Plated steel material

Abstract

This plated steel material comprises a plating layer disposed on the surface of a base steel material, wherein: the chemical composition of the plating layer contains, by mass, over 10.0% to 40.0% of Al, over 4.0% to 15.0% of Mg, and 0 to 5.0% of Fe, the balance being Zn and impurities; either or both of Co and Ni are present in a specific region from the interface between the plating layer and a chemical conversion treatment layer to the surface of the chemical conversion treatment layer; the total amount of Co and Ni in the specific region per unit surface area of the plating layer is 1.0-8.0 mg / m2; a Zn-containing oxide having a thickness of 0.02 to 0.10 μm is present on the surface of the plating layer; and the CIE 1976 brightness index L* of the plated steel material is lower than 40.

Description

Plated steel

[0001] This application claims priority from Japanese Patent Application No. 2024-072606, filed on April 26, 2024, the contents of which are incorporated herein by reference.

[0002] Hot-dip galvanized steel sheets used in the fields of building materials, civil engineering, home appliances, and automobiles are generally produced by removing grease and oxide films from the surface of the steel sheet, immersing the steel sheet in a hot-dip galvanizing bath, withdrawing it, immediately controlling the coating weight to a predetermined amount by gas wiping, and then cooling it by air cooling, water cooling, or air-water cooling. Hot-dip galvanized steel sheets produced in this manner have a glossy surface of the coating layer, but this gloss may make them unsuitable for some applications. For example, in the field of building materials, when hot-dip galvanized steel sheets are used without coating for roofing and wall materials of buildings, back panels of home appliances, etc., glare due to reflected light from the sun or lighting can be a problem from the perspectives of discomfort and safety. For this reason, surface-treated steel sheets with reduced glare have been developed.

[0003] For example, Patent Document 1 discloses a method for manufacturing a ferroelectric ceramic substrate containing Al: 1.0 to 22.0 mass %, Mg: 1.3 to 10.0 mass %, and Zn. ２ The document describes a black-plated steel sheet having a surface that is blackened by bringing a base sheet, which is a plated steel sheet having a hot-dip Al / Mg-containing Zn plating layer in which an Mg phase is distributed in the plating layer, into contact with water vapor in a sealed container.

[0004] Patent Document 2 describes a hot-dip Mg-containing Zn plating layer having a Mg content of 0.1 to 48.0 mass% and an Al content of less than 1.0 mass%, the hot-dip Mg-containing Zn plating layer containing black oxides, and the surface brightness of the hot-dip Mg-containing Zn plating layer is L ＊ A black-plated steel sheet having a value of less than 40 is described.

[0005] Patent Document 3 discloses a steel sheet having a base steel sheet and a hot-dip Al, Mg-containing Zn plating layer laminated on the surface of the base steel sheet, the hot-dip Al, Mg-containing Zn plating layer having an Al content of 1.0 mass % or more and 10.0 mass % or less, an Mg content of 0.1 mass % or more and 1.5 mass % or less, and in which a phase containing oxides or hydroxides exhibiting a metallic black color is distributed in the form of islands in the plating layer, and the lightness of the surface of the hot-dip Al, Mg-containing Zn plating layer is L ＊ A black-plated steel sheet having a value of 60 or less is described.

[0006] Patent Document 4 describes a plated steel sheet having a Zn-Al-Mg coating layer on the surface of a base steel sheet, the Zn-Al-Mg coating layer consisting of, by mass %, Al: 1.0 to 22.0%, Mg: 1.3 to 10.0%, Si: 0 to 2.0%, Ti: 0 to 0.10%, B: 0 to 0.05%, Fe: 2.0% or less, the balance being Zn and unavoidable impurities, and black oxides of Zn are distributed in the Zn-Al-Mg coating layer, and the lightness L of the surface is ＊ The document describes a black surface-coated, high-strength hot-dip Zn-Al-Mg plated steel sheet having a surface roughness of 60 or less.

[0007] Patent Document 5 describes a steel substrate and a hot-dip Al, Mg-containing Zn plating layer on the surface of the steel substrate, the hot-dip Al, Mg-containing Zn plating layer containing Al: 0.1 to 22.0 mass % and Mg: 0.1 to 10.0 mass % and having black oxide of Zn distributed in the plating layer, and the lightness of the surface of the hot-dip Al, Mg-containing Zn plating layer is L ＊ A black-plated structural member having a value of 60 or less is described.

[0008] Patent Document 6 describes a structural member having a base steel material and a black-plated layer on the surface of the base steel material, the black-plated layer containing Al, Mg, and a molten Al, Mg-containing Zn plating layer containing Al: 0.1 to 22.0 mass % and Mg: 0.1 to 10.0 mass % and having black oxide of Zn distributed in the plating layer, and the lightness of the surface of the hot-dip Al, Mg-containing Zn plating layer is 60 or less in terms of L* value.

[0009] The inventions described in Patent Documents 1 to 6 all involve exposing the plating layer to a high-temperature water vapor atmosphere, thereby subjecting the surface of the plating layer to steam oxidation and blackening. Therefore, it is conceivable to utilize the methods described in Patent Documents 1 to 6 in order to blacken a Zn—Al—Mg-based plating layer, which has even better corrosion resistance than conventional Zn—Al—Mg-based plating layers. However, when a hot-dip Zn—Al—Mg-based plating layer, which has excellent corrosion resistance, is subjected to steam oxidation treatment, there is a risk that the corrosion resistance of the plating layer will be reduced.

[0010] JP 2016-141869 A JP 2017-128752 A JP 2017-186606 A JP 2018-131669 A JP 2017-190496 A JP 2017-190497 A

[0011] An object of the present invention is to provide a plated steel material whose surface is sufficiently blackened and which has superior corrosion resistance to conventional black-plated steel materials.

[0012] In order to solve the above problems, the present invention employs the following configuration. [1] A plated steel material having a base steel material, a plating layer disposed on a surface of the base steel material, and a chemical conversion treatment layer disposed on the surface of the plating layer, wherein the chemical composition of the plating layer is, in mass%, Al: more than 10.0 to 40.0%, Mg: more than 4.0 to 15.0%, Si: 0 to 1.0%, Sn: 0 to 0.7%, Bi: 0 to 0.3%, In: 0 to 0.3%, total amount of Sn, Bi, and In ΣX: 0 to 0.7%, Ca: 0 to 0.6%, Y: 0 to 0.3%, La: 0 to 0.3%, Ce: 0 to 0.3%, Sr: 0 to 0.3%, Li: 0 to 0.3%, total amount of Ca, Y, La, Ce, Sr, and Li ΣYa: 0 to 0.6%, Cr: 0 to 1.0%, Ni: 0 to 1.0%, Mo: 0 to 0.25%, Cu: 0 to 1.0%, Ag: 0 to 0.25%, Sb: 0 to 0.25%, Pb: 0 to 0.25%, Total amount of Cr, Ni, Mo, Cu, Ag, Sb, and Pb ΣYb: 0 to 1.0%, B: 0 to 0.5%, P: 0 to 0.5%, Total amount of B and P ΣYc: 0 to 0.5%, Ti: 0 to 0.25%, Co: 0 to 0.25%, V: 0 to 0.25%, Nb: 0 to 0.25%, Mn: 0 to 0.25%, Zr: 0 to 0.25%, W: 0 to 0.25%, The total amount ΣZ of Ti, Co, V, Nb, Mn, Zr, and W is 0 to 0.25%, Fe is 0 to 5.0%, and the balance is Zn and impurities, and the total amount of Co and Ni in a specific region from the interface between the plating layer and the chemical conversion treatment layer to the surface of the chemical conversion treatment layer is 1.0 to 8.0 mg / m per surface area of ​​the plating layer. ２ a Zn-containing oxide having a thickness of 0.02 to 0.10 μm is present on the surface of the plating layer, and the plated steel material has a CIE 1976 lightness index L ＊ [2] A plated steel material having a total amount of Co and Ni at the interface between the plated layer and the chemical conversion treatment layer of 1.0 to 8.0 mg / m2 per surface area of ​​the plated layer. ２ and the total amount of Co and Ni in the specific region other than the interface between the plating layer and the chemical conversion treatment layer is 1.0 mg / m2 per surface area of ​​the plating layer. ２[3] The plated steel material according to [1], wherein the total amount of Co and Ni at the interface between the plated layer and the chemical conversion treatment layer is less than 1.0 mg / m per surface area of ​​the plated layer. ２ and the total amount of Co and Ni in the specific region other than the interface between the plating layer and the chemical conversion treatment layer is 1.0 to 8.0 mg / m2 per surface area of ​​the plating layer. ２ [4] The plated steel material according to [1], wherein the plated steel material does not have the chemical conversion treatment layer, and the specific region is only the interface between the plated layer and the chemical conversion treatment layer.

[0013] According to the present invention, it is possible to provide a plated steel product whose surface is sufficiently blackened and which has superior corrosion resistance to conventional black-plated steel products.

[0014] 1 is a schematic cross-sectional view showing an example of a plated steel material according to an embodiment of the present invention; 2 is a schematic cross-sectional view showing another example of a plated steel material according to an embodiment of the present invention; 3 is a schematic cross-sectional view showing another example of a plated steel material according to an embodiment of the present invention;

[0015] The present inventors investigated the possibility of blackening the surface of a highly corrosion-resistant Zn-Al-Mg-based plating layer containing more than 10.0% to 40.0% Al, more than 4.0% to 15.0% Mg, 0 to 5.0% Fe, and the balance being Zn and impurities, by subjecting the plating layer to steam oxidation treatment. However, because the corrosion resistance of a plating layer having the above chemical composition is significantly higher than that of conventional plating layers, steam oxidation treatment did not sufficiently blacken the plating layer. Furthermore, excessive steam oxidation treatment could lead to oxidation not only on the surface of the plating layer but also into the interior of the plating layer, potentially reducing the corrosion resistance of the plating layer.

[0016] Therefore, the inventors conducted research and found that by performing a steam oxidation treatment in a state in which a certain proportion of Ni or Co is present in the region between the surface of the plating layer and the surface of the chemical conversion treatment layer, it is possible to blacken the surface of the plating layer as expected and to prevent a decrease in the corrosion resistance of the plating layer.

[0017] Hereinafter, a hot-dip plated steel material according to an embodiment of the present invention will be described.

[0018] The hot-dip plated steel material of this embodiment is a plated steel material having a base steel material, a plating layer disposed on the surface of the base steel material, and a chemical conversion treatment layer disposed on the surface of the plating layer, and the chemical composition of the plating layer is, in mass %, Al: more than 10.0 to 40.0%, Mg: more than 4.0 to 15.0%, Si: 0 to 1.0%, Sn: 0 to 0.7%, Bi: 0 to 0.3%, In: 0 to 0.3%. %, total amount of Sn, Bi and In ΣX: 0 to 0.7%, Ca: 0 to 0.6%, Y: 0 to 0.3%, La: 0 to 0.3%, Ce: 0 to 0.3%, Sr: 0 to 0.3%, Li: 0 to 0.3%, total amount of Ca, Y, La, Ce, Sr and Li ΣYa: 0 to 0.6%, Cr: 0 to 1.0%, Ni: 0 to 1.0%, Mo: 0 to 0.25%, Cu: 0 to 1.0% , Ag: 0 to 0.25%, Sb: 0 to 0.25%, Pb: 0 to 0.25%, total amount of Cr, Ni, Mo, Cu, Ag, Sb and PbΣYb: 0 to 1.0%, B: 0 to 0.5%, P: 0 to 0.5%, total amount of B and PΣYc: 0 to 0.5%, Ti: 0 to 0.25%, Co: 0 to 0.25%, V: 0 to 0.25%, Nb: 0 to 0.25%, Mn: 0 to 0.25%, Zr: 0 to 0.25%, W: 0 to 0.25%, the total amount ΣZ of Ti, Co, V, Nb, Mn, Zr and W: 0 to 0.25%, Fe: 0 to 5.0%, the balance: Zn and impurities, and the total amount of Co and Ni in a specific region from the interface between the plating layer and the chemical conversion coating layer to the surface of the chemical conversion coating layer is 1.0 to 8.0 mg / m of surface area of ​​the plating layer. ２ The surface of the plating layer has a Zn-containing oxide having a thickness of 0.02 to 0.10 μm, and the plated steel has a CIE 1976 lightness index L ＊ The plated steel material of this embodiment has a total amount of Co and Ni at the interface between the plating layer and the chemical conversion treatment layer of 1.0 to 8.0 mg / m2 per surface area of ​​the plating layer. ２ and the total amount of Co and Ni in a specific region other than the interface between the plating layer and the chemical conversion treatment layer is 1.0 mg / m per surface area of ​​the plating layer. ２ In addition, in the plated steel material of this embodiment, the total amount of Co and Ni at the interface between the plated layer and the chemical conversion treatment layer may be less than 1.0 mg / m per surface area of ​​the plated layer. ２and the total amount of Co and Ni in a specific region other than the interface between the plating layer and the chemical conversion treatment layer is 1.0 to 8.0 mg / m per surface area of ​​the plating layer. ２ Furthermore, the plated steel material of this embodiment may not have a chemical conversion treatment layer, and the specific region may be only the interface between the plated layer and the chemical conversion treatment layer.

[0019] In the following description, the "%" used to indicate the content of each element in the chemical composition means "mass %." Furthermore, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. Furthermore, when the numerical values ​​before and after "to" are followed by "greater than" or "less than," the numerical range does not include these numerical values ​​as the lower or upper limit.

[0020] In the following description, "corrosion resistance" refers to flat surface corrosion resistance. "Flat surface corrosion resistance" refers to the property of the plating layer (specifically, the Zn-Al-Mg alloy layer) itself to be resistant to corrosion. "Sacrificial corrosion protection" refers to the property of inhibiting corrosion of the base steel material at exposed steel material parts (for example, cut end surfaces of plated steel material, areas where the plating layer breaks during processing, and areas where the base steel material is exposed due to peeling of the plating layer).

[0021] 1 , the plated steel material 1 of this embodiment preferably comprises a base steel material 11, a plating layer 12 disposed on a surface 11a of the base steel material 11, and a chemical conversion treatment layer 13 disposed on a surface 12a of the plating layer 12. In this case, the surface 13a of the chemical conversion treatment layer 13 becomes the surface of the plated steel material 1.

[0022] 2 , the plated steel material 1 of this embodiment may include a base steel material 11, a plating layer 12 disposed on the surface 11a of the base steel material 11, a chemical conversion treatment layer 13 disposed on the surface 12a of the plating layer 12, and an organic resin film 14 disposed on the surface 13a of the chemical conversion treatment layer 13. In this case, the surface 14a of the organic resin film 14 becomes the surface of the plated steel material 1.

[0023] 3, the plated steel material 1 of this embodiment may include a base steel material 11 and a plating layer 12 disposed on a surface 11a of the base steel material 11. In this case, the surface 12a of the plating layer 12 becomes the surface of the plated steel material 1.

[0024] Furthermore, in the plated steel material 1 shown in Figures 1 to 3, a Zn-containing oxide 15 having a thickness of 0.02 to 0.10 µm is present on the surface 12a of the plating layer 12. The presence of the Zn-containing oxide 15 on the surface 12a of the plating layer 12 makes the surface of the plated steel material 1 of this embodiment appear black to the naked eye. As shown in Figures 1 to 3, the Zn-containing oxide 15 may be formed in a layer, but the presence form of the Zn-containing oxide 15 is not limited to a layer. For convenience of illustration, the thickness ratios of the plating layer 12, the Zn-containing oxide 15, the chemical conversion treatment layer 13, and the organic resin film 14 in Figures 1 to 3 differ from the actual thickness ratios thereof.

[0025] The plated steel material 1 of this embodiment will be described in detail below. First, the base steel material 11 will be described. The base steel material 11 is, for example, mainly a steel plate, steel wire rod, or steel wire, but its size is not particularly limited. For example, the steel plate may be any steel plate that is applicable to a typical hot-dip galvanizing process. Specifically, this applies to steel plates that are applicable to processes in which the steel plate is immersed in molten metal and solidified, such as continuous hot-dip galvanizing lines (CGLs). The steel plate size may be, for example, a plate thickness of 10 mm or less and a plate width of 2000 mm or less, but the steel plate size is not limited thereto. Examples of steel plate shapes include checkered steel plates, which have macroscopic surface irregularities previously imparted. The steel wire rod or steel wire may also be any steel plate that is applicable to a typical hot-dip galvanizing process. Components manufactured by processing steel plates, such as angle iron and L-angles, are also included in the base steel material 11.

[0026] There are no particular limitations on the material of the base steel material 11. For example, the base steel material 11 can be general steel, pre-plated steel thinly plated with various metals, Al-killed steel, ultra-low carbon steel, high carbon steel, various high-tensile steels, and some high alloy steels (steels containing elements that strengthen corrosion resistance, such as Ni and Cr).

[0027] Furthermore, the manufacturing process for the base steel material 11 includes common processes such as iron and steel making processes using a blast furnace or electric furnace, hot rolling processes, pickling processes, cold rolling processes, and heat treatment processes, but the base steel material 11 of this embodiment may have undergone any of these processes, and the processing conditions for each process are not limited.

[0028] Next, the plating layer 12 will be described. The plating layer 12 according to this embodiment includes a Zn-Al-Mg alloy layer. The reason for this selection is that Zn-Al-Mg alloys have high corrosion resistance. The plating layer 12 may also include an Al-Fe interface alloy layer. The Al-Fe interface alloy layer is disposed closer to the base steel material 11 than the Zn-Al-Mg alloy layer.

[0029] The thickness of the plating layer 12 is the sum of the thicknesses of the Zn-Al-Mg alloy layer and the Al-Fe interfacial alloy layer. The plating layer 12 needs to have a certain thickness to form Zn-containing oxides 15 on the surface 12a of the plating layer 12 and blacken it. A certain thickness is also necessary to ensure a certain level of corrosion resistance. Therefore, the thickness of the plating layer 12 is preferably at least 5 μm or more, and may be 10 μm or more, 15 μm or more, or 20 μm or more as needed. On the other hand, the thickness of the plating layer 12 formed on a steel sheet, steel wire rod, or steel wire by a conventional hot-dip plating method is affected by the withdrawal speed of the base steel from the plating bath and the wiping conditions, and the maximum thickness is often 100 μm or less. Therefore, the thickness of the plating layer 12 of the plated steel material 1 of this embodiment may be, for example, 100 μm or less. The thickness of the plating layer 12 may be 90 μm or less, 80 μm or less, 70 μm or less, or 60 μm or less as needed.

[0030] The Zn—Al—Mg alloy layer is made of a Zn—Al—Mg alloy, which means a ternary alloy whose main elements are Zn, Al, and Mg and further contains optional elements in addition to these main elements.

[0031] The Al—Fe-based interfacial alloy layer is an interfacial alloy layer between the base steel material 11 and the Zn—Al—Mg-based alloy layer, and is in contact with the surface 11 a of the base steel material 11 .

[0032] The thickness of the Al-Fe interfacial alloy layer is preferably 2 μm or less, may be 1 μm or less, or may be 0.7 μm or less, more preferably 0.5 μm or less, or may be 0.3 μm or less. Usually, the Al-Fe interfacial alloy layer is thinner than the thickness of the Zn-Al-Mg alloy layer, and preferably accounts for 10% or less of the entire plating layer.

[0033] The plating layer 12 may have a single-layer structure of a Zn—Al—Mg alloy layer, or a laminated structure including a Zn—Al—Mg alloy layer and an Al—Fe interfacial alloy layer. In the case of a laminated structure, the Zn—Al—Mg alloy layer is disposed on the surface 12 a side of the plating layer 12.

[0034] The thickness of the plating layer 12 is measured by exposing a cross section of the plating layer 12 in the thickness direction and observing the cross section with a scanning electron microscope (SEM) equipped with an energy dispersive X-ray elemental analyzer (EDS). The chemical composition of the plating layer is analyzed with EDS to identify the range where the Zn concentration is 40 mass% or more, and this range is designated as the plating layer. The thickness of the plating layer is measured. The thickness is measured at three arbitrary locations. The arithmetic mean of the thicknesses measured at the three locations is designated as the thickness of the plating layer.

[0035] Next, the chemical composition of the plating layer 12 will be described. When the plating layer 12 has a single-layer structure of a Zn-Al-Mg alloy layer, the chemical composition of the entire plating layer 12 is the chemical composition of the Zn-Al-Mg alloy layer. When the plating layer 12 has a laminate structure of an Al-Fe interfacial alloy layer and a Zn-Al-Mg alloy layer, the chemical composition is the combined chemical composition of the Al-Fe interfacial alloy layer and the Zn-Al-Mg alloy layer. In the plating layer 12 defined in the present invention, the thickness of the Al-Fe interfacial alloy layer is preferably small, 10% or less of the overall thickness of the plating layer 12, and therefore the Fe concentration of the plating layer 12 is often within 5%. Therefore, the chemical composition of the plating layer 12 can be generally regarded as the components of a Zn-Al-Mg alloy layer without any problems. Furthermore, traces of the base steel 11, which is the base material for plating, are unlikely to remain as chemical components of the plating layer 12. Therefore, the chemical composition of the plating layer 12 can be considered to be substantially the same as the components of the plating bath used in its production.

[0036] The chemical composition of the plating layer 12 according to this embodiment is, in mass %, Al: more than 10.0 to 40.0%, Mg: more than 4.0 to 15.0%, Si: 0 to 1.0%, Sn: 0 to 0.7%, Bi: 0 to 0.3%, In: 0 to 0.3%, a total amount of Sn, Bi, and In ΣX: 0 to 0.7%, Ca: 0 to 0.6%, Y: 0 to 0.3%, La: 0 to 0.3%, Ce: 0 to 0.3%, Sr: 0 to 0.3%, Li: 0 to 0.3%, a total amount of Ca, Y, La, Ce, Sr, and Li ΣYa: 0 to 0.6%, Cr: 0 to 1.0%, Ni: 0 to 1.0%, Mo: 0 to 0.25%, and Cu: 0 to 1.0%. %, Ag: 0 to 0.25%, Sb: 0 to 0.25%, Pb: 0 to 0.25%, the total amount of Cr, Ni, Mo, Cu, Ag, Sb, and Pb ΣYb: 0 to 1.0%, B: 0 to 0.5%, P: 0 to 0.5%, the total amount of B and P ΣYc: 0 to 0.5%, Ti: 0 to 0.25%, Co: 0 to 0.25%, V: 0 to 0.25%, Nb: 0 to 0.25%, Mn: 0 to 0.25%, Zr: 0 to 0.25%, W: 0 to 0.25%, the total amount of Ti, Co, V, Nb, Mn, Zr, and W ΣZ: 0 to 0.25%, Fe: 0 to 5.0%, and the balance: Zn and impurities.

[0037] The content of each element will be specifically described below.

[0038] Al: More than 10.0% to 40.0% Al, together with Zn, is an element that mainly constitutes the plating layer 12. In Zn-Al-Mg-based plating, it mainly forms an Al phase in the plating layer. An Al content of 10.0% or less is undesirable because it reduces the corrosion resistance of the plating layer and causes the hardness of the plating layer 12 to fall outside the appropriate range. Therefore, the Al content is set to more than 10.0%. An Al content of more than 40.0% is undesirable because it reduces the Zn content relatively and reduces sacrificial corrosion protection. Therefore, the Al content is set to 40.0% or less. The Al content is preferably 15.0% or more or 19.0% or more. Furthermore, the Al content is preferably 35.0% or less or 30.0% or less.

[0039] Mg: More than 4.0% to 15.0% Mg, together with Al and Zn, is an element that mainly constitutes the plating layer 12. If Mg is insufficient, the sacrificial corrosion protection of the plating layer 12 will decrease, so the Mg content is set to more than 4.0%. If the Mg content exceeds 15.0%, the corrosion resistance of the plating layer 12 will deteriorate. Therefore, the Mg content is set to 15.0% or less. The Mg content is preferably 5.0% or more or 6.0% or more. Furthermore, the Mg content is preferably 8.0% or less or 7.0% or less.

[0040] The elements described below can all be added arbitrarily, and therefore the lower limit of the content of each of the following elements is 0%.

[0041] Si: 0 to 1.0% Si may or may not be contained in the coating layer 12, with the lower limit of the Si content being 0%. The inclusion of Si in the coating layer 12 has the effect of forming intermetallic compounds in the coating layer 12. The coating composition in this embodiment has a high melting point, and therefore, hot-dip coating is performed at an operating temperature of approximately 500°C. At such an operating temperature, when the base steel 11 is immersed in the coating bath, active interdiffusion occurs between Al and Zn and Fe to form Fe-based intermetallic compounds. However, Si suppresses this excessive reaction. Therefore, when Si is contained, a content of 0.01% or more significantly suppresses the Fe diffusion reaction, making it easier to control the formation of Fe-based intermetallic compounds contained in the coating layer 12. On the other hand, excessive Si content saturates the effect, so the Si content is set to 1.0% or less. The Si content is preferably 0.05% or more or 0.25% or more. Furthermore, the Si content is preferably 0.75% or less.

[0042] Element Group X Sn: 0-0.7% Bi: 0-0.3% In: 0-0.3% Total Amount of Sn, Bi, and In ΣX: 0-0.7% Each element in element group X (Sn, Bi, In) can be optionally contained, so the content of each is set to 0% or more. The inclusion of these elements enhances the sacrificial corrosion protection effect. Each element has an upper limit on its content, and even if a large amount is added, the effect saturates. Therefore, the upper limits for these elements are set to 0.7% or less for Sn, and 0.3% or less for Bi and In, and the total amount ΣX is also limited to 0.7% or less.

[0043] Element Group Ya Ca: 0-0.6% Y: 0-0.3% La: 0-0.3% Ce: 0-0.3% Sr: 0-0.3% Li: 0-0.3% Total Amount of Ca, Y, La, Ce, Sr, and Li ΣYa: 0-0.6% Each element in the element group Ya (Ca, Y, La, Ce, Sr, Li) can be optionally contained, and therefore the content of each is set to 0% or more. These elements, together with Si, control the reaction rate of the coating layer and can also control Fe diffusion in the coating bath. Furthermore, the formation reaction of intermetallic compounds containing these elements between the base steel material 11 and the Al-Fe-based interfacial alloy layer can ensure adhesion between the base steel material 11 and the Al-Fe-based interfacial alloy layer. To achieve this effect, it is preferable that the Ca content be 0.03% or more. However, excessive Ca forms various floating dross in the coating bath, increasing coating defects, and extremely increasing the viscosity of the coating bath, reducing the amount of molten metal adhering to the base steel material 11 when the base steel material 11 is pulled out of the coating bath, resulting in an extremely thin coating layer 12 and a deterioration in corrosion resistance. Furthermore, the hardness of the coating layer 12 becomes excessively high. Therefore, the upper limit of Ca is set to 0.6%.

[0044] Each element in the element group Ya other than Ca can be added as a substitute for Ca because it has effects similar to those of Ca. However, they cannot be added in amounts as large as Ca. That is, the content of each element in the element group Ya other than Ca is 0 to 0.3%, preferably 0.01 to 0.3%. The total amount ΣYa of the element group Ya including Ca is 0 to 0.6%.

[0045] Element group Yb Cr: 0-1.0% Ni: 0-1.0% Mo: 0-0.25% Cu: 0-1.0% Ag: 0-0.25% Sb: 0-0.25% Pb: 0-0.25% ΣYb of the total amount of element group Yb (Cr, Ni, Mo, Cu, Ag, Sb, and Pb): 0-1.0%. Elements in element group Yb (Cr, Ni, Mo, Cu, Ag, Sb, Pb) can be optionally contained, so the content of each is set to 0% or more. Elements in element group Yb have properties similar to Zn and can be contained in relatively large amounts. When these elements are contained within the above concentration ranges, they have the effect of improving corrosion resistance. This effect is apparent at a content of about 0.1%. However, if the total content of these elements becomes excessive, the effect saturates. Therefore, the Cr content is set to 0 to 1.0%, preferably 0.01 to 1.0%, the Ni and Cu contents are set to 0 to 1.0%, the Mo, Ag, Sb and Pb contents are set to 0 to 0.25%, and the total amount ΣYb is set to 0 to 1.0%.

[0046] Element group Yc B: 0-0.5% P: 0-0.5% Total amount of B and P ΣYc: 0-0.5% The elements in the element group Yc (B, P) can be contained arbitrarily, so the content of each is set to 0% or more. When these elements are contained within the above concentration ranges, they have the effect of improving corrosion resistance. This effect appears when their total content is about 0.05%. On the other hand, even if these elements are contained in large amounts, the effect saturates. Therefore, the content of each element in the element group Yc is set to 0-0.5%. The total amount ΣYc is set to 0-0.5%.

[0047] Element Group Z Ti: 0-0.25% Co: 0-0.25% V: 0-0.25% Nb: 0-0.25% Mn: 0-0.25% Zr: 0-0.25% W: 0-0.25% Total Amount ΣZ of Element Group Z (Ti, Co, V, Nb, Mn, Zr, and W): 0-0.25%. Elements in element group Z (Ti, Co, V, Nb, Mn, Zr, and W) can be optionally contained, and therefore the content of each is set to 0% or more. When elements in element group Z are contained in the plating layer 12, corrosion resistance is improved. This effect is apparent when the total concentration is approximately 0.1%. However, even if these elements are contained in large amounts, the effect saturates. Therefore, the content of each element in element group Z is set to 0-0.25%. The total amount ΣZ is set to 0-0.25%.

[0048] Fe: 0 to 5.0% The plated steel material 1 of this embodiment is produced by a hot-dip galvanizing method, so Fe may diffuse from the base steel material 11 to the plated layer 12 during production. As described above, in this embodiment, the Al concentration of the plated layer 12 is high, and an Al-Fe-based interfacial alloy layer may be formed, but its thickness is thin. As a result, the plated layer 12 may contain up to 5.0% Fe, but as long as the Fe concentration is limited to 5.0% or less, there is no effect on the frequency of crack occurrence in the plated layer 12. Therefore, the Fe content is set to 0 to 5.0%. The lower limit of the Fe content is 0%, but the Fe content may exceed 0%.

[0049] Balance: Zn and impurities The balance preferably contains Zn. Since the plated steel material 1 of this embodiment is a highly versatile Zn-based plated steel material, the element constituting the main phase of the plating layer 12 is Zn. The Zn content is preferably 34.65 to 86.00%. The Zn content may be 40.00% or more, 50.00% or more, or 60.00% or more. In addition, the Zn content may be 90.00% or less, 80.00% or less, or 78.00% or less.

[0050] Impurities refer to components contained in raw materials or components mixed in during the manufacturing process, but not intentionally added. For example, trace amounts of components other than Fe may be mixed into the plating layer 12 as impurities due to mutual atomic diffusion between the base steel material 11 and the plating bath. The content of each impurity element is preferably 0.10% or less. The total amount of impurity elements is preferably 2.00% or less. If necessary, the total amount of impurity elements may be 1.50% or less, 1.00% or less, 0.60% or less, or 0.30% or less.

[0051] The chemical composition of the plating layer 12 can be measured using the following method. First, a sample of the plating layer 12 measuring 30 mm x 30 mm is taken from the plated steel material 1. Next, the surface of the plating layer 12 is polished with abrasive paper. The polishing is performed so that at least 80% of the thickness of the plating layer 12 remains. If an organic resin film 14 or a chemical conversion layer 13 is present on the surface of the plating layer 12, these are also removed by polishing. The plating layer 12 is then stripped and dissolved using an acid containing an inhibitor that suppresses corrosion of the base steel material 11 to obtain an acid solution. The resulting acid solution is then analyzed using ICP atomic emission spectroscopy or ICP-MS to obtain the chemical composition. The inhibitor can be, for example, Hibilon (A-6) (manufactured by Sugimura Chemical Industry Co., Ltd.), a pickling corrosion inhibitor. Specifically, a 10% hydrochloric acid solution containing 1% Hibilon (A-6) can be used as the inhibitor-containing acid.

[0052] Next, we will explain Ni or Co present in a specific region between the interface between the plating layer 12 and the chemical conversion treatment layer 13 (that is, also the surface 12a of the plating layer 12, hereinafter also referred to as "the surface 12a of the plating layer 12" or "the surface 12a") and the surface 13a of the chemical conversion treatment layer 13. In the plated steel material 1 of this embodiment, either Co or Ni, or both, are present in a specific region between the surface 12a of the plating layer 12 and the surface 13a of the chemical conversion treatment layer 13. The total amount of Co and Ni in the specific region is 1.0 to 8.0 mg / m2 in total per surface area of ​​the plating layer 12 (total amount per area). ２The presence of Co or Ni in the specific region suppresses the penetration of oxygen into the plating layer 12 when the plating layer 12 is subjected to steam oxidation treatment, thereby suppressing oxidation of the entire plating layer and preventing deterioration of the corrosion resistance of the plating layer 12. Furthermore, the continued presence of Co or Ni in the specific region even after steam oxidation treatment reduces the corrosion rate in a corrosive environment and improves the corrosion resistance of the plating layer.

[0053] The total amount of Co and Ni per surface area of ​​the plating layer 12 in the specific region (total amount per area) is 1.0 to 8.0 mg / m ２ The total amount is 1.0 mg / m ２ If the total amount is less than 8.0 mg / m, it is not possible to prevent oxygen from penetrating into the plating layer 12 when the plating layer 12 is subjected to a steam oxidation treatment, which is undesirable as it will result in a deterioration in the corrosion resistance of the plating layer 12. ２ If the temperature exceeds this range, blackening will not proceed easily during the steam oxidation treatment, which is not preferable.

[0054] Here, the presence of either Co or Ni or both in the specific region includes, for example, the following forms.

[0055] In FIGS. 1 and 2, the specific region in the case of the plated steel material 1 having the chemical conversion treatment layer 13 is the range from the surface 12 a of the plated layer 12 to the surface 13 a of the chemical conversion treatment layer 13 .

[0056] In the case of the plated steel material 1 shown in Fig. 1 or 2, Co or Ni may be present both at the interface between the plated layer 12 and the chemical conversion treatment layer 13 and in the chemical conversion treatment layer 13. The total amount of Co and Ni in the entire specific region is 1.0 to 8.0 mg / m per surface area of ​​the plated layer. ２ is.

[0057] 1 or 2, Co or Ni may be present mainly at the interface between the plating layer 12 and the chemical conversion treatment layer 13. That is, in the specific region, the total amount of Co and Ni at the interface between the plating layer 12 and the chemical conversion treatment layer 13 is 1.0 to 8.0 mg / m per surface area of ​​the plating layer 12. ２The total amount of Co and Ni in a specific region other than the interface between the plating layer 12 and the chemical conversion treatment layer 13 is 1.0 mg / m per surface area of ​​the plating layer 12. ２ It may be less than.

[0058] Furthermore, in the case of the plated steel material 1 shown in Fig. 1 or 2, Co or Ni may be present mainly in the chemical conversion treatment layer. That is, in the specific region, the total amount of Co and Ni at the interface between the plated layer 12 and the chemical conversion treatment layer 13 is 1.0 mg / m per surface area of ​​the plated layer. ２ and the total amount of Co and Ni in a specific region other than the interface between the plating layer 12 and the chemical conversion treatment layer 13 is 1.0 to 8.0 mg / m2 per surface area of ​​the plating layer. ２ may be.

[0059] Next, as shown in Fig. 3, the specific region in the case of a plated steel material 1 that does not have a chemical conversion treatment layer 13 or an organic resin film 14 is regarded as the surface 12a of the plated layer 12. Therefore, in the case of the plated steel material 1 shown in Fig. 3, the total amount of Co and Ni in the surface 12a of the plated layer 12 is 1.0 to 8.0 mg / m ２ That is, the specific region is originally the region from the interface between the plating layer 12 and the chemical conversion layer 13 to the surface 13a of the chemical conversion layer 13, but when the chemical conversion layer 13 is not present as in FIG. 3, the surface 12a of the plating layer is regarded as the surface 13a of the chemical conversion layer. In other words, when the chemical conversion layer 13 is not present, only the interface between the plating layer 12 and the chemical conversion layer 13 is determined to be the specific region. The total amount of Co and Ni at this "interface between the plating layer 12 and the chemical conversion layer 13" (the specific region when the chemical conversion layer 13 is not present) is 1.0 to 8.0 mg / m2 per surface area of ​​the plating layer 12. ２ Let's say.

[0060] The chemical conversion treatment layer 13 is not particularly limited, but is preferably a so-called chromate-free chemical conversion treatment layer 13. The chemical conversion treatment layer 13 may be an inorganic chemical conversion treatment layer, an organic chemical conversion treatment layer, or an organic-inorganic composite chemical conversion treatment layer. In this embodiment, the material of the chemical conversion treatment layer 13 (i.e., whether it is inorganic, organic, or organic-inorganic composite) does not affect the blackening of the surface of the plating layer 12.

[0061] For example, a chemical conversion treatment layer 13 containing a resin and silica particles can be exemplified as the organic chemical conversion treatment layer 13. This chemical conversion treatment layer 13 is a coating obtained by applying an aqueous composition containing a resin and silica particles to the plating layer 12 and drying it.

[0062] The resin contained in the organic chemical conversion treatment layer 13 may be any common resin, such as polyolefin resin, fluororesin, acrylic resin, urethane resin, polyester resin, epoxy resin, phenolic resin, etc. The resin may be contained in the chemical conversion treatment layer 13 in a proportion of, for example, 20% by mass or more.

[0063] Silica particles are blended to improve the corrosion resistance of the organic chemical conversion coating layer 13. Silica particles having an average particle size in the range of 5 to 200 nm are suitable. The silica particles are preferably contained in the chemical conversion coating layer 13 at a ratio of 1 to 20 mass %.

[0064] Furthermore, in order to improve the corrosion resistance of the organic chemical conversion coating layer 13, titania particles, alumina particles, zirconia particles, etc. may be contained in addition to silica particles.

[0065] The organic chemical conversion treatment layer 13 may further contain either or both of an Nb compound and a phosphate compound. When an Nb compound or a phosphate compound is contained, the corrosion resistance of the plating layer 12 is improved.

[0066] The organic chemical conversion treatment layer 13 may contain at least one crosslinking agent selected from the group consisting of a silane coupling agent, a crosslinkable zirconium compound, and a crosslinkable titanium compound in order to improve adhesion to the plating layer 12. These may be used alone or in combination of two or more.

[0067] When the organic chemical conversion treatment layer contains either Ni or Co, or both, it is preferable to use a chemical conversion treatment solution containing either Co or Ni. The content of Co or Ni contained in the chemical conversion treatment solution depends on the target value for the "total amount per area of ​​Co and Ni per surface area of ​​the plating layer 12" in a specific region and the thickness (or deposition amount) of the chemical conversion treatment layer 13, but is preferably 0.5 to 3 mass % in terms of Ni and Co.

[0068] The amount of the chemical conversion layer 13 applied to one side of the plating layer 12 is 0.1 to 15 g / m, regardless of the material of the chemical conversion layer 13. ２ The coating amount is preferably 0.1 to 15 g / m ２ If so, the amount of adhesion of the chemical conversion treatment layer 13 will be sufficient, and the corrosion resistance of the plating layer 12 can be improved.

[0069] Next, a method for measuring the amount of Ni or Co present in a specific region will be described. The measurement method described below will be explained using an example in which the chemical conversion coating layer 13 and the organic resin film 14 are formed on the surface of the plating layer 12.

[0070] The cases where a chemical conversion treatment layer 13 is formed on the surface of the plating layer 12 but an organic resin film 14 is not formed, and the cases where a chemical conversion treatment layer 13 and an organic resin film 14 are not formed on the surface of the plating layer 12 will be described later.

[0071] The measurement combines sputtering of the surface of the plated steel material 1 (i.e., scraping off the surface) with measurement of element concentrations using XPS (X-ray photoelectron spectroscopy). The sputtering area is 1.0 mm x 1.0 mm, and sputtering is performed with argon. Sputtering is performed to a depth of 10 nm per run. After each 10 nm of sputtering, the concentrations of C, O, Si, Zn, Al, Mg, Co, and Ni are measured using XPS on the surface newly revealed by sputtering. This combination of sputtering and XPS measurement is repeated. Sputtering and XPS measurement are performed until the sputtering depth reaches the plating layer 12. Whether the sputtering depth has reached the plating layer 12 is determined when the O (oxygen) concentration drops to 0.7 mass %. This is because the oxygen concentration in the plating layer 12 is lower than that in the chemical conversion layer 13 and the organic resin film 14 .

[0072] By repeating sputtering and measurement by the XPS method, the concentrations of C, O, Si, Zn, Al, Mg, Co, and Ni are obtained for each sputtering depth. Based on the obtained concentration measurement results of each element, the interface between the organic resin film 14 and the chemical conversion layer 13 and the interface between the chemical conversion layer 13 and the plating layer 12 are identified, and the range of the specific region is also identified. The method for identifying these interfaces and specific regions will be described later. Then, based on the concentrations of Ni and Co in the specific region, the amounts of Co and Ni per area (mg / m ２ ) is calculated.

[0073] The conditions for measuring the element concentration by sputtering and XPS method are as follows: <Sputtering> Acceleration voltage of Ar ion gun: 1 kV Irradiation angle of Ar ion beam to sample: 45° Sputtering rate: Si measured separately ２ O sputtering rate <XPS analysis> X-ray source: mono-Al Kα X-ray output: 15 kV, 25 W X-ray diameter: 100 μmφ Measurement area: 300 μm × 300 μm

[0074] Hereinafter, a method for identifying the organic resin film 14, the chemical conversion coating layer 13, and the interface and the specific region of the chemical conversion coating layer 13 will be described.

[0075] When sputtering begins from the surface of the plated steel material 1 (surface 14a of the organic resin film 14), sputtering occurs in the order of the organic resin film 14, the chemical conversion treatment layer 13, and the plating layer 12. The specific region is the region from the interface between the organic resin film 14 and the chemical conversion treatment layer 13 to the interface between the chemical conversion treatment layer 13 and the plating layer 12, and the position of each interface is determined from the measurement results of the XPS method.

[0076] When the organic resin film 14 is subjected to XPS analysis while being sputtered (but only before the sputtering of the organic resin film 14 is completed), the C concentration is 8.0% or more, and the concentrations of the main constituent elements of the chemical conversion treatment layer 13 are less than 8.0%.

[0077] Next, when the organic or organic-inorganic composite chemical conversion coating layer 13 is sputtered (after the sputtering of the organic resin coating 14 is completed) and subjected to XPS analysis, the concentration of the main constituent elements that make up the chemical conversion coating layer 13 is found to be 8.0 mass % or more.

[0078] Here, the term "major constituent element" refers to an element that has the highest concentration in the chemical conversion treatment layer 13 among elements (excluding C, Co, and Ni) whose concentration in the organic resin film 14 is less than 8.0 mass %. An example of such an element is Si.

[0079] Furthermore, when XPS analysis is performed while sputtering the inorganic chemical conversion coating layer 13 (after sputtering and etching of the organic resin coating 14 is completed), the C concentration is found to be less than 8.0 mass %.

[0080] From the above, the interface between the organic resin film 14 and the organic or organic-inorganic composite chemical conversion coating layer 13 (i.e., the surface 13a of the chemical conversion coating layer) is set to a depth position where the concentration of the main constituent elements is 8.0 mass %.

[0081] The interface between the organic resin film 14 and the inorganic chemical conversion coating layer 13 (i.e., the surface 13a of the chemical conversion coating layer) is located at a depth where the C concentration is 8.0 mass %.

[0082] In this way, the position of one interface of the specific region can be identified.

[0083] Next, when chemical conversion layer 13 is subjected to XPS analysis while being sputtered (after sputtering of organic resin coating 14 has been completed), the O concentration is found to be 0.7 mass% or more, but when plating layer 12 is subjected to XPS analysis while being sputtered (after sputtering of chemical conversion layer 13 has been completed), the O concentration is found to be less than 0.7 mass%. This decrease in O concentration accompanying sputtering from chemical conversion layer 13 to plating layer 12 always occurs regardless of the material of chemical conversion layer 13 (specifically, whether it is organic, organic-inorganic composite, or inorganic).

[0084] From the above, the interface between the chemical conversion layer 13 and the plating layer 12 is defined as the region between the depth at which the O concentration becomes 0.7% (as will be described later, this depth position is the end of the specific region) and a depth 50 nm away from the depth at which the O concentration becomes 0.7% toward the surface 13a of the chemical conversion layer 13. Furthermore, in this embodiment, the interface between the chemical conversion layer 13 and the plating layer 12 is not interpreted as an "interface" with no thickness. In this embodiment, the interface between the chemical conversion layer 13 and the plating layer 12 is considered to be "the depth at which the O concentration becomes 0.7% and a depth 50 nm away from the depth at which the O concentration becomes 0.7% toward the surface 13a of the chemical conversion layer 13 (toward the base steel 11)." Therefore, the end of the specific region is the depth position at which the O concentration becomes 0.7 mass%.

[0085] The specific region is defined as the region between the depth position of the interface between the organic resin film 14 and the chemical conversion layer 13 and the depth position of the interface between the chemical conversion layer 13 and the plating layer 12. In other words, the start of the specific region (when performing XPS analysis while sputtering) of the plated steel material 1 having the organic resin film 14 and the chemical conversion layer 13 is the depth position where the concentration of the main constituent element is 8.0 mass % in the case of an organic or organic-inorganic composite chemical conversion layer 13, and the start of the specific region is the depth position where the C concentration is 8.0 mass % in the case of an inorganic chemical conversion layer 13.

[0086] A method for determining whether the chemical conversion layer 13 is organic, organic-inorganic composite, or inorganic will now be described. In the plated steel material 1 of this embodiment, if the C concentration in a region 30 nm deep immediately before the Zn concentration reaches 15.0 mass% near the interface between the chemical conversion layer 13 and the plating layer 12 is less than 5%, the chemical conversion layer 13 is determined to be inorganic. On the other hand, if the C concentration in this region is 5% or greater, the chemical conversion layer 13 is determined to be organic or organic-inorganic composite. Those skilled in the art can easily determine whether the chemical conversion layer 13 is organic, organic-inorganic composite, or inorganic from the element concentration measurement results obtained by XPS analysis while sputtering. For example, the C concentration of the chemical conversion layer 13 can easily determine whether it is organic, organic-inorganic composite, or inorganic.

[0087] The concentrations of Co and Ni in the sputtered area (i.e., the area of ​​10 nm thickness removed by sputtering) are considered to be the same as the concentrations of Co and Ni measured by XPS on the surface before sputtering. In a specific area, the amounts of Co and Ni deposited per sputtered thickness (i.e., 10 nm) (the amounts of Co and Ni deposited per surface area of ​​the plating layer at a thickness of 10 nm, unit: mg / m) are calculated. ２ ) is added up to calculate the total amount per area of ​​Co and Ni per surface area of ​​the plating layer 12 in the specific region. However, if the sputtered range includes the start of the specific region, the entire range is considered to be the specific region, and the Co and Ni deposition amounts in this range are summed up. If the O concentration in the XPS analysis after sputtering is 0.7%, that is, if it is determined to be the end of the specific region, it is not necessary to sum up the Co and Ni deposition amounts in that XPS analysis result. In other words, the Co and Ni deposition amounts in the XPS analysis result up to the point immediately before it is determined to be the end of the specific region are summed up. The analytical value obtained by the XPS method is the average of measurements taken at any five locations on each surface to be analyzed.

[0088] The total amount per area of ​​Co and Ni per surface area of ​​plating layer 12 only at the interface between plating layer 12 and chemical conversion layer 13 is calculated by summing the amounts of Co and Ni deposited in the sputtered range from "a position 50 nm away from the depth position where the O concentration is 0.7 mass% toward chemical conversion layer 13" to "a depth position where the O concentration is 0.7 mass%." The total amount per area of ​​Co and Ni per surface area of ​​plating layer 12 in a specific region other than the interface between plating layer 12 and chemical conversion layer 13 is calculated by subtracting the total amount of Co and Ni deposited in the range including "a position 50 nm away from the depth position where the O concentration is 0.7 mass% toward chemical conversion layer 13" from the total amount of Co and Ni per surface area of ​​plating layer 12 in the specific region.

[0089] The concentration of each element determined by XPS analysis is expressed as a mass percentage relative to the total amount of C, O, Si, Zn, Al, Mg, Co, Zr, V, Cr, F, S, Ti, and Ni.

[0090] Further, a supplementary explanation will be given regarding the method for measuring Ni and Co when an organic resin film 14 is not formed on the surface of the plating layer 12. First, the determination of whether or not an organic resin film 14 is formed is performed in the following order: Sputtering and measurement by XPS are started from the surface of the plated steel material 1, and measurement by XPS is performed while sputtering is continued in 10 nm increments from the surface to a depth of 50 nm. If the C concentration is always less than 8.0 mass % down to a depth of 50 nm from the surface, or if the main constituent elements of the chemical conversion treatment layer 13 are 8.0 mass % or more, it is determined that an organic resin film 14 is not present on the surface of the plated steel material 1, and that a chemical conversion treatment layer 13 is present.

[0091] When the organic resin film 14 is not present on the surface of the plated steel material 1 but the chemical conversion layer 13 is present, the range of the specific region is defined as a depth position from the surface 13a of the chemical conversion layer 13 to the interface between the chemical conversion layer 13 and the plating layer 12 (the deepest depth position where analysis by sputtering and XPS is performed) where the O concentration is 0.7 mass%. In other words, the start of the specific region is the surface 13a of the chemical conversion layer 13, and the end of the specific region is defined as a depth position where the O concentration is 0.7 mass%. The total amount per area of ​​Co and Ni per surface area of ​​the plating layer 12 only at the interface between the plating layer 12 and the chemical conversion layer 13, and the total amount per area of ​​Co and Ni per surface area of ​​the plating layer 12 in the specific region other than the interface between the plating layer 12 and the chemical conversion layer 13, can also be calculated by the above-mentioned method.

[0092] Next, we will provide additional information on the method for measuring Ni and Co when the organic resin film 14 and chemical conversion treatment layer 13 are not formed on the surface of the plating layer 12. As described above, sputtering and XPS measurement are started from the surface of the plated steel material 1, and measurement by XPS is performed while sputtering is continued in 10 nm increments from the surface to a depth of 50 nm. In other words, the start of the specific region is the surface of the plated steel material 1, and the end of the specific region is set to a depth of 50 nm from the surface. If the O concentration is less than 0.7 mass % before reaching a depth of 50 nm from the surface, it is determined that the organic resin film 14 and chemical conversion treatment layer 13 are not present on the surface of the plated steel material 1.

[0093] The range of the specific region when it is assumed that the organic resin film 14 and the chemical conversion treatment layer 13 are not present on the surface of the plated steel material 1 is up to a depth of 50 nm from the surface 12a of the plated layer 12 (towards the base steel material 11).

[0094] Next, the brightness of the plated steel material 1 will be described. The brightness of the surface of the plated steel material 1 of this embodiment is determined by the CIE 1976 brightness index L 2 as specified in JIS Z 8781-4:2013. ＊ (CIE 1976 lightness). In this embodiment, the CIE 1976 lightness index L ＊ is less than 40. CIE 1976 Lightness Index L＊ When the value is less than 40, the surface of the plating layer 12 is sufficiently blackened.

[0095] CIE 1976 Lightness Index L ＊ A Zn-containing oxide 15 is formed on the surface of the plating layer 12 having a ρ of less than 40. The Zn-containing oxide 15 contains at least Zn oxide. Part or all of the Zn oxide is oxygen-deficient Zn oxide. Therefore, the Zn-containing oxide 15 appears black or nearly black to the naked eye. The Zn-containing oxide 15 may contain Zn hydroxide in addition to Zn oxide. The Zn-containing oxide 15 is formed by heating the plating layer 12 to 100°C or higher in an atmosphere with a relative humidity of 90% or higher, as described below.

[0096] The thickness of the Zn-containing oxide 15 on the surface of the plating layer 12 is set to a range of 0.02 to 0.10 μm. If the thickness of the Zn-containing oxide 15 is less than 0.02 μm, the blackening is insufficient and the CIE 1976 lightness index L ＊ It becomes difficult to make the thickness of the Zn-containing oxide 15 less than 40. If the thickness of the Zn-containing oxide 15 exceeds 0.10 μm, the plating layer 12 will be excessively oxidized, which may result in a decrease in corrosion resistance of the plating layer 12. If necessary, the thickness of the Zn-containing oxide layer may be set to 0.03 μm or more, 0.04 μm or more, or 0.05 μm or more, or may be set to 0.09 μm or less, or 0.08 μm or less.

[0097] The method for measuring the thickness of the Zn-containing oxide 15 will be described. First, to cut out a thin film sample for TEM measurement, the plating layer 12 is extracted from the plated steel material 1 by processing using a focused ion beam (FIB) method to obtain a thin section sample measuring approximately 10 μm × 10 μm × 100 nm in thickness. Next, the oxygen concentration and Zn concentration on the surface of the plating layer 12 are measured using a transmission electron microscope (TEM-EDS) equipped with an X-ray elemental analyzer (EDS) at an acceleration voltage of 300 kV. The region where the oxygen concentration is 5.0 mass% or more and the Zn concentration is 5.0 mass% or more is identified as the Zn-containing oxide 15, and its thickness is measured. In the TEM observation, a field of view in which the Zn-containing oxide / plating layer interface falls within a 5 μm area is defined as one field of view, and the thickness of the Zn-containing oxide 15 is measured in each of three fields of view. The arithmetic mean of the thicknesses of the Zn-containing oxide 15 in each field of view is defined as the thickness of the Zn-containing oxide 15.

[0098] CIE 1976 lightness index L of plated steel material 1 ＊ is measured by a spectral reflectance measurement method using a spectrophotometer in accordance with JIS K 5600-4-5:1999. The spectrophotometer may be, for example, a spectrophotometer (TC-1800) manufactured by Tokyo Denshoku Co., Ltd. The measurement conditions are as follows:

[0099] Optical conditions: d / 8° method (double beam optical system) Field of view: 2-degree field of view Measurement method: reflected light measurement Standard light: C Color system: CIELAB Measurement wavelength: 380 to 780 nm Measurement wavelength interval: 5 nm Spectrometer: diffraction grating 1200 / mm Illumination: halogen lamp (voltage 12 V, power 50 W, rated life 2000 hours) Measurement area: 7.25 mmφ Detector: photomultiplier tube (R928; Hamamatsu Photonics K.K.) Reflectance: 0-150% Measurement temperature: 23°C Standard plate: white

[0100] The measurement is carried out by drawing grid lines at 20 mm intervals vertically and horizontally on the surface of the plating layer 12, and measuring nine points in total within a range of three vertical points and three horizontal points among the intersections of the grid lines, within a circular area with a radius of 10 mm centered on the measurement points. ＊ The average of the values ​​is calculated as the CIE 1976 lightness index L ＊ Let's say.

[0101] In addition, when a chemical conversion coating layer 13 or an organic resin film 14 is formed on the surface of the plating layer 12, the CIE 1976 lightness index L ＊ Measurements of

[0102] As already mentioned, the plated steel material 1 of this embodiment may have an organic resin coating 14 formed of an organic resin on the surface of the chemical conversion treatment layer 13. The organic resin that forms the organic resin coating 14 may be a urethane-based resin, an epoxy-based resin, an olefin-based resin, a styrene-based resin, a polyester-based resin, an acrylic-based resin, a fluorine-based resin, a copolymer or modified product of these resins, or a combination of these resins. The use of these flexible organic resins can improve the corrosion resistance of the plating layer 12.

[0103] The organic resin coating 14 may contain a lubricant. By including a lubricant, friction between the mold and the surface of the plated steel material 1 can be reduced during processing such as press working, and galling of the surface of the plated steel material 1 can be suppressed. The type of lubricant is not particularly limited, and may be selected from known lubricants. Examples of lubricants include organic waxes such as fluorine-based, polyethylene-based, and styrene-based, and inorganic lubricants such as molybdenum disulfide and talc.

[0104] The organic resin film 14 may be a coating layer or a laminate layer. From the viewpoint of making the most of the black appearance of the plated steel material 1, the organic resin film 14 is preferably a clear coating film.

[0105] Next, a method for manufacturing the plated steel material 1 of this embodiment will be described. The manufacturing method of this embodiment includes a hot-dip galvanizing step for forming the plated layer 12 by hot-dip galvanizing, and a step for adding at least one of Co and Ni to the surface of the plated layer 12 obtained by the hot-dip galvanizing step in an amount of 1.0 to 8.0 mg / m ２ and a heating step of subjecting the plating layer 12 obtained by the metal deposition step to a heat treatment under conditions of a relative humidity of 90% or more, a soaking temperature of 100°C or more and 210°C or less, and a soaking time of 20 hours or more and 40 hours or less. Each step will be described below.

[0106] First, the base steel material 11 to be plated is annealed in a reducing atmosphere. The reducing atmosphere and annealing conditions are not particularly limited. By this annealing, oxides present on the surface of the base steel material 11 are removed as much as possible.

[0107] (Hot-dip coating process) Next, the base steel material 11 immediately after annealing is immersed in a hot-dip coating bath. The chemical composition of the coating bath may be adjusted appropriately so as to obtain the chemical composition of the coating layer 12 described above. The temperature of the coating bath is not particularly limited, and any temperature at which hot-dip coating can be performed may be selected appropriately. For example, the temperature of the coating bath may be set to a value that is at least about 20°C higher than the melting point of the coating bath.

[0108] Next, the base steel material 11 is pulled up from the coating bath. The deposition weight of the plating layer 12 can be controlled by controlling the pulling speed of the base steel material 11. If necessary, the deposition weight of the plating layer 12 may be controlled by wiping the base steel material 11 to which the plating layer 12 is attached. The deposition weight of the plating layer 12 is not particularly limited and can be, for example, within the above-mentioned range.

[0109] Next, the plating layer 12 is cooled. There are no particular limitations on the cooling conditions, and the cooling may be performed by spraying a cooling gas or mist, or by allowing the plating layer 12 to cool naturally.

[0110] (Metal Adhesion Process) In the metal adhesion process, either or both of an adhesion process or a chemical conversion treatment process, which will be described below, are performed. The adhesion process is a process in which a solution containing at least one of Co and Ni is applied to the surface of the plating layer 12 and then dried. The chemical conversion treatment process is a process in which a chemical conversion treatment layer 13 is formed on the surface of the plating layer 12 using a chemical conversion treatment solution containing at least one of Co and Ni.

[0111] (Deposition Step) In the deposition step, first, a solution containing at least one of Co and Ni is prepared. The solution is either a Co source or a Ni source, or an aqueous solution containing either one. For example, cobalt sulfate can be used as the Co source. For example, nickel sulfate can be used as the Ni source. The content of the Co source or Ni source compound in the solution is preferably 0.6 to 15 g / L, for example, in terms of Ni and Co. The temperature of the solution is preferably 30 to 50°C.

[0112] The prepared solution is then applied to the surface of the plating layer 12. Specifically, for example, the plating layer 12 may be immersed in a solution containing Co or Ni and then pulled out, the solution containing Co or Ni may be sprayed onto the surface of the plating layer 12, or the solution containing Co or Ni may be applied to the roll surface of a roll and then pressed against the surface of the plating layer 12 to apply the solution.

[0113] After the solution is applied to the surface of the plating layer 12, it may be dried. The drying may be natural drying or hot air drying.

[0114] (Chemical conversion treatment step) In the chemical conversion treatment step, first, a chemical conversion treatment solution is prepared. For example, when forming an organic chemical conversion treatment layer, an aqueous chemical conversion treatment solution containing at least a resin and silica particles is prepared. In addition to the resin and silica particles, the chemical conversion treatment solution may contain titania particles, alumina particles, zirconia particles, etc., or may contain either or both of an Nb compound and a phosphate compound, and may contain at least one crosslinking agent selected from the group consisting of a silane coupling agent, a crosslinkable zirconium compound, and a crosslinkable titanium compound. When forming an organic-inorganic composite chemical conversion treatment layer or an inorganic chemical conversion treatment layer, the chemical conversion treatment solution is prepared by a known method, except for the inclusion of either Co or Ni as described below.

[0115] The chemical conversion treatment solution contains either Co or Ni. The content of Co or Ni contained in the chemical conversion treatment solution is preferably 0.5 to 3 mass % in terms of Ni and Co combined. The temperature of the chemical conversion treatment solution is preferably 15 to 50°C.

[0116] Next, the plating layer 12 is immersed in the prepared chemical conversion treatment solution and then pulled out. Thereafter, by heating to, for example, 50 to 110°C, a chemical conversion treatment layer 13 containing Co or Ni is formed on the surface of the plating layer 12.

[0117] The metal deposition step includes the following four modes. In the first mode, a deposition step is performed in which at least one of Co and Ni is deposited on the surface of the plating layer 12. Next, a chemical conversion treatment step is performed on the plating layer 12 after the deposition step using a chemical conversion treatment solution containing either Co or Ni, or both. In this case, one of Co and Ni is deposited on the surface of the plating layer 12 in the deposition step, and the other of Co and Ni can also be contained in the chemical conversion treatment layer 13 in the chemical conversion treatment step. By carrying out the first mode, Co or Ni can be deposited in a specific region including the interface between the plating layer 12 and the chemical conversion treatment layer 13. In this case, the total deposition amount of Co and Ni in the specific region including the interface between the plating layer 12 and the chemical conversion treatment layer 13 is 1.0 to 8.0 mg / m ２ becomes.

[0118] In a second embodiment, an attachment step is performed in which at least one of Co and Ni is attached to the surface of the plating layer 12. Next, a chemical conversion treatment step is performed on the plating layer 12 after the attachment step using a chemical conversion treatment solution that does not contain Co or Ni. By carrying out the second embodiment, Co or Ni can be attached to the interface (specific region) between the plating layer 12 and the chemical conversion treatment layer 13. In this case, the total amount of Co and Ni attached at the interface between the plating layer 12 and the chemical conversion treatment layer 13 is 1.0 to 8.0 mg / m ２ In a specific region other than the interface between the plating layer 12 and the chemical conversion treatment layer 13, the total amount of Co and Ni deposited is 1.0 mg / m ２ It will be less than.

[0119] In a third embodiment, the deposition step is not performed, and instead a chemical conversion treatment step using a chemical conversion treatment solution containing either Co or Ni or both is performed on the plating layer 12. By performing the third embodiment, Co or Ni can be deposited in a specific region excluding the interface between the plating layer 12 and the chemical conversion treatment layer 13. In this case, the total deposition amount of Co and Ni in the interface (specific region) between the plating layer 12 and the chemical conversion treatment layer 13 is 1.0 mg / m ２ In a specific region other than the interface between the plating layer 12 and the chemical conversion treatment layer 13, the total amount of Co and Ni deposited is 1.0 to 8.0 mg / m ２ becomes.

[0120] In a fourth embodiment, a deposition step of depositing at least one of Co and Ni on the surface of the plating layer 12 is performed, without performing a chemical conversion treatment step. By carrying out the fourth embodiment, Co or Ni can be deposited on the surface (specific region) of the plating layer 12. In this case, the total deposition amount of Co and Ni on the surface (specific region) of the plating layer 12 is 1.0 to 8.0 mg / m ２ This becomes:

[0121] (Heating Step) Next, the plated steel material 1 after the adhering step is heated under conditions of a relative humidity of 90% RH or higher, a soaking temperature of 100°C or higher and 210°C or lower, and a soaking time of 20 hours or higher but 40 hours or lower, thereby performing steam oxidation treatment to form a Zn-containing oxide 15 on the surface of the plating layer 12. The thickness of the Zn-containing oxide 15 is 0.02 μm or higher, preferably 0.03 μm or higher, 0.04 μm or higher, or 0.05 μm or higher. This results in the plating layer 12 having a black appearance. Heating in an atmosphere of 90% RH or higher forms a Zn-containing oxide 15 containing oxygen-deficient oxides with a relatively low oxygen content compared to heating in air. The oxygen-deficient oxides have a black color. Furthermore, since one or both of Co and Ni are present on the surface of the plating layer 12 before the heating step, the progression of oxidation into the plating layer 12 during the steam oxidation treatment is suppressed.

[0122] The soaking temperature is set to 100°C or higher to sufficiently form the Zn-containing oxide 15. The higher the soaking temperature, the faster the Zn-containing oxide 15 forms. However, once the Zn-containing oxide 15 reaches a certain thickness, the oxygen on the surface of the plating layer 12 becomes diffusion-limited, and the degree of blackening and the growth of its thickness stop. Therefore, if the soaking temperature in the heating step is set too high, the white oxide and the plating layer 12 begin to dissolve. Therefore, the soaking temperature is set to 210°C or lower.

[0123] The soaking time is set to a range of 20 to 40 hours. If the soaking time is less than 20 hours, the formation of the Zn-containing oxide 15 does not proceed sufficiently, and the average brightness of the surface of the plating layer 12 cannot be sufficiently reduced. On the other hand, if the soaking time exceeds 40 hours, oxidation of the inside of the plating layer 12 proceeds, and the corrosion resistance of the plating layer 12 deteriorates.

[0124] The timing of the heating step is not particularly limited as long as it is performed after either or both of Co and Ni are attached to the specific region. For example, the heating step may be performed after the chemical conversion treatment step in which Co and Ni are attached. Also, the heating step may be performed between the above-mentioned attachment step and the chemical conversion treatment step in which Co and Ni are not attached. Furthermore, the heating step may be performed after the above-mentioned attachment step.

[0125] In the manufacturing method of this embodiment, an optional step may be a film formation step in which the organic resin film 14 is formed. The film formation step may be performed after either or both of the adhesion step and the chemical conversion treatment step, or may be performed after the heating step. In other words, the heating step may be performed after the formation of the organic resin film 14 or before the formation of the organic resin film 14.

[0126] For example, when the organic resin coating 14 is a coating layer, an organic paint containing an organic resin may be applied to the surface of the plated steel material 1 and then dried without rinsing with water. Examples of application methods include roll coating, spin coating, and spraying. On the other hand, when the organic resin coating 14 is a laminate layer, a film containing an organic resin may be laminated on the surface of the plated steel material 1.

[0127] Examples of the present invention will be described below. However, the conditions in the examples are merely examples adopted to confirm the feasibility and effects of the present invention. The present invention is not limited to these examples. Various conditions may be adopted in the present invention as long as they do not deviate from the gist of the present invention and the object of the present invention is achieved.

[0128] A cold-rolled steel plate (SPCC JIS G3141:2021) measuring 200 mm x 100 mm x 1.2 mm thick was used as the base steel. A hot-dip galvanizing simulator manufactured by Rhesca was used to prepare an alloy by mixing a predetermined amount of pure metals and the like with this base steel. This alloy was melted to form a hot-dip galvanizing bath, and the base steel was immersed in the hot-dip galvanizing bath and then pulled out. Details are described below.

[0129] Before plating, the base steel is ２ -H ２ The surface of the base steel material was fully reduced by holding it at 800°C for 1 minute in a 5% N atmosphere (dew point -40°C). After that, it was immersed in a plating bath (melting point of plating bath +30°C) for 3 seconds and then pulled out. ２ Gas wiping was applied to achieve a coating thickness of 2 to 80 μm. Immediately after wiping, the steel was cooled to room temperature at an average cooling rate of 10° C. / sec. Thus, a plated steel material was produced.

[0130] Next, as a metal deposition step, either one or both of a deposition step and a chemical conversion treatment step was performed. When both the deposition step and the chemical conversion treatment step were performed, they were performed in this order.

[0131] (Deposition Step) In the deposition step, first, a solution containing at least one of Co and Ni was prepared. The solution was either a Co source or a Ni source, or an aqueous solution containing either. Cobalt sulfate was used as the Co source. Nickel sulfate was used as the Ni source. The content of the Co source or Ni source compound in the solution was 0.5 to 15 g / L in total, calculated as Ni and Co. The temperature of the solution was 45°C.

[0132] Next, the plated steel sheet was immersed in the prepared solution and then pulled out, so that the solution was adhered to the surface of the plated steel sheet, which was then immediately dried with hot air.

[0133] The test examples in which the deposition step was performed are Examples 1 to 13, 18, and 19, Comparative Examples 1 to 6, Comparative Examples 8 to 13, and Comparative Example 16. Table 4 shows the target deposition amounts of Co and Ni, and the Co and Ni contents in each solution, calculated as Co and Ni.

[0134] (Chemical Conversion Treatment Step for Adhering Co and Ni) Examples 1 to 19 and Comparative Examples 1 to 16 used an organic-inorganic composite chemical conversion treatment layer, Example 21 used an inorganic chemical conversion treatment layer, and Example 22 used an organic chemical conversion treatment layer. Specifically, Example 21 used a chemical conversion treatment solution containing at least one crosslinking agent selected from the group consisting of a silane coupling agent, a crosslinkable zirconium compound, and a crosslinkable titanium compound. Example 22 used an aqueous chemical conversion treatment solution containing a resin and silica particles. In addition to the resin and silica particles, the chemical conversion treatment solution contained titania particles, alumina particles, zirconia particles, etc. Also, it contained either a Nb compound or a phosphate compound, or both. In Examples 1 to 19 and Comparative Examples 1 to 16, a mixture of the chemical conversion treatment solutions used in Examples 21 and 22 was used. Note that in Example 20, no chemical conversion treatment was performed, and a plated steel material without a chemical conversion treatment layer was used.

[0135] The chemical conversion treatment solution contained either Co or Ni, or both. The total content of Co or Ni in the chemical conversion treatment solution was 0.5 to 3 mass % calculated as Ni and Co. The temperature of the chemical conversion treatment solution was 30°C.

[0136] Next, the plated steel material was immersed in the prepared chemical conversion treatment solution and then pulled out, and then heated to 80° C. to form a chemical conversion treatment layer containing Co or Ni.

[0137] Test examples in which a chemical conversion treatment step to deposit Co and Ni was carried out are Examples 5 to 19, 21, and 22, and Comparative Examples 7 to 13 and 16. Note that in Examples 1 to 4 and Comparative Examples 1 to 6, 14, and 15, chemical conversion treatment was carried out using a chemical conversion treatment solution that did not contain Co or Ni.

[0138] Table 4 shows the target deposition amounts of Co and Ni, and the Co and Ni contents in the chemical conversion treatment solution, calculated as Co and Ni.

[0139] (Heating Step) Next, after the metal deposition step, the plated steel sheet was subjected to a heat treatment at 87 to 95% RH, a soaking temperature of 95 to 220°C, and atmospheric pressure for 15 to 50 hours to form a black oxide on the surface of the plating layer. However, in Example 19, the heat treatment was performed after the deposition step, and the chemical conversion treatment step was performed after the heating step. In Comparative Example 16, the heating step was not performed. In this manner, the plated steel materials of Examples 1 to 19 and Comparative Examples 1 to 16 were produced.

[0140] In Example 18, an organic resin film was formed after the heating step.

[0141] The chemical composition of the plating layer was identified as follows. First, a sample was taken from plated steel material 1 to obtain a plating layer measuring 30 mm x 30 mm. Next, the surface of the plating layer was polished with abrasive paper. The polishing was performed so that at least 80% of the plating layer thickness remained. If an organic resin film or chemical conversion treatment layer was present on the surface of the plating layer, these were also removed by polishing. The plating layer was then stripped and dissolved using an acid containing an inhibitor that suppresses corrosion of the base steel to obtain an acid solution. The resulting acid solution was then analyzed using ICP atomic emission spectroscopy or ICP-MS to determine its chemical composition. The inhibitor used was Hibilon (A-6) (manufactured by Sugimura Chemical Industry Co., Ltd.), a pickling corrosion inhibitor. Specifically, a 10% aqueous hydrochloric acid solution containing 1% Hibilon (A-6) was used as the inhibitor-containing acid. The results are shown in Tables 1 to 3. Σ in Tables 1 to 3 represents the total amount of each element group.

[0142] The thickness of the plating layer was measured by exposing a cross section of the plating layer in the thickness direction and observing the cross section with a scanning electron microscope (SEM) equipped with an energy dispersive X-ray elemental analyzer (EDS). The chemical composition of the plating layer was analyzed with EDS to identify the range in which the Zn concentration was 40 mass% or more. This range was designated as the plating layer, and the thickness of the plating layer was measured. The thickness was measured at three arbitrary locations, and the arithmetic mean of the thicknesses at the three locations was designated as the thickness of the plating layer.

[0143] The amounts of Ni and Co present on the surface of the plating layer were measured as follows.

[0144] The measurements were performed by sputtering the surface of the plated steel (i.e., scraping off the surface) in combination with measurement of element concentrations using XPS (X-ray photoelectron spectroscopy). The sputtering area was 1.0 mm x 1.0 mm, and sputtering was performed with argon. Sputtering was performed to a depth of 10 nm per run. After each 10 nm of sputtering, the concentrations of C, O, Si, Zn, Al, Mg, Co, and Ni were measured using XPS on the surface newly revealed by sputtering. This sputtering and XPS measurement were repeated. Sputtering and XPS measurements were performed until the sputtering depth reached the plating layer. The determination of whether the sputtering depth had reached the plating layer was made when the O (oxygen) concentration decreased to 0.7 mass %.

[0145] By repeating sputtering and measurement by XPS, the concentrations of C, O, Si, Zn, Al, Mg, Co, and Ni were obtained for each sputtering depth. Based on the obtained concentration measurement results of each element, the interface between the organic resin film and the chemical conversion layer, and the interface between the chemical conversion layer and the plating layer were identified, and the range of the specific region was also identified. The method for identifying these interfaces and specific regions is as described below. Then, based on the measurement results of the concentrations of Ni and Co in the specific region, the amounts of Co and Ni per area (mg / m ２ ) was calculated.

[0146] The conditions for measuring the element concentration by sputtering and XPS method were as follows: <Sputtering> Acceleration voltage of Ar ion gun: 1 kV Irradiation angle of Ar ion beam to sample: 45° Sputtering rate: Si measured separately ２ O sputtering rate <XPS analysis> X-ray source: mono-Al Kα X-ray output: 15 kV, 25 W X-ray diameter: 100 μmφ Measurement area: 300 μm × 300 μm

[0147] Hereinafter, a method for identifying the organic resin film, the chemical conversion coating layer, and the interface of each of the chemical conversion coating layers, as well as a method for identifying the specific region, will be described.

[0148] When sputtering begins on the surface of the plated steel material, in Example 18, since an organic resin film is formed, sputtering occurs in the order of the organic resin film, the chemical conversion coating layer, and the plating layer. In Example 20, since neither an organic resin film nor a chemical conversion coating layer is formed, the plating layer is sputtered. In the test examples other than Examples 18 and 20, sputtering occurs in the order of the chemical conversion coating layer and the plating layer.

[0149] The specific region in Example 18 was the region from the interface between the organic resin film and the chemical conversion coating layer to the interface between the chemical conversion coating layer and the plating layer, and the position of each interface was determined from the measurement results of the XPS method. The specific region in Example 20 was the region ranging from the surface of the plating layer to a depth of 50 nm. Furthermore, the specific regions in the test examples other than Examples 18 and 20 were the region from the surface of the chemical conversion coating layer to the interface between the chemical conversion coating layer and the plating layer, and the position of each interface was determined from the measurement results of the XPS method.

[0150] The determination method is described below. For Example 18, when the organic resin film was subjected to XPS analysis while being sputtered, the C concentration was 8.0% or more and the concentrations of the main constituent elements of the chemical conversion coating layer 13 were less than 8.0%.

[0151] Next, (after sputtering of the organic resin film was completed) an organic-inorganic composite chemical conversion coating layer was sputtered and subjected to XPS analysis. The concentration of Si, the main constituent element of the chemical conversion coating layer, was found to be 8.0 mass % or more.

[0152] From the above, in Example 18, the interface between the organic resin film and the organic-inorganic composite chemical conversion coating layer was set at a depth where the Si concentration was 8.0 mass %.

[0153] As a result, the position of one interface of the specific region was identified for Example 18.

[0154] Next, for Example 18, when XPS analysis was performed while sputtering the chemical conversion treatment layer, the O concentration was 0.7 mass% or more. However, when XPS analysis was performed while sputtering the plating layer (after sputtering of the chemical conversion treatment layer was completed), the O concentration became less than 0.7 mass%.

[0155] From the above, in Example 18, the interface between the chemical conversion layer and the plating layer was determined to be the region between the depth where the O concentration was 0.7% (as will be described later, this depth position is the end of the specific region) and a depth 50 nm away from the depth where the O concentration was 0.7% toward the surface of the chemical conversion layer. This allowed the position of the other interface of the specific region to be identified. Furthermore, in this example, the interface between the chemical conversion layer and the plating layer was not interpreted as an "interface" with no thickness. In this example, the interface between the chemical conversion layer and the plating layer was considered to be the depth where the O concentration was 0.7% and a depth 50 nm away from the depth where the O concentration was 0.7% toward the surface 13a of the chemical conversion layer. Therefore, the end of the specific region was determined to be the depth position where the O concentration was 0.7 mass%.

[0156] The specific region was defined as the region extending from the depth position of the interface between the organic resin film and the chemical conversion layer to the depth position of the interface between the chemical conversion layer and the plating layer.

[0157] The Co and Ni concentrations in the sputtered area (i.e., the 10-nm-thick area removed by sputtering) were considered to be the same as the Co and Ni concentrations measured by XPS on the surface before sputtering. The total amount of Co and Ni per surface area of ​​the plating layer in the specific area (total amount per area) was calculated by summing the Co and Ni deposition amounts for each sputtered thickness (i.e., 10 nm) in the specific area. However, if the sputtered area included the beginning of the specific area, the entire area was considered to be the specific area, and the Co and Ni deposition amounts in this area were summed. If the O concentration in the XPS analysis after sputtering was 0.7%, i.e., if the area was determined to be the end of the specific area, it was unnecessary to sum the Co and Ni deposition amounts in the XPS analysis results. In other words, the Co and Ni deposition amounts in the XPS analysis results immediately before the end of the specific area were summed. The analytical value by the XPS method was the average value of measurements taken at any five points on each surface to be analyzed.

[0158] The total amount of Co and Ni per surface area of ​​the plating layer only at the interface between the plating layer and the chemical conversion layer (total amount per area) was calculated by summing the amounts of Co and Ni deposited in the sputtered range from "a position 50 nm away from the depth position where the O concentration is 0.7 mass% toward the chemical conversion layer" to "a position 50 nm away from the depth position where the O concentration is 0.7 mass%." The total amount of Co and Ni per surface area of ​​the plating layer in a specific region other than the interface between the plating layer and the chemical conversion layer (total amount per area) was calculated by subtracting the total amount of Co and Ni deposited in the range including "a position 50 nm away from the depth position where the O concentration is 0.7 mass% toward the chemical conversion layer" from the total amount of Co and Ni per surface area of ​​the plating layer in the specific region.

[0159] The concentration of each element determined by XPS analysis was expressed as a mass percentage relative to the total amount of C, O, Si, Zn, Al, Mg, Co, Zr, V, Cr, F, S, Ti, and Ni.

[0160] Furthermore, we will provide additional information regarding the measurement methods for Ni and Co in Examples 1 to 19, 21, and 22 and Comparative Examples 1 to 16, in which no organic resin film was formed on the surface of the plating layer. When no organic resin film was present on the surface of the plated steel material but a chemical conversion coating layer was present, the range of the specific region was defined as the depth position from the surface of the chemical conversion coating layer where the O concentration was 0.7 mass % at the interface between the chemical conversion coating layer and the plating layer (the deepest depth position where analysis was performed by sputtering and XPS). In other words, the start of the specific region was the surface of the chemical conversion coating layer, and the end of the specific region was defined as the depth position where the O concentration was 0.7 mass %.

[0161] Furthermore, in Example 20, sputtering was started on the surface of the plating layer, and the specific region was defined as a range from the surface of the plating layer to a depth of 50 nm.

[0162] Table 4 lists the Co and Ni concentrations at the interface between the plating layer and the chemical conversion layer and those in specific regions other than the interface between the plating layer and the chemical conversion layer separately. The interface between the plating layer and the chemical conversion layer was defined as the region between the depth where the O concentration was 0.7% and a depth 50 nm away from the depth where the O concentration was 0.7% toward the surface of the chemical conversion layer. The results are shown in Table 5.

[0163] The thickness of the Zn-containing oxide was measured as follows. First, to cut out a thin film sample for TEM measurement, the plating layer was extracted from the plated steel material by processing using a focused ion beam (FIB) method, to obtain a thin section sample measuring 10 μm × 10 μm × 100 nm in thickness. Next, the oxygen concentration and Zn concentration on the surface of the plating layer were measured using a transmission electron microscope (TEM-EDS) equipped with an X-ray elemental analyzer (EDS) at an acceleration voltage of 300 kV. Regions where the oxygen concentration was 5.0 mass% or more and the Zn concentration was 5.0 mass% or more were identified as Zn-containing oxides, and their thicknesses were measured. In the TEM observation, a field of view in which the interface between the Zn-containing oxide and the plating layer fell within 5 μm was defined as one field of view, and the thickness of the Zn-containing oxide was measured in each of three fields of view. The arithmetic mean of the thicknesses of the Zn-containing oxide in each field of view was defined as the thickness of the Zn-containing oxide. The results are shown in Table 5.

[0164] CIE 1976 lightness index L of plated steel surface ＊was measured by a spectral reflectance measurement method in accordance with JIS K 5600-4-5:1999 using a spectrophotometer. The spectrophotometer used was a spectrophotometer (TC-1800) manufactured by Tokyo Denshoku Co., Ltd. The measurement conditions were as follows. The results are shown in Table 5.

[0165] Optical conditions: d / 8° method (double beam optical system) Field of view: 2-degree field of view Measurement method: reflected light measurement Standard light: C Color system: CIELAB Measurement wavelength: 380 to 780 nm Measurement wavelength interval: 5 nm Spectrometer: diffraction grating 1200 / mm Illumination: halogen lamp (voltage 12 V, power 50 W, rated life 2000 hours) Measurement area: 7.25 mmφ Detector: photomultiplier tube (R928; Hamamatsu Photonics K.K.) Reflectance: 0-150% Measurement temperature: 23°C Standard plate: white

[0166] The measurement was carried out by drawing grid lines at 20 mm intervals vertically and horizontally on the surface of the plating layer, and measuring points were set at nine points within a range of three vertical points and three horizontal points, and measurements were made within a circular area with a radius of 10 mm centered on the measurement points. ＊ The average of the values ​​is calculated as the CIE 1976 lightness index L ＊ It was decided.

[0167] If a chemical conversion coating or organic resin film is formed on the surface of the plating layer, these may remain attached to the L. ＊ The values ​​were measured.

[0168] The flat surface corrosion resistance was evaluated as follows. The obtained plated steel material was cut into 100 mm x 50 mm pieces and subjected to a flat surface corrosion resistance evaluation test. The flat surface corrosion resistance was evaluated according to JIS H 8502:1999 8.1 Neutral Salt Spray Cycle Test Method, and the corrosion weight loss was compared after 90 cycles. The evaluation criteria were as follows, with "AAA", "AA", and "A" being considered acceptable.

[0169] AAA: Corrosion weight loss 30g / m ２ Less than AA: Corrosion weight loss 30g / m ２ 60g / m or more ２ Less than A: Corrosion weight loss 60g / m ２ 90g / m or more ２ Less than B: Corrosion weight loss 90g / m２ End

[0170] As shown in Tables 1 to 5, in Examples No. 1 to 22, the chemical composition of the plating layer satisfies the range of the present invention, and either or both of Co and Ni are present on the surface of the plating layer in a total amount of 1.0 to 8.0 mg / m ２ The manufacturing conditions were within the scope of the present invention. ＊ The value of the blackening coefficient was less than 40. Therefore, Examples Nos. 1 to 22 had a sufficiently blackened surface and excellent corrosion resistance. In particular, the corrosion resistance was better than that of Comparative Examples Nos. 13 and 14, which were produced according to conventional methods.

[0171] On the other hand, in Comparative Example No. 1, the Mg content of the plating layer was insufficient. ＊ The blackening was insufficient, and the corrosion resistance was also poor.

[0172] Comparative Example No. 2 had an excessive Mg content in the plating layer, which resulted in poor corrosion resistance.

[0173] In the comparative example No. 3, the Al content of the plating layer was insufficient. ＊ The blackening was insufficient, and the corrosion resistance was also poor.

[0174] Comparative Example No. 4 had an excessive Al content in the plating layer. ＊ The blackening was insufficient, and the corrosion resistance was also poor.

[0175] Comparative Example No. 5 had an excessive Si content in the plating layer, which resulted in poor corrosion resistance.

[0176] Comparative Examples Nos. 6 to 8 have a total of 8.0 mg / m of Co and Ni on the surface of the plating layer. ２ Therefore, the corrosion resistance was good, but the CIE 1976 lightness index L ＊ was over 40, resulting in insufficient blackening.

[0177] In the comparative example No. 9, the soaking temperature of the steam oxidation treatment was less than 100°C. Therefore, the CIE 1976 lightness index L ＊ was over 40, resulting in insufficient blackening.

[0178] In Comparative Example No. 10, the soaking temperature of the steam oxidation treatment exceeded 210° C. As a result, oxidation progressed to the inside of the plating layer, resulting in poor corrosion resistance.

[0179] In the comparative example No. 11, the relative humidity during the steam oxidation treatment was less than 90%. Therefore, the CIE 1976 lightness index L ＊ The value was over 40, and the blackening was insufficient.

[0180] In the comparative example No. 12, the soaking time for the steam oxidation treatment was less than 20 hours. Therefore, the CIE 1976 lightness index L ＊ The value was over 40, and the blackening was insufficient.

[0181] In Comparative Example No. 13, the soaking time for the steam oxidation treatment exceeded 40 hours, which resulted in oxidation progressing to the interior of the plating layer and inferior corrosion resistance.

[0182] Comparative Examples No. 14 and No. 15 were subjected to steam oxidation treatment without the presence of Co or Ni on the surface of the plating layer, resulting in poor corrosion resistance.

[0183] Comparative Example No. 16 was not subjected to the steam oxidation treatment, and therefore had a CIE 1976 lightness index L ＊ The value was over 40, and the blackening was insufficient.

[0184]

[0185]

[0186]

[0187]

[0188]

[0189] It is possible to provide a plated steel material whose surface is sufficiently blackened and which has superior corrosion resistance to conventional black-plated steel materials.

[0190] REFERENCE SIGNS LIST 1... Plated steel material 11... Base steel material 12... Plated layer 13... Chemical conversion treatment layer 14... Organic resin film 15... Zn-containing oxide

Claims

1. A plated steel material having a base steel, a plating layer disposed on the surface of the base steel, and a chemical conversion treatment layer disposed on the surface of the plating layer, wherein the chemical composition of the plating layer is, in mass%, Al: more than 10.0 to 40.0%, Mg: more than 4.0 to 15.0%, Si: 0 to 1.0%, Sn: 0 to 0.7%, Bi: 0 to 0.3%, In: 0 to 0.3%, total amount of Sn, Bi, and In ΣX: 0 to 0.7%, Ca: 0 to 0.6%, Y: 0 to 0.3%, La: 0 to 0.3%, Ce: 0 to 0.3%, Sr: 0 to 0.3%, Li: 0 to 0.3%, total amount of Ca, Y, La, Ce, Sr, and Li ΣYa: 0 to 0.6%, Cr: 0 to 1.0%, Ni: 0 to 1.0%, Mo: 0 to 0.25%, Cu: 0 to 1.0%, Ag: 0 to 0.25%, Sb: 0 to 0.25%, Pb: 0 to 0.25%, Total amount of Cr, Ni, Mo, Cu, Ag, Sb, and Pb ΣYb: 0 to 1.0%, B: 0 to 0.5%, P: 0 to 0.5%, Total amount of B and P ΣYc: 0 to 0.5%, Ti: 0 to 0.25%, Co: 0 to 0.25%, V: 0 to 0.25%, Nb: 0 to 0.25%, Mn: 0 to 0.25%, Zr: 0 to 0.25%, W: 0 to 0.25%, The total amount ΣZ of Ti, Co, V, Nb, Mn, Zr, and W is 0 to 0.25%, Fe is 0 to 5.0%, and the balance is Zn and impurities, and the total amount of Co and Ni in a specific region from the interface between the plating layer and the chemical conversion treatment layer to the surface of the chemical conversion treatment layer is 1.0 to 8.0 mg / m per surface area of ​​the plating layer. ２ a Zn-containing oxide having a thickness of 0.02 to 0.10 μm is present on the surface of the plating layer, and the plated steel material has a CIE 1976 lightness index L ＊ A plated steel material having a hardness of less than 40.

2. The total amount of Co and Ni at the interface between the plating layer and the chemical conversion treatment layer is 1.0 to 8.0 mg / m of surface area of ​​the plating layer. ２ and the total amount of Co and Ni in the specific region other than the interface between the plating layer and the chemical conversion treatment layer is 1.0 mg / m2 per surface area of ​​the plating layer. ２ The plated steel product according to claim 1, wherein the Cr content is less than 100%.

3. The total amount of Co and Ni at the interface between the plating layer and the chemical conversion treatment layer is less than 1.0 mg / m per surface area of ​​the plating layer. ２ and the total amount of Co and Ni in the specific region other than the interface between the plating layer and the chemical conversion treatment layer is 1.0 to 8.0 mg / m2 per surface area of ​​the plating layer. ２ The plated steel material according to claim 1, wherein 4. The plated steel material according to claim 1, which does not have the chemical conversion coating layer, and the specific region is only the interface between the plated layer and the chemical conversion coating layer.

Images