Plated steel material

Abstract

The present invention adopts a plated steel material provided with a plating layer formed on at least part of a surface of a base steel material, wherein: at least part of a surface of the plating layer has a site where a plurality of cracks is observed; the plurality of cracks extends in substantially the same direction as one another; and in the site, when a cross-section that is perpendicular to the direction in which the plurality of cracks extends and perpendicular to a surface of the plated steel material and that has a length of 200 μm in the direction parallel to the surface is taken as an observation region, the number ratio of cracks inclined at an angle of 35° to 55° with respect to the thickness direction of the plating layer is 80% or more based on all cracks observed in the observation region, the number ratio of distances Lc satisfying formula (1) is 80% or more based on all distances Lc observed in the observation region, and the average value of widths Wc of the cracks at a thickness position T / 2 away from the surface of the plating layer is 10 μm or less in the observation region, wherein a distance between adjacent cracks is denoted as Lc, and the thickness of the plating layer is denoted as T.　(1): 0.3T ≤ Lc ≤ 1.6T

Description

TITLE OF INVENTION: PLATED STEEL MATERIAL TECHNICAL FIELD

[0001] The present invention relates to a plated steel material. BACKGROUND ART

[0002] A Zn-Al-Mg-based plated steel sheet including a Zn-Al-Mg-based plated layer containing Zn, Al, and Mg is excellent in corrosion resistance, particularly sacrificial corrosion resistance, and thus is used in the fields of building materials and civil engineering. When a Zn-Al-Mg-based plated steel sheet is used in these fields, the Zn-Al-Mg-based plated steel sheet may be processed into various shapes to form a plated steel material having a bent portion. However, in the Zn-Al-Mg-based plated layer, the corrosion resistance of the bent portion may be deteriorated as compared with a general Zn plated layer.

[0003] Patent Document 1 describes a plated steel material including a steel material and a plated layer including a Zn-Al-Mg alloy layer disposed on a surface of the steel material, in which the Zn-Al-Mg alloy layer has a Zn phase and contains a Mg-Sn intermetallic compound phase in the Zn phase, the plated layer includes, in mass%, Zn: more than 65.0%, Al: more than 5.0% to less than 25.0%, Mg: more than 3.0% to less than 12.5%, and Sn: 0.1% to 20.0%, and has a chemical composition satisfying following formulas 1 to 5. However, the corrosion resistance of the bent portion has not been examined. Formula 1: Bi + In < Sn Formula 2: Y + La + Ce < Ca Formula 3: Si < Sn Formula 4: 0 < Cr + Ti + Ni + Co + V + Nb + Cu + Mn < 0.25 Formula 5: 0 < Sr + Sb + Pb + B < 0.5 In the formulas 1 to 5, the element symbol indicates the content of each element in mass%.

[0004] Patent Document 2 describes a hot-dip plated steel material including a steel material and a hot-dip plated layer disposed on a surface of the steel material, in which the hot-dip plated layer has a chemical composition containing, in mass%, Al: 10.0 to 30.0%, Mg: 3.0 to 15.0%, and Fe: 0.01 to 15.0%, with balance: Zn and impurities, and a diffraction intensity obtained from an X-ray diffraction measurement result of the hot-dip plated layer satisfies a relationship of the following formulas (1a) and (2a). However, the corrosion resistance of the bent portion has not been examined. 0.3 < I(002)MgZn2 / {I(100)MgZn2 + I(101)MgZn2} < 3.0... (1a) 5.0 < I(111)a / I(200)a < 40.0... (2a) wherein, in the formula (1a), I(002)MgZn2 represents a MgZn2 phase (002) diffraction intensity, I(100)MgZn2 represents a MgZn2 phase (100) diffraction intensity, and I(101)MgZn2 represents a MgZn2 phase (101) diffraction intensity, and in the formula (2a), I(111)a represents an a phase (111) diffraction intensity and I(200)a represents an a phase (200) diffraction intensity.

[0005] Patent Document 3 describes a hot-dip Zn-based plated steel sheet including a steel sheet and a plated layer formed on at least a part of a sheet surface, in which the plated layer has a chemical composition consisting of, in mass%, Al: 6.00 to 35.00%, Mg: 2.00 to 12.00%, Ca: 0.005 to 2.00%, and balance: Zn and impurities, the plated layer has an area fraction of a MgZn2 phase of 15 to 60% in a cross section in a thickness direction, and the MgZn2 phase contains a Ca-based intermetallic compound having a circle equivalent diameter of 0.10 pm or less. However, the corrosion resistance of the bent portion has not been examined. Citation List Patent Documents

[0006] Patent Document 1: PCT International Publication No. WO 2018 / 139619 Patent Document 2: PCT International Publication No. WO 2023 / 182398 Patent Document 3: PCT International Publication No. WO 2022 / 080004 SUMMARY OF INVENTION Technical Problem

[0007] The present invention has been made in view of the above circumstances, and an object thereof is to provide a plated steel material having excellent sacrificial corrosion resistance and corrosion resistance of a bent portion. Solution to Problem

[0008] In order to solve the above problem, the present invention adopts the following configurations. [1] A plated steel material including a base steel material and a plated layer formed on at least a part of a surface of the base steel material, wherein the plated layer has a chemical composition comprising, by mass%, Al: 1.0 to 30.0%, Mg: 1.0 to 10.0%, Fe: 0 to 2.0%, Si: 0 to 2.0%, Ni: 0 to 1.00%, Ca: 0 to 1.00%, Sb: 0 to 0.50%, Pb: 0 to 0.50%, Sn: 0 to 1.00%, Cu: 0 to 1.00%, Ti: 0 to 1.00%, Cr: 0 to 1.00%, Nb: 0 to 1.00%, Zr: 0 to 1.00%, Mn: 0 to 1.00%, Mo: 0 to 1.00%, Ag: 0 to 1.00%, Li: 0 to 1.00%, Bi: 0 to 1.00%, V: 0 to 1.00%, Co: 0 to 1.00%, In: 0 to 1.00%, La: 0 to 0.50%, Ce: 0 to 0.50%, B: 0 to 0.50%, Y: 0 to 0.50%, P: 0 to 0.50%, Sr: 0 to 0.50%, and balance comprising 50.0 to 98.0% of Zn, and impurities, the total of Sb, Pb, Cu, Sn, Ti, Cr, Nb, Zr, Mn, Mo, Ag, Li, Bi, V, Co, In, La, Ce, B, Y, P, and Sr is 0 to 5.00%, at least a part of a surface of the plated layer has a portion where a plurality of cracks are observed, the plurality of cracks extend in substantially the same direction in the portion, when a cross section of the plated steel material that is perpendicular to a direction in which the plurality of cracks extend and is perpendicular to the surface of the plated steel material and has a length of 200 pm in a direction parallel to the surface is set as an observation region in the portion, a proportion of the number of cracks inclined at an angle of 35° to 55° with respect to a thickness direction of the plated layer among all the cracks observed in the observation region is 80% or more, when an interval between the adjacent cracks is Lc and the thickness of the plated layer is T, a proportion of the number of intervals Lc satisfying a following formula (1) among all the intervals Lc observed in the observation region is 80% or more, and an average value of widths Wc of the cracks at a thickness position away from the surface of the plated layer by T / 2 in the observation region is 10 pm or less. 0.3T < Lc < 1.6T... (1) [2] The plated steel material according to [1], wherein a proportion of the number of cracks inclined at an angle of 40° to 50° with respect to the thickness direction of the plated layer among all the cracks observed in the observation region of the portion is 70% or more. [3] The plated steel material according to [1] or [2], wherein in the chemical composition of the plated layer, contents of Al and Mg are Al: 10.0 to 30.0 mass% and Mg: 4.0 to 10.0 mass%, respectively, and a proportion of the number of intervals Lc satisfying a following formula (2) among all the intervals Lc observed in the observation region is 80% or more. 0.5T < Lc < 1.4T... (2) [4] The plated steel material according to [1] or [2], wherein in the chemical composition of the plated layer, contents of Al and Mg are Al: 15.0 to 30.0 mass% and Mg: 5.0 to 8.0 mass%, respectively, and a proportion of the number of intervals Lc satisfying a following formula (3) among all the intervals Lc observed in the observation region is 80% or more. 0.5T < Lc < 1.2T... (3) [5] The plated steel material according to any one of [1] to [4], wherein the average value of widths Wc of the cracks at a thickness position away from the surface of the plated layer by T / 2 in the observation region is 3 pm or less. [6] The plated steel material according to any one of [1] to [5], wherein the portion is present in a bent inner side of a bent portion of the base steel material. [7] The plated steel material according to any one of [1] to [6], wherein the portion is present in a bent-back portion of the base steel material. Advantageous Effects of Invention

[0009] According to the present invention, it is possible to provide a plated steel material having excellent sacrificial corrosion resistance and corrosion resistance of a processed portion. BRIEF DESCRIPTION OF DRAWINGS

[0010] [FIG. 1] A schematic cross-sectional view illustrating a plated steel material according to an embodiment of the present invention. [FIG. 2A] A schematic cross-sectional view showing a bent portion of the plated steel material according to an embodiment of the present invention. [FIG. 2B] An enlarged cross-sectional view of the bent portion in FIG. 2A. [FIG. 3] A schematic cross-sectional view showing a bent-back portion of the plated steel material according to an embodiment of the present invention. [FIG. 4] A view illustrating a surface of a plated layer of the plated steel material according to an embodiment of the present invention, and is a schematic plan view illustrating a crack. [FIG. 5] A schematic cross-sectional view of the plated layer of the plated steel material according to an embodiment of the present invention. [FIG. 6] An enlarged schematic cross-sectional view of the plated layer of the plated steel material according to an embodiment of the present invention. DESCRIPTION OF EMBODIMENTS

[0011] When a plated steel sheet including a Zn-Al-Mg-based plated layer is processed into plated steel materials having various shapes by bending or the like, cracks may occur in the plated layer in a bent portion or a bent-back portion. Cracks are likely to occur when compressive stress is applied to the plated layer in bending, but according to the present inventors, it has been found that particularly when irregular cracks occur in the plated layer, corrosion resistance is deteriorated, and on the other hand, when regular cracks occur in the plated layer, the compressive stress is relaxed, and the corrosion resistance of the bent portion is not deteriorated. Here, the regular crack means that the direction of the crack that propagates in the depth direction of the plated layer is inclined with respect to the thickness direction of the plated layer, and the intervals between the cracks are substantially the same. Therefore, as a result of examination, by controlling the cooling conditions in the step of manufacturing the plated layer, regular cracks occur in the plated layer of the bent portion, thereby successfully suppressing deterioration of corrosion resistance of the processed portion. Based on the above findings, the present inventors have completed the present invention.

[0012] A plated steel material according to an embodiment of the present invention is a plated steel material including a base steel material and a plated layer formed on at least a part of a surface of the base steel material, wherein the plated layer has a chemical composition comprising, by mass%, Al: 1.0 to 30.0%, Mg: 1.0 to 10.0%, Fe: 0 to 2.0%, Si: 0 to 2.0%, Ni: 0 to 1.00%, Ca: 0 to 1.00%, Sb: 0 to 0.50%, Pb: 0 to 0.50%, Sn: 0 to 1.00%, Cu: 0 to 1.00%, Ti: 0 to 1.00%, Cr: 0 to 1.00%, Nb: 0 to 1.00%, Zr: 0 to 1.00%, Mn: 0 to 1.00%, Mo: 0 to 1.00%, Ag: 0 to 1.00%, Li: 0 to 1.00%, Bi: 0 to 1.00%, V: 0 to 1.00%, Co: 0 to 1.00%, In: 0 to 1.00%, La: 0 to 0.50%, Ce: 0 to 0.50%, B: 0 to 0.50%, Y: 0 to 0.50%, P: 0 to 0.50%, Sr: 0 to 0.50%, and balance comprising 50.0 to 98.0% of Zn, and impurities, the total of Sb, Pb, Cu, Sn, Ti, Cr, Nb, Zr, Mn, Mo, Ag, Li, Bi, V, Co, In, La, Ce, B, Y, P, and Sr is 0 to 5.00%, at least a part of a surface of the plated layer has a portion where a plurality of cracks are observed, the plurality of cracks extend in substantially the same direction in the portion, when a cross section of the plated steel material that is perpendicular to a direction in which the plurality of cracks extend and is perpendicular to the surface of the plated steel material and has a length of 200 pm in a direction parallel to the surface is set as an observation region in the portion, a proportion of the number of cracks inclined at an angle of 35° to 55° with respect to a thickness direction of the plated layer among all the cracks observed in the observation region is 80% or more, when an interval between the adjacent cracks is Lc and the thickness of the plated layer is T, a proportion of the number of intervals Lc satisfying a following formula (1) among all the intervals Lc observed in the observation region is 80% or more, and an average value of widths Wc of the cracks at a thickness position away from the surface of the plated layer by T / 2 in the observation region is 10 pm or less. 0.3T < Lc < 1.6T... (1)

[0013] Also, in the plated steel material according to the embodiment of the present invention, a proportion of the number of cracks inclined at an angle of 40° to 50° with respect to the thickness direction of the plated layer among all the cracks observed in the observation region of the portion is preferably 70% or more. Also, in the plated steel material according to the embodiment of the present invention, in the chemical composition of the plated layer, the contents of Al and Mg are Al: 10.0 to 30.0 mass% and Mg: 4.0 to 10.0 mass%, respectively, and a proportion of the number of intervals Lc satisfying a following formula (2) among all the intervals Lc observed in the observation region is preferably 80% or more. 0.5T < Lc < 1.4T... (2) Also, in the plated steel material according to the embodiment of the present invention, in the chemical composition of the plated layer, the contents of Al and Mg are Al: 15.0 to 30.0 mass% and Mg: 5.0 to 8.0 mass%, respectively, and a proportion of the number of intervals Lc satisfying a following formula (3) among all the intervals Lc observed in the observation region is preferably 80% or more. 0.5T < Lc < 1.2T... (3) Also, in the plated steel material according to the embodiment of the present invention, the average value of widths Wc of the cracks at a thickness position away from the surface of the plated layer by T / 2 in the observation region is preferably 3 pm or less. Also, the portion is preferably present in a bent inner side of a bent portion of the base steel material. Also, the portion is preferably present in a bent-back portion of the base steel material.

[0014] The plated steel material of the present embodiment is manufactured through forming working such as pressing, roll forming, and bending on a plated steel sheet as a material. Therefore, at least one or more bent portions are provided in the plated steel material. The plated steel material may also have a bent-back portion. The bent-back portion is formed by bending a plated steel sheet as a material to form a bent portion and then unbending the bent portion.

[0015] FIG. 1 illustrates a schematic cross-sectional view of a plated steel material 1. As illustrated in FIG. 1, the plated steel material 1 according to the present embodiment includes a base steel material 11 and a plated layer 12 formed on at least a part of a surface of the base steel material 11. The base steel material 11 is finally formed into various shapes by subjecting the steel sheet to forming working. The shape of the base steel material 11 constituting the plated steel material 1 is not particularly limited. The base steel material 11 may be one that is used as, for example, a steel pipe, a civil engineering and construction material (fence culvert, corrugated pipe, drain channel lid, splash-preventing plate, bolt, wire mesh, guard rail, water stop wall, or the like), a home electric appliance member (a housing of an outdoor unit of an air conditioner, or the like), or an automobile member (a suspension member, an exterior member, an interior member, a structural member, or the like).

[0016] The material of the base steel material 11 is not particularly limited. The base steel material 11 may be made of, for example, various steels, such as general steel, Al-killed steel, ultra-low carbon steel, high carbon steel, various high tensile strength steels, and some high alloy steels (a steel containing a reinforcing element such as Ni, Cr, etc.). As with the base steel sheets of various hot-dip galvanized steel sheets and steel strips described in JIS G 3302:2010 (so-called plating original sheet), the base steel material 11 may be a hot-rolled steel sheet, a hot-rolled steel strip, a cold-rolled steel sheet, a cold-rolled steel strip, or the like. The chemical composition and manufacturing method (hot rolling method, pickling method, cold rolling method, or the like) of the steel sheet to be a material of the base steel material 11, specific manufacturing conditions thereof, and the like are also not particularly limited.

[0017] The plated steel material 1 according to the embodiment has a plated layer 12 arranged on at least a part of the surface of the base steel material 11. The plated layer 12 is preferably a plating film produced by the so-called hot-dip plating treatment. In the plated steel material 1 of the present embodiment, the plated layer 12 may be formed on at least a part of the surface of the base steel material 11.

[0018] The plated layer 12 is mainly made of a Zn-Al-Mg alloy layer due to the chemical composition described later. The plated layer 12 may include an Fe-Al-based interfacial alloy layer containing Fe and Al as main components between the base steel material 11 and the Zn-Al-Mg alloy layer. That is, the plated layer 12 may have a single-layer structure of the Zn-Al-Mg alloy layer or a laminate structure including the Zn-Al-Mg alloy layer and the Fe-Al-based interfacial alloy layer.

[0019] In the following description, a numerical value range indicated by using “to” means a range including the numerical values described before and after “to” as a lower limit and an upper limit. Note that “more than” or “less than” is attached to the numerical values described before and after “to”, it means a range not including these numerical values as the lower limit or the upper limit. Next, the chemical composition of the plated layer 12 will be explained below, but the expression “%” of the content of each element in a chemical composition means “mass%”. The content of an element in the chemical composition may be referred to as an element concentration (for example, Zn concentration, Mg concentration, or the like).

[0020] The “corrosion resistance of the processed portion” refers to a property of suppressing occurrence of red rust in a bent portion 24 or a bent-back portion 22A of the plated steel material 1. The “sacrificial corrosion resistance” refers to a property of suppressing corrosion of the base steel material 11 at a bare portion of the base steel material 11 (for example, a cut end surface portion where the plated steel material 1 is cut, a portion where the plated layer 12 is cracked due to processing, and a portion where the base steel material 11 is exposed due to peeling of the plated layer 12). The “substrate corrosion resistance” indicates a property that the plated layer 12 itself is hardly corroded. The “wear resistance” indicates a property that the plated layer 12 is hardly worn.

[0021] The plated layer 12 according to the present embodiment contains Zn and other alloying elements. Also, the plated layer 12 may contain Zn and other alloying elements, and balance impurities. Further, the plated layer 12 may be a plated layer which contains Zn and other alloying elements, and balance impurities. The chemical composition of the plated layer 12 will be described in detail below. Note that the elements the concentration of which has a lower limit of 0% as described are not essential for solving the problem, but are optional elements which are allowed to be contained in the plated layer 12 for the purpose of improving characteristics or the like.

[0022] <Al: 1.0 to 30.0%> Al contributes to improvement in flat surface corrosion resistance and workability. Therefore, the Al concentration is set to 1.0% or more. On the other hand, when there is excess Al, the Mg concentration and the Zn concentration relatively decrease, and sacrificial corrosion resistance deteriorates. Therefore, the Al concentration is set to 30.0% or less. The Al concentration may be 5.0% or more, 10.0% or more, or 12.0% or more, and may be 28.0% or less, 25.0% or less, or 20.0% or less.

[0023] <Mg: 1.0 to 10.0%> Mg is an element essential for securing flat surface corrosion resistance. Mg is also necessary to crystallize a Mg2Sn phase. Therefore, the Mg concentration is set to 1.0% or more. On the other hand, when the Mg concentration is excessive, the plated layer 12 may become hard, the proportion of the number of cracks 101 at inclination angles of 35 to 55° may decrease, the corrosion resistance of the processed portion may be deteriorated, and the flat surface corrosion resistance may be further deteriorated. Therefore, the Mg concentration is set to 10.0% or less. The Mg concentration may be 3.0% or more or 5.0% or more, and 8.0% or less or 7.0% or less.

[0024] Moreover, in the plated steel material 1 of the present embodiment, the contents of Al and Mg may be Al: 10.0 to 30.0 mass% and Mg: 4.0 to 10.0 mass%. As a result, the proportion of the number of the cracks 101 at inclination angles of 40 to 50° becomes 70% or more. Further, in the plated steel material 1 of the present embodiment, the contents of Al and Mg are limited to Al: 10.0 to 30.0 mass% and Mg: 4.0 to 10.0 mass%, and the proportion of the number of intervals Lc satisfying the formula (2) is 80% or more by setting the manufacturing conditions to suitable conditions. Accordingly, the processed portion corrosion resistance and the sacrificial corrosion resistance are further enhanced. Furthermore, in the plated steel material 1 of the present embodiment, the contents of Al and Mg are limited to Al: 15.0 to 30.0 mass% and Mg: 5.0 to 8.0 mass%, and the proportion of the number of intervals Lc satisfying the formula (3) is 80% or more by setting the manufacturing conditions to suitable conditions. Accordingly, the processed portion corrosion resistance and the sacrificial corrosion resistance are still further enhanced.

[0025] Since the elements described below are all arbitrary additive elements except Zn, the lower limit thereof is set to 0%. <Fe: 0 to 2.0%> The concentration of Fe may be 0%, but Fe may be contained in the plated layer 12 in an amount of 0.01% or more because Fe may be mixed into the plated layer 12 from steel. It has been confirmed that, when the Fe concentration is 2.0% or less, the performance of the plated layer 12 is not adversely affected. The Fe concentration may be, for example, 0.01% or more, 0.1% or more, or 0.3% or more, and may be 1.0% or less, 0.8% or less, or 0.7% or less.

[0027] <Si: 0% to 2.0%> The Si concentration may be 0%. On the other hand, Si contributes to improvement in flat surface corrosion resistance. Therefore, the Si concentration may be more than 0%, 0.01% or more, 0.1% or more, or 0.2% or more. On the other hand, when the Si concentration is excessive, flat surface corrosion resistance is deteriorated. Therefore, the Si concentration is set to 2.0% or less. The Si concentration may be 1.0% or less, 0.8% or less, or 0.5% or less.

[0028] <Ni: 0 to 1.00%> The Ni concentration may be 0%. On the other hand, Ni contributes to improvement in sacrificial corrosion resistance. Therefore, the Ni concentration may be 0.001% or more. On the other hand, when the Ni concentration is excessive, flat surface corrosion resistance is deteriorated. Therefore, the Ni concentration is set to 1.00% or less. The Ni concentration may be 0.80% or less, 0.60% or less, or 0.50% or less.

[0029] <Ca: 0 to 1.00%> The Ca concentration may be 0%. On the other hand, Ca is an element capable of adjusting the optimum Mg elution amount for imparting flat surface corrosion resistance. Therefore, the Ca concentration may be 0.01% or more or 0.05% or more. On the other hand, when the Ca concentration is excessive, flat surface corrosion resistance and workability are deteriorated. Therefore, the Ca concentration is set to 1.00% or less. The Ca concentration may be 0.50% or less, 0.30% or less, or 0.20% or less.

[0030] <Sb, Pb: 0 to 0.50% each> The concentrations of Sb and Pb may be 0%. On the other hand, Sb and Pb contribute to improvement in sacrificial corrosion resistance. Therefore, the concentration of each of Sb and Pb may be 0.001% or more, 0.003% or more, or 0.005% or more. On the other hand, when the concentration of Sb and Pb is excessive, flat surface corrosion resistance is deteriorated. Therefore, the concentration of each of Sb and Pb is set to 0.50% or less. The concentration of each of Sb and Pb may be 0.40% or less.

[0031] <Sn: 0 to 1.00%> The Sn concentration may be 0%. On the other hand, Sn is an element that forms an intermetallic compound with Mg and improves the flat surface corrosion resistance of the plated layer 12. Therefore, the Sn concentration may be 0.01% or more or 0.05% or more. However, when the Sn concentration is excessive, flat surface corrosion resistance deteriorates. Therefore, the Sn concentration is set to 1.00% or less. The Sn concentration may be 0.80% or less, 0.60% or less, 0.50% or less, or

[0032] <Cu, Ti, Cr, Nb, Zr, Mn, Mo, Ag, and Li: 0 to 1.00% each> The concentration of each of Cu, Ti, Cr, Nb, Zr, Mn, Mo, Ag, and Li may be 0%. On the other hand, they contribute to improvement in sacrificial corrosion resistance. Therefore, the concentration of each of these elements may be 0.001% or more. On the other hand, when the concentration of each of these elements is excessive, flat surface corrosion resistance is deteriorated. Therefore, the concentration of each of these elements is set to 1.00% or less. The concentration of each of these elements may be 0.90% or less, 0.80% or less, 0.50% or less, 0.30% or less, or 0.20% or less.

[0033] <Bi, V, Co, and In: 0 to 1.00% each> The concentration of each of Bi, V, Co, and In may be 0%. On the other hand, each of these elements contributes to improvement in sacrificial corrosion resistance. Therefore, the concentration of each of these elements may be 0.001% or more or 0.01% or more. On the other hand, when the concentration of these elements is excessive, flat surface corrosion resistance is deteriorated. Therefore, the concentration of each of Bi, V, Co, and In is set to 1.00% or less. The concentration of each of these elements may be 0.90% or less, 0.50% or less, and 0.30% or less.

[0034] <La and Ce: 0 to 0.50% each> The concentrations of La and Ce may be 0%. On the other hand, La and Ce contribute to improvement in sacrificial corrosion resistance. Therefore, the concentration of each of these elements may be 0.001% or more. On the other hand, when the concentration of each of La and Ce is excessive, flat surface corrosion resistance deteriorates. Therefore, the concentration of each of these elements is set to 0.50% or less. The concentration of each of these elements may be 0.30% or less, 0.20% or less, or 0.10% or less.

[0035] <P: 0 to 0.50%> The P concentration may be 0%. On the other hand, P contributes to improvement in sacrificial corrosion resistance. Therefore, the P concentration may be 0.001% or more, 0.005% or more, or 0.01% or more. On the other hand, when the P concentration is excessive, flat surface corrosion resistance is deteriorated. Therefore, the P concentration is set to 0.50% or less. The P concentration may be 0.30% or less.

[0036] <B, Y, and Sr: 0 to 0.50% each> The concentration of each of B, Y, and Sr may be 0%. On the other hand, B, Y, and Sr contribute to improvement in sacrificial corrosion resistance. Therefore, the concentration of each of these elements may be 0.001% or more, 0.005% or more, or 0.01% or more. On the other hand, when the concentration of each of B, Y, and Sr is excessive, flat surface corrosion resistance deteriorates. Therefore, the concentration of each of these elements is set to 0.50% or less. The concentration of each of these elements may be 0.40% or less and 0.30% or less.

[0037] <Total of Sb, Pb, Cu, Sn, Ti, Cr, Nb, Zr, Mn, Mo, Ag, Li, Bi, V, Co, In, La, Ce, B, Y, P, and Sr: 0 to 5.00%> The total of these elements is 0 to 5.00%. When the total exceeds 5.00%, flat surface corrosion resistance or sacrificial corrosion resistance may be deteriorated.

[0038] <Balance: Zn and impurities> The balance of the chemical composition of the plated layer 12 according to the present embodiment is 50.0 to 98.0% of Zn and impurities. Since Zn is an element that brings flat surface corrosion resistance and sacrificial corrosion resistance to the plated layer 12, the plated layer 12 needs to contain 50.0% or more of Zn. Zn may be 60.0% or more, 65.0% or more, 70.0% or more, 80.0% or more, or 90.0% or more. Also, Zn is set to 98.0% or less. The impurities are elements mixed from a raw material or the like mainly in a manufacturing process. The total concentration of impurities is usually 0.5% or less, but may be 0.4% or less, 0.3% or less, 0.2% or less, or 0.1% or less in total. For various reasons such as reduction in raw material cost, raw materials having a relatively large content of elements including Zn other than the above-described elements may be intentionally used. Therefore, in the present embodiment, these elements (elements other than the above-described elements, including Zn) are all regarded as impurity elements regardless of mixing or intentional addition of these elements.

[0039] In addition, the plated layer 12 of the plated steel material 1 according to the present embodiment may contain elements other than the alloying elements, Zn, and impurities described above.

[0040] The chemical composition of the plated layer 12 is measured with the following method. First, an acid solution in which the plated layer 12 is peeled off and dissolved is obtained using an acid containing an inhibitor that suppresses corrosion of the base steel material 11. Next, the obtained acid solution is subjected to ICP analysis. Thereby, the chemical composition of the plated layer 12 can be determined. As the inhibitor, for example, HIBIRON (A-6) which is a pickling corrosion inhibitor can be used. Specifically, as an acid containing an inhibitor, a 10% aqueous hydrochloric acid solution containing HIBIRON (A-6) at a concentration of 1% can be used.

[0041] Next, the plated layer 12 of the plated steel material 1 of the present embodiment will be described. There is a portion where a plurality of cracks are observed on at least a part of the surface of the plated layer 12 of the present embodiment. The portion where a plurality of cracks 101 are observed is preferably in a bent inner side 24A of the bent portion 24. In addition, the portion where a plurality of cracks are observed may be in a bent-back portion 22A of the plated steel material 1.

[0042] Here, “a plurality of cracks are observed” means that the external appearance of the cracks 101 can be recognized when the surface of the plated layer 12 is observed with the naked eye, a magnifying glass, an optical microscope, or an electron microscope. Also, the “portion where a plurality of cracks are observed” may be any portion where a plurality of cracks 101 are present adjacent to each other on the surface of the plated layer 12, and the size and shape of the portion are not particularly limited.

[0043] Further, in the present embodiment, the bent portion 24 refers to a part where the radius R of the bent inner side 24A is 10 times or less the sheet thickness t of the plated steel material 1 (that is, R < 10t). The bending angle of the bent portion 24 is not particularly limited, and may be, for example, 10° or more, 30° or more, 45° or more, 60° or more, 90° or more, or 120° or more, and is not limited to these exemplary angles.

[0044] Furthermore, in the present embodiment, the bent-back portion 22A refers to a part subjected to unbending after performing bending in which the bending radius R is 10 times or less the sheet thickness t of the plated steel material (that is, R < 10t).

[0045] In the present embodiment, even if there is a portion where a plurality of cracks 101 are observed on at least a part of the plated layer 12, the plurality of cracks 101 are observed, and it is not necessary to satisfy the requirements described later (specifically, Requirement 1: the proportion of the number of cracks 101 inclined at an angle of 35° to 55° with respect to the thickness direction of the plated layer 12 is 80% or more; Requirement 2: the proportion of the number of intervals Lc satisfying a formula (1) is 80% or more; and Requirement 3: the average value of the widths Wc of the cracks 101 at a thickness position away from the surface of the plated layer 12 by T / 2 is 10 pm or less). When a plurality of cracks 101 are observed in at least a part of the plated layer 12 and measured according to the measurement method described later, it is sufficient if a portion where the plurality of cracks 101 satisfying the requirements described later are observed is present.

[0046] When a plurality of cracks 101 are observed on the bent inner side 24A of the bent portion 24 having a bending radius R < 10t and measured according to the measurement method described later, a portion where a plurality of cracks 101 satisfying the requirements described later are observed is present. Similarly, when a plurality of cracks 101 are observed on one surface of the bent-back portion 22A subjected to unbending after bending of a bending radius R < 10t (the surface that was the bent inner side 24A in the first bending) and measured according to the measurement method described later, a portion where a plurality of cracks 101 satisfying the requirements described later are observed is present. In addition, even if the radius R of the bent inner side 24A is less than 10 times the sheet thickness t of the plated steel material 1, a portion where a plurality of cracks 101 are observed in the bent inner side 24A, and a plurality of cracks 101 satisfying the requirements described later are observed may be present. Similarly, regardless of the bending radius R, when a plurality of cracks 101 are observed on one surface or both surfaces of the bent-back portion 22A subjected to unbending after bending and measured according to the measurement method described later, a portion where a plurality of cracks 101 satisfying the requirements described later are observed may be present.

[0048] For example, a plated steel material 1 illustrated in FIG. 2A has a hat-shaped cross section, is provided with a flat portion 21, a vertical wall portion 22, and a flange portion 23, and is provided with a bent portion 24 between the flat portion 21 and the vertical wall portion 22. Moreover, there is a portion where a plurality of cracks 101 are observed on the surface of the bent inner side 24A of the bent portion 24.

[0049] FIG. 2B is an enlarged cross-sectional view of a bent portion 24 of the hatshaped plated steel material 1 illustrated in FIG. 2A. As illustrated in FIG. 2B, a plurality of cracks 101 occur in the plated layer 12 on the bent inner side 24A. The extending direction of these cracks 101 is substantially along the extending direction of the bent portion 24 (the direction perpendicular to the paper surface of FIGS. 2A and 2B). That is, the extending direction of these cracks 101 is substantially the same as the extending direction of the bent portion 24.

[0050] In addition, a plated steel material 1 illustrated in FIG. 3 has a hat-shaped cross section, is provided with a flat portion 21, a vertical wall portion 22, and a flange portion 23, and is provided with a bent-back portion 22A at the center portion of the width of the vertical wall portion 22. The bent-back portion 22A is formed by unbending the bent portion. Moreover, there is a portion where a plurality of cracks 101 are observed on the surface of the portion of the bent-back portion 22A that was on the bent inner side of the bent portion.

[0051] FIG. 4 is a partially enlarged view of the surface of the plated layer 12, and illustrates a portion where a plurality of cracks 101 are observed. As illustrated in FIG. 4, the plurality of cracks 101 extend in substantially the same direction, and are arranged substantially aligned in a direction orthogonal to the extending direction of the crack 101. The extending direction of the crack 101 is substantially the same as the extending direction of the bent portion 24. The crack 101 may be linear, but may have an indefinite shape as illustrated in FIG. 4.

[0052] Next, the form of the crack 101 in the cross section of the plated layer 12 will be described. FIG. 5 illustrates a cross section perpendicular to a direction in which the plurality of cracks 101 extend and perpendicular to the surface of the plated steel material 1. FIG. 5 is a cross-sectional view of the plated layer 12 in observation region K. The observation region K is a cross section of the plated steel material 1 that is substantially perpendicular to the direction in which the plurality of cracks 101 extend and has a length of 200 pm in a direction parallel to the surface of the plated steel material 1. The plurality of cracks 101 are observed in the plated layer 12 in the observation region K. In addition, the number of observation regions K in the plated layer 12 is set to five. A procedure for preparing observation regions K is as follows. An observation sample (for example, a size of sheet thickness x 100 mm x 50 mm) is cut out by machining at the time of cross-sectional observation so as not to damage the plated layer 12, and embedded in a resin to prepare a test piece. After embedding the resin, the test piece is cut and polished to mirror polishing finish to expose the cross sections of the plated layer and the base steel material. When cutting, the test piece is cut in a direction perpendicular to the surface of the plated steel material 1 (the plated layer 12). The cross section of the test piece is observed with a scanning electron microscope (SEM), observation regions K are set, and then the cracks in the cross section of the plated layer are observed.

[0054] Although FIG. 5 illustrates a state in which tips of all the cracks 101 in the observation region K reach an interface between the base steel material 11 and the plated layer 12, the present invention is not limited thereto, and there may be a crack 101 whose tip does not reach the interface between the base steel material 11 and the plated layer 12 as illustrated in FIG. 2B. As illustrated in FIG. 2B, the crack 101 whose tip does not reach the interface between the base steel material 11 and the plated layer 12 is also included as a measurement target.

[0055] In the present embodiment, in the portion where a plurality of cracks 101 are observed, the direction in which the plurality of cracks 101 extend in the depth direction of the plated layer 12 is inclined with respect to the thickness direction of the plated layer 12, and the interval Lc between the adjacent cracks 101 is substantially constant. The presence of the cracks 101 at such regular intervals improves the corrosion resistance of the processed portion, that is, the bent inner side 24A of the bent portion 24 and the bent-back portion 22A.

[0056] In the present embodiment, with respect to the direction of the crack 101 extending in the depth direction of the plated layer 12, the proportion of the number of the cracks 101 inclined at an angle 0 of 35° to 55° with respect to the thickness direction of the plated layer 12 among all the cracks 101 observed in the five observation regions K is 80% or more. When the proportion of the number of the cracks 101 having an inclination angle 0 in the range of 35° to 55° is 80% or more in the observation region K, a compressive stress applied to the plated layer 12 during bending can be relaxed, the occurrence of irregular cracks 101 is suppressed, and the corrosion resistance of the bent inner side 24A and the bent-back portion 22A of the bent portion 24 is improved. The proportion of the number of the cracks 101 having an angle 0 of 35° to 55° may be 85% or more, 90% or more, 95% or more, or 98% or more.

[0057] In addition, preferably, the proportion of the number of the cracks 101 having an inclination angle 0 in the range of 40° to 50° may be 70% or more. The proportion of the number of the cracks 101 having an angle 0 of 40° to 50° may be 80% or more, 85% or more, 90% or more, 95% or more, or 98% or more.

[0058] The cross-sectional shape of the crack 101 is not particularly limited, and may be a substantially V shape as illustrated in FIG. 5, or may be a crack having an indefinite cross-sectional shape, such as a crack 101A drawn at the right end of FIG. 5.

[0059] As for the inclination angle 0 of the crack 101, as illustrated in FIGS. 5 and 6, when an inclined imaginary line L1 connecting a central position of width W1 of an opening part of the crack 101 on the surface of the plated layer 12 (a width-directional central position of width W1 of an opening part) and a central position of an opening width W2 of the crack 101 on the base steel material 11 side (a width-directional central position of an opening width W2) is set, an angle 0 formed by the imaginary line Li and the thickness direction of the plated layer 12 is defined as an inclination angle of the crack 101. Note that W1 / 2 and W2 / 2 in FIG. 6 indicate 1 / 2 length of the widths W1 and W2 of the opening part. When the tip of the crack 101 does not reach the interface between the base steel material 11 and the plated layer 12, a line connecting the position of the tip and the central position of width W1 of the opening part of the crack on the surface of the plated layer 12 (the width-directional central position of width W1 of the opening part) may be defined as an inclined imaginary line L1.

[0060] Next, the interval Lc between the cracks 101 will be described. When an interval between the adjacent cracks 101 is Lc and the thickness of the plated layer 12 is T, the proportion of the number of intervals Lc satisfying the following formula (1) among all the intervals Lc observed in the five observation regions K needs to be 80% or more. When Lc is less than 0.3T, the interval Lc between the cracks 101 is too narrow, the cracks 101 are rather likely to have irregular intervals, and the corrosion resistance of the processed portion is deteriorated. When Lc exceeds 1.6T, the interval Lc between the cracks 101 is too wide, and the cracks 101 are likely to have irregular intervals. Furthermore, when the proportion of the number of intervals Lc satisfying the following formula (1) is less than 80%, the occurrence of the cracks 101 at irregular intervals cannot be sufficiently suppressed, and the corrosion resistance of the processed portion may be deteriorated. In order to further improve the corrosion resistance of the processed portion, among all the intervals Lc observed in the five observation regions K, the proportion of the number of intervals Lc satisfying the following formula (2) is preferably 80% or more, and the proportion of the number of intervals Lc satisfying the following formula (3) is more preferably 80% or more. In order to set the proportion of the number of intervals Lc satisfying the following formula (2) or (3) to 80% or more, as described above, the Al content and the Mg content of the plated layer 12 may be set to more preferable ranges, and the manufacturing conditions may be limited to preferable ranges. As a result, the processed portion corrosion resistance and the sacrificial corrosion resistance are further enhanced. The proportion of the number of intervals Lc satisfying the following formula (1) may be 85% or more, 90% or more, or 95% or more. Similarly, the proportion of the number of intervals Lc satisfying the following formula (2) may be 85% or more, 90% or more, or 95% or more, and the proportion of the number of intervals Lc satisfying the following formula (3) may be 85% or more, 90% or more, or 95% or more.

[0062] 0.3T < Lc < 1.6T... (1) 0.5T < Lc < 1.4T... (2) 0.5T < Lc < 1.2T... (3)

[0063] As illustrated in FIGS. 5 and 6, the interval Lc between the cracks 101 is an interval between the central positions of widths W1 of the opening parts of each of the cracks 101 (the width-directional central positions of widths W1 of the opening parts at the time of the cross-sectional observation) on the surface of the plated steel material 1 (that is, the surface of the plated layer 12) in the five observation regions K. Also, the proportion of the number of the cracks 101 satisfying each of formulas (1) to (3) is the proportion obtained by setting the number of intervals of all the cracks 101 observed in the five observation regions K as a denominator and setting the number of intervals satisfying each formula (that is, formula (1), formula (2), or formula (3)) as a numerator. For example, in FIG. 5, the total of four cracks 101 are observed. In addition, the total of three intervals Lc between the cracks are observed.

[0064] Next, in the five observation regions K, the average value of the widths Wc of the cracks at a thickness position away from the surface of the plated layer 12 by T / 2 (hereinafter, referred to as T / 2 position.) needs to be 10 pm or less. When the width Wc of the crack 101 exceeds 10 pm, the corrosion resistance of the processed portion is deteriorated, which is not preferable. The width Wc of the crack 101 may be 5 pm or less or 3 pm or less. The lower limit of the width Wc of the crack 101 is not particularly limited, and may be about 0 pm, that is, may be such a width that a trace of cracking of the plated layer 12 can be observed in the observation region K.

[0065] Next, when the plated layer 12 contains a Mg2Sn phase, the substrate corrosion resistance of the plated steel material 1 is further improved, and thus it is preferable that the plated layer 12 contains a Mg2Sn phase. Since the amount of the Mg2Sn phase is small, the presence thereof is confirmed by X-ray diffraction measurement. In order to include the Mg2Sn phase, in the chemical composition of the plated layer 12, Sn is preferably Sn: 0.02 to 1.0%.

[0066] The X-ray diffraction measurement is performed by a 0-20 method. An X-ray diffractometer is RINT1500 manufactured by Rigaku Corporation or an apparatus having performance equal to or higher than that of RINT1500. As an X-ray source, a Ka ray of a Cu tube is used. X-ray output conditions are a voltage of 40 kV and a current of 150 mA. The measurement range is 20 = 10 to 30° and 0.02° steps. When a diffraction peak is detected at 23.4 ± 0.3°, it is determined that the Mg2Sn phase is present.

[0067] The thickness of the plated layer 12 may be, for example, within a range of 5 to 100 ^m. When the thickness of the plated layer 12 is 5 ^m or more, flat surface corrosion resistance and sacrificial corrosion resistance of the plated steel material 1 can be further enhanced. On the other hand, when the thickness is 100 ^m or less, regular cracks 101 are likely to occur, and corrosion resistance of the processed portion can be improved. The thickness of the plated layer 12 may be 10 ^m or more, 25 ^m or more, or 30 ^m or more. The thickness of the plated layer 12 may be 70 ^m or less, 60 ^m or less, or 50 ^m or less.

[0068] Next, the method for manufacturing a plated steel material 1 according to the present embodiment will be described, but the method for manufacturing a plated steel material 1 according to the present embodiment is not particularly limited. For example, according to the manufacturing conditions described below, the plated steel material 1 according to the present embodiment can be obtained.

[0069] As described above, the plated steel material 1 of the present embodiment is manufactured by subjecting a plated steel sheet as a material to forming working such as pressing, roll forming, and bending. A plated steel sheet is manufactured by forming a plated layer on a sheet surface by a hot-dip plating method and controlling cooling conditions after being pulled up from a plating bath. Then, the plated steel material 1 of the present embodiment is manufactured by subjecting the plated steel sheet to forming working. When the plated steel sheet is subjected to forming working, compressive stress is applied to the plated layer 12 at the bent inner side 24A of the bent portion 24, and regular cracks 101 occur. Similarly, regular cracks 101 also occur when bending is performed at the time of forming the bent-back portion 22A. Thus, the plated layer 12 according to the present embodiment is obtained.

[0070] Therefore, in the following description, first, a method for manufacturing a plated steel sheet as a material of the plated steel material 1 will be described.

[0071] In the method for manufacturing a plated steel sheet, a steel sheet is annealed in a reducing atmosphere, the annealed steel sheet is immersed in a hot-dip plating bath, and the steel sheet is pulled up from the hot-dip plating bath to form a plated layer 12 on the sheet surface. Next, the plated layer 12 is cooled at an average cooling rate of 15 to 19 °C / sec while a cooling gas is sprayed at a flux of 30000 to 40000 (L / min / m2) in a range where the temperature of the plated layer 12 reaches 390°C from the bath temperature, and then cooled at an average cooling rate of 20 to 40 °C / sec in a range of 390 to 20°C while a cooling gas is sprayed. Furthermore, after completion of cooling, reheating is performed under conditions of a soaking temperature of 70 to 230°C and a soaking time of 10 to 2000 seconds.

[0072] The steel sheet as a plating original sheet is annealed in a reducing atmosphere. The reducing atmosphere and the annealing conditions are not particularly limited. By this annealing, the oxide present on the sheet surface is removed as much as possible. Subsequently, the steel sheet immediately after annealing is immersed in a hot-dip plating bath. Before immersing the steel sheet in the plating bath, the steel sheet immediately after annealing may be cooled with a cooling gas such as nitrogen until the temperature of the steel sheet reaches about (plating bath temperature + 20)°C.

[0074] The chemical composition of the plating bath may be appropriately adjusted so as to obtain the chemical composition of the plated layer 12 described above. In addition, the temperature of the plating bath is also not particularly limited, and a temperature at which hot-dip plating can be performed can be appropriately selected. For example, the plating bath temperature may be higher than the melting point of the plating bath by about 20°C or more.

[0075] Next, the steel sheet is pulled up from the hot-dip plating bath. The thickness of the plated layer 12 can be controlled by controlling the pulling speed of the steel sheet. If necessary, the steel sheet with the plated layer 12 adhering thereto may be subjected to wiping to control the thickness of the plated layer 12. The thickness of the plated layer 12 is not particularly limited, and can fall, for example, within the range described above.

[0076] Next, the plated layer 12 is cooled. Regarding the cooling, the plated layer 12 is first cooled at an average cooling rate of 15 to 19 °C / sec until the temperature of the plated layer 12 reaches 390°C from the bath temperature. The cooling is performed by, for example, spraying a cooling gas, but the steel sheet being transported is vibrated by setting the flux of the cooling gas at that time to a range of 30000 to 40000 (L / min / m2). When the cooling gas is sprayed for cooling, a plurality of blowing nozzles for the cooling gas may be arranged along the conveying path of the steel sheet, and the cooling gas may be sprayed from the nozzles.

[0077] By spraying a cooling gas of a predetermined flux until the temperature of the plated layer 12 reaches 390°C from the bath temperature, the surface of the plated layer 12 is subcooled and vibrated. As a result, nucleation of phases and microstructures constituting a relatively hard region progresses on the surface of the plated layer 12. Then, by setting the flux of the cooling gas to a range of 30000 to 40000 (L / min / m2), cracks 101 are likely to occur regularly in the subsequent forming working, and the corrosion resistance of the processed portion is improved.

[0078] In addition, when the average cooling rate until the temperature of the plated layer 12 reaches 390°C from the bath temperature is 15 °C / sec or more, the formation of phases and microstructures constituting a relatively hard region on the surface of the plated layer 12 becomes sufficient, a relatively soft region is not excessively precipitated, and cracks 101 are likely to occur regularly during the subsequent forming working. On the other hand, when the average cooling rate is 19 °C / sec or less, the formation of phases and microstructures constituting a relatively hard region on the surface of the plated layer 12 becomes sufficient, and cracks 101 are likely to occur regularly during the subsequent forming working. When the average cooling rate exceeds 19 °C / sec, the entire plated layer is subcooled, the phase and microstructure region constituting the hard region crystallizes not only on the surface of the plated layer but also inside, and it becomes difficult to localize the hard region on the surface of the plated layer.

[0079] Subsequently, the plated layer 12 is cooled in a range of 390 to 20°C at an average cooling rate of 20 to 40°C / sec while a cooling gas is sprayed. Also in this case, a plurality of blowing nozzles for the cooling gas is arranged along the conveying path of the steel sheet, but the flux of the cooling gas during cooling in the range of 390 to 20°C is not particularly limited. After completion of cooling, reheating is performed under conditions of a soaking temperature of 70 to 230°C and a soaking time of 10 to 2000 seconds.

[0080] When the cooling finishing temperature is higher than 20°C, an aging effect on the phases and microstructures constituting a relatively hard region is insufficient, and as a result, a relatively soft region is excessively precipitated, and cracks 101 are not likely to occur regularly. Therefore, cooling at an average rate of 20 °C / sec or more needs to be continued until the temperature reaches 20°C.

[0081] By setting the average cooling rate in the range of 390 to 20°C to 20 °C / sec or more, the formation of phases and microstructures constituting the relatively hard region becomes sufficient, a relatively soft region is not excessively precipitated, and cracks 101 are likely to occur regularly during the subsequent forming working. In addition, when the average cooling rate is 40 °C / sec or less, the formation of phases and microstructures constituting a relatively hard region becomes sufficient, and cracks 101 are likely to occur regularly during the subsequent forming working. When the average cooling rate exceeds 40 °C / sec, pores serving as a driving force for aging precipitation are excessively introduced, and on the contrary, it becomes difficult to control the strengthening state by aging precipitation in the subsequent heat treatment step (reheating). Therefore, the average cooling rate in the range of 390 to 20°C is set to 40 °C / sec or lower.

[0082] The range of 390 to 20°C is cooled at an average cooling rate of 20 to 40 °C / sec, and then reheated. By reheating, formation of a relatively soft region inside the plated layer 12 can be promoted, and a distribution state of the soft regions in the plated layer 12 can be controlled to a preferable state, so that cracks 101 are likely to occur regularly during the subsequent forming working. The reheating after cooling is performed under the conditions of a soaking temperature of 70 to 230°C and a soaking time of 10 to 2000 seconds as described above. More preferably, the reheating is performed under the conditions of a soaking temperature of 120 to 180°C and a soaking time of 120 to 2000 seconds.

[0083] In the cooling in the range of the bath temperature to 390°C and in the range of 390°C to 20°C, the type of cooling gas to be sprayed is not particularly limited, and may be a non-oxidizing gas such as nitrogen, an inert gas such as argon, or air, or a mixed gas thereof.

[0084] When the flux of the cooling gas is controlled, the diameter of the gas nozzle from which the cooling gas is blown out is set, for example, in a range of 1 to 50 mm. The angle formed by the tip of the gas nozzle and the steel material is set, for example, in a range of 70 to 110°, more preferably 90° (right angle). The distance between the tip of the gas nozzle and the steel sheet is set in a range of 30 to 1000 mm.

[0085] Next, the manufactured plated steel sheet is subjected to forming working. The forming working conditions are not particularly limited, and pressing, roll forming working, bending, and the like can be applied. The forming working is preferably a working including bending of at least 10T bending or more. The 10T bending refers to bending in which the bending radius R of the bent inner side 24A of the bent portion 24 is 10 times or less the sheet thickness t of the plated steel sheet (R < 10t). In addition, the forming working may be a working including unbending. The unbending refers to a working in which bending is performed under a condition that the bending radius R is 10t or less, and then unbending is performed.

[0086] The plated steel material 1 of the present embodiment is manufactured by performing forming working. The plated steel material 1 includes a portion where a plurality of cracks 101 are observed in at least a part of the plated layer 12. The plurality of cracks 101 extend in substantially the same direction. Then, in the observation region K, the proportion of the number of cracks 101 inclined at an angle of 35° to 55° is 80% or more, the proportion of the number of intervals Lc satisfying the formula (1) is 80% or more, and the average value of the widths Wc of the cracks 101 at the T / 2 position is 10 pm or less.

[0087] Also, in order for the plated steel material 1 to satisfy the formula (2), in the chemical composition of the plated layer 12, the contents of Al and Mg may be adjusted to Al: 10.0 to 30.0 mass% and Mg: 4.0 to 10.0 mass%, respectively, and the reheating is preferably performed under suitable conditions, that is, under conditions of a soaking temperature of 120 to 180°C and a soaking time of 120 to 2000 seconds.

[0088] Further, in order for the plated steel material 1 to satisfy the formula (3), in the chemical composition of the plated layer 12, the contents of Al and Mg may be adjusted to Al: 15.0 to 30.0 mass% and Mg: 5.0 to 8.0 mass%, respectively, the average cooling rate in the range of 390 to 20°C may be adjusted to 30 °C / sec or more, and the reheating is preferably performed under the conditions of a soaking temperature of 120 to 180°C and a soaking time of 120 to 2000 seconds.

[0089] Furthermore, in order to set the average value of the widths Wc of the cracks 101 to 3 pm or less, the average cooling rate in the range of 390 to 20°C is preferably set to 35 °C / sec or more, and the reheating is preferably performed under conditions of a soaking temperature of 120 to 180°C and a soaking time of 120 to 2000 seconds. Examples

[0090] Hereinafter, examples of the present invention will be described. However, the conditions in examples are merely one condition example adopted to confirm the operability and effects of the present invention. The present invention is not limited to this one condition example. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

[0091] As a base steel sheet which is a plating original sheet, a cold-rolled steel sheet having a sheet thickness of 1.0 mm (steel type A in Table 1-1 and Table 1-2) or a hot-rolled steel sheet having a sheet thickness of 3.2 mm (steel type B in Table 1-1 and Table 1-2) was used. The chemical composition of the base steel sheet was 0.05%C-0.1%Si-0.2%Mn. The base steel sheet was annealed. The annealing conditions were a soaking temperature of 600°C and a soaking time of 2 minutes in a N2-4%H2 atmosphere in which the oxygen concentration was controlled to 20 ppm or less. Next, the annealed base steel sheet was air-cooled with N2 gas to adjust the temperature at the time of being immersed in the plating bath to be (plating bath temperature + 20°C), then, immersed in various hot-dip plating baths, and then lifted at a lifting rate of 20 to 200 mm / sec. At the time of pulling out the base steel sheet, the plating adhesion amount was controlled with a N2 wiping gas. After the base steel sheet was pulled out from the plating bath, the base steel material was cooled under the conditions shown in Table 2-1 and Table 2-2.

[0092] In the cooling in the range of the bath temperature to 390°C and the cooling in the range of 390 to 20°C, a N2 gas was used respectively as the cooling gas. In the cooling in the range of the bath temperature to 390°C, the gas flux was controlled as shown in Table 2-1 and Table 2-2. The diameter of the gas nozzle from which the cooling gas was blown out was 6 mm, the angle formed by the tip of the gas nozzle and the steel sheet was a right angle, and the distance between the tip of the gas nozzle and the steel sheet was 35 mm.

[0093] Further, the plated steel sheet after completion of cooling was reheated under the conditions shown in Table 2-1 and Table 2-2. In this way, a plated steel sheet was manufactured.

[0094] The resulting plated steel sheet was subjected to pressing using a punch and a die to manufacture plated steel materials Nos. 1 to 43 having a hat-shaped cross-sectional view as illustrated in FIG. 2A.

[0095] In the pressing, when the bent portion between the flat portion and the vertical wall portion was used, the bending radius R was adjusted so as to be 3 times the sheet thickness t (3T bending) or 10 times the sheet thickness t (10T bending) of the plated steel sheet. In addition, some plated steel materials were processed by pressing so as to have a hat-shaped cross-sectional view, and then unbending was performed on the bent portion between the flat portion and the vertical wall portion to form a bent-back portion. In the columns of processing in Table 2-1 and Table 2-2, it is indicated as follows.

[0096] A: Bent portion (bending radius R = sheet thickness (mm) x 3 (3T bending)) B: Bent portion (bending radius R = sheet thickness (mm) x 10 (10T bending)) C: Bent-back portion (bent at bending radius R = 5 mm and then unbent)

[0097] The chemical composition of the plated layer was as shown in Table 1-1 and Table 1-2. Furthermore, the processed portion corrosion resistance and sacrificial corrosion resistance of the plated steel material were evaluated, and the results are shown in Table 5-1 and Table 5-2.

[0098] Hereinafter, an evaluation method will be described.

[0099] The chemical composition of the plated layer was measured by immersing a sample cut into a 30 mm x 30 mm size in a 10% HCl aqueous solution to which 1% of an inhibitor (HIBIRON (A-6)) was added to pickle and peel off the plated layer, and ICP analysis was then performed on elements eluted in the aqueous solution. The results are shown in Table 1.

[0100] Further, the presence of the Mg2Sn phase in the plated layer was confirmed by X-ray diffraction measurement. The X-ray diffraction measurement was performed by a 0-20 method. As an X-ray diffractometer, RINT1500 manufactured by Rigaku Corporation was used. As an X-ray source, a Ka ray of a Cu tube was used. X-ray output conditions were a voltage of 40 kV and a current of 150 mA. The measurement range was 20 = 10 to 30° and 0.02° steps. When a diffraction peak was detected at 23.4 ± 0.3°, it was determined that the Mg2Sn phase was present. The presence or absence of the Mg2Sn phase is shown in Table 4-1 and Table 4-2.

[0101] Next, the state of occurrence of cracks in the plated steel material was confirmed. A bent portion or a bent-back portion was cut out from the manufactured plated steel material to obtain a test piece. The size of the test piece was 100 mm in length and 50 mm in width. The test piece was embedded in resin, and then polished to mirror polishing finish to expose the cross sections of the plated layer and the base steel material. The test piece was observed with a scanning electron microscope (SEM) for the state of occurrence of cracks in the cross section of the plated layer. The results are shown in Table 3-1 to Table 4-2.

[0102] A method for confirming cracks was described as follows. The observation region when observing the cross section of the plated layer with a scanning electron microscope (SEM) was a region that is a cross section perpendicular to a direction in which the plurality of cracks extend and perpendicular to the surface of the plated steel material and has a length of 200 pm in a direction parallel to the surface. The number of observation regions K was five.

[0103] Then, the proportion of the number of cracks inclined at an angle 0 of 35° to 55° with respect to the thickness direction of the plated layer was determined among all the cracks observed in the five observation regions. Similarly, the proportion of the number of cracks having an inclination angle 0 in the range of 40° to 50° was determined. The cross-sectional shape of the crack to be measured is not particularly limited, and for example, as illustrated in FIG. 5, not only a crack having a substantially V shape but also a crack having an indefinite cross-sectional shape, such as a crack 101A drawn at the right end of FIG. 5, were targeted for measurement.

[0105] As for the inclination angle 0 of the crack 101, for example, as illustrated in FIGS. 5 and 6, when an inclined imaginary line L1 connecting a central position of the width W1 of the opening part of the crack on the surface of the plated layer (a widthdirectional central position of width W1 of an opening part) and a central position of an opening width W2 of the crack on the base steel material side (a width-directional central position of width W2 of an opening part) is set, an angle 0 formed by the imaginary line L1 and the thickness direction of the plated layer was defined as an inclination angle of the crack 101.

[0106] As illustrated in FIGS. 5 and 6, the interval Lc between the cracks was defined as an interval between the central positions of the widths W1 of the opening parts of the adjacent cracks on the surface of the plated layer in the five observation regions. In addition, the proportion of the number of cracks satisfying each of the formulas (1) to (3) was defined as the proportion of the number to the number of intervals of cracks observed in the five observation regions K.

[0107] Next, as illustrated in FIG. 5, the width Wc of the crack was defined as a width Wc of the crack at T / 2 position. The average value of the widths Wc of all the cracks observed in the five observation regions K was obtained. <Processed portion corrosion resistance> The processed portion corrosion resistance was evaluated as follows. A bent portion or a bent-back portion was cut out from the manufactured plated steel material to obtain a test piece. The size of the test piece was 100 mm in length and 50 mm in width. The longitudinal direction of the test piece was made to coincide with the bending axial direction of the bent portion or the bending axial direction of the bent-back portion. A corrosion acceleration test as defined in 8.1 cyclic neutral salt spray test method of JIS H8502:1999 was performed on a portion where a plurality of cracks were observed in the bent portion or the bent-back portion of the test piece. Then, the number of cycles until red rust occurred was measured in the bent portion or the bent-back portion. The evaluation criteria were as follows, and AAA, AA, and A were regarded as acceptable.

[0109] AAA: Red rust occurrence cycle is 360 cycles or more AA: Red rust occurrence cycle is 240 cycles or more and less than 360 cycles A: Red rust occurrence cycle is 120 cycles or more and less than 240 cycles B: Red rust occurrence cycle is less than 120 cycles

[0110] <Sacrificial corrosion resistance> The sacrificial corrosion resistance was evaluated as follows. The plated steel sheet before being subjected to forming working was cut in a direction perpendicular to the surface of the plated steel sheet using a fine cutter to expose a cut end surface. The cross section of the plated layer and the cross section of the base steel material were exposed on the cut end surface. The cut end surface was subjected to a neutral salt spray test specified in JIS Z2371:2015, and the time (h) when red rust occurred was measured at the cut end surface. The evaluation criteria were as follows, with B regarded as unacceptable, and AAA, AA, and A regarded as acceptable.

[0111] AAA: 2400 h or more AA: 1500 h or more and less than 2400 h A: 720 h or more and less than 1500 h B: Less than 720 h

[0112] As shown in Tables 1-1 to 5-1, in Nos. 1 to 28 as invention examples, a portion where a plurality of cracks were observed in the bent portion or the bent-back portion was confirmed. The plurality of cracks extended in substantially the same direction, the extending direction of each crack was along the longitudinal direction of the bent portion or the longitudinal direction of the bent-back portion, and the cracks were aligned with each other along the direction orthogonal to the crack propagation direction. In addition, the chemical composition of the plated layer and the definition of cracks were within the scope of the present invention. As a result, the processed portion corrosion resistance and sacrificial corrosion resistance of the plated layer were excellent.

[0113] In Nos. 1, 2, 4, 6, 8 to 24, and 26 to 28, the proportion of the number of cracks inclined at an angle of 40° to 50° with respect to the thickness direction of the plated layer was 80% or more, and the processed portion corrosion resistance and the sacrificial corrosion resistance were good.

[0114] Further, in Nos. 2, 6, 10, 11, 18, and 28, the proportion of the number of the interval Lc between the cracks satisfying the formula (2) was 80% or more. Furthermore, in Nos. 1, 8, 9, 12 to 17, 19 to 24, 26, and 27, the proportion of the number of the interval Lc between the cracks satisfying the formula (2) was 80% or more, and the proportion of the number of the interval Lc between the cracks satisfying the formula (3) was 80% or more. In all of these Examples, the processed portion corrosion resistance and the sacrificial corrosion resistance were particularly good.

[0115] On the other hand, in No. 29 as a comparative example, the Mg concentration in the plated layer was insufficient. In addition, the proportion of the number of cracks inclined at an angle of 35° to 55° with respect to the thickness direction of the plated layer was less than 80%, and the proportion of the number of the interval Lc between the cracks satisfying the formula (1) was less than 80%. As a result, the processed portion corrosion resistance and the sacrificial corrosion resistance were deteriorated.

[0116] In No. 30, the Mg concentration in the plated layer was excessive. In addition, the proportion of the number of cracks inclined at an angle of 35° to 55° with respect to the thickness direction of the plated layer was less than 80%, and the proportion of the number of the interval Lc between the cracks satisfying the formula (1) was less than 80%, and the width Wc of the crack exceeded 10 pm. As a result, the processed portion corrosion resistance was deteriorated.

[0117] In Nos. 31 and 39, the reheating temperature was low. As a result, cracks were not likely to occur regularly during forming working, and therefore the proportion of the number of cracks inclined at an angle of 35° to 55° with respect to the thickness direction of the plated layer was less than 80%, the proportion of the number of the interval Lc between the cracks satisfying the formula (1) was less than 80%, and the width Wc of the crack exceeded 10 pm. As a result, the processed portion corrosion resistance was deteriorated.

[0118] In No. 32, the Al concentration in the plated layer was insufficient. In addition, the proportion of the number of cracks inclined at an angle of 35° to 55° with respect to the thickness direction of the plated layer was less than 80%, and the proportion of the number of the interval Lc between the cracks satisfying the formula (1) was less than 80%, and the width Wc of the crack exceeded 10 pm. The plurality of cracks occurred in almost one place intensively and were not regular. As a result, the processed portion corrosion resistance was deteriorated.

[0119] In No. 33, the Al concentration in the plated layer was excessive. In addition, the proportion of the number of cracks inclined at an angle of 35° to 55° with respect to the thickness direction of the plated layer was less than 80%, and the proportion of the number of the interval Lc between the cracks satisfying the formula (1) was less than 80%, and the width Wc of the crack exceeded 10 pm. As a result, the processed portion corrosion resistance was deteriorated.

[0120] In No. 34, the average cooling rate in the range of 390 to 20°C was insufficient. As a result, cracks were not likely to occur regularly during forming working. Therefore, the proportion of the number of cracks inclined at an angle of 35° to 55° with respect to the thickness direction of the plated layer was less than 80%, and the proportion of the number of the interval Lc between the cracks satisfying the formula (1) was less than 80%, and the width Wc of the crack exceeded 10 pm. As a result, the processed portion corrosion resistance was deteriorated.

[0121] In No. 35, the cooling finishing time was set to 45°C in cooling from 390°C. As a result, cracks were not likely to occur regularly during forming working, and therefore the proportion of the number of cracks inclined at an angle of 35° to 55° with respect to the thickness direction of the plated layer was less than 80%, the proportion of the number of the interval Lc between the cracks satisfying the formula (1) was less than 80%, and the width Wc of the crack exceeded 10 pm. As a result, the processed portion corrosion resistance was deteriorated.

[0122] In No. 36, the average cooling rate in the range of the bath temperature to 390°C was insufficient. As a result, cracks were not likely to occur regularly during forming working. Therefore, the proportion of the number of cracks inclined at an angle of 35° to 55° with respect to the thickness direction of the plated layer was less than 80%, and the proportion of the number of the interval Lc between the cracks satisfying the formula (1) was less than 80%, and the width Wc of the crack exceeded 10 pm. As a result, the processed portion corrosion resistance was deteriorated.

[0123] In No. 37, the flux of the cooling gas in the range of the bath temperature to 390°C was excessive. As a result, cracks were not likely to occur regularly during forming working. Therefore, the proportion of the number of cracks inclined at an angle of 35° to 55° with respect to the thickness direction of the plated layer was less than 80%, and the proportion of the number of the interval Lc between the cracks satisfying the formula (1) was less than 80%, and the width Wc of the crack exceeded 10 pm. As a result, the processed portion corrosion resistance was deteriorated. In No. 38, the reheating time was 2010 seconds. As a result, cracks were not likely to occur regularly during forming working, and therefore the proportion of the number of cracks inclined at an angle of 35° to 55° with respect to the thickness direction of the plated layer was less than 80%, the proportion of the number of the interval Lc between the cracks satisfying the formula (1) was less than 80%, and the width Wc of the crack exceeded 10 pm. As a result, the processed portion corrosion resistance was deteriorated.

[0125] In No. 40, the reheating temperature was high. As a result, cracks were not likely to occur regularly during forming working, and therefore the proportion of the number of cracks inclined at an angle of 35° to 55° with respect to the thickness direction of the plated layer was less than 80%, the proportion of the number of the interval Lc between the cracks satisfying the formula (1) was less than 80%, and the width Wc of the crack exceeded 10 pm. As a result, the processed portion corrosion resistance was deteriorated.

[0126] In No. 41, the average cooling rate in the range of the bath temperature to 390°C was excessive. As a result, cracks were not likely to occur regularly during forming working. Therefore, the proportion of the number of cracks inclined at an angle of 35° to 55° with respect to the thickness direction of the plated layer was less than 80%, and the proportion of the number of the interval Lc between the cracks satisfying the formula (1) was less than 80%, and the width Wc of the crack exceeded 10 pm. As a result, the processed portion corrosion resistance was deteriorated. In No. 42, the reheating time was 0 seconds. As a result, cracks were not likely to occur regularly during forming working, and therefore the proportion of the number of cracks inclined at an angle of 35° to 55° with respect to the thickness direction of the plated layer was less than 80%, the proportion of the number of the interval Lc between 5 the cracks satisfying the formula (1) was less than 80%, and the width Wc of the crack exceeded 10 pm. As a result, the processed portion corrosion resistance was deteriorated.

[0128] In No. 43, the average cooling rate in the range of 390 to 20°C was excessive. 10 As a result, cracks were not likely to occur regularly during forming working. Therefore, the proportion of the number of cracks inclined at an angle of 35° to 55° with respect to the thickness direction of the plated layer was less than 80%, and the proportion of the number of the interval Lc between the cracks satisfying the formula (1) was less than 80%, and the width Wc of the crack exceeded 10 pm. As a result, the 15 processed portion corrosion resistance was deteriorated.

[0129] No. Classification Steel type Chemical composition of plated layer (mass%) (balance: impurities) Zn Al Mg Fe Si Ca Sn Others Element (mass%) Total of Sb to Sr (mass%) 1 Invention Example A 60.2 30.0 8.0 0.9 0.4 0.30 0.05 - - - 2 Invention Example A 80.0 14.4 4.3 0.2 - - 0.06 Nb 0.88 0.94 3 Invention Example A 88.2 10.0 1.3 0.1 - - - V 0.33 0.33 4 Invention Example A 85.4 10.1 4.0 0.2 - - - Ce 0.20 0.20 5 Invention Example A 97.6 1.0 1.0 0.1 - - - La Ce 0.10 0.11 0.21 6 Invention Example A 74.2 18.7 5.8 0.1 0.1 0.08 0.05 In 0.82 0.87 7 Invention Example A 93.6 5.0 1.0 0.2 - - 0.05 In Bi 0.10 0.10 0.25 8 Invention Example A 75.1 17.8 6.1 0.1 0.1 0.09 0.06 Ni 0.55 0.61 9 Invention Example A 74.2 19.0 6.0 0.1 0.1 0.10 0.05 P 0.29 0.34 10 Invention Example A 85.1 10.0 4.1 0.2 - - - B 0.45 0.45 11 Invention Example A 83.4 11.8 4.0 0.2 - - 0.05 Sr 0.42 0.47 12 Invention Example A 72.5 18.9 7.4 0.4 0.1 0.19 0.20 Zr 0.21 0.41 13 Invention Example A 69.3 19.9 8.0 0.1 2.0 0.52 0.07 - - 0.07 14 Invention Example A 79.4 15.0 5.0 0.3 0.1 - - Ag 0.11 0.11 15 Invention Example A 69.6 22.5 6.1 0.5 0.5 0.28 0.07 Cr 0.38 0.45 16 Invention Example A 68.5 23.5 7.2 0.2 0.2 0.20 0.05 - - 0.05 17 Invention Example B 74.3 19.1 5.9 0.1 0.1 0.08 0.06 Pb 0.30 0.36 18 Invention Example A 82.8 12.0 4.1 0.1 - - 0.05 Bi 0.89 0.94 19 Invention Example A 73.3 18.9 7.2 0.1 0.1 0.11 0.06 Cu 0.10 0.16 20 Invention Example A 71.3 20.0 8.1 0.1 0.1 0.12 - Ti 0.19 0.19 21 Invention Example A 71.3 20.1 7.9 0.2 0.2 0.10 0.05 Mo 0.10 0.15 22 Invention Example A 67.2 24.2 7.1 0.5 0.2 0.21 0.06 Mn 0.45 0.51 [Table 1-2] No. Classification Steel type Chemical composition of plated layer (mass%) (balance: impurities) Zn Al Mg Fe Si Ca Sn Others Element (mass%) Total of Sb to Sr (mass%) 23 Invention Example A 70.3 21.0 7.3 0.3 0.5 0.18 0.05 Y 0.22 0.27 24 Invention Example A 64.5 26.7 7.0 0.2 0.3 0.21 0.05 Co 0.90 0.95 25 Invention Example A 68.2 28.2 2.2 0.9 0.3 - 0.05 - - 0.05 26 Invention Example A 69.8 22.1 6.9 0.2 0.2 0.10 0.07 Sb 0.49 0.56 27 Invention Example A 74.1 19.0 6.0 0.3 0.1 0.23 0.05 Sr Sb 0.10 0.10 0.25 28 Invention Example A 66.1 25.1 6.9 0.6 0.3 0.20 - Li 0.71 0.71 29 Comparative Example A 92.9 6.0 0.7 0.2 0.1 - - - - - 30 Comparative Example A 80.6 7.0 12.0 0.2 0.1 - - - - - 31 Comparative Example A 71.4 20.0 8.1 0.1 0.1 0.12 - - - - 32 Comparative Example A 97.8 0.8 1.1 0.2 - - - - - - 33 Comparative Example A 55.3 33.0 7.0 4.5 - - - - - - 34 Comparative Example A 88.7 10.0 1.1 0.1 - - - - - - 35 Comparative Example A 71.5 20.0 8.0 0.1 0.2 0.10 - - - - 36 Comparative Example A 86.6 10.0 2.8 0.5 - - - - - - 37 Comparative Example A 86.6 10.1 3.0 0.2 - - - - - - 38 Comparative Example A 88.8 10.0 1.0 0.1 - - - - - - 39 Comparative Example A 82.6 16.1 1.2 0.1 - - - - - - 40 Comparative Example A 86.7 10.0 3.0 0.1 0.1 - - - - - 41 Comparative Example A 85.7 12.1 2.0 0.1 - - - - - - 42 Comparative Example A 75.9 16.0 7.9 0.1 - - - - - - 43 Comparative Example A 88.8 10.0 1.0 0.1 - - - - - - Underlined portions indicate that those fall outside the scope of the present invention. [Table 2-1] No. Classification Plating bath temperature Cooling 1 Bath temperature to 390°C Cooling 2 390°C to cooling finishing temperature Reheating Working (°C) Average cooling rate (°C / s) Flux (L / min / m2) Average cooling rate (°C / s) Cooling finishing temperature (°C) Temperature (°C) Time (s) 1 Invention Example 680 15 40000 40 20 120 2000 A 2 Invention Example 460 15 40000 35 20 120 140 A 3 Invention Example 460 15 40000 35 20 120 120 A 4 Invention Example 460 15 30000 20 20 100 20 A 5 Invention Example 460 15 30000 20 20 70 10 A 6 Invention Example 520 15 40000 20 20 120 180 A 7 Invention Example 460 15 30000 20 20 120 10 B 8 Invention Example 520 15 40000 30 20 120 230 A 9 Invention Example 520 15 40000 40 20 120 180 A 10 Invention Example 460 15 40000 35 20 120 140 A 11 Invention Example 460 15 30000 20 20 120 140 A 12 Invention Example 500 15 40000 30 20 120 190 A 13 Invention Example 680 15 40000 30 20 120 190 A 14 Invention Example 460 15 40000 40 20 120 120 A 15 Invention Example 530 19 30000 40 20 120 190 A 16 Invention Example 600 15 40000 30 20 120 190 A 17 Invention Example 520 15 40000 40 20 120 180 B 18 Invention Example 420 15 40000 35 20 120 140 A 19 Invention Example 520 15 40000 40 20 120 230 A 20 Invention Example 520 15 40000 40 20 120 190 A 21 Invention Example 520 15 40000 40 20 120 190 A 22 Invention Example 600 19 40000 30 20 120 190 C No. Classification Plating bath temperature Cooling 1 Bath temperature to 390°C Cooling 2 390°C to cooling finishing temperature Reheating Working (°C) Average cooling rate (°C / s) Flux (L / min / m2) Average cooling rate (°C / s) Cooling finishing temperature (°C) Temperature (°C) Time (s) 23 Invention Example 660 15 40000 40 20 120 190 A 24 Invention Example 600 15 40000 40 20 120 180 A 25 Invention Example 660 15 30000 20 20 100 20 A 26 Invention Example 600 15 40000 40 20 120 180 A 27 Invention Example 520 15 40000 40 20 120 180 A 28 Invention Example 600 15 30000 35 20 100 20 A 29 Comparative Example 460 15 30000 20 20 70 10 A 30 Comparative Example 460 15 30000 20 20 70 10 A 31 Comparative Example 480 15 30000 20 20 60 10 A 32 Comparative Example 460 15 30000 20 20 70 10 A 33 Comparative Example 720 15 30000 20 20 70 10 A 34 Comparative Example 480 15 30000 15 20 70 10 A 35 Comparative Example 480 15 30000 20 45 120 10 A 36 Comparative Example 420 13 30000 20 20 70 10 A 37 Comparative Example 420 15 90000 20 20 70 10 A 38 Comparative Example 480 15 30000 20 20 70 2010 A 39 Comparative Example 480 15 30000 20 20 60 10 A 40 Comparative Example 480 15 30000 20 20 240 10 A 41 Comparative Example 480 21 30000 20 20 70 10 A 42 Comparative Example 480 15 30000 20 20 70 0 A 43 Comparative Example 480 15 30000 45 20 70 10 A Underlined portions indicate that those fall outside the range of the preferred manufacturing conditions. No. Classification Thickness of plated layer ifm> Microstructure of plated layer Proportion of the number of cracks at inclination angle of 35° to 55° (%) Proportion of the number of cracks at inclination angle of 40° to 50° (%) 1 Invention Example 25 100 100 2 Invention Example 25 100 100 3 Invention Example 25 100 78 4 Invention Example 49 100 80 5 Invention Example 25 80 70 6 Invention Example 24 100 80 7 Invention Example 24 90 75 8 Invention Example 70 100 100 9 Invention Example 10 100 100 10 Invention Example 25 100 100 11 Invention Example 26 100 100 12 Invention Example 25 100 100 13 Invention Example 25 100 100 14 Invention Example 25 100 100 15 Invention Example 31 100 100 16 Invention Example 25 100 100 17 Invention Example 26 100 100 18 Invention Example 25 100 100 19 Invention Example 33 100 100 20 Invention Example 25 100 100 21 Invention Example 25 100 100 22 Invention Example 31 100 100 No. Classification Thickness of plated layer ifm> Microstructure of plated layer Proportion of the number of cracks at inclination angle of 35° to 55° (%) Proportion of the number of cracks at inclination angle of 40° to 50° (%) 23 Invention Example 30 100 100 24 Invention Example 25 100 100 25 Invention Example 29 100 75 26 Invention Example 30 100 100 27 Invention Example 10 100 100 28 Invention Example 25 100 90 29 Comparative Example 25 50 41 30 Comparative Example 25 55 45 31 Comparative Example 25 55 40 32 Comparative Example 25 60 55 33 Comparative Example 40 55 45 34 Comparative Example 40 66 60 35 Comparative Example 25 56 40 36 Comparative Example 25 45 40 37 Comparative Example 40 60 55 38 Comparative Example 25 60 45 39 Comparative Example 25 70 55 40 Comparative Example 25 50 40 41 Comparative Example 40 69 60 42 Comparative Example 40 60 40 43 Comparative Example 40 66 60 Underlined portions indicate that those fall outside the scope of the present invention.

[0135] [Table 4-1] Proportion of the number of interval Lc between cracks satisfying formula (1) (%) Proportion of the number of interval Lc between cracks satisfying formula (2) (%) Proportion of the number of interval Lc between cracks satisfying formula (3) (%) Average value of Wc ifm> Presence or absence of Mg2Sn 1 Invention Example 100 100 100 3 Present 2 Invention Example 100 88 79 3 Present 3 Invention Example 90 75 68 3 Absent 4 Invention Example 90 78 70 7 Absent 5 Invention Example 86 71 65 10 Absent 6 Invention Example 100 89 75 3 Present 7 Invention Example 86 75 65 4 Present 8 Invention Example 100 100 88 2 Present 9 Invention Example 100 100 89 2 Present 10 Invention Example 100 88 75 2 Absent 11 Invention Example 100 88 71 5 Present 12 Invention Example 100 100 100 1 Present 13 Invention Example 100 100 100 3 Present 14 Invention Example 100 89 80 3 Absent 15 Invention Example 100 100 100 3 Present 16 Invention Example 100 100 100 3 Present 17 Invention Example 100 100 100 2 Present 18 Invention Example 100 86 75 2 Present 19 Invention Example 100 100 92 3 Present 20 Invention Example 100 100 100 2 Absent 21 Invention Example 100 100 100 3 Present 22 Invention Example 100 100 100 3 Present

[0136] [Table 4-2] Proportion of the number of interval Lc between cracks satisfying formula (1) (%) Proportion of the number of interval Lc between cracks satisfying formula (2) (%) Proportion of the number of interval Lc between cracks satisfying formula (3) (%) Average value of Wc (^m) Presence or absence of Mg2Sn 23 Invention Example 100 100 100 2 Present 24 Invention Example 100 100 100 2 Present 25 Invention Example 100 78 76 5 Present 26 Invention Example 100 100 100 3 Present 27 Invention Example 100 100 89 1 Present 28 Invention Example 100 89 74 4 Absent 29 Comparative Example 45 40 25 4 Absent 30 Comparative Example 45 40 25 11 Absent 31 Comparative Example 40 35 20 11 Absent 32 Comparative Example 50 40 30 11 Absent 33 Comparative Example 50 35 30 12 Absent 34 Comparative Example 55 50 30 12 Absent 35 Comparative Example 43 32 19 12 Absent 36 Comparative Example 40 40 30 13 Absent 37 Comparative Example 55 45 35 11 Absent 38 Comparative Example 45 40 30 11 Absent 39 Comparative Example 60 50 20 11 Absent 40 Comparative Example 40 45 20 15 Absent 41 Comparative Example 56 50 30 11 Absent 42 Comparative Example 50 40 20 16 Absent 43 Comparative Example 55 50 30 12 Absent Underlined portions indicate that those fall outside the scope of the present invention.

[0137] [Table 5-1] No. Classification Processed portion corrosion resistance Sacrificial corrosion resistance 1 Invention Example AAA AAA 2 Invention Example AA AAA 3 Invention Example AA A 4 Invention Example A AA 5 Invention Example A A 6 Invention Example AA AAA 7 Invention Example A AA 8 Invention Example AAA AAA 9 Invention Example AAA AAA 10 Invention Example AA AA 11 Invention Example AA AAA 12 Invention Example AAA AAA 13 Invention Example AAA AA 14 Invention Example AAA AA 15 Invention Example AAA AAA 16 Invention Example AAA AAA 17 Invention Example AAA AAA 18 Invention Example AA AAA 19 Invention Example AAA AAA 20 Invention Example AAA AA 21 Invention Example AAA AAA 22 Invention Example AAA AAA

[0138] [Table 5-2] No. Classification Processed portion corrosion resistance Sacrificial corrosion resistance 23 Invention Example AAA AAA 24 Invention Example AAA AAA 25 Invention Example A AA 26 Invention Example AAA AAA 27 Invention Example AAA AAA 28 Invention Example AA AA 29 Comparative Example B B 30 Comparative Example B A 31 Comparative Example B A 32 Comparative Example B A 33 Comparative Example B A 34 Comparative Example B A 35 Comparative Example B A 36 Comparative Example B A 37 Comparative Example B A 38 Comparative Example B A 39 Comparative Example B A 40 Comparative Example B A 41 Comparative Example B A 42 Comparative Example B A 43 Comparative Example B A INDUSTRIAL APPLICABILITY

[0139] The present invention is industrially applicable in that it is possible to provide a 5 plated steel material having excellent sacrificial corrosion resistance and corrosion resistance of a processed portion. REFERENCE SIGNS LIST

[0140] 1 Plated steel material 10            11 Base steel material 12 Plated layer 22A Bent-back portion 24 Bent portion 24A Bent inner side of bent portion 15 101 Crack

Claims

1. A plated steel material comprising a base steel material and a plated layer formed on at least a part of a surface of the base steel material,whereinthe plated layer has a chemical composition comprising, by mass%,Al: 1.0 to 30.0%,Mg: 1.0 to 10.0%,Fe: 0 to 2.0%,Si: 0 to 2.0%,Ni: 0 to 1.00%,Ca: 0 to 1.00%,Sb: 0 to 0.50%,Pb: 0 to 0.50%,Sn: 0 to 1.00%,Cu: 0 to 1.00%,Ti: 0 to 1.00%,Cr: 0 to 1.00%,Nb: 0 to 1.00%,Zr: 0 to 1.00%,Mn: 0 to 1.00%,Mo: 0 to 1.00%,Ag: 0 to 1.00%,Li: 0 to 1.00%,Bi: 0 to 1.00%,V: 0 to 1.00%,Co: 0 to 1.00%,In: 0 to 1.00%,La: 0 to 0.50%,Ce: 0 to 0.50%,B: 0 to 0.50%,Y: 0 to 0.50%,P: 0 to 0.50%,Sr: 0 to 0.50%, andbalance comprising 50.0 to 98.0% of Zn, and impurities,a total of Sb, Pb, Cu, Sn, Ti, Cr, Nb, Zr, Mn, Mo, Ag, Li, Bi, V, Co, In, La, Ce, B, Y, P, and Sr is 0 to 5.00%,at least a part of a surface of the plated layer has a portion where a plurality of cracks are observed,the plurality of cracks extend in substantially the same direction in the portion, when a cross section of the plated steel material that is perpendicular to a direction in which the plurality of cracks extend and is perpendicular to the surface of the plated steel material and has a length of 200 pm in a direction parallel to the surface is set as an observation region in the portion, a proportion of the number of cracks inclined at an angle of 35° to 55° with respect to a thickness direction of the plated layer among all the cracks observed in the observation region is 80% or more,when an interval between the adjacent cracks is Lc and the thickness of the plated layer is T, a proportion of the number of intervals Lc satisfying a following formula (1) among all the intervals Lc observed in the observation region is 80% or more, andan average value of widths Wc of the cracks at a thickness position away fromthe surface of the plated layer by T / 2 in the observation region is 10 pm or less.0.3T < Lc < 1.6T... (1)

2. The plated steel material according to claim 1, wherein a proportion of the number of cracks inclined at an angle of 40° to 50° with respect to the thickness direction of the plated layer among all the cracks observed in the observation region of the portion is 70% or more.

3. The plated steel material according to claim 1 or 2, whereinin the chemical composition of the plated layer, contents of Al and Mg are Al:10.0 to 30.0 mass% and Mg: 4.0 to 10.0 mass%, respectively, anda proportion of the number of intervals Lc satisfying a following formula (2) among all the intervals Lc observed in the observation region is 80% or more.0.5T < Lc < 1.4T... (2)

4. The plated steel material according to claim 1 or 2, whereinin the chemical composition of the plated layer, contents of Al and Mg are Al:15.0 to 30.0 mass% and Mg: 5.0 to 8.0 mass%, respectively, anda proportion of the number of intervals Lc satisfying a following formula (3) among all the intervals Lc observed in the observation region is 80% or more.0.5T < Lc < 1.2T... (3)

5. The plated steel material according to any one of claims 1 to 4, wherein the average value of widths Wc of the cracks at a thickness position away from the surface of the plated layer by T / 2 in the observation region is 3 pm or less.

6. The plated steel material according to any one of claims 1 to 5, wherein the portion is present in a bent inner side of a bent portion of the base steel material.

7. The plated steel material according to any one of claims 1 to 6, wherein theportion is present in a bent-back portion of the base steel material.

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