Plated steel sheet and vehicle member

Abstract

The plated steel sheet is provided with a plating layer disposed on at least a part of the surface of the steel sheet, the plating layer containing 10.00-30.00% of Al, 1.00-15.00% of Mg, 0.01-15.00% of Fe, and the remainder being Zn and impurities, the surface of the plating layer being set as a rugged surface, and in the cross section of the plating layer, the thickness of the plating layer is less than or equal to 10 [mu] m, and the thickness of the plating layer is less than or equal to 10 [mu] m. The relationship between the length (Lo) of the plating layer in the longitudinal direction in the observation region of the cross section and the total length (Lr) of the contour line of the surface of the plating layer in the observation region satisfies formula (1), and the plating layer includes one or both of a plurality of block-shaped binary eutectic structures or a plurality of block-shaped ternary eutectic structures. At least a part of the plurality of block-shaped binary eutectic structures or the plurality of block-shaped ternary eutectic structures continuously exists from the surface of the plating layer to a position at 1 / 2 of the average thickness of the plating layer. (1) (Lr-Lo) / Lo * 100 > = 2.0 (%).

Description

Technical Field

[0001] The present invention relates to a plated steel sheet and an automobile component.

[0002] This application claims priority based on Japanese Patent Application No. 2023-087179 filed in Japan on May 26, 2023, the contents of which are incorporated herein by reference. Background Art

[0003] Zn-Al-Mg hot-dip coated steel sheets, which have a hot-dip Zn coating layer containing Al and Mg, have excellent corrosion resistance. Therefore, they are widely used, for example, as structural components requiring corrosion resistance, such as building materials. Furthermore, due to the high corrosion resistance of Zn-Al-Mg hot-dip coating, research is underway to apply Zn-Al-Mg hot-dip coating to high-strength steel sheets, such as high-strength steel, for automotive components.

[0004] Patent document 1 describes a plated steel material comprising a steel material and a plating layer comprising a Zn-Al-Mg alloy layer disposed on a surface of the steel material, wherein the Zn-Al-Mg alloy layer comprises a Zn phase and contains a Mg-Sn intermetallic compound phase in the Zn phase, and the plating layer has the following chemical composition: in mass %, comprising Zn: greater than 65.0%, Al: greater than 5.0% and less than 25.0%, Mg: greater than 3.0% and less than 12.5%, Sn: 0.1% to 20.0%, and impurities, and satisfies the following Formulas 1 to 5.

[0005] Formula 1: Bi+In <Sn

[0006] Formula 2: Y+La+Ce≤Ca

[0007] Formula 3: Si <Sn

[0008] Formula 4: O≤Cr+Ti+Ni+Co+V+Nb+Cu+Mn<0.25 Formula 5: O≤Sr+Sb+Pb+B<0.5

[0009] Patent document 2 describes a plated steel material comprising a steel material and a plating layer disposed on the surface of the steel material and comprising a Zn-Al-Mg alloy layer, wherein, in a cross section of the Zn-Al-Mg alloy layer, the area fraction of the MgZn2 phase is 45 to 75%, the combined area fraction of the MgZn2 phase and the Al phase is 70% or more, and the area fraction of the Zn-Al-MgZn2 ternary eutectic structure is 0 to 5%, and the plating layer has the following chemical composition: in terms of mass %, Zn: more than 44.90% and less than 79.90%, Al: more than 15% and less than 35%, Mg: more than 5% and less than 20%, and Ca: 0.1% or more and less than 3.0%. and impurities, when element group A is set to Y, La and Ce, element group B is set to Cr, Ti, Ni, Co, V, Nb, Cu and Mn, element group C is set to Sr, Sb and Pb, and element group D is set to Sn, Bi and In, the total content of elements selected from element group A is 0% to 0.5%, the total content of Ca and elements selected from the above-mentioned element group A is 0.1% or more and less than 3.0%, the total content of elements selected from element group B is 0% to 0.25%, the total content of elements selected from element group C is 0% to 0.5%, and the total content of elements selected from element group D is 0% to 20.00%.

[0010] Plated steel sheets for automotive applications require not only corrosion resistance of the cut end surface, i.e., end surface corrosion resistance, but also excellent paint adhesion when applied to the plated surface. However, technologies for improving the paint adhesion of a plated layer containing a Zn-Al-Mg alloy layer have not been studied.

[0011] Prior art literature

[0012] Patent Literature

[0013] Patent Document 1: International Publication No. 2018 / 139619

[0014] Patent Document 2: International Publication No. 2018 / 139620 Summary of the Invention

[0015] Problems to be solved by the invention

[0016] The present disclosure has been made in view of the above circumstances, and an object of the present invention is to provide a plated steel sheet and an automobile component having excellent paint adhesion and end surface corrosion resistance.

[0017] Means for solving problems

[0018] In order to solve the above-mentioned problems, the present disclosure adopts the following configuration.

[0019] [1] A plated steel sheet comprising a steel sheet and a plating layer disposed on at least a portion of a surface of the steel sheet.

[0020] The average chemical composition of the coating comprises, in mass %,:

[0021] Al: 10.00~30.00%,

[0022] Mg: 1.00~15.00%,

[0023] Sn: 0.00~1.00%,

[0024] Si: 0.00-2.00%,

[0025] Ca: 0.00~2.00%,

[0026] Ni: 0.00~1.00%,

[0027] Fe: 0.01~15.00%,

[0028] Sb: 0.00~0.50%,

[0029] Pb: 0.00~0.50%,

[0030] Cu: 0.00~1.00%,

[0031] Ti: 0.00~1.00%,

[0032] Cr: 0.00~1.00%,

[0033] Nb: 0.00~1.00%,

[0034] Zr: 0.00~1.00%,

[0035] Mn: 0.00~1.00%,

[0036] Mo: 0.00~1.00%,

[0037] Ag: 0.00~1.00%,

[0038] Li: 0.00~1.00%,

[0039] Bi: 0.00~1.00%,

[0040] V: 0.00~1.00%,

[0041] Co: 0.00~1.00%,

[0042] In: 0.00~1.00%,

[0043] W: 0.00~1.00%,

[0044] P: 0.00~1.00%,

[0045] La: 0.00~0.50%,

[0046] Ce: 0.00~0.50%,

[0047] B: 0.00~0.50%,

[0048] Y: 0.00~0.50%,

[0049] Sr: 0.00~0.50%,

[0050] Total of Sb, Pb, Cu, Ti, Cr, Nb, Zr, Mn, Mo, Ag, Li, Bi, V, Co, P, In, W, La, Ce, B, Y, Sr: 0.00~5.00%,

[0051] The rest: Zn and impurities,

[0052] The surface of the coating is set to be a concave-convex surface,

[0053] In the cross section of the plating layer, the relationship between the length Lo of the plating layer in the longitudinal direction within the observation area of ​​the cross section and the total length Lr of the contour line of the surface of the plating layer within the observation area satisfies the following formula (1):

[0054] The coating layer contains one or both of a plurality of bulk binary eutectic structures or a plurality of bulk ternary eutectic structures,

[0055] At least a portion of the plurality of blocks of the binary eutectic structures or the plurality of blocks of the ternary eutectic structures exists continuously from the surface of the plating layer to a position of 1 / 2 of the average thickness of the plating layer.

[0056] (Lr-Lo) / Lo×100≥2.0(%) (1)

[0057] [2] The plated steel sheet according to [1], wherein the plated layer includes an Fe-Al-based interface alloy layer in contact with the steel sheet,

[0058] At least a portion of the plurality of blocks of the binary eutectic structures or the plurality of blocks of the ternary eutectic structures exist continuously from the surface of the plating layer to the Fe—Al-based interface alloy layer.

[0059] [3] The plated steel sheet according to [1], wherein the number of locations where at least a portion of the plurality of blocks of the binary eutectic structure or the plurality of blocks of the ternary eutectic structure continuously exists from the surface of the coating to a position of 1 / 2 of the average thickness of the coating is 1 to 15 in each rectangular area on the surface of the coating with a long side of 500 μm and a short side of 150 μm.

[0060] [4] The plated steel sheet according to [1], which satisfies the following formula (2) instead of the formula (1):

[0061] The number of locations where at least a portion of the multiple blocks of the binary eutectic structure or the multiple blocks of the ternary eutectic structure continuously exist from the surface of the coating to a position of 1 / 2 of the average thickness of the coating is 3 to 15 within each rectangular area on the surface of the coating with a long side of 500 μm and a short side of 150 μm.

[0062] (Lr-Lo) / Lo×100≥6.0(%) (2)

[0063] [5] The plated steel sheet according to [1], which satisfies the following formula (3) instead of the formula (1):

[0064] The number of locations where at least a portion of the multiple blocks of the binary eutectic structure or the multiple blocks of the ternary eutectic structure continuously exist from the surface of the coating to a position of 1 / 2 of the average thickness of the coating is 5 to 15 within each rectangular area on the surface of the coating with a long side of 500 μm and a short side of 150 μm.

[0065] (Lr-Lo) / Lo×100≥8.0(%) (3)

[0066] [6] A coated steel sheet according to any one of [1], [3], [4], and [5], wherein at least a portion of the plurality of blocks of the binary eutectic structure or the plurality of blocks of the ternary eutectic structure continuously exists from the surface of the coating to a position of 1 / 2 of the average thickness of the coating, and is located in a concave portion of the concave-convex surface of the coating.

[0067] [7] The plated steel sheet according to [2], wherein at least a portion of the plurality of blocks of the binary eutectic structure or the plurality of blocks of the ternary eutectic structure continuously exist from the surface of the coating to the location of the Fe-Al based interface alloy layer and are located in the concave portion of the concave-convex surface of the coating.

[0068] [8] The plated steel sheet according to [1], wherein the average chemical composition of the plating layer comprises Al: 10.00 to 25.00% and Mg: 4.50 to 15.00%.

[0069] [9] The plated steel sheet according to [1], wherein the average chemical composition of the plating layer comprises Al: 15.00 to 22.00% and Mg: 5.00 to 15.00%.

[0070]

[10] The plated steel sheet according to [1], [8] or [9], wherein the average chemical composition of the plated layer contains 0.05% to 0.50% Sn,

[0071] The Mg2Sn phase detected by X-ray diffraction measurement exists in the plating layer.

[0072]

[11] The plated steel sheet according to [1], [8] or [9], wherein the average chemical composition of the coating layer contains one or both of La and Ce, and the total amount of La and Ce is 0.05 to 0.50%.

[0073]

[12] The plated steel sheet according to

[10] , wherein the average chemical composition of the coating layer contains one or both of La and Ce, and the total amount of La and Ce is 0.05 to 0.50%.

[0074]

[13] An automotive component comprising a steel material, a plating layer disposed on at least a portion of a surface of the steel material, and a paint film disposed on a surface of the plating layer.

[0075] The average chemical composition of the coating comprises, in mass %,:

[0076] Al: 10.00~30.00%,

[0077] Mg: 1.00~15.00%,

[0078] Sn: 0.00~1.00%,

[0079] Si: 0.00-2.00%,

[0080] Ca: 0.00~2.00%,

[0081] Ni: 0.00~1.00%,

[0082] Fe: 0.01~15.00%,

[0083] Sb: 0.00~0.50%,

[0084] Pb: 0.00~0.50%,

[0085] Cu: 0.00~1.00%,

[0086] Ti: 0.00~1.00%,

[0087] Cr: 0.00~1.00%,

[0088] Nb: 0.00~1.00%,

[0089] Zr: 0.00~1.00%,

[0090] Mn: 0.00~1.00%,

[0091] Mo: 0.00~1.00%,

[0092] Ag: 0.00~1.00%,

[0093] Li: 0.00~1.00%,

[0094] Bi: 0.00~1.00%,

[0095] V: 0.00~1.00%,

[0096] Co: 0.00~1.00%,

[0097] In: 0.00~1.00%,

[0098] W: 0.00~1.00%,

[0099] P: 0.00~1.00%,

[0100] La: 0.00~0.50%,

[0101] Ce: 0.00~0.50%,

[0102] B: 0.00~0.50%,

[0103] Y: 0.00~0.50%,

[0104] Sr: 0.00~0.50%,

[0105] Total of Sb, Pb, Cu, Ti, Cr, Nb, Zr, Mn, Mo, Ag, Li, Bi, V, Co, P, In, W, La, Ce, B, Y, Sr: 0.00~5.00%,

[0106] The rest: Zn and impurities,

[0107] The surface of the coating is set to be a concave-convex surface,

[0108] In the cross section of the plating layer, the relationship between the length Lo of the plating layer in the longitudinal direction within the observation area of ​​the cross section and the total length Lr of the contour line of the surface of the plating layer within the observation area satisfies the following formula (4):

[0109] The coating layer contains one or both of a plurality of bulk binary eutectic structures or a plurality of bulk ternary eutectic structures,

[0110] At least a portion of the plurality of blocks of the binary eutectic structures or the plurality of blocks of the ternary eutectic structures exists continuously from the surface of the plating layer to a position of 1 / 2 of the average thickness of the plating layer.

[0111] (Lr-Lo) / Lo×100≥2.0(%) (4)

[0112] Effects of the Invention

[0113] According to the present disclosure, it is possible to provide a plated steel sheet and an automobile component that are excellent in both end surface corrosion resistance and paint adhesion. BRIEF DESCRIPTION OF THE DRAWINGS

[0114] Figure 1 1 is a schematic cross-sectional view of a plated steel sheet according to one embodiment of the present disclosure.

[0115] Figure 2 This is a schematic diagram showing an example of the observation field when observing a cross section of a plating layer using a scanning electron microscope.

[0116] Figure 3 This is a schematic diagram showing an example of the observation field when observing a cross section of a plating layer using a scanning electron microscope.

[0117] Figure 4 This is a schematic diagram showing an example of an observation field when observing a cross section of a plating layer of a conventional plated steel material using a scanning electron microscope.

[0118] Figure 5 This is a flowchart of an example of a method for producing a plated steel sheet according to one embodiment of the present disclosure. DETAILED DESCRIPTION

[0119] The inventors of the present invention have conducted research on methods for improving the adhesion of coatings to coatings. The metal structure of Zn-Al-Mg hot-dip coatings containing Al, Mg, and Zn includes various phases or structures. For example, it is known that Al phases and MgZn2 phases crystallize in the early stages of solidification, while binary or ternary eutectic structures crystallize in the later stages of solidification. The inventors of the present invention have conducted research and found that binary or ternary eutectic structures exhibit superior adhesion to coating films compared to Al phases and MgZn2 phases.

[0120] In addition, in conventional Zn-Al-Mg hot-dip coatings, binary or ternary eutectic structures may be exposed on the surface of the coating. Moreover, these binary or ternary eutectic structures are mostly distributed in the surface layer of the coating, specifically in the range from the surface of the coating to a depth of 1 / 4 or even 1 / 3 of the average thickness of the coating. In the past, it was believed that by exposing these eutectic structures on the surface of the coating, the coating adhesion was improved. However, when manufacturing automotive components from plated steel sheets, it is necessary to obtain the desired shape of the automotive components by performing various processing on the plated steel sheets, but the processed coating may produce fine cracks on its surface due to the strain during processing. It has been found that if such cracks occur around the eutectic structure exposed on the surface of the coating, the eutectic structure surrounded by the cracks may fall off from the coating, causing so-called powdering or surface peeling, which will not contribute to the improvement of coating adhesion.

[0121] In particular, Zn-Al-Mg hot-dip coatings are harder than conventional Zn-based coatings and therefore may generate relatively more cracks, increasing the frequency of eutectic structure falling off from the coating and causing concern about reduced paint adhesion.

[0122] Furthermore, it is expected that coating adhesion can be improved when the surface of the plating layer is a concave-convex surface compared to a flat surface.

[0123] Therefore, the inventors of the present invention conducted research and found that, after a hot-dip coating bath is applied to a steel sheet by hot-dip coating, the atmosphere from the time of removal from the coating bath to the start of cooling is controlled, the cooling rate during cooling is adjusted, and an appropriate cooling gas is selected. This allows a binary or ternary eutectic structure to continue to a depth deeper than the surface layer of the coating layer, specifically, from the surface of the coating layer to a depth of at least 1 / 2 the average thickness of the coating layer. Even if cracks occur, the eutectic structure does not fall off the coating layer, thereby preventing a decrease in paint adhesion. Furthermore, the inventors found that by controlling the atmosphere, adjusting the cooling rate, and selecting an appropriate cooling gas, the coating layer surface becomes uneven, further improving paint adhesion.

[0124] Hereinafter, the plated steel sheet and the automobile exterior material according to the embodiments of the present disclosure will be described.

[0125] The plated steel sheet of the present embodiment includes a steel sheet and a plating layer disposed on at least a portion of a surface of the steel sheet, wherein the average chemical composition of the plating layer comprises, in mass %, Al: 10.00-30.00%, Mg: 1.00-15.00%, Sn: 0.00-1.00%, Si: 0.00-2.00%, Ca: 0.00-2.00%, Ni: 0.00-1.00%, Fe: 0.01-15.00%, Sb: 0.00-0.50%, and Pb: 0.00-0. 50%, Cu: 0.00~1.00%, Ti: 0.00~1.00%, Cr: 0.00~1.00%, Nb: 0.00~1.00%, Zr: 0.00~1.00%, Mn: 0.00~1.00%, Mo: 0.00~1.00%, Ag: 0.00~1.00%, Li: 0.00~1.00%, Bi: 0.00~1.00%, V: 0.00~1.00%, Co: 0.00~1.00%, In: 0.0 0~1.00%, W: 0.00~1.00%, P: 0.00~1.00%, La: 0.00~0.50%, Ce: 0.00~0.50%, B: 0.00~0.50%, Y: 0.00~0.50%, Sr: 0.00~0.50%, total of Sb, Pb, Cu, Ti, Cr, Nb, Zr, Mn, Mo, Ag, Li, Bi, V, Co, P, In, W, La, Ce, B, Y, Sr: 0.00~5.00%, The remainder: Zn and impurities; the surface of the coating is set to a concave-convex surface; in a cross section of the coating, the relationship between the length Lo of the coating in the longitudinal direction within the observation area of ​​the cross section and the total length Lr of the contour line of the surface of the coating within the observation area satisfies the following formula (1); the coating contains one or both of a plurality of block-shaped binary eutectic structures or a plurality of block-shaped ternary eutectic structures, and at least a portion of the plurality of block-shaped binary eutectic structures or the plurality of block-shaped ternary eutectic structures exists continuously from the surface of the coating to a position of 1 / 2 of the average thickness of the coating.

[0126] (Lr-Lo) / Lo×100≥2.0(%) (1)

[0127] In addition, in the plated steel sheet of this embodiment, it is preferred that the coating layer includes an Fe-Al interface alloy layer in contact with the steel sheet, and at least a portion of a plurality of block-shaped binary eutectic structures or a plurality of block-shaped ternary eutectic structures exist continuously from the surface of the coating layer to the Fe-Al interface alloy layer.

[0128] In addition, in the plated steel sheet of this embodiment, it is preferred that at least a portion of the multiple block-shaped binary eutectic structures or the multiple block-shaped ternary eutectic structures exist continuously from the surface of the coating to a position 1 / 2 of the average thickness of the coating is located in the concave portion of the concave-convex surface of the coating.

[0129] Furthermore, in the plated steel sheet of this embodiment, it is preferred that at least a portion of the plurality of block-shaped binary eutectic structures or the plurality of block-shaped ternary eutectic structures exist continuously from the surface of the coating to the location of the Fe-Al interface alloy layer located in the concave portion of the above-mentioned concave-convex surface of the coating.

[0130] Figure 1 A schematic cross-sectional view of the plated steel sheet 1 is shown. Figure 1 It is a schematic diagram for explaining the positional relationship between the steel plate 11 and the coating 12. Figure 1 In FIG, description of the uneven surface of the surface of the plating layer 12 is omitted.

[0131] like Figure 1 As shown in , the plated steel sheet 1 of this embodiment includes a steel sheet 11. There is no particular limitation on the shape of the steel sheet 11. In addition, the steel sheet 11 may be, for example, a base steel sheet that is formed into steel pipes, civil engineering materials (gate channels, corrugated pipes, drain covers, anti-sand plates, bolts, metal mesh, guardrails, waterproof walls, etc.), home appliance components (housings of outdoor units of air conditioners, etc.), and automobile components (travel components, exterior components, interior components, structural components, etc.). Forming processes include various plastic working methods such as pressing, roll forming, and bending.

[0132] The material of the steel plate 11 is not particularly limited. The steel plate 11 can be, for example, ordinary steel, Al-killed steel, ultra-low carbon steel, high-carbon steel, various high-tensile steels, and some high-alloy steels (steels containing strengthening elements such as Ni and Cr). The steel plate 11 can also be a hot-rolled steel plate, hot-rolled steel strip, cold-rolled steel plate, or cold-rolled steel strip as described in JIS G 3302:2010. The manufacturing method (hot rolling, pickling, cold rolling, etc.) and its specific manufacturing conditions are also not particularly limited.

[0133] Furthermore, the steel sheet 11 constituting the plated steel sheet 1 of the present embodiment may be a high-tensile steel sheet for automobile components.

[0134] The plated steel sheet 1 of this embodiment has a plated layer 12 disposed on at least a portion of the surface of a steel sheet 11. Figure 1 In the embodiment, the plating layer 12 is formed on one side of the steel plate 11, but the plating layer 12 may be formed on both sides of the steel plate 11. The plating layer 12 is preferably a plating film produced by a so-called hot-dip plating process.

[0135] The coating 12 is primarily composed of a Zn-Al-Mg alloy layer, resulting from a chemical composition described below. Furthermore, the coating 12 of the plated steel sheet 1 of this embodiment may include an Fe-Al interface alloy layer primarily composed of Fe and Al between the steel sheet 11 and the Zn-Al-Mg alloy layer. Specifically, the coating 12 may have a single-layer structure consisting of a Zn-Al-Mg alloy layer or a laminated structure consisting of a Zn-Al-Mg alloy layer and a Fe-Al interface alloy layer.

[0136] The chemical composition of the plating layer is described below. The "%" expression of the content of each element in the chemical composition refers to "mass %." The content of an element in the chemical composition may be expressed as element concentration (for example, Zn concentration, Mg concentration, etc.).

[0137] In addition, "paint adhesion" means the property that the paint film is not easily peeled off when a paint film is provided on the surface of the plated layer, or when a chemical conversion treatment film and a paint film are provided on the surface of the plated layer.

[0138] The “plane corrosion resistance” refers to the property that the plating layer (specifically, the Zn—Al—Mg alloy layer) itself is not easily corroded.

[0139] “End surface corrosion resistance” refers to a property of suppressing corrosion of a steel sheet at an exposed portion of the steel sheet (for example, a cut end surface of a plated steel sheet).

[0140] The coating layer of this embodiment contains Zn and other alloying elements. The chemical composition of the coating layer is described in detail below. It should be noted that elements whose lower concentration limit is indicated as 0.00% are optional elements. While they are not essential for resolving the issues of the plated steel sheet of this embodiment, they may be included in the coating layer for the purpose of improving properties, etc.

[0141] <Al:10.00~30.00%>

[0142] Al contributes to the improvement of plane corrosion resistance and workability. Therefore, the Al concentration is set to 10.00% or more. On the other hand, when Al is excessive, the Mg concentration and the Zn concentration are relatively reduced, and the end face corrosion resistance deteriorates. Therefore, the Al concentration is set to 30.00% or less. The Al concentration can also be set to 10.00-25.00% or 15.00-22.00%. The Al concentration can also be set to 11.00% or more, 13.00% or more, or 16.00% or more. The Al concentration can also be set to 28.00% or less, 24.00% or less, or 20.00% or less.

[0143] <Mg:1.00~15.00%>

[0144] Mg is an element necessary to ensure plane corrosion resistance. In addition, it is also necessary to crystallize binary eutectic structure, ternary eutectic structure, Mg2Sn phase, etc. Therefore, the Mg concentration is set to 1.00% or more. On the other hand, if the Mg concentration is excessive, the workability, especially the powdering property, may deteriorate, and the plane corrosion resistance may deteriorate. Therefore, the Mg concentration is set to 15.00% or less. The Mg concentration can also be set to 4.50-15.00% or 5.00-15.00%. The Mg concentration can also be set to 2.00% or more, 3.00% or more, or 4.00% or more. The Mg concentration can also be set to 13.00% or less, 10.00% or less, or 8.00% or less.

[0145] Since the elements described below are all optional added elements except Fe and Zn, the lower limit thereof is set to 0%.

[0146] <Sn:0.00~1.00%>

[0147] The Sn concentration can also be 0%. On the other hand, Sn is an element that forms an intermetallic compound with Mg and improves the flat corrosion resistance of the coating. Therefore, the Sn concentration can be set to 0.05% or more, 0.10% or more, or 0.20% or more. However, if the Sn concentration is excessive, the flat corrosion resistance deteriorates. Therefore, the Sn concentration is set to 1.00% or less. The Sn concentration can also be set to 0.80% or less, 0.60% or less, 0.50% or less, 0.20% or less, or 0.06% or less.

[0148] <Si:0.00%~2.00%>

[0149] The Si concentration can also be 0.00%. On the other hand, Si contributes to the improvement of plane corrosion resistance. In addition, it is an element required for the crystallization of the Mg2Si phase. Therefore, the Si concentration can also be set to more than 0.00%, more than 0.01%, more than 0.05%, or more than 0.10%. On the other hand, if the Si concentration is excessive, the plane corrosion resistance deteriorates. Therefore, the Si concentration is set to 2.00% or less. The Si concentration can also be set to less than 1.80%, less than 1.50%, less than 1.20%, or less than 1.00%.

[0150] <Ca:0.00~2.00%>

[0151] The Ca concentration can also be 0%. On the other hand, Ca is an element that can adjust the optimal Mg dissolution amount for imparting planar corrosion resistance. Therefore, the Ca concentration can also be 0.01% or more, or 0.02% or more. On the other hand, if the Ca concentration is excessive, the planar corrosion resistance and workability deteriorate. Therefore, the Ca concentration is set to 2.00% or less. The Ca concentration can also be set to 1.00% or less, 0.50% or less, 0.10% or less, or 0.05% or less.

[0152] <Ni: 0.00 to 1.00%>

[0153] The Ni concentration can also be 0.00%. On the other hand, Ni contributes to the improvement of end face corrosion resistance. Therefore, the Ni concentration can also be set to 0.001% or more. On the other hand, if the Ni concentration is excessive, the planar corrosion resistance deteriorates. Therefore, the Ni concentration is set to 1.00% or less. The Ni concentration can also be set to 0.50% or less, 0.10% or less, or 0.01% or less.

[0154] <Fe: 0.01 to 15.00%>

[0155] The Fe concentration can also be 0%, but since Fe may sometimes be mixed into the coating from the base steel plate, it can also contain 0.01% or more in the coating. It has been confirmed that if the Fe concentration is 15.00% or less, there is no adverse effect on the performance of the coating. The Fe concentration can also be set, for example, to 0.01% or more, 0.10% or more, or 0.50% or more. The Fe concentration is set to 15.00% or less. The Fe concentration can also be set to 10.00% or less, 5.00% or less, 2.00% or less, or 1.00% or less.

[0156] <Sb, Pb: 0.00 to 0.50% respectively>

[0157] The Sb, Pb concentrations can also be 0.00%. On the other hand, Sb, Pb contribute to the improvement of end face corrosion resistance. Therefore, the concentrations of Sb and Pb can also be set to 0.01% or more, 0.03% or more, or 0.05% or more respectively. On the other hand, if the concentrations of Sb, Pb are excessive, the planar corrosion resistance deteriorates. Therefore, the concentrations of Sb and Pb are set to 0.50% or less respectively. The concentrations of Sb and Pb can also be set to 0.40% or less, 0.20% or less, or 0.10% or less respectively.

[0158] <Cu, Ti, Cr, Nb, Zr, Mn, Mo, Ag and Li: 0.00 to 1.00% respectively>

[0159] The concentrations of Cu, Ti, Cr, Nb, Zr, Mn, Mo, Ag, and Li can also be 0% respectively. On the other hand, they contribute to the improvement of the end face corrosion resistance. Therefore, the concentrations of these elements can also be set to 0.01% or more respectively. On the other hand, if the concentrations of these elements are excessive respectively, the planar corrosion resistance deteriorates. Therefore, the concentrations of these elements are set to 1.00% or less respectively. The concentrations of these elements can also be set to 0.50% or less, 0.10% or less, 0.05% or less, or 0.03% or less respectively.

[0160] <Bi, V, Co, In, W: 0.00 - 1.00% respectively>

[0161] The concentrations of Bi, V, Co, In, and W can also be 0% respectively. On the other hand, these elements contribute to the improvement of the end face corrosion resistance respectively. Therefore, the concentrations of these elements can also be set to 0.001% or more or 0.01% or more respectively. On the other hand, if the concentrations of these elements are excessive, the planar corrosion resistance deteriorates. Therefore, the concentrations of Bi, V, Co, In, and W are set to 1.00% or less respectively. The concentrations of these elements can also be set to 0.50% or less, 0.10% or less, 0.02% or less, or 0.01% or less respectively.

[0162] <P: 0.00 - 1.00%>

[0163] The concentration of P can also be 0%. On the other hand, P contributes to the improvement of the end face corrosion resistance. Therefore, the concentration of P can also be set to 0.00^5% or more or 0.01% or more. On the other hand, if the concentration of P is excessive, the planar corrosion resistance deteriorates. Therefore, the concentration of P is set to 1.00% or less. The concentration of P can also be set to 0.05% or less, 0.03% or less, or 0.01% or less.

[0164] <B, Y, and Sr: 0.00 - 0.50% respectively>

[0165] The concentrations of B, Y, and Sr can also be 0.00% respectively. On the other hand, B, Y, and Sr contribute to the improvement of the end face corrosion resistance. Therefore, the concentrations of these elements can also be set to 0.001% or more or 0.01% or more respectively. On the other hand, if the concentrations of B, Y, and Sr are excessive, the planar corrosion resistance deteriorates. Therefore, the concentrations of these elements are set to 0.50% or less respectively. The concentrations of these elements can also be set to 0.10% or less, 0.02% or less, or 0.01% or less respectively.

[0166] <La, Ce: 0.00 - 0. / 50% respectively>

[0167] The concentrations of La and Ce can also be 0%. On the other hand, La and Ce contribute to the improvement of the end face corrosion resistance. Therefore, the concentrations of these elements can also be set to be 0.01% or more respectively. On the other hand, if the concentrations of La and Ce are excessive, the planar corrosion resistance deteriorates. Therefore, the concentrations of these elements are set to be 0.50% or less respectively. The concentrations of these elements can also be set to be 0.10% or less, 0.05% or less, or 0.02% or less respectively. In addition, the total amount of La and Ce is preferably set to 0.05 - 0.50%.

[0168] <Total of Sb, Pb, Cu, Ti, Cr, Nb, Zr, Mn, Mo, Ag, Li, Bi, V, Co, In, W, P, La, Ce, B, Y, Sr: 0.00 - 5.00%>

[0169] The total of these elements is set to 0 - 5%. If the total exceeds 5%, it is possible that the planar corrosion resistance or the end face corrosion resistance decreases.

[0170] <The remainder: Zn and impurities>

[0171] The remainder of the composition of the coating layer of the present embodiment is Zn and impurities. Zn is an element that gives the coating layer planar corrosion resistance and end face corrosion resistance. Impurities refer to the components contained in the raw materials or the components mixed in during the manufacturing process, and are components that are not intentionally contained. For example, in the coating layer, it is possible that in addition to Fe, other components are also slightly mixed as impurities through the mutual atomic diffusion between the base steel plate and the plating bath.

[0172] In addition, in the coating layer of the present embodiment, it is preferable that the total of Al, Mg and Zn is 74.00% or more, and it can also be 80.00% or more, 90.00% or more, 95.00% or more, or 98.00% or more.

[0173] The chemical composition of the coating layer is measured by the following method. First, the coating layer is stripped and dissolved using an acid containing an inhibitor that suppresses the corrosion of the steel plate to obtain an acid solution. Then, the obtained acid solution is subjected to ICP analysis. Thereby, the chemical composition of the coating layer can be obtained. The type of acid only needs to be an acid that can dissolve the coating layer, and there is no particular limitation. It should be noted that the chemical composition measured by the above means is the average chemical composition of the entire coating layer.

[0174] <The surface of the coating layer>

[0175] The surface of the coating of this embodiment is set to be a concave-convex surface. The roughness of the concave-convex surface is represented by the relationship between Lo and Lr as shown in the following formula (1). That is, (Lr-Lo) / Lo×100 needs to be 2.0(%) or more. When (Lr-Lo) / Lo×100 is lower than 2.0(%), the roughness of the concave-convex surface is small and the coating adhesion cannot be improved. (Lr-Lo) / Lo×100 more preferably satisfies the following formula (2), and further preferably satisfies the following formula (3). There is no particular upper limit for (Lr-Lo) / Lo×100, but if it is too large, the surface smoothness of the coating is reduced, and the surface flatness of the coating film is also reduced, so it is preferably 40(%) or less, 20(%) or less, or 12(%) or less.

[0176] (Lr-Lo) / Lo×100≥2.0(%) (1)

[0177] (Lr-Lo) / Lo×100≥6.0(%) (2)

[0178] (Lr-Lo) / Lo×100≥8.0(%) (3)

[0179] It should be noted that the length Lo in formulas (1) to (3) is the length of the coating in the longitudinal direction of the coating within the observation area of ​​the cross section, and Lr is the total length of the contour line of the surface of the coating within the observation area. The observation area refers to the observation field when observing the cross section of the coating with a scanning electron microscope. The length of the coating in the longitudinal direction included in the observation field is Lo, and the total length of the contour line of the surface of the coating corresponding to the length Lo in the longitudinal direction of the coating is Lr. When measuring Lo and Lr, it is preferred to set the observation field when observing with a scanning electron microscope in such a way that the length Lo in the longitudinal direction of the coating becomes 500 μm. In addition, it is also possible to combine multiple observation fields to synthesize an observation field in which the length Lo in the longitudinal direction of the coating becomes 500 μm.

[0180] The observation field is positioned at least 5 mm from the end of the plated steel sheet. If the plated steel sheet has a weld, the observation field is positioned at least 1 mm from the weld bead. Furthermore, if the plated steel sheet has a bend, the observation field is positioned at least 2 mm from the bend. This eliminates the effects of cutting, welding, and bending the plated steel sheet on the surface properties of the coating from the measurement results.

[0181] The observation field is preferably located in a flat area. However, the plated steel sheet may not have a flat area. For example, when the plated steel sheet is used as an automotive exterior component, the plated steel sheet may have an overall gently curved shape and no flat areas. In this case, the observation field is preferably located in an area with a curvature radius of 5 mm or greater.

[0182] The number of observation fields was set to 5. First, (Lr-Lo) / Lo×100 was calculated for each of the five observation fields, and then the arithmetic mean of these values ​​was determined. This arithmetic mean was regarded as (Lr-Lo) / Lo×100 of the plated steel sheet.

[0183] exist Figure 2 An example of the observation field when observing with a scanning electron microscope is shown as a schematic diagram in FIG. Figure 2 The relationship between Lo and Lr is shown in Figure 2 In the figure, symbol 11 is the steel plate, symbol 12 is the coating, and symbol 13 is the interface alloy layer. The double-arrow lines of symbols Lo and Lr schematically represent the lengths of Lo and Lr, respectively. Figure 2 , the concavo-convex surface of the plating layer is schematically shown.

[0184] <Plating Structure>

[0185] The coating of this embodiment includes one or both of a plurality of block-shaped binary eutectic structures or a plurality of block-shaped ternary eutectic structures. The binary eutectic structure is a eutectic structure of an η-Zn phase and an Al-Zn phase, and the ternary eutectic structure is a eutectic structure of an Al phase, a Zn phase, and a MgZn2 phase. These eutectic structures can also be a lamellar collection of the phases constituting the eutectic structure. That is, the binary eutectic structure can also have a lamellar structure in which a layered η-Zn phase and a layered Al-Zn phase overlap. The ternary eutectic structure can also have a lamellar structure in which a layered Al phase, a layered Zn phase, and a layered MgZn2 phase overlap.

[0186] In addition to these eutectic structures, the coating also contains massive Al phase, Al-Zn phase, Zn phase, MgZn2 phase, etc. In addition, a eutectoid structure containing a layered Zn phase and a layered Al phase may be formed in the coating. This eutectoid structure has a lamellar structure but does not belong to a binary eutectic structure or a ternary eutectic structure.

[0187] In the coating of the present embodiment, at least a portion of a plurality of block-shaped binary eutectic structures or ternary eutectic structures continuously exists from the surface of the coating to a position of 1 / 2 of the average thickness of the coating. On the surface of the coating, at least a portion of these block-shaped binary eutectic structures or ternary eutectic structures is exposed on the surface of the coating. Compared with other phases such as Al phase and Al-Zn phase, the binary eutectic structure or ternary eutectic structure has excellent adhesion to the coating film. Therefore, by exposing the binary eutectic structure or ternary eutectic structure to the surface of the coating, the adhesion of the coating film of the entire coating is improved.

[0188] In addition, when cracks are generated in the coating during the processing of the plated steel sheet, the generated cracks will mostly develop along the boundary surface between the binary eutectic structure or the ternary eutectic structure and other phases / structures. In this embodiment, at least a portion of the binary eutectic structure or the ternary eutectic structure continues to exist to a position 1 / 2 of the average thickness of the coating. Therefore, the cracks generated by the bending process tend to develop from the surface of the coating toward the steel sheet side, and become difficult to develop in a direction parallel to the surface of the coating. Therefore, even if cracks are generated, the eutectic structure becomes difficult to fall off from the coating, and powdering or surface peeling can be suppressed. Therefore, even if the coating is processed, the coating adhesion of the coating will not be reduced.

[0189] The coating of this embodiment preferably has multiple blocks of binary eutectic structures or ternary eutectic structures that are continuous from the surface of the coating to the Fe-Al interface alloy layer. This can further suppress powdering or surface peeling and further improve the coating adhesion of the coating.

[0190] exist Figure 3 An enlarged schematic diagram of an example of the coating of this embodiment is shown in FIG. The existence state of the binary eutectic structure or the ternary eutectic structure is shown. Figure 3 In the figure, the concave and convex surface of the coating 12 is schematically shown, and the existence state of the binary eutectic structure or the ternary eutectic structure is shown. The oblique line portion in the figure is the binary eutectic structure or the ternary eutectic structure. Figure 3 In the figure, symbol 11 is a steel plate, symbol 12 is a coating, symbol 13 is an interface alloy layer, and symbol 14 is a binary eutectic structure or a ternary eutectic structure.

[0191] like Figure 3 As shown in FIG, it is known that the binary eutectic structure or ternary eutectic structure 14 is continuous from the surface of the coating 12 toward the steel plate 11 side. Moreover, it is known that the binary eutectic structure or ternary eutectic structure 14 is continuous to the Fe-Al interface alloy layer 13 on the steel plate 11 side of the coating 12. Figure 3 , an example is shown in which the binary eutectic structure or ternary eutectic structure 14 is mostly continuous to the Fe-Al interface alloy layer 13 on the steel plate 11 side of the coating 12, but the present embodiment is not limited to this and may also include a binary eutectic structure or ternary eutectic structure 14 that is continuous to the 1 / 2 position of the coating 12.

[0192] For reference, a schematic cross-sectional view of a conventional plating layer is shown in FIG. Figure 4 The surface of the conventional coating 112 is flat, and the binary eutectic structure or ternary eutectic structure 114 is distributed near the interface alloy layer 113 of the coating 112 or near the surface of the coating. No binary eutectic structure or ternary eutectic structure 114 is found to extend to the 1 / 2 position of the coating 112.

[0193] In addition, the surface of the plating layer 12 of this embodiment is as follows Figure 2 、 Figure 3 As shown in the example, the concave and convex surface is continuous, but the binary eutectic structure or ternary eutectic structure 14 exists continuously to a depth of 1 / 2 of the average thickness of the coating layer 12. Figure 3 As shown in , most of the eutectic structure 14 is present in the concave portions of the uneven surface. As will be discussed later, this is because the binary or ternary eutectic structure 14 crystallizes in the latter half of the solidification process of the coating. The concentration of the binary or ternary eutectic structure 14 in the concave portions, combined with the effect of the uneven surface shape, can improve coating adhesion.

[0194] In addition, in the present embodiment, the binary eutectic structure or the ternary eutectic structure that exists continuously from the surface of the plating layer to the Fe—Al-based interface alloy layer may exist mostly in the concave portions of the concavo-convex surface.

[0195] As will be described later in the description of the manufacturing method, the binary eutectic structure or the ternary eutectic structure begins to crystallize after the Al phase and the Al-Zn phase have crystallized. It is believed that the crystallization of these eutectic structures begins in the region on the steel sheet side of the coating, more specifically, with nucleation at the surface of the Fe-Al interface alloy layer. Furthermore, it is believed that the crystallization of the eutectic structure proceeds toward the surface of the coating. Therefore, it is believed that the binary eutectic structure or the ternary eutectic structure of this embodiment often exists continuously from the surface of the coating to the Fe-Al interface alloy layer.

[0196] However, when observing the internal structure of the coating at any cross-section, the entire binary eutectic structure or ternary eutectic structure is not always observed as a continuous structure extending from the surface of the coating to the Fe-Al interface alloy layer. This is because the bulk binary eutectic structure or ternary eutectic structure has an indefinite shape, and therefore the appearance of the binary eutectic structure or ternary eutectic structure varies depending on the cross-sectional position.

[0197] The inventors of the present invention conducted research and concluded that if at least a portion of a plurality of block-shaped binary eutectic structures or ternary eutectic structures is observed to exist continuously from the surface of the coating to a position 1 / 2 of the average thickness of the coating, there is a high possibility that the binary eutectic structure or ternary eutectic structure exists mostly in a form of continuous from the surface of the coating to the Fe-Al interface alloy layer, and it is speculated that the coating adhesion is improved.

[0198] In this embodiment, the number of locations where the binary eutectic structure or the ternary eutectic structure continuously exists from the surface of the coating to a position of 1 / 2 of the average thickness of the coating is preferably 1 to 15 locations in a rectangular region with a long side of 500 μm and a short side of 150 μm on the surface of the coating. When the number of locations is less than 1, the coating adhesion becomes insufficient, so it is not preferred. In addition, when the above formula (2) is established, the number of the locations is preferably 3 to 15. Furthermore, when the above formula (3) is established, the number of the locations is preferably 5 to 15.

[0199] The presence of a binary eutectic structure or a ternary eutectic structure is confirmed as follows.

[0200] A rectangular region with a long side of 500 μm and a short side of 150 μm was set on the surface of the plated layer. The position of the region was determined by the same method as the observation field for evaluating the roughness of the uneven surface of the plated layer.

[0201] In this area, the number and position of the binary eutectic structure or ternary eutectic structure exposed on the surface of the coating are confirmed. Next, the surface of the coating containing this area is ground to a depth of 1 / 4 position, 1 / 2 position, 3 / 4 position, and 9 / 10 position of the average thickness of the coating, and further mirror polished to form an observation surface. Then, at the depth of 1 / 4 position, 1 / 2 position, 3 / 4 position, and 9 / 10 position, the number and position of the binary eutectic structure or ternary eutectic structure in the observation surface of each depth are confirmed. Then, the number of binary eutectic structures or ternary eutectic structures appearing at the same position in all of the surface, 1 / 4 position, and 1 / 2 position depths of the coating is counted. As for whether the structure appears at the same position, as long as the eutectic structure is within a projection range of a radius of 15 μm from the center of gravity of the eutectic structure in the coating surface, it can be considered to appear at the same position. The binary eutectic structure or ternary eutectic structure appearing at the same position is determined to be present continuously from the surface of the coating layer to a position half the average thickness of the coating layer. The grinding method is not particularly limited, but examples thereof include precision machining such as lapping, focused ion beam machining (FIB machining), and the like.

[0202] Furthermore, the presence of a binary or ternary eutectic structure at the same location was confirmed at the surface, 1 / 4 depth, 1 / 2 depth, 3 / 4 depth, and 9 / 10 depth of the coating layer. The results confirmed that the binary or ternary eutectic structure at the same location existed continuously from the surface of the coating layer to the Fe-Al interface alloy layer.

[0203] In addition, the average thickness of the plating layer was set as the average thickness of the plating layer in the rectangular region with a long side of 500 μm and a short side of 150 μm.

[0204] Then, based on the position of the interface between the steel plate and the coating, the position corresponding to the height of the average thickness of the coating is estimated as the average surface position of the coating. Based on the estimated surface position, the depth of 1 / 4 position, 1 / 2 position, 3 / 4 position and 9 / 10 position of the average thickness of the coating is determined.

[0205] When the coating contains 0.05-0.5% Sn, it is preferred that the coating contain an Mg2Sn phase. Since the Mg2Sn phase is present in small amounts, its presence is detected and confirmed by X-ray diffraction analysis using the θ-2θ method. The inclusion of the Mg2Sn phase in the coating further improves the corrosion resistance of the coating's end faces. Detection of the Mg2Sn phase can be performed using the θ-2θ method.

[0206] The coating weight per single side of the plating layer is set to, for example, 20 to 200 g / m 2 By setting the adhesion amount per single side to 20g / m 2 The above can further improve the flat corrosion resistance and end surface corrosion resistance of the plated steel sheet. On the other hand, by setting the coating amount per single side to 200g / m 2 The following can further improve the workability of the plated steel sheet.

[0207] The coated steel sheet of this embodiment may also have a film formed on the coating. The film may be formed into one layer or two or more layers. Examples of the type of film directly above the coating include chromate films, phosphate films, and chromate-free films. These films can be formed using known methods such as chromate treatment, phosphate treatment, and chromate-free treatment, as described below.

[0208] The plated steel sheet according to the present embodiment described above is excellent in coating adhesion and end surface corrosion resistance.

[0209] In addition, the automotive component of the present embodiment is formed by cutting the plated steel sheet of the present embodiment into a predetermined planar shape by press forming or the like, processing it into a predetermined three-dimensional shape, and then forming a coating film. That is, the automotive component of the present embodiment comprises a steel material, a coating layer disposed on at least a portion of the surface of the steel material, and a coating film disposed on the surface of the coating layer. The average chemical composition of the coating layer is as described above. The surface of the coating layer is configured to be a concave-convex surface. In a cross section of the coating layer, the relationship between the length Lo of the coating layer in the longitudinal direction within the observation area of ​​the cross section and the total length Lr of the contour line of the surface of the coating layer within the observation area satisfies the following formula (4). The coating layer contains one or both of a plurality of blocky binary eutectic structures or a plurality of blocky ternary eutectic structures. At least a portion of the plurality of blocky binary eutectic structures or the plurality of blocky ternary eutectic structures exists continuously from the surface of the coating layer to a position 1 / 2 of the thickness of the coating layer.

[0210] (Lr-Lo) / Lo×100≥2.0 (4)

[0211] The automotive member of the present embodiment described above is excellent in paint adhesion and end surface corrosion resistance.

[0212] Next, a method for producing the plated steel sheet of the present embodiment will be described. The production method does not need to be limited to a specific method as long as the plated steel sheet of the present embodiment can be produced. However, for example, the plated steel sheet of the present embodiment can be easily obtained according to the production conditions described below.

[0213] The method for manufacturing a coated steel sheet according to the present embodiment forms a coating on the surface of the steel sheet by annealing the steel sheet in a reducing atmosphere, immersing the immediately annealed steel sheet in a hot dip coating bath, and then pulling it out. Next, cooling is performed by blowing a cooling gas while the coating temperature rises from the bath temperature to 260°C. At this time, the oxygen concentration in the atmosphere on the bath surface of the coating bath and the oxygen concentration in the atmosphere from the time the steel sheet is pulled out of the coating bath to the end of cooling are controlled within the range of 100 to 5000 ppm. In addition, the average cooling rate from the bath temperature to the time the coating temperature reaches 260°C is set to 15°C / second or more. Furthermore, cooling is performed by spraying a cooling gas, but the dew point of the cooling gas is set to 0°C or more.

[0214] That is, the manufacturing method of the plated steel sheet of this embodiment is as follows Figure 5 As shown in the flowchart, with:

[0215] (S1) annealing the steel plate in a reducing atmosphere;

[0216] (S2) a step of immersing the steel sheet in a hot dip coating bath;

[0217] (S3) a step of lifting the steel sheet from the hot dip coating bath; and

[0218] (S4) a step of blowing cooling gas onto the steel plate to which the hot dip coating bath is applied,

[0219] (A) During the immersion S2 and the retrieval S3, the oxygen concentration in the atmosphere above the bath surface of the hot-dip coating bath is set to a range of 100 to 5000 ppm.

[0220] (B) In the blowing step S4, the dew point of the cooling gas is set to 0°C or higher.

[0221] (C) In the coating step S4, the average cooling rate of the coating layer from the temperature of the hot-dip coating bath to 260° C. is set to 15° C. / s or more.

[0222] (D) In ​​the spraying step S4, the oxygen concentration in the atmosphere from the time the steel sheet is removed from the coating bath until the cooling is completed is set to a range of 100 to 5000 ppm. By combining all of conditions A, B, C, and D, the plated steel sheet of this embodiment can be obtained. The details of the production method will be described in order below.

[0223] (S1 annealing)

[0224] Annealing of the steel sheet to be plated is performed in a reducing atmosphere. The reducing atmosphere and annealing conditions are not particularly limited. This annealing removes as much oxide as possible from the surface of the steel sheet.

[0225] (S2 impregnation)

[0226] Next, the immediately annealed steel sheet is immersed in a hot-dip coating bath. The chemical composition of the coating bath can be adjusted appropriately to achieve the chemical composition of the coating layer described above. The temperature of the coating bath is also not particularly limited; a temperature suitable for hot-dip coating can be selected as appropriate. For example, the coating bath temperature can be set at a value approximately 20°C or higher than the melting point of the coating bath.

[0227] (Pick up S3)

[0228] Next, the steel sheet is removed from the coating bath. The amount of coating deposited can be controlled by controlling the speed at which the steel sheet is removed. If necessary, the coated steel sheet can be wiped to control the amount of coating deposited. The amount of coating deposited is not particularly limited and can, for example, be set within the above-mentioned range.

[0229] (S4 Blowing Attachment)

[0230] Next, the coating is cooled. Cooling is performed by blowing cooling gas onto the steel sheet immediately after it is removed from the hot-dip coating bath. Cooling by blowing cooling gas is performed continuously until the steel sheet reaches 260°C from the bath temperature. Cooling conditions below 260°C are not particularly limited; cooling by blowing cooling gas or natural cooling may be performed.

[0231] The oxygen concentration in the atmosphere on the bath surface of the coating bath and the oxygen concentration in the atmosphere from the time the steel plate is scooped out of the coating bath to the end of cooling are controlled within the range of 100 to 5000 ppm. Preferably, the oxygen concentration in these atmospheres is within the range of 100 to 1000 ppm. When the molten metal in the coating bath attached to the steel plate solidifies, an oxide film is formed on the outermost surface of the molten metal in the early stage of solidification, but the thickness of the oxide film is affected by the oxygen concentration in the atmosphere. If the oxide film has a moderate thickness, the oxide film will follow the shape change of the surface of the coating during the subsequent solidification process, forming a concave-convex surface that satisfies the above formula (1).

[0232] When the oxygen concentration in the atmosphere on the bath surface of the coating bath and from the time the steel plate is lifted out of the coating bath to the time the cooling is completed is less than 100 ppm, an oxide film of sufficient thickness cannot be formed, making it difficult to set the surface of the coating to a concave-convex surface. In addition, if the oxygen concentration in the atmosphere exceeds 5000 ppm, an oxide film with a relatively thick film thickness and a flat surface shape is formed in the early stage of the solidification stage. The oxide film does not follow the shape changes of the surface of the coating during the solidification process, and the surface of the coating after solidification becomes a flat surface, resulting in failure to satisfy the above formula (1). In addition, if the oxygen concentration in the atmosphere exceeds 5000 ppm, the oxide film becomes prone to cracking, and it is possible that it becomes difficult to maintain the shape of the coating during solidification.

[0233] The method for setting the oxygen concentration in the atmosphere above the coating bath surface to within a range of 100 to 5000 ppm is not particularly limited. For example, a cover covering the surface of the coating bath can be provided, and a gas with an oxygen concentration of 100 to 5000 ppm can be supplied into the cover. The type of gas supplied to the coating bath surface is not particularly limited, as long as the oxygen concentration is within the range of 100 to 5000 ppm. It can be a non-oxidizing gas such as nitrogen, an inert gas such as argon, or a mixture thereof.

[0234] To maintain the oxygen concentration in the atmosphere between the time the steel sheet is removed from the coating bath and the time the steel sheet is cooled, the oxygen concentration of the cooling gas blown onto the steel sheet can be set within the range of 100 to 5000 ppm. If atmospheric air is used as the cooling gas, the oxygen concentration in the cooling gas becomes excessive, and an appropriate coating cannot be obtained.

[0235] Furthermore, by setting the dew point of the cooling gas to 0°C or higher, the shape-maintaining function of the oxide film can be maintained. If the dew point of the cooling gas is lower than 0°C, a coating having a surface shape satisfying the above formula (1) cannot be obtained. The type of cooling gas is not particularly limited as long as the oxygen concentration is within the range of 100 to 5000 ppm. It can be a non-oxidizing gas such as nitrogen, an inert gas such as argon, or a mixture thereof.

[0236] In addition, the average cooling rate of the coating from the bath temperature to 260°C is set to 15°C / second or more. The upper limit of the average cooling rate is not particularly limited, but may be, for example, 200°C / second or less. By setting the average cooling rate to 15°C / second or more, the primary Al crystal (Al phase) and the Al-Zn phase are fully crystallized in the initial stage of the solidification process. It should be noted that the average cooling rate of the coating from the bath temperature to 260°C refers to the value calculated by the following formula. The cooling time refers to the time from when the steel plate is pulled out of the coating bath to when the temperature of the coating drops to 260°C.

[0237] Average cooling rate = (bath temperature - 260) ÷ cooling time

[0238] As the Al primary crystal (Al phase) and Al-Zn phase are fully crystallized in the initial stage of the solidification process, the amount of molten metal on the surface of the steel plate decreases. Moreover, if the crystallization of the binary eutectic structure and the ternary eutectic structure begins as the temperature of the molten metal decreases, these eutectic structures are formed in a manner that fills the area around the already crystallized Al phase and Al-Zn phase. The crystallization of the eutectic structure begins at the stage when the remaining amount of molten metal becomes less, so the binary eutectic structure and the ternary eutectic structure become the concave part of the coating. In addition, the crystallization of the eutectic structure mainly starts from the area of ​​the coating close to the steel plate, more specifically, starting from the nucleation at the surface of the Fe-Al interface alloy layer, and crystallization proceeds toward the surface of the coating. As a result, the binary eutectic structure and the ternary eutectic structure become continuous from the steel plate side of the coating to the surface side.

[0239] After the plating layer is formed, various chemical conversion treatments and coating treatments may be performed.

[0240] The hot-dip coated steel material of this embodiment may also have a film formed on the coating. The film may be formed as one layer or two or more layers. Examples of the type of film directly above the coating include chromate films, phosphate films, and chromate-free films. These films can be formed using known methods such as chromate treatment, phosphate treatment, and chromate-free treatment.

[0241] Chromate treatments include electrolytic chromate treatments, which form a chromate film through electrolysis; reactive chromate treatments, which form a film through a reaction with the raw material and then rinse away excess treatment liquid; and coating chromate treatments, which form a film by applying the treatment liquid to the substrate and drying it without rinsing. Any of these treatments can be used.

[0242] Examples of the electrolytic chromate treatment include electrolytic chromate treatment using chromic acid, silica sol, resin (phosphoric acid, acrylic resin, vinyl ester resin, vinyl acetate acrylic emulsion, carboxylated styrene butadiene latex, diisopropanolamine-modified epoxy resin, etc.), and hard silica.

[0243] Examples of the phosphate treatment include zinc phosphate treatment, calcium zinc phosphate treatment, and manganese phosphate treatment.

[0244] Chromate-free treatment is particularly suitable because it has little impact on the environment. Chromate-free treatments include electrolytic treatments, which form a chromate-free film through electrolysis; reactive treatments, which form a film through a reaction with the raw material and then rinse away excess treatment liquid; and coating treatments, which form a film by applying the treatment liquid to the substrate and drying it without rinsing. Any of these treatments can be used.

[0245] Furthermore, one or more layers of organic resin films may be present on the film directly above the plating layer. The organic resin is not limited to a specific type, and examples thereof include polyester resins, polyurethane resins, epoxy resins, acrylic resins, polyolefin resins, or modified forms of these resins. Modified forms herein are resins obtained by reacting reactive functional groups contained in the structures of these resins with other compounds (monomers, crosslinking agents, etc.) containing functional groups reactive with these functional groups.

[0246] As such organic resins, one or more organic resins (unmodified resins) may be mixed and used, or one or more organic resins obtained by modifying at least one other organic resin in the presence of at least one organic resin may be mixed and used. Furthermore, the organic resin film may contain any coloring pigment or rust-proof pigment. Aqueous resins made by dissolving or dispersing in water may also be used.

[0247] It should be noted that as long as the necessary conditions shown in this disclosure are met, the method for manufacturing the plated steel sheet is not limited to the above content. Instead of hot dipping, electroplating, vapor deposition coating, spraying, cold spraying, etc. can also be used.

[0248] Example

[0249] The following describes an embodiment of the present invention. However, the conditions in the embodiment are merely examples of conditions adopted to confirm the feasibility and effectiveness of the present invention. The present invention is not limited to this example of conditions. Various conditions can be adopted in the present invention as long as they do not deviate from the main purpose of the present invention and achieve the purpose of the present invention.

[0250] For the plated original plate, a cold-rolled steel plate (0.05C-0.1Si-0.2Mn) with a plate thickness of 1.6 mm was used. First, the steel plate was annealed. The annealed steel plate was immersed in various hot-dip coating baths and then removed, so that a coating was attached to the surface of the steel plate. Next, various plated steel plates were manufactured by cooling with a cooling gas from the time the steel plate was removed from the coating bath until the coating reached 260°C. The cooling gas was set to be mainly composed of nitrogen. The oxygen concentration and dew point of the cooling gas were set as shown in Table 2A and Table 2B.

[0251] Regarding the annealing conditions for steel sheets annealed in a reducing atmosphere, the soaking temperature is set at 800°C and the soaking time is set at 10 seconds. The annealing atmosphere is a reducing atmosphere consisting of a mixed gas containing 5% hydrogen and the remainder nitrogen. The oxygen concentration in the annealing atmosphere is set to 20 ppm or less. The annealed steel sheets are then air-cooled with nitrogen until the dip plate temperature reaches the bath temperature + 20°C. After immersion in the hot-dip coating bath for approximately 3 seconds, the sheets are removed. The removal speed is set at 20 to 200 mm / second. During removal, N2 wiping gas is used to control the amount of coating deposited.

[0252] The chemical composition of the coating is shown in Tables 1A and 1B. The manufacturing conditions were set as shown in Tables 2A and 2B. Furthermore, the morphology of the binary eutectic structure or ternary eutectic structure in the coating was evaluated, and the results are shown in Tables 3A and 3B. Furthermore, the coating adhesion and end surface corrosion resistance of the plated steel sheets were evaluated, and the results are shown in Tables 3A and 3B.

[0253] The chemical composition and metallographic structure of the coating, as well as the surface irregularities of the coating, were evaluated using the aforementioned methods. It should be noted that the evaluation of the surface irregularities of the coating was performed using an observation field with a length Lo in the longitudinal direction of the coating of 500 μm. Furthermore, the presence of the Mg2Sn phase was determined by X-ray diffraction analysis of the coating surface, with the presence of Mg2Sn diffraction peaks determined.

[0254] For end surface corrosion resistance (simulated end surface corrosion resistance), the plated steel sheet was cut at an arbitrary location to expose the cut end surface. The cut end surface was then subjected to a neutral salt water spray test specified in JIS Z 2371. Evaluation was based on the occurrence of red rust on the cut end surface. The evaluation criteria for the red rust area ratio are shown below. "AAA," "AA," and "A" were considered acceptable. The results are shown in Tables 3A and 3B.

[0255] (evaluate)

[0256] AAA: Red rust area rate is less than 10% after 2500h

[0257] AA: Red rust area rate is less than 10% after 2000h

[0258] A: After 1500h, the red rust area rate is less than 20%

[0259] B: Red rust area rate exceeds 20% at 1500h

[0260] Regarding paint adhesion (adhesive strength), 50×100 mm samples were collected from the plated steel sheets and zinc phosphate treated (SD5350 system: Nipponpaint Industrial Coatings, Inc. standard). Electrodeposition coating (PN110 Powernix (registered trademark) Gray: Nipponpaint Industrial Coatings, Inc. standard) was then applied to a thickness of 20 μm. The samples were then baked at 150°C for 20 minutes. The steel sheets were then subjected to a V-bend using a die with a 60° curvature radius of 10 mm. After rebending, the sheets were immersed in a 5% NaAl aqueous solution at 50°C for 1000 hours. A tape peel test was performed in which adhesive tape was applied only to the V-bend surface and instantly peeled off. The percentage of the area where the paint peeled off was determined for the area where the tape was applied, and the results were evaluated as follows. "AAA," "AA," and "A" were considered acceptable. The results are shown in Tables 3A and 3B.

[0261] (evaluate)

[0262] AAA: peeling area ratio is less than 13%

[0263] AA: The peeling area ratio is 13% or more and less than 25%

[0264] A: The peeling area ratio is 25% or more and less than 35%

[0265] B: The peeling area ratio is 35% or more

[0266] In the case of the plated steel sheets No. 1 to 31, the surface of the coating is a concave-convex surface, and a plurality of blocky binary eutectic structures or one or both of the ternary eutectic structures are present in the coating. A portion of the eutectic structure that continuously exists from the coating surface to 1 / 2 of the thickness of the coating or the depth of the Fe-Al interface alloy layer is located in the concave part of the concave-convex surface. The chemical composition of the coating and the morphology of the eutectic structure are within the scope of the present disclosure, and both the end face corrosion resistance and the paint adhesion are excellent.

[0267] The amount of Al in the plating layer of No. 32 was insufficient. Therefore, (Lr-Lo) / Lo×100 was small in No. 32, and the coating adhesion was insufficient.

[0268] In No. 33, the amount of Al in the plating layer was excessive. Therefore, (Lr-Lo) / Lo×100 was small in No. 33, and the coating adhesion was insufficient.

[0269] The amount of Mg in the plating layer of No. 34 is insufficient. Therefore, (Lr - Lo) / Lo × 100 is small in No. 34, resulting in insufficient coating adhesion. In addition, the end surface corrosion resistance is also reduced.

[0270] The amount of Mg in the plating layer of No. 35 was excessive. Therefore, in No. 35, (Lr-Lo) / Lo×100 became small, and the coating adhesion was insufficient.

[0271] In No. 36, the oxygen concentration in the atmosphere from the top of the coating bath to the end of the cooling step exceeded 5000 ppm. Therefore, in No. 36, (Lr-Lo) / Lo×100 became small, and the coating adhesion was insufficient.

[0272] In No. 37, the average cooling rate from the coating bath temperature to 260° C. was low. Therefore, in No. 37, the primary Al crystals (Al phase or Al—Zn phase) were not sufficiently crystallized, (Lr—Lo) / Lo×100 was small, and the coating adhesion was insufficient.

[0273] [Table 1A]

[0274]

[0275] The underlined parts are outside the scope of the present disclosure.

[0276] [Table 1B]

[0277]

[0278] The underlined parts are outside the scope of the present disclosure.

[0279] [Table 2A]

[0280]

[0281] The underlined portion indicates conditions outside the range of preferred production conditions.

[0282] [Table 2B]

[0283]

[0284] The underlined portion indicates conditions outside the range of preferred production conditions.

[0285] [Table 3A]

[0286]

[0287] The underlined parts are outside the scope of the present disclosure.

[0288] [Table 3B]

[0289]

[0290] The underlined parts are outside the scope of the present disclosure.

[0291] Explanation of symbols

[0292] 1 Coated steel sheet

[0293] 11 Steel Plate

[0294] 12, 112 coating

[0295] 13, 113 interface alloy layer

[0296] 14, 114 binary eutectic or ternary eutectic

Claims

1. A plated steel sheet comprising a steel sheet and a plating layer disposed on at least a portion of a surface of the steel sheet. The average chemical composition of the coating comprises, in mass %,: Al：10.00～30.00％、 Mg: 1.00~15.00%, Sn: 0.00~1.00%, Si: 0.00-2.00%, Ca: 0.00~2.00%, Ni: 0.00~1.00%, Fe: 0.01~15.00%, Sb: 0.00~0.50%, Pb: 0.00~0.50%, Cu: 0.00~1.00%, Ti: 0.00~1.00%, Cr：0.00～1.00％、 Nb: 0.00~1.00%, Zr：0.00～1.00％、 Mn: 0.00~1.00%, Mo: 0.00~1.00%, Ag: 0.00~1.00%, Li: 0.00~1.00%, Bi: 0.00~1.00%, V：0.00～1.00％、 Co: 0.00~1.00%, In: 0.00~1.00%, W：0.00～1.00％、 P：0.00～1.00％、 La: 0.00~0.50%, Ce: 0.00~0.50%, B：0.00～0.50％、 Y：0.00～0.50％、 Sr：0.00～0.50％、 Total of Sb, Pb, Cu, Ti, Cr, Nb, Zr, Mn, Mo, Ag, Li, Bi, V, Co, P, In, W, La, Ce, B, Y, Sr: 0.00~5.00%, The rest: Zn and impurities, The surface of the coating is set to be a concave-convex surface, In the cross section of the plating layer, the relationship between the length Lo of the plating layer in the longitudinal direction within the observation area of ​​the cross section and the total length Lr of the contour line of the surface of the plating layer within the observation area satisfies the following formula (1): The coating layer contains one or both of a plurality of bulk binary eutectic structures or a plurality of bulk ternary eutectic structures, At least a portion of the plurality of blocks of the binary eutectic structure or the plurality of blocks of the ternary eutectic structure exists continuously from the surface of the coating layer to a position of 1 / 2 of the average thickness of the coating layer, (Lr-Lo) / Lo×100≥2.0(%) (1).

2. The plated steel sheet according to claim 1, wherein the plated layer includes an Fe-Al based interface alloy layer in contact with the steel sheet. At least a portion of the plurality of blocks of the binary eutectic structures or the plurality of blocks of the ternary eutectic structures exist continuously from the surface of the plating layer to the Fe—Al-based interface alloy layer.

3. The plated steel sheet according to claim 1, wherein The number of locations where at least a portion of the multiple blocks of the binary eutectic structure or the multiple blocks of the ternary eutectic structure continuously exist from the surface of the coating to a position of 1 / 2 of the average thickness of the coating is 1 to 15 in each rectangular area on the surface of the coating with a long side of 500 μm and a short side of 150 μm.

4. The plated steel sheet according to claim 1, which satisfies the following formula (2) instead of the formula (1): The number of locations where at least a portion of a plurality of blocks of the binary eutectic structures or a plurality of blocks of the ternary eutectic structures continuously exists from the surface of the coating layer to a position of 1 / 2 of the average thickness of the coating layer is 3 to 15 locations within a rectangular region on the surface of the coating layer, each of which has a long side of 500 μm and a short side of 150 μm. (Lr-Lo) / Lo×100≥6.0(%) (2).

5. The plated steel sheet according to claim 1, which satisfies the following formula (3) instead of the formula (1): The number of locations where at least a portion of a plurality of blocks of the binary eutectic structure or a plurality of blocks of the ternary eutectic structure continuously exists from the surface of the coating layer to a position of 1 / 2 of the average thickness of the coating layer is 5 to 15 locations within a rectangular region on the surface of the coating layer, each of which has a long side of 500 μm and a short side of 150 μm. (Lr-Lo) / Lo×100≥8.0(%) (3).

6. The plated steel sheet according to any one of claims 1, 3, 4 and 5, wherein At least a portion of the plurality of blocks of the binary eutectic structures or the plurality of blocks of the ternary eutectic structures continuously exists from the surface of the plating layer to a position of 1 / 2 of the average thickness of the plating layer, and is located in the concave portion of the concave-convex surface of the plating layer.

7. The plated steel sheet according to claim 2, wherein At least a portion of the plurality of blocks of the binary eutectic structures or the plurality of blocks of the ternary eutectic structures continuously exists from the surface of the coating layer to the Fe-Al based interface alloy layer and is located in the concave portion of the concave-convex surface of the coating layer. 8 . The plated steel sheet according to claim 1 , wherein the average chemical composition of the plated layer comprises Al: 10.00 to 25.00% and Mg: 4.50 to 15.00%. 9 . The plated steel sheet according to claim 1 , wherein the average chemical composition of the plated layer comprises Al: 15.00 to 22.00% and Mg: 5.00 to 15.00%.

10. The plated steel sheet according to claim 1, claim 8 or claim 9, wherein in the average chemical composition of the plated layer, Sn is 0.05 to 0.50%. The Mg2Sn phase detected by X-ray diffraction measurement exists in the plating layer.

11. The plated steel sheet according to claim 1, claim 8 or claim 9, wherein the average chemical composition of the plated layer contains one or both of La and Ce, and the total amount of La and Ce is 0.05 to 0.50%. 12 . The plated steel sheet according to claim 10 , wherein the average chemical composition of the plated layer contains one or both of La and Ce, and the total amount of La and Ce is 0.05 to 0.50%.

13. An automobile component comprising a steel material, a plating layer disposed on at least a portion of a surface of the steel material, and a paint film disposed on a surface of the plating layer. The average chemical composition of the coating comprises, in mass %,: Al：10.00～30.00％、 Mg: 1.00~15.00%, Sn: 0.00~1.00%, Si: 0.00-2.00%, Ca: 0.00~2.00%, Ni: 0.00~1.00%, Fe: 0.01~15.00%, Sb: 0.00~0.50%, Pb: 0.00~0.50%, Cu: 0.00~1.00%, Ti: 0.00~1.00%, Cr：0.00～1.00％、 Nb: 0.00~1.00%, Zr：0.00～1.00％、 Mn: 0.00~1.00%, Mo: 0.00~1.00%, Ag: 0.00~1.00%, Li: 0.00~1.00%, Bi: 0.00~1.00%, V：0.00～1.00％、 Co: 0.00~1.00%, In: 0.00~1.00%, W：0.00～1.00％、 P：0.00～1.00％、 La: 0.00~0.50%, Ce: 0.00~0.50%, B：0.00～0.50％、 Y：0.00～0.50％、 Sr：0.00～0.50％、 Total of Sb, Pb, Cu, Ti, Cr, Nb, Zr, Mn, Mo, Ag, Li, Bi, V, Co, P, In, W, La, Ce, B, Y, Sr: 0.00~5.00%, The rest: Zn and impurities, The surface of the coating is set to be a concave-convex surface, In the cross section of the plating layer, the relationship between the length Lo of the plating layer in the longitudinal direction within the observation area of ​​the cross section and the total length Lr of the contour line of the surface of the plating layer within the observation area satisfies the following formula (4): The coating layer contains one or both of a plurality of bulk binary eutectic structures or a plurality of bulk ternary eutectic structures, At least a portion of the plurality of blocks of the binary eutectic structure or the plurality of blocks of the ternary eutectic structure exists continuously from the surface of the coating layer to a position of 1 / 2 of the average thickness of the coating layer, (Lr-Lo) / Lo×100≥2.0(%) (4).

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