Plated steel and solar power generation mounting systems

Abstract

This plated steel product has a steel sheet, a plating layer formed on the steel sheet, and an oxide layer formed on the plating layer, wherein the plating layer has a chemical composition containing, by mass%, 1.0-60.0% Al, 1.0-15.0% Mg, 0-2.0% Si, 0-2.0% Ca, and 0-2.0% Fe, with the balance being Zn and impurities, the oxide layer has a thickness of 5 nm or more, and an (Al+Mg) / Zn intensity ratio, which is the ratio of the sum of the maximum intensity of Al and the maximum intensity of Mg to the maximum intensity of Zn in energy dispersive X-ray analysis of the oxide layer, is 1.0 or more, and the oxide layer contains an amorphous structure.

Description

[Technical field]

[0001] The present disclosure relates to a plated steel material and a solar power generation mounting system. [Background technology]

[0002] Steel materials with a hot-dip Zn-coated layer containing Al and Mg formed on the surface (hot-dip Zn-Al-Mg-coated steel materials) have excellent corrosion resistance, and are therefore widely used as materials for structural members such as building materials that require corrosion resistance.

[0003] For example, Patent Document 1 discloses a steel sheet having a plating layer formed on at least a part of the surface of the steel sheet, and an oxide layer formed on at least a part of the surface of the plating layer, and when XPS measurement was performed at a position 5.0 nm from the surface of the oxide layer in the thickness direction, IMg / IMg Ox is 0.00 or more and 1.20 or less. Patent Document 1 discloses that the above-mentioned configuration makes it possible to increase the proportion of Mg contained in the plating layer that exists as an oxide [MgO] or hydroxide [Mg(OH)2] and to decrease the proportion of Al contained in the plating layer that exists as an oxide [Al2O3] or hydroxide [Al(OH)3], thereby improving the lubricity and chemical conversion treatability of the plating layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2022 / 153840 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, hot-dip Zn-Al-Mg-plated steel materials are also required to have corrosion resistance in flowing water. The corrosion resistance in flowing water is the corrosion resistance when exposed to flowing water. In a flowing water environment, the corrosion products attached to the surface of the hot-dip plating layer are washed away, and the rust-preventive effect of the corrosion products is impaired. Therefore, the corrosion resistance of steel materials in flowing water is evaluated by a method different from that of ordinary corrosion resistance. For example, high corrosion resistance in flowing water is required for materials used as various building materials used outdoors, such as guardrails installed on roads, solar power generation racks, and the walls of irrigation channels through which rainwater and industrial water always flow.

[0006] In the prior art, there has been little consideration of flowing water corrosion resistance. For example, the corrosion resistance of flat surfaces, which is a well-known conventional evaluation method, is often evaluated in accordance with JASO M609-91, in which the corrosive solution is assumed to be in a stationary state.

[0007] Furthermore, the inventors have found that even hot-dip Zn-Al-Mg-plated steel materials, which are generally highly corrosion-resistant, do not have sufficient corrosion resistance in running water. For example, Patent Document 1 specifies the ratio of each oxide in the oxide layer on the surface of the plating layer, but the inventors have found that this alone may make the steel susceptible to corrosion in a running water environment, that is, may result in insufficient corrosion resistance in running water.

[0008] The present disclosure has been made in consideration of the above-mentioned circumstances. The present disclosure has an object to provide a plated steel material and a solar power generation rack having excellent corrosion resistance against running water. [Means for solving the problem]

[0009] The gist of the present disclosure is as follows. [1] A plated steel material according to one aspect of the present invention includes a steel sheet, a plating layer formed on the steel sheet, and an oxide layer formed on the plating layer; having The plating layer comprises, in mass %, Al: 1.0-60.0%, Mg: 1.0-15.0%, Si: 0-2.0%, Ca: 0-2.0%, and Fe: 0-2.0%, and further comprising Ni: 0 to 1.000%, La: 0 to 0.500%, Ce: 0 to 0.500%, Sb: 0 to 0.500%, Pb: 0~0.500%, Sr: 0 to 0.500%, Bi: 0 to 0.500%, Sn: 0~1.000%, Cu: 0-1.000%, Ti: 0 to 1.000%, Mn: 0 to 1.000%, Cr: 0~1.000%, Nb: 0 to 1.000%, Zr: 0 to 1.000%, Mo: 0~1.000%, V: 0 to 1.000%, In: 0 to 1.000%, Co: 0 to 1.000%, Ag: 0~1.000%, Li: 0~1.000%, B: 0 to 0.500%, Y: 0 to 0.500%, and P: 0 to 0.500%, and a chemical composition containing 5.0% or less of one or more selected from the group consisting of, with the balance being Zn and impurities; The thickness of the oxide layer is 5 nm or more, the oxide layer has an (Al+Mg) / Zn intensity ratio, which is a ratio of the sum of the maximum intensity of Al and the maximum intensity of Mg to the maximum intensity of Zn in an energy dispersive X-ray analysis, of 1.0 or more; The oxide layer includes an amorphous structure. [2] The plated steel material according to the above item [1], wherein the chemical composition of the plating layer is, in mass%, Si: 0.1 to 2.0%, Ca: 0.1-2.0%, Fe: 0.1-2.0%, Ni: 0.001 to 1.000%, La: 0.010 to 0.500%, Ce: 0.010-0.500%, Sb: 0.001 to 0.500%, Pb: 0.001~0.500%, Sr: 0.001 to 0.500%, Bi: 0.001 to 0.500%, Sn: 0.050~1.000%, Cu: 0.001 to 1.000%, Ti: 0.001 to 1.000%, Mn: 0.001 to 1.000%, Cr: 0.001 to 1.000%, Nb: 0.001 to 1.000%, Zr: 0.001 to 1.000%, Mo: 0.001 to 1.000%, V: 0.001 to 1.000%, In: 0.001 to 1.000%, Co: 0.001 to 1.000%, Ag: 0.001~1.000%, Li: 0.001 to 1.000%, B: 0.001 to 0.500%, Y: 0.010 to 0.500%, and P: 0.001 to 0.500%, It may contain one or more of the above. [3] The plated steel material according to the above [1] or [2], in the chemical composition of the plating layer, Al: 10.0~30.0% by mass, Mg:4.0~15.0% by mass and The (Al+Mg) / Zn intensity ratio of the oxide layer may be 2.0 or more. [4] The plated steel material according to any one of the above [1] to [3], in the chemical composition of the plating layer, Al: 15.0~30.0% by mass, Mg:4.0~15.0% by mass and The (Al+Mg) / Zn intensity ratio of the oxide layer may be 3.0 or more. [5] In the plated steel material according to any one of the above [1] to [4], no diffraction spots indicative of a crystalline structure may be detected in an electron beam diffraction image obtained by analyzing a cross section of the oxide layer using electron beam diffraction. [6] A photovoltaic power generation rack according to an aspect of the present invention includes the plated steel material according to any one of the above [1] to [5]. Effect of the Invention

[0010] According to the above aspects of the present disclosure, it is possible to provide a plated steel material and a solar power generation rack having excellent resistance to corrosion by running water. [Brief description of the drawings]

[0011] [Figure 1] 1 is an electron beam diffraction image of a cross section of an oxide layer in a plated steel material according to an embodiment of the present invention, taken with a TEM (transmission electron microscope). [Diagram 2] 1 is an electron beam diffraction image of a cross section of an oxide layer in a plated steel material according to an embodiment of the present invention, taken with a TEM (transmission electron microscope). [Diagram 3] FIG. 1 is a schematic diagram showing an example of a photovoltaic power generation stand according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] A plated steel material according to an embodiment of the present disclosure (hereinafter, may be referred to as the plated steel material according to the present embodiment) will be described. However, the present disclosure is not limited to the configuration disclosed in the present embodiment, and various modifications are possible without departing from the spirit of the present disclosure.

[0013] Each of the constituent elements of the present disclosure will be described in detail below. In the following, the numerical ranges described with "~" include the lower and upper limits. Numerical values ​​indicated as "less than" or "greater than" are not included in the numerical range. In the following description, % for chemical composition is mass % unless otherwise specified.

[0014] [Hot-dip galvanized steel] The plated steel material according to the present embodiment includes a steel sheet, a plating layer formed on the steel sheet, and an oxide layer formed on the plating layer. In the plated steel material according to the present embodiment, the oxide layer has a thickness of 5 nm or more, an (Al+Mg) / Zn intensity ratio, which is a ratio of the sum of the maximum intensity of Al and the maximum intensity of Mg to the maximum intensity of Zn in an energy dispersive X-ray analysis of the oxide layer, is 1.0 or more, and the oxide layer includes an amorphous structure.

[0015] <Steel> The steel material to be plated will now be explained. The steel material is, for example, mainly a steel plate, but there is no particular limit to the size thereof. The steel sheet may be any steel sheet that can be used in a normal hot-dip galvanizing process. Specifically, this applies to steel sheets that can be used in processes such as continuous hot-dip galvanizing lines (CGLs) where the steel sheet is immersed in molten metal and solidified. The size of the steel sheet that can be used is, for example, 10 mm or less in thickness and 2000 mm or less in width, but is not limited to this.

[0016] There are no particular limitations on the quality of the steel material. Examples of applicable steel materials include various steel plates such as general steel, Al-killed steel, extra-low carbon steel, high carbon steel, various high tensile steels, some high alloy steels (steels containing elements that enhance corrosion resistance such as Ni and Cr), steel for bolts, and steel wire for bridge cables. More specifically, for example, cold-rolled steel sheets defined in JIS G 3131, 3141:2017, which are included in general structural rolled steel materials corresponding to so-called SS materials, so-called general steels included in hot-rolled steel sheets defined in JIS G3193:2008, pre-plated steels such as JIS H8641, JIS G 3302, 3303, 3313, 3314, 3315, 3317, and 3321 thinly plated with various metals, JIS G 3136 Al-killed steel, extra-low carbon steel, high carbon steel, and various high-tensile steels described in JIS G 3113, 3134, and 3135 are applicable.

[0017] <Oxide layer> The plated steel material according to this embodiment has an oxide layer on a plating layer. When the plating layer is on both sides of the steel material, the oxide layer may be provided on one side of the plating layer or on both sides.

[0018] The present inventors have investigated methods for improving the corrosion resistance of running water in plated steel (particularly Zn-Al-Mg plated steel). As a result, they have found that the inclusion of an amorphous structure in an oxide layer improves the corrosion resistance of running water. Specifically, they have found that the corrosion resistance of running water is improved when the (Al+Mg) / Zn intensity ratio, which is the ratio of the sum of the maximum intensity of Al and the maximum intensity of Mg to the maximum intensity of Zn in energy dispersive X-ray analysis of the oxide layer, is 1.0 or more.

[0019] The reason why the inclusion of an amorphous structure in the oxide layer improves the corrosion resistance of the plating layer in running water is not clear, but the present inventors believe that the reason is as follows. First, as the amorphization of the structure in the oxide layer progresses, the number of grain boundaries decreases. Since grain boundaries are generally susceptible to corrosion, it is believed that the amorphization of the structure reduces the presence of grain boundaries, thereby improving corrosion resistance in flowing water.

[0020] It is also preferable that the oxide layer does not contain crystalline structures. In other words, it is preferable that all of the oxides constituting the oxide layer are amorphous. However, it is the surface layer of the oxide layer that has a large effect on the corrosion resistance in running water. Therefore, it is sufficient that the surface layer of the oxide layer is amorphous. Note that the "surface layer" here refers to the region from the outermost surface of the oxide layer to a depth of 100 nm.

[0021] Whether the structure contained in the oxide layer is amorphous or crystalline can be confirmed by an electron beam diffraction image of the cross section of the oxide layer taken with a TEM (transmission electron microscope). If the structure is amorphous, a halo pattern is observed, and if a crystalline structure (metallic phase) is contained, diffraction spots indicating a crystalline structure (crystal diffraction spots) are observed around the halo pattern.

[0022] 1 and 2 are electron beam diffraction images of a cross section of an oxide layer in a plated steel material according to this embodiment taken with a TEM (transmission electron microscope). In the case of the electron beam diffraction image shown in FIG. 1, only a halo pattern is observed, which indicates that the structure contained in the oxide layer is an amorphous structure. In the case of the electron beam diffraction image shown in FIG. 2, crystal diffraction spots are observed around the halo pattern, which indicates that both an amorphous structure and a metal phase are contained in the oxide layer. In this embodiment, either the pattern in FIG. 1 or FIG. 2 may be used. In other words, it is sufficient that a halo pattern is observed in the electron beam diffraction image.

[0023] A method for determining the structure contained in the oxide layer will be described below. In this embodiment, first, a 10 μm square analysis sample is taken from the plated steel material so as to include a cross section of the oxide layer along the sheet thickness direction, and the sample is sliced ​​to a thickness of 50 to 100 nm. Next, the sample surface corresponding to the cross section of the oxide layer is measured at five points every 2 μm in the direction along the plate surface using a TEM ("JEM-2100F", manufactured by JEOL Ltd.) with an electron beam probe diameter of 3 nm, to obtain five electron beam diffraction images. If at least one of the obtained electron beam diffraction images shows a halo pattern, the oxide layer is deemed to contain an amorphous structure. The accelerating voltage during observation with the TEM is 200 kV. If the sample for analysis also contains the plating layer, the plating layer is excluded from the measurement target, and only the oxide layer is measured.

[0024] Moreover, the (Al+Mg) / Zn intensity ratio, which is the ratio of the sum of the maximum intensity of Al and the maximum intensity of Mg to the maximum intensity of Zn in energy dispersive X-ray analysis of the oxide layer, is set to 1.0 or more. Al and Mg are elements that are more likely to form a passive film than Zn. In other words, the higher the content of Al and Mg in the oxide layer, the greater the effect of improving corrosion resistance. In addition, Al oxide is likely to be amorphous. On the other hand, Zn oxide is likely to be crystalline, so an amorphous oxide layer can be easily obtained by increasing the content of Al and Mg in the oxide layer more than that of Zn. From this perspective, the (Al+Mg) / Zn intensity ratio is 1.0 or more. It is preferably 2.0 or more, more preferably 3.0 or more. The upper limit of the (Al+Mg) / Zn intensity ratio is not particularly limited, but may be 6.0 or less.

[0025] The (Al+Mg) / Zn intensity ratio can be determined by the following method. First, a 10 μm square analysis sample is taken from the plated steel material so as to include a cross section of the oxide layer along the sheet thickness direction, and the sample is sliced ​​to a thickness of 50 to 100 nm. Then, the cross section of the oxide layer is observed using a transmission electron microscope (TEM-EDS) equipped with an energy dispersive X-ray analyzer (EDS; "JED-2300Tx2", manufactured by JEOL Ltd.) with an electron beam probe diameter of 3 nm and an irradiation current (set value) of 1.0 nA, and EDS analysis is performed at five points every 2 μm along the sheet surface. The observation position using the TEM is the 1 / 2 thickness position of the cross section of the oxide layer, the accelerating voltage during observation is 200 kV, and the electron beam irradiation time is until the maximum peak intensity in the spectrum obtained by EDS measurement reaches 2000 counts or more. Next, from the obtained X-ray analysis results, the maximum intensity (cps) of Zn, the maximum intensity (cps) of Al, and the maximum intensity (cps) of Mg are obtained, and the ratio of the sum of the maximum intensity of Al and the maximum intensity of Mg to the maximum intensity of Zn is calculated. The intensity ratio is obtained at each of the obtained five points, and the average of them is defined as the "(Al+Mg) / Zn intensity ratio" in this embodiment. In addition, in the obtained X-ray analysis results, "Zn" shows a peak in the range of 1.01±0.1 eV, "Al" shows a peak in the range of 1.49±0.1 eV, and "Mg" shows a peak in the range of 1.25±0.1 eV. By analyzing the peaks in these ranges, the maximum intensity (cps) of Zn, the maximum intensity (cps) of Al, and the maximum intensity (cps) of Mg can be obtained.

[0026] The thickness of the oxide layer is 5 nm or more. If the thickness of the oxide layer is too small, sufficient corrosion resistance to flowing water may not be obtained. Therefore, the thickness of the oxide layer is 5 nm or more. It is preferably 10 nm or more, more preferably 15 nm or more, and even more preferably 20 nm or more. The upper limit of the thickness of the oxide layer is not particularly limited, but is, for example, 50 nm or less.

[0027] The thickness of the oxide layer is measured by the following method. Using a transmission electron microscope (TEM-EDS) image obtained in the same manner as in the measurement of the (Al+Mg) / Zn intensity ratio above, the thickness of the oxide layer was measured at five points at 1 nm pitch on the cross section of the oxide layer, and the average value was defined as the "thickness of the oxide layer."

[0028] <Plating layer> The plated steel material according to this embodiment includes a plating layer on a steel material. The plating layer may be formed on one surface or both surfaces of the steel material. The coating weight of the plating layer is 15 to 250 g / m per side. 2 is preferred.

[0029] (Plating layer structure) In the plated steel sheet according to the present embodiment, the plated structure is not particularly limited. According to the chemical composition of the plated layer of the plated steel sheet according to the present embodiment, the plated structure includes, for example, (Al-Zn) dendrites, a lamellar structure of an (Al-Zn) phase / MgZn2 phase, a lamellar structure of a Zn phase / MgZn2 phase, a ternary eutectic structure of Zn / Al / MgZn2, an MgZn2 phase, a dendrite or amorphous Zn phase, an Mg2Si phase, and / or other intermetallic compound phases.

[0030] (Chemical composition of plating layer) The chemical composition of the plating layer of the plated steel material according to this embodiment will be described below. All percentages relating to the chemical composition below are by mass percent.

[0031] Al: 1.0-60.0% Al is an element effective for ensuring corrosion resistance in a plating layer containing aluminum (Al), zinc (Zn) and magnesium (Mg). In order to fully obtain the above effect, the Al content is set to 1.0% or more. The Al content is preferably 5.0% or more, and more preferably 10.0% or more. On the other hand, if the Al content exceeds 60.0%, the corrosion resistance and the corrosion resistance of the cut end surface of the plating layer are reduced. In addition, the generation of Al oxide increases, and the crystallinity of the oxide layer may increase. Therefore, the Al content is set to 60.0% or less. The Al content is preferably 50.0% or less, and more preferably 40.0% or less.

[0032] Mg: 1.0-15.0% Mg is an element that has the effect of increasing the corrosion resistance of the plating layer. In order to fully obtain this effect, the Mg content is set to 1.0% or more. The Mg content is preferably 4.0% or more, and more preferably 5.0% or more. On the other hand, if the Mg content exceeds 15.0%, the corrosion resistance decreases. Also, problems in production occur, such as an increase in the amount of dross generated in the plating bath. Therefore, the Mg content is set to 15.0% or less. The Mg content is preferably 11.0% or less.

[0033] Si: 0 to 2.0% Si is an element that forms a compound with Mg and contributes to improving the corrosion resistance of the plating layer. In addition, Si is also an element that has the effect of suppressing the formation of an excessively thick alloy layer between the steel sheet and the plating layer when forming a plating layer on a steel sheet, thereby improving the adhesion between the steel sheet and the plating layer. Therefore, it may be contained. It is not necessarily required to contain Si, and the lower limit is 0%, but when obtaining the above effect, it is preferable that the Si content is 0.1% or more. On the other hand, if the Si content exceeds 2.0%, excessive Si crystallizes in the coating layer, the lamellar structure is not sufficiently formed, and the corrosion resistance after painting is reduced. In addition, the workability of the coating layer is reduced. Therefore, the Si content is set to 2.0% or less. The Si content is more preferably 1.5% or less.

[0034] Ca: 0-2.0% When Ca is contained in the coating layer, the amount of dross that is easily formed during coating operation decreases with an increase in the Mg content, improving coating manufacturability. Therefore, Ca may be contained. Ca does not necessarily have to be contained, and the lower limit is 0%, but to obtain the above effect, it is preferable that the Ca content be 0.1% or more. On the other hand, if the Ca content is excessive, the corrosion resistance tends to decrease. Therefore, the Ca content is set to 2.0% or less, and preferably 1.0% or less.

[0035] Fe: 0-2.0% When the plating layer is produced, Fe may be mixed into the plating layer as an impurity from the steel sheet or the like that is the plating base material. It may be contained up to about 2.0%, but within this range, the adverse effect on the properties of the plated steel sheet according to the present embodiment is small. Therefore, the Fe content is preferably 2.0% or less. The Fe content is more preferably 1.5% or less, and further preferably 1.0% or less. On the other hand, since completely preventing the inclusion of Fe would be extremely costly, the Fe content may be set to 0.1% or more.

[0036] The chemical composition of the plating layer of the plated steel material according to this embodiment has the above-mentioned chemical composition, with the remainder being Zn and impurities. The plating layer of the plated steel material according to this embodiment may further contain, in place of a part of Zn, one or more elements selected from the group consisting of Ni, La, Ce, Sb, Pb, Sr, Bi, Sn, Cu, Ti, Mn, Cr, Nb, Zr, Mo, V, In, Co, Ag, Li, B, Y, and P in the following ranges and in a total amount of 5.000% or less. These elements do not necessarily have to be contained, so the lower limit of each content is 0%. It is more preferable that the content of these elements is 3.000% or less in total.

[0037] La: 0 to 0.500% Ce: 0 to 0.500% Y: 0~0.500% La, Ce, and Y are elements that contribute to improving the corrosion resistance of the plating layer. Therefore, any one or more of La, Ce, and Y may be contained. It is not necessary to contain any one of La, Ce, and Y, and the lower limit is 0%, but in order to obtain the above effect, the content of each of La, Ce, and Y is preferably 0.010% or more. On the other hand, if the content of La, Ce, or Y exceeds 0.500%, the viscosity of the coating bath increases, making it difficult to prepare the coating bath itself, and it is not possible to produce a coated steel sheet with good coating properties. Therefore, the content of each of La, Ce, and Y is set to 0.500% or less.

[0038] Sb: 0 to 0.500% Pb: 0 to 0.500% Sr: 0 to 0.500% Bi: 0 to 0.500% Sb, Pb, Sr and Bi contribute to improving corrosion resistance. In order to fully obtain this effect, it is preferable that the content of any one of Sb, Pb, Sr and Bi is 0.001% or more. The contents of Sb, Pb, Sr and Bi are each more preferably 0.005% or more, and further preferably 0.050% or more. On the other hand, if the content of any one of Sb, Pb, Sr and Bi exceeds 0.500%, the corrosion resistance may deteriorate. Therefore, the content of Sb, Pb, Sr and Bi is set to 0.500% or less. The content of Sb, Pb, Sr and Bi is preferably 0.300% or less, more preferably 0.200% or less.

[0039] Sn: 0 to 1.000% Sn is an element that increases the Mg dissolution rate in a plating layer containing Zn, Al, and Mg. If the Mg dissolution rate increases, the corrosion resistance of the flat portion may deteriorate. Therefore, the upper limit of the Sn content is 1.000% or less. The Sn content is preferably 0.500% or less. On the other hand, Sn is an element that contributes to improving sacrificial corrosion protection. To fully obtain this effect, the Sn content is preferably 0.050% or more. The Sn content is more preferably 0.100% or more.

[0040] Cu: 0 to 1.000% Ti: 0 to 1.000% Cr: 0~1.000% Nb: 0 to 1.000% Ni: 0 to 1.000% Mn: 0 to 1.000% Mo: 0 to 1.000% V: 0 to 1.000% In:0~1.000% Co: 0 to 1.000% Cu, Ti, Cr, Nb, Ni, Mn, Mo, V, In and Co contribute to improving corrosion resistance. To obtain this effect sufficiently, it is preferable that the content of any one of the above elements is 0.001% or more. The content of each of the above elements is more preferably 0.005% or more, and further preferably 0.050% or more. On the other hand, if the content of any one of the above elements exceeds 1.000%, red rust resistance may deteriorate. Therefore, the content of each of the above elements is 1.000% or less. The content of each of the above elements is preferably 0.300% or less, more preferably 0.200% or less.

[0041] Zr: 0 to 1.000% Ag: 0~1.000% Li: 0~1.000% Zr, Ag and Li are elements that improve the corrosion resistance of the coating layer. To obtain this effect sufficiently, the content of any one of Zr, Ag and Li is preferably 0.001% or more. The content of Zr, Ag and Li is more preferably 0.005% or more, and further preferably 0.020% or more. On the other hand, if the content of Zr, Ag, and Li is excessively high, the corrosion resistance may deteriorate. If the content of any one of Zr, Ag, and Li exceeds 1.000%, the red rust resistance deteriorates significantly. Therefore, the content of Zr, Ag, and Li is 1.000% or less. The content of Zr, Ag, and Li is preferably 0.500% or less, more preferably 0.100% or less.

[0042] B: 0 to 0.500%, P: 0~0.500% B and P are elements for improving the appearance. To obtain this effect sufficiently, the content of at least one of B and P is preferably 0.001% or more. The contents of B and P are each more preferably 0.005% or more, and further preferably 0.020% or more. On the other hand, if the content of B and P is excessively high, the corrosion resistance may deteriorate. If the content of either B or P exceeds 0.500%, the corrosion resistance deteriorates significantly. Therefore, the content of B and P is 1.000% or less. The content of B and P is preferably 0.500% or less, more preferably 0.100% or less.

[0043] In the present embodiment, the impurities may include those mixed in from the manufacturing environment, etc., and / or elements within a range that does not adversely affect the properties of the plated steel material according to the present embodiment.

[0044] The chemical composition of the plating layer is measured by the following method. First, a rectangular sample of 50 mm x 50 mm including the entire thickness of the plating layer is taken from the plating layer, and the plating layer of the sample is dissolved in 10 vol. % HCl containing 0.04 vol. % IBIT 710 (manufactured by Asahi Chemical Industry Co., Ltd.), an inhibitor that suppresses corrosion of the base steel (steel sheet), to obtain an acid solution. The sample is taken from a portion where the structure of the plating layer is not affected by processing, heat treatment, etc. (for example, a portion avoiding processed parts and welded parts, etc.). Next, the obtained acid solution is measured by ICP analysis to obtain the chemical composition of the plating layer. There is no particular restriction on the type of acid as long as it is an acid that can dissolve the plating layer. The chemical composition of the plating layer in this embodiment is the average of measurements taken on three samples.

[0045] [Method of manufacturing plated steel products] Next, a preferred method for producing the plated steel material according to the present embodiment will be described. The effects of the plated steel sheet according to the present embodiment can be obtained as long as it has the above-mentioned characteristics, regardless of the production method. However, the following method is preferred because it allows stable production of the plated steel material according to the present embodiment. Specifically, the plated steel material according to this embodiment can be produced by a production method including the following steps (I) to (III).

[0046] (I) Annealing process for reducing steel sheet (II) A plating step in which the steel sheet is immersed in a plating bath containing Al, Mg, and Zn to obtain a plating base sheet; (III) A controlled cooling step in which the plating base sheet is cooled at an average cooling rate of 7°C / sec or less in a N2 gas atmosphere having a dew point of 0°C or higher in a temperature range from the bath temperature to the controlled cooling temperature. Preferred conditions for each step will now be described.

[0047] First, a steel material (base steel) for forming a plating layer is prepared. Suitable steel materials are as described above, and examples thereof include general steel, high-tensile steel, and low-carbon steel.

[0048] When a pre-plated steel material is used as the steel material, a pre-plated layer is formed on the steel material surface before the annealing process. An example of the pre-plated layer is a Ni pre-plated layer. By providing a pre-plated layer on the steel material surface, it is possible to promote the amorphization of the plating layer formed in a later process. The plating method may be hot-dip plating, electroplating, displacement plating, or vapor deposition (PVD, etc.). Furthermore, the pre-plated layer may be heated and alloyed. When a pre-plated layer is provided on the steel material surface, the steel material to which the pre-plated layer has been applied is used as a base sheet to be subjected to hot-dip plating.

[0049] In the manufacturing method of the pre-plating layer, electroplating is suitable because it can form a thin plating layer. Vapor deposition (PVD) is also applicable.

[0050] The deposition weight of the pre-plating layer by electroplating can be adjusted by controlling the cumulative current application time. When a Ni pre-plating layer is formed as the pre-plating layer, the deposition weight is, for example, 0.1 to 2.5 g / m 2 is preferred.

[0051] <Annealing process> Prior to the plating process, reduction annealing may be performed on the steel material obtained by a known method. The steel material may be, for example, a hot-rolled steel sheet or a cold-rolled steel sheet. The annealing conditions may be known conditions, for example, heating to 750 to 900°C in a 5% H2-N2 gas atmosphere with a dew point of -10°C or higher, and holding for 30 to 240 seconds.

[0052] <Plating process> After annealing, the steel material, which is the original sheet to be plated, is immersed in a plating bath. The composition of the plating bath is adjusted so that the plating layer has the above-mentioned chemical composition of the plating layer. The bath temperature of the plating bath is preferably 420 to 700°C. If the bath temperature is too low, the plating layer may begin to solidify during the plating process. Therefore, a higher bath temperature is preferable, but if it is too high, the manufacturing cost increases. Therefore, the bath temperature of the plating bath is preferably in the range of 420 to 700°C.

[0053] <Controlled cooling process> In the controlled cooling process, the plating thickness of the plated original sheet after the plating process is adjusted using a wiping gas such as N2 gas, and then the plated original sheet is cooled under predetermined conditions. Specifically, the original sheet for plating pulled out of the plating bath is cooled to below the controlled cooling temperature. At this time, the temperature of the original sheet for plating is equivalent to the temperature of the plating bath. The controlled cooling temperature is a temperature that changes the atmosphere from a slow cooling and high dew point atmosphere to a rapid cooling and low dew point atmosphere, and is 300°C to 330°C. In the controlled cooling process, the average cooling rate from the bath temperature to the controlled cooling temperature is 7°C / sec or less, and the dew point of the atmosphere during cooling from the bath temperature to the controlled cooling temperature is 0°C or more. Examples of the atmospheric gas during cooling include N2 gas and Ar gas.

[0054] When the average cooling rate from the bath temperature to the controlled cooling temperature is reduced, the coating layer on the steel material remains in a molten state and is cooled slowly, so that the surface portion of the coating layer is likely to become amorphous. When the surface portion of the coating layer becomes amorphous, the oxide layer formed thereon can also contain an amorphous structure. Here, the surface portion of the coating layer refers to the peripheral region of the interface between the oxide layer and the coating layer. In addition, by slowly cooling from the bath temperature to the controlled cooling temperature, the thickness of the oxide layer formed on the coating layer can be increased, and as a result, the corrosion resistance in running water can be improved. Furthermore, by slowly cooling from the bath temperature to the controlled cooling temperature, the content of Al and Mg in the oxide layer can be made higher than that of Zn, and the (Al+Mg) / Zn intensity ratio can be increased. On the other hand, when the average cooling rate from the bath temperature to the controlled cooling temperature exceeds 7°C / sec, the coating layer may solidify from the surface, and a crystalline metal layer may be formed on the surface of the coating layer. In that case, there is a risk that a large amount of crystalline oxide may be formed in the oxide layer formed on the coating layer. Therefore, the average cooling rate from the bath temperature to the controlled cooling temperature is set to 7°C / sec or less. From the viewpoint of forming an oxide layer having a sufficient thickness, the average cooling rate from the bath temperature to the controlled cooling temperature is preferably 4° C. / sec or less, more preferably 2° C. / sec or less. The lower limit of the average cooling rate from the bath temperature to the controlled cooling temperature is not particularly limited, but may be 1.5° C. / sec or more from the viewpoint of production costs.

[0055] In addition, if the dew point of the atmosphere from the bath temperature to the controlled cooling temperature is less than 0°C, the thickness of the oxide layer may not be sufficiently secured. In addition, if the cooling process is performed in an air atmosphere, the water vapor in the air may promote the nucleation of crystals, and the plating layer may solidify from the surface, forming a crystalline metal layer. Therefore, the dew point of the atmosphere from the bath temperature to the controlled cooling temperature is set to 0°C or higher. The upper limit of the dew point of the atmosphere from the bath temperature to the controlled cooling temperature is not particularly limited, but may be set to 40°C or lower from the viewpoint of manufacturing costs. The atmosphere gas may be N2 gas, Ar gas, or the like.

[0056] In the temperature range below the controlled cooling temperature, the plated original sheet is cooled at an average cooling rate of 15°C / sec or more and at an atmospheric dew point of -30°C or less. In order to maintain the amorphous oxide layer formed in the temperature range from the bath temperature to the controlled cooling temperature, the plated original sheet is quenched at a low dew point in the temperature range below the controlled cooling temperature. Therefore, in the temperature range below the controlled cooling temperature, the average cooling rate is set to 15°C / sec or more. The upper limit of the average cooling rate in the temperature range below the controlled cooling temperature is not particularly limited, but may be 80°C / sec or less from the viewpoint of manufacturing costs. In addition, by setting the atmospheric dew point in the temperature range below the controlled cooling temperature to a low dew point of -30°C or less, the growth of oxides can be suppressed, and by quenching, the transformation from an amorphous structure to a crystalline structure can be suppressed. The atmospheric dew point in the temperature range below the controlled cooling temperature is preferably -40°C or less. The lower limit of the atmospheric dew point in the temperature range below the controlled cooling temperature is not particularly limited, but may be -70°C or more from the viewpoint of manufacturing costs. Low dew point and rapid cooling may be performed to 70°C.

[0057] By the method described above, the plated steel material according to this embodiment can be stably produced.

[0058] [Solar power generation mounting system] The plated steel material of this embodiment has excellent resistance to corrosion caused by running water, and is therefore used, for example, for photovoltaic power generation stands. Fig. 3 is a perspective view showing an example of a photovoltaic power generation stand 10.

[0059] The photovoltaic power generation rack 10 has, for example, a plurality of pillars 11 and a plurality of support members 12. The plated steel material of this embodiment is suitable for use in the pillars 11 and the support members 12. The photovoltaic power generation rack 10 satisfies the characteristics of the plating layer and the oxide layer in the plated steel material of this embodiment, and therefore has excellent durability.

[0060] The plated steel material of this embodiment may also be applied to a foundation structure 20 for mounting the photovoltaic power generation rack 10. The foundation structure 20 is constructed, for example, with a concrete or the like foundation, and in this case, the plated steel material of this embodiment may be embedded in the concrete or other foundation. EXAMPLES

[0061] The effects of one embodiment of the present invention will be explained more specifically with reference to an example. However, the conditions in the example are merely an example of conditions adopted to confirm the feasibility and effects of the present invention. The present invention is not limited to this example of conditions. 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.

[0062] A cold-rolled steel sheet (0.05%C-0.1%Si-0.2%Mn) having a thickness of 2.3 mm was prepared as a base steel material to be annealed and plated. This base steel material was cut into a size of 100 mm×200 mm (×plate thickness), and then annealed and hot-dip plated in succession using a batch-type hot-dip plating test device.

[0063] Before immersion in the plating bath, the base steel was subjected to a heating and reducing treatment at 600°C in a N2-5% H2 gas atmosphere in a furnace with an oxygen concentration of 20 ppm or less. The base steel was then air-cooled with N2 gas, and after the sheet temperature at the time of immersion reached the bath temperature + 20°C, it was immersed in the plating bath with the bath temperature shown in Table 1 for approximately 3 seconds. The steel substrate was then pulled up to allow the plating layer to adhere to the surface of the steel substrate. During the pull-up process, the plating thickness was controlled with N2 wiping gas. The plating layer was then cooled under various conditions to produce various plated steel products. The chemical compositions of the plating layer were as shown in Table 2. The manufacturing conditions were as shown in Table 1. The sheet temperature during manufacturing was measured using a thermocouple spot-welded to the center of the original plated sheet.

[0064] The results of EDS analysis and evaluation of crystallinity of the oxide layer are shown in Table 3. Furthermore, the corrosion resistance of the plated steel material in running water was evaluated, and the results are shown in Table 3.

[0065] The chemical composition of the plating layer and the analysis and evaluation of the oxide layer were performed by the methods described above. Note that a Ni pre-plating layer was formed on some of the base steel materials before the plating process. The Ni adhesion weight of the Ni pre-plating layer was as shown in Table 1. The components of the Ni pre-plating are included in the chemical components of the plating layer disclosed in Table 2.

[0066] The evaluation of the running water corrosion resistance was carried out by the following method. The plated steel material thus obtained was cut to prepare test pieces measuring 200 mm x 100 mm (x steel thickness). The prepared test pieces were placed on a table inclined at 45° to the horizontal plane. Next, a droplet (Cl) was placed on the surface of the test piece (evaluation surface). - Concentration: 10ppm, SO4 2- A solution of 20 ppm (concentration) was dripped at a flow rate of 2 mL / min, and the number of days until the appearance of white rust and red rust was evaluated. The droplets were dripped from 10 mm above the evaluation surface. The test environment was air, and the temperature was kept at 25°C. The running water corrosion resistance was evaluated according to the number of days until the appearance of white rust and red rust, based on the following evaluation criteria.

[0067] Evaluation criteria AAA: White rust for over 7 days and red rust for over 120 days AA: <1> White rust for more than 7 days and red rust for more than 30 days but less than 120 days, or <2> White rust: 5-7 days, red rust: over 60 days A: White rust 5-7 days, red rust 30-60 days B: <1> Rust less than 30 days old, or <2> White rust: Less than 5 days

[0068] Plated steel products with evaluation results of A to AAA were judged to have excellent running water corrosion resistance. Evaluation B was given to steel products in which the number of days since red rust developed was less than 30, regardless of the number of days since white rust developed, or in which the number of days since red rust developed was less than 5, regardless of the number of days since red rust developed. Such plated steel products were judged to have poor running water corrosion resistance. According to the above evaluation method, plated steel products with high running water corrosion resistance can also be judged to have high flat surface corrosion resistance. The results are shown in Table 3.

[0069] [Table 1]

[0070] [Table 2]

[0071] [Table 3]

[0072] As can be seen from Tables 1 to 3, excellent running water corrosion resistance was obtained in the invention examples Nos. 1 to 31. In contrast, the running water corrosion resistance was deteriorated in the comparative examples Nos. 32 to 41 because the chemical composition of the coating layer or the cooling conditions in the controlled cooling process were outside the preferred range. [Industrial Applicability]

[0073] The Zn-Al-Mg-based hot-dip plated steel member of the present disclosure has excellent corrosion resistance and adhesion of a chemical conversion coating layer, and even when a chemical conversion coating layer is formed, has excellent electrical conductivity with a welding electrode. Furthermore, the member has an excellent appearance in which scratches are less noticeable, and thus has high industrial applicability. [Explanation of symbols]

[0074] 10...Solar power generation stand 11...Strut 12...Support member 20…Foundation structure

Claims

1. Steel plate and A plating layer formed on the steel plate, The oxide layer formed on the aforementioned plating layer, It has, The aforementioned plating layer is, by mass%, Al: 1.0-60.0%, Mg: 1.0-15.0%, Si: 0-2.0%, Ca: 0-2.0%, and Fe: 0-2.0%, It contains, and further, Ni: 0-1.000%, La: 0 to 0.500%, Ce: 0-0.500%, Sb: 0 to 0.500%, Pb: 0 to 0.500%, Sr: 0-0.500%, Bi: 0-0.500%, Sn: 0-1.000%, Cu: 0 to 1.000%, Ti: 0 to 1.000%, Mn: 0 to 1.000%, Cr: 0-1.000%, Nb: 0 to 1.000%, Zr: 0 to 1.000%, Mo: 0-1.000%, V: 0 to 1.000%, In: 0 to 1.000%, Co: 0-1.000%, Ag: 0-1.000%, Li: 0 to 1.000%, B: 0 to 0.500%, Y: 0 to 0.500%, and P: 0 to 0.500%, It has a chemical composition in which it contains one or more elements selected from the group consisting of the following in total amount of 5,000% or less, with the remainder being Zn and impurities. The thickness of the oxide layer is 5 nm or more. The (Al + Mg) / Zn intensity ratio, which is the ratio of the sum of the maximum intensities of Al and Mg to the maximum intensity of Zn in the energy-dispersive X-ray analysis of the oxide layer, is 1.0 or greater. A plated steel material in which the oxide layer contains an amorphous structure.

2. The chemical composition of the aforementioned plating layer is, in mass%, Si: 0.1-2.0%, Ca: 0.1-2.0%, Fe: 0.1-2.0%, Ni: 0.001 to 1.000%, La: 0.010-0.500%, Ce: 0.010-0.500%, Sb: 0.001 to 0.500%, Pb: 0.001 to 0.500%, Sr: 0.001-0.500%, Bi: 0.001-0.500%, Sn: 0.050-1.000%, Cu: 0.001 to 1.000%, Ti: 0.001 to 1.000%, Mn: 0.001 to 1.000%, Cr: 0.001-1.000%, Nb: 0.001-1.000%, Zr: 0.001 to 1.000%, Mo: 0.001 to 1.000%, V: 0.001 to 1.000%, In: 0.001 to 1.000%, Co: 0.001 to 1.000%, Ag: 0.001-1.000%, Li: 0.001 to 1.000%, B: 0.001-0.500%, Y: 0.010 to 0.500%, and P: 0.001-0.500%, The plated steel material according to claim 1, characterized by containing one or more of the above.

3. In the chemical composition of the plating layer, Al: 10.0-30.0%, Mg: 4.0-15.0% And, The plated steel material according to claim 1, wherein the (Al + Mg) / Zn strength ratio of the oxide layer is 2.0 or more.

4. In the chemical composition of the plating layer, Al: 15.0-30.0%, Mg: 4.0-15.0% And, The plated steel material according to claim 1, wherein the (Al + Mg) / Zn strength ratio of the oxide layer is 3.0 or more.

5. The plated steel material according to any one of claims 1 to 4, wherein no diffraction spots indicating a crystalline structure are detected in the electron diffraction pattern obtained by analyzing the cross-section of the oxide layer using electron diffraction.

6. A mounting frame for solar power generation comprising plated steel material according to any one of claims 1 to 4.

7. A mounting frame for solar power generation comprising the plated steel material described in Claim 5.

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