeds and / or thicknesses are controlled mechanically and various operating conditions such as the preheating temperature of the steel plate and / or the temperature of the hot-dip bath are unified, the temperature of the entire coating at that moment under the manufacturing conditions can be roughly and accurately monitored. Thus, the cooling treatment in the first cooling process and the second cooling process can be precisely controlled. It should be noted that, although not as accurate as the contact type, the surface temperature of the coating can also be measured by a non-contact radiation thermometer.

[0201] In addition, the relationship between the surface temperature of the coating and the average temperature of the entire coating can also be obtained by simulating the heat conduction analysis. Specifically, based on various manufacturing conditions such as the preheating temperature of the steel plate and / or the temperature of the hot dip coating bath, the speed at which the steel plate is lifted from the coating bath, the thickness of the steel plate, the thickness of the coating, the heat exchange amount between the coating and the manufacturing equipment, and the heat release of the coating, the surface temperature of the coating and the average temperature of the entire coating can be obtained. Then, using the obtained results, the relationship between the surface temperature of the coating and the average temperature of the entire coating can be obtained. Thus, by measuring the surface temperature of the coating when manufacturing the coated steel plate, the average temperature of the entire coating at that moment under the manufacturing conditions can be estimated. As a result, the cooling process in the first cooling process and the second cooling process can be precisely controlled.

[0202] Next, strain is applied to the plated steel sheet obtained as described above. This causes cracks to form in the plated layer 13 having the α-precipitated η phase 101. The method for applying strain is not particularly limited, and may include bending and stretching using a tension leveler, rolling using a skin-pass mill, or cold pressing when the plated steel sheet is formed into a desired shape.

[0203] Here, in the above-mentioned treatment for imparting strain, it is preferable to impart a strain of 0.2% or more of total elongation to the plated steel sheet. By imparting a strain corresponding to such a total elongation, when an arbitrary 130 μm × 100 μm region of the surface of the plated layer 13 is observed using an electron microscope, the total length of cracks existing in the region can be made to be 50 μm or more. Here, the total elongation R TOTAL (Unit: %) is a value determined by the following formula (101). In the following formula (101), L0 is the length in the tape direction of any section X in the plated steel sheet before the treatment for imparting strain (unit: m), and L1 is the length in the tape direction of the portion of the plated steel sheet from any section X in the tape direction after the treatment for imparting strain. The total elongation is more preferably 0.6% or greater.

[0204] R TOTAL (%)={(L1-L0) / L0}×100···(101)

[0205] In addition, the total elongation R TOTAL There is no particular upper limit, but approximately 1.5% is the practical upper limit.

[0206] It should be noted that the above-mentioned treatment for imparting strain can be performed at any time, and can be performed without interruption after the above-mentioned two-stage cooling process, or can be performed after a certain period of time has passed after the completion of the two-stage cooling process. In the plated steel sheet of this embodiment, by undergoing the above-mentioned two-stage cooling process, α-precipitated η phase 101 is generated in the coating layer 13 at a desired average area ratio. Therefore, as long as the treatment for imparting strain is performed at any time after the two-stage cooling process, cracks 105 can be generated in the coating layer 13.

[0207] An example of the method for producing a plated steel sheet according to the present embodiment has been specifically described above.

[0208] It should be noted that in the method for producing a plated steel sheet of this embodiment, a treatment for forming one or more layers of various coatings may be further performed after the second cooling step. Examples of such treatments include chromate treatment, phosphate treatment, chromate-free treatment, and organic resin coating formation.

[0209] Chromate treatment includes: electrolytic chromate treatment in which a chromate coating is formed by electrolysis; reactive chromate treatment in which a coating is formed by reaction with the workpiece and then excess treatment liquid is washed away; and coating chromate treatment in which a treatment liquid is applied and dried without washing to form a coating. Any of these chromate treatments can be used.

[0210] Examples of the electrolytic chromate treatment include electrolytic chromate treatment using chromic acid, silica sol, resin (phosphoric acid resin, acrylic resin, vinyl ester resin, vinyl acetate acrylic emulsion, carboxylated styrene butadiene latex, diisopropanolamine-modified epoxy resin, etc.), and hard silica.

[0211] Examples of the phosphate treatment include zinc phosphate treatment, calcium zinc phosphate treatment, and manganese phosphate treatment.

[0212] Chromate-free treatment is particularly environmentally friendly and therefore preferred. Chromate-free treatments include electrolytic treatments that form a chromate-free coating by electrolysis; reactive treatments that form a coating by reacting with the workpiece and then rinsing away excess treatment liquid; and coating treatments that form a coating by applying a treatment liquid and drying it without rinsing. Any of these chromate-free treatments can be used.

[0213] The organic resin used in the organic resin film formation process is not limited to a specific resin, and various resins such as polyester resins, polyurethane resins, epoxy resins, acrylic resins, polyolefin resins, and modified forms of these resins can be used. Here, the modified form refers to a resin obtained by reacting the reactive functional groups contained in the structure of these resins with other compounds (e.g., monomers and / or crosslinking agents) containing functional groups capable of reacting with these functional groups.

[0214] As the organic resin, one of the above-mentioned organic resins may be used alone, or two or more organic resins (unmodified organic resins) may be used in combination. Alternatively, one organic resin obtained by modifying at least one other organic resin in the presence of at least one organic resin may be used alone, or two or more organic resins may be used in combination. Furthermore, organic resins made water-based by dissolving or dispersing in water may also be used. Furthermore, the organic resin film may contain various coloring pigments and / or rust-preventive pigments.

[0215] Example

[0216] The plated steel sheet of the present invention will be described in detail below with reference to Examples and Comparative Examples. It should be noted that the following Examples are merely examples of the plated steel sheet of the present invention, and the plated steel sheet of the present invention is not limited to the following Examples.

[0217] Cold-rolled steel sheets a to e (all manufactured by Nippon Steel Corporation) each having a thickness of 1.6 mm were used as the plated base sheets. The chemical composition of each cold-rolled steel sheet is as follows, with the balance being Fe and impurities.

[0218] Cold-rolled steel sheet a: 0.04 mass% C-0.40 mass% Si-2.20 mass% Mn

[0219] b: 0.09 mass% C-0.40 mass% Si-2.20 mass% Mn

[0220] c: 0.20 mass% C-0.80 mass% Si-2.20 mass% Mn

[0221] d: 0.25 mass% C-0.40 mass% Si-2.40 mass% Mn

[0222] e: 0.35 mass% C-0.70 mass% Si-2.40 mass% Mn

[0223] For each of the cold-rolled steel sheets a to e, JIS 13B test pieces were collected from arbitrary locations on the cold-rolled steel sheets in accordance with JIS Z2201:1998, and the tensile strength was measured using a commercially available tensile testing machine. The results showed that the tensile strengths of the cold-rolled steel sheets a to e were 590 MPa (cold-rolled steel sheet a), 980 MPa (cold-rolled steel sheet b), 1180 MPa (cold-rolled steel sheet c), 1470 MPa (cold-rolled steel sheet d), and 2500 MPa (cold-rolled steel sheet e), respectively.

[0224] The plated sheets were cut into 100 mm x 200 mm pieces and then plated using our intermittent hot-dip testing equipment. Multiple plated steel sheets with the coating compositions shown in Table 1 were produced for each level. The sheet temperature was measured using a thermocouple spot-welded to the center of the plated sheets. Prior to immersion in the plating bath, the surface of the plated sheets was subjected to a heat reduction treatment at 800°C in an N2-5% H2 atmosphere in a furnace with an oxygen concentration of less than 20 ppm. Following the heat reduction treatment, the sheets were air-cooled with N2 gas. Once the sheet temperature reached the bath temperature + 20°C, the sheets were immersed in the plating bath at the bath temperature shown in Table 1 for approximately 3 seconds.

[0225] After immersion in the coating bath, the steel sheet was pulled out at a speed of 20-200 mm / s. During removal, N2 wiping gas was used to control the coating deposition. After removal from the coating bath, the steel sheet was cooled from the coating bath temperature to room temperature under the conditions shown in Table 1.

[0226] A sample having a size of 200 mm×80 mm was collected from each of the obtained plated steel sheets and rolled using a skin pass rolling mill to obtain the total elongation shown in Table 1 below, thereby imparting strain to the plated layer.

[0227] The surface of each plated steel sheet after strain was observed using SEM according to the method described above, and the average area ratio of the α-precipitated η phase and the total length of cracks existing in an arbitrary 130 μm×100 μm region were calculated.

[0228] It should be noted that the composition of the coating in each plated steel sheet was determined as follows: a sample cut into 30 mm × 30 mm was immersed in a 10% HCl aqueous solution to which an inhibitor was added. After the coating was pickled and peeled off, the elements dissolved in the aqueous solution were subjected to ICP analysis to thereby determine the composition of the coating in each plated steel sheet.

[0229] The obtained plated steel sheets were evaluated for hydrogen desorption and coating film expansion. The evaluation methods were as follows.

[0230] <Hydrogen Desorption Properties>

[0231] A sample of 50 mm × 30 mm in size was collected from each plated steel plate after strain was applied. The obtained sample was intentionally filled with hydrogen while the plating layer was present. The amount of hydrogen in the sample just after hydrogenation was determined as follows: the sample was heated from room temperature to 250°C at a heating rate of 100°C / h in an N2 atmosphere, and the amount of hydrogen released with the temperature increase was analyzed using a gas chromatograph (manufactured by J-SCIENCE LAB CO., Ltd., CHROMATOGRAPH G2800) to determine the amount of hydrogen in the sample just after hydrogenation. The measured sample was placed in a constant temperature and humidity chamber at 25°C and RH30% for 24 hours, and the amount of diffusible hydrogen was determined by the same temperature rise desorption method.

[0232] [Hydrogen charging conditions]

[0233] Electrolyte: 3.0% NH4SCN + 33.0% NaCl aqueous solution

[0234] Current density: 1.0 mA / cm 2

[0235] Inflation time: 18 hours

[0236] Liquid temperature: rt (about 25°C)

[0237] [Heat-rise separation method]

[0238] Measuring temperature: room temperature ~ 250℃

[0239] Heating rate: 100℃ / h

[0240] Measurement interval: 5 minutes

[0241] The hydrogen desorption property was evaluated based on the ratio (unit: %) of the amount of diffusible hydrogen in the sample after standing for 24 hours divided by the amount of hydrogen in the sample immediately after hydrogen charging. The evaluation criteria were as follows: a score of "A" or higher was considered acceptable.

[0242] [Evaluation Criteria]

[0243] Rating AAA: less than 5%

[0244] AA: 5% or more and 20% or less

[0245] A: More than 20% and less than 50%

[0246] B: More than 50%

[0247] <Corrosion resistance after painting>

[0248] Samples of 50 mm × 100 mm in size were collected from each plated steel plate and evaluated for corrosion resistance after painting. In more detail, the obtained samples were subjected to Zn phosphate treatment (SD5350 system: standard made by Nippon Paint Industrial Coding Co., Ltd.). Thereafter, electroplating was performed in a manner such that the thickness became 20 μm (PN110 Power Nix Gray-: standard made by Nippon Paint Industrial Coding Co., Ltd.), and sintering was performed at a sintering temperature of 150°C for 20 minutes. After sintering, a cut was introduced into the center of the sample to reach the ferrite. Then, a combined cycle corrosion test according to JASO (M609-91) was performed for 180 cycles to measure the coating expansion width. The obtained coating expansion width was evaluated based on the following evaluation criteria. The evaluation criteria are as follows, and a score of "A" or above is qualified. It should be noted that if the score of the coating expansion width is A or above, it can be said that the plated steel plate in question has excellent corrosion resistance after painting.

[0249] [Evaluation Criteria]

[0250] Rating AAA: Coating expansion width less than 2mm

[0251] AA: Coating expansion width exceeds 2mm and is less than 3mm

[0252] A: The coating expansion width is more than 3mm and less than 4mm

[0253] B: Coating expansion width exceeds 4mm [Table 1]

[0254]

[0255] As can be seen from Table 1, the plated steel sheets corresponding to the examples of the present invention exhibited excellent hydrogen desorption properties, whereas the plated steel sheets corresponding to the comparative examples of the present invention exhibited poor hydrogen desorption properties.

[0256] While preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to these embodiments. It is obvious that anyone with ordinary knowledge in the technical field to which the present invention pertains would be able to conceive of various variations and modifications within the scope of the technical concept set forth in the claims, and such variations and modifications are naturally understood to fall within the technical scope of the present invention.

[0257] The embodiments disclosed herein are illustrative and non-restrictive in all respects. The above-mentioned embodiments may be omitted, replaced, or changed in various ways without departing from the appended claims, the configurations belonging to the technical scope of the present invention described later, and the gist thereof. For example, the constituent elements of the above-mentioned embodiments may be arbitrarily combined within the scope that does not impair their effects. In addition, according to this arbitrary combination, it is of course possible to obtain the effects and effects of the various constituent elements involved in the combination, and according to the description of this specification, it is possible to obtain other effects and other effects that are clear to those skilled in the art.

[0258] In addition, the effects described in this specification are merely illustrative or exemplary and are not limiting. That is, the technology involved in the present invention can also produce other effects that are obvious to those skilled in the art based on the description of this specification in addition to or instead of the above effects.

[0259] It should be noted that the following configurations also fall within the technical scope of the present invention. (1)

[0261] A plated steel plate having a plated layer on its surface.

[0262] The aforementioned coating has the following chemical composition:

[0263] Contains by mass%

[0264] Al: 0.50~5.00%

[0265] Mg: 0.50~3.00%

[0266] Fe: 0.01~15.00%,

[0267] further optionally containing one or more elements selected from the group consisting of the following element group A, element group B, element group C, element group D, element group E, element group F, and element group G,

[0268] The balance is Zn and impurities,

[0269] In the surface structure of the plated layer when viewed from above, the average area ratio of the α-precipitated η phase in the metallographic structure obtained by precipitation of the α phase in the η matrix phase is 5 to 95%.

[0270] When a 130 μm×100 μm region on the surface of the plating layer was observed with an electron microscope, the total length of cracks present in the region was 50 μm or more.

[0271] [Element Group A]: One or two elements selected from the group consisting of Si: more than 0% and 2.00% or less and Ca: more than 0% and 2.00% or less

[0272] [Element Group B]: One or more elements selected from the group consisting of Sb: more than 0% and 0.5000% or less, Pb: more than 0% and 0.5000% or less, and Sr: more than 0% and 0.5000% or less

[0273] [Element Group C]: One or more elements selected from the group consisting of Cu: more than 0% and 1.0000%, Ti: more than 0% and 1.0000%, Cr: more than 0% and 1.0000%, Nb: more than 0% and 1.0000%, Ni: more than 0% and 1.0000%, Mn: more than 0% and 1.0000%, Mo: more than 0% and 1.0000%, Co: more than 0% and 1.0000%, and V: more than 0% and 1.0000%.

[0274] [Element Group D]: One or more elements selected from the group consisting of Sn: more than 0% and 1.0000% or less, In: more than 0% and 1.0000% or less, and Bi: more than 0% and 1.0000% or less

[0275] [Element Group E]: One or more elements selected from the group consisting of Zr: more than 0% and 1.0000% or less, Ag: more than 0% and 1.0000% or less, and Li: more than 0% and 1.0000% or less

[0276] [Element Group F]: one or more elements selected from the group consisting of La: more than 0% and 0.5000% or less, Ce: more than 0% and 0.5000% or less, and Y: more than 0% and 0.5000% or less

[0277] [Element Group G]: B: more than 0% and 0.5000% or less (2)

[0279] The plated steel sheet according to (1) has a chemical composition containing the element group A. (3)

[0281] The plated steel sheet according to (1) has a chemical composition containing the aforementioned element group B. (4)

[0283] The plated steel sheet according to (1) has a chemical composition containing the aforementioned element group C. (5)

[0285] The plated steel sheet according to (1) has a chemical composition containing the element group D. (6)

[0287] The plated steel sheet according to (1) has a chemical composition containing the element group E. (7)

[0289] The plated steel sheet according to (1) has a chemical composition containing the element group F. (8)

[0291] The plated steel sheet according to (1) has a chemical composition containing the element group G. (9)

[0293] The plated steel sheet according to any one of (1) to (8), wherein the plated layer contains 1.00 to 5.00 mass% of Al and 1.00 to 3.00 mass% of Mg. (10)

[0295] The plated steel sheet according to any one of (1) to (9), wherein the tensile strength of the steel sheet is 980 MPa or more. (11)

[0297] The plated steel sheet according to any one of (1) to (10), wherein the tensile strength of the steel sheet is 1180 MPa or more. (12)

[0299] The plated steel sheet according to any one of (1) to (11), wherein the average area ratio of the α-precipitated η phase is 5 to 70%. (13)

[0301] The plated steel sheet according to any one of (1) to (12), wherein the average area ratio of the α-precipitated η phase is 5 to 40%.

[0302] Description of Reference Numerals

[0303] 1 Coated steel sheet

[0304] 11 Steel Plate

[0305] 13 Plating

[0306] 101α precipitation η phase

[0307] 103 Hard tissue

[0308] 105 Crack

[0309] 111 α phase

[0310] 113 η parent phase

Claims

1. A plated steel sheet having a plated layer on its surface, The coating has the following chemical composition: Contains by mass% Al：0.50～5.00％ Mg: 0.50~3.00% Fe: 0.01~15.00%, further optionally containing one or more elements selected from the group consisting of the following element group A, element group B, element group C, element group D, element group E, element group F, and element group G, The balance is Zn and impurities, In the surface structure of the plated layer when viewed from above, the average area ratio of the α-precipitated η phase in the metallographic structure obtained by precipitation of the α phase in the η matrix phase is 5 to 95%. When a 130 μm×100 μm region on the surface of the plating layer is observed with an electron microscope, the total length of cracks present in the region is 50 μm or more. [Element Group A]: one or two elements selected from the group consisting of Si: more than 0% and 2.00% or less and Ca: more than 0% and 2.00% or less; [Element Group B]: one or more elements selected from the group consisting of Sb: more than 0% and 0.5000% or less, Pb: more than 0% and 0.5000% or less, and Sr: more than 0% and 0.5000% or less; [Element Group C]: one or more elements selected from the group consisting of Cu: more than 0% and 1.0000%, Ti: more than 0% and 1.0000%, Cr: more than 0% and 1.0000%, Nb: more than 0% and 1.0000%, Ni: more than 0% and 1.0000%, Mn: more than 0% and 1.0000%, Mo: more than 0% and 1.0000%, Co: more than 0% and 1.0000%, and V: more than 0% and 1.0000%; [Element Group D]: one or more elements selected from the group consisting of Sn: more than 0% and 1.0000% or less, In: more than 0% and 1.0000% or less, and Bi: more than 0% and 1.0000% or less; [Element Group E]: one or more elements selected from the group consisting of Zr: more than 0% and 1.0000% or less, Ag: more than 0% and 1.0000% or less, and Li: more than 0% and 1.0000% or less; [Element Group F]: one or more elements selected from the group consisting of La: more than 0% and 0.5000% or less, Ce: more than 0% and 0.5000% or less, and Y: more than 0% and 0.5000% or less; [Element Group G]: B: exceeds 0% and is 0.5000% or less. 2 . The plated steel sheet according to claim 1 , having a chemical composition containing the element group A. The plated steel sheet according to claim 1 , having a chemical composition containing the element group B. The plated steel sheet according to claim 1 , having a chemical composition containing the element group C. The plated steel sheet according to claim 1 , having a chemical composition containing the element group D. The plated steel sheet according to claim 1 , having a chemical composition containing the element group E. 7 . The plated steel sheet according to claim 1 , having a chemical composition containing the element group F. 8 . The plated steel sheet according to claim 1 , having a chemical composition containing the element group G.

9. The plated steel sheet according to any one of claims 1 to 8, wherein The plating layer contains 1.00 to 5.00 mass % of Al and 1.00 to 3.00 mass % of Mg.

10. The plated steel sheet according to claim 1, wherein The tensile strength of the steel plate is 980 MPa or more.

11. The plated steel sheet according to claim 1, wherein The tensile strength of the steel plate is greater than 1180 MPa.

12. The plated steel sheet according to claim 1, wherein The average area ratio of the α-precipitated η phase is 5 to 70%.

13. The plated steel sheet according to claim 1, wherein The average area ratio of the α-precipitated η phase is 5 to 40%.

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