Plated checkered steel plate

Abstract

A plated checkered steel plate comprising, on one plate surface, a base checkered steel plate provided with protruding parts having a height of 3 mm or less and flat parts, a plating layer including a zinc-based alloy layer arranged on the plate surface of the base checkered steel plate where the protruding parts and flat parts are provided, and a chemical conversion coating layer provided on the surface of the plating layer, wherein the film thickness of the chemical conversion coating layer on the flat parts of the base checkered steel plate is 0.10 to 5.00 μm per side, and the film thickness ratio of the chemical conversion coating layer on the protruding parts and the flat parts of the base checkered steel plate (film thickness of the chemical conversion coating layer on the flat parts / film thickness of the chemical conversion coating layer on the protruding parts) is 0.2 to 5.0.

Description

Plated checkered steel sheet

[0001] The present disclosure relates to plated checkered steel sheet.

[0002] Checkered steel plate is a steel plate with a continuous series of anti-slip convexities (i.e., protrusions) formed on the surface by rolling. Generally, the convexities have a certain width, length, and height, and are arranged at a certain angle and pitch relative to the rolling direction. Checkered steel plate is usually manufactured by hot rolling. Checkered steel plate is used for floor plates or steps of large vehicles (buses, trucks, etc.), floor plates of multi-story parking garages, floor plates of factories, decks of ships, temporary scaffolding or stairs at construction sites, etc.

[0003] For example, Patent Document 1 discloses "a coating method for coating the decorative surface of a substrate with a roll coater, characterized in that the decorative surface of the substrate is an uneven surface having an uneven pattern, and at least the surface of the coating roller of the roll coater is made elastic, and the coating roller is rotated approximately in sync with the transport speed of the substrate and the coating roller is brought into contact with the uneven surface with a pressing force."

[0004] Japanese Patent Application Publication No. 2-17972

[0005] Checkered steel sheets are coated with a chemical conversion coating to prevent primary rust prevention failure. Unlike ordinary flat steel sheets, checkered steel sheets have both convex and flat portions, which can lead to large thickness variations in the chemical conversion coating layer between the convex and flat portions, resulting in primary rust prevention failure.

[0006] Therefore, an object of the present disclosure is to provide a plated checkered steel sheet that suppresses primary rust prevention defects.

[0007] Means for solving the above problems include the following aspects. <1> A plated checkered steel sheet comprising: a base checkered steel sheet having convex portions and flat portions each having a height of 3.0 mm or less on one sheet surface; a plating layer including a zinc-based alloy layer disposed on the sheet surface of the base checkered steel sheet where the convex portions and flat portions are provided; and a chemical conversion coating layer provided on the surface of the plating layer, wherein the film thickness of the chemical conversion coating layer on the flat portions of the base checkered steel sheet is 0.10 to 5.00 μm per side, and a film thickness ratio of the chemical conversion coating layer between the flat portions and the convex portions of the base checkered steel sheet (film thickness of the chemical conversion coating layer on the flat portions / film thickness of the chemical conversion coating layer on the convex portions) is 0.2 to 5.0. <2> The plated checkered steel sheet according to <1>, wherein the film thickness ratio of the chemical conversion coating layer between the flat portions and the convex portions of the base checkered steel sheet is 0.4 to 1.5. <3> The plated checkered steel sheet according to <1> or <2>, wherein the film thickness ratio of the chemical conversion coating layer between the flat portions and the convex portions of the base checkered steel sheet is 0.2 or more and less than 0.8, or 1.5 or more and 5.0 or less.

[0008] According to the present disclosure, it is possible to provide a plated checkered steel sheet in which primary rust prevention defects are suppressed.

[0009] 1A 。 FIG. 1B is a schematic plan view showing an example of a base checkered steel plate for the plated checkered steel plate of the present disclosure. FIG. 1C is a schematic cross-sectional view showing an example of a base checkered steel plate for the plated checkered steel plate of the present disclosure, which is a schematic cross-sectional view of G-G in FIG. 1A. FIG. 1D is a schematic cross-sectional view showing an example of a base checkered steel plate for the plated checkered steel plate of the present disclosure, which is a schematic cross-sectional view of F-F in FIG. 1A. FIG. 1E is a schematic view showing an example of an application device used in the method for producing a plated checkered steel plate of the present disclosure. FIG. 1F is a schematic view showing an example of a grooved applicator roll used in the method for producing a plated checkered steel plate of the present disclosure.

[0010] An example of the present disclosure will be described below. In this disclosure, the "%" representation of the content of each element in a chemical composition means "mass %." A numerical range expressed using "to" means a range that includes the numerical values ​​written before and after "to" as the lower and upper limits. When "greater than" or "less than" is added to the numerical values ​​written before and after "to", the numerical range does not include these numerical values ​​as the lower or upper limit. The content of an element in a chemical composition may be expressed as an element concentration (e.g., Zn concentration, Mg concentration, etc.).

[0011] The plated checkered steel sheet of the present disclosure comprises a base checkered steel sheet having convex portions and flat portions on one sheet surface, a plating layer including a zinc-based alloy layer disposed on the sheet surface of the base checkered steel sheet having the convex portions and flat portions, and a chemical conversion coating layer disposed on the surface of the plating layer. The film thickness of the chemical conversion coating layer on the flat portions of the base checkered steel sheet is 0.10 to 5.00 μm per side. The film thickness ratio of the chemical conversion coating layer on the flat portions to the convex portions of the base checkered steel sheet (film thickness of the chemical conversion coating layer on the flat portions / film thickness of the chemical conversion coating layer on the convex portions) is 0.20 to 5.00.

[0012] The plated checkered steel sheet of the present disclosure, due to the above configuration, is a plated checkered steel sheet in which primary rust prevention defects are suppressed.

[0013] Hereinafter, the plated checkered steel sheet of the present disclosure will be described in detail.

[0014] (Balanced Checkered Steel Plate) The bare checkered steel plate is the steel plate on which a coating layer is formed. The bare checkered steel plate has a convex portion and a flat portion on one sheet surface. The height of the convex portion of the bare checkered steel plate (i.e., the stripe height) is 3.0 mm or less. If the height difference from the flat portion becomes large, the rolling force of the grooved applicator roll used to form the chemical conversion coating layer on the bare checkered steel plate becomes unstable. As a result, areas where the chemical conversion solution runs out occur, the film thickness ratio of the chemical conversion coating layer between the convex portion and the flat portion increases, white rust is likely to occur, and primary rust prevention is poor. Therefore, the height of the convex portion of the bare checkered steel plate is set to the above range. The height of the convex portion of the bare checkered steel plate is preferably 2.5 mm or less. However, from the perspective of preventing slippage when used as a floor plate, the lower limit of the height of the convex portion of the bare checkered steel plate is set to, for example, 0.5 mm or more. Here, the height of the convex portion of the base checkered steel plate is the height of the center of the convex portion in the length direction and the center of the width direction (see H in Figures 1B and 1C).

[0015] Other shapes of the checkered steel sheet are, for example, as shown in Figures 1A to 1C. In Figure 1, A, B, C, D, and E respectively represent the following: A: Arrangement angle of the protrusions (angle of the protrusions in the lengthwise direction relative to the rolling direction) = 35 to 55° (preferably 40 to 50°) B: Length of the protrusions = 15 to 50 mm (preferably 20 to 40 mm) C: Maximum width of the protrusions = 3 to 8 mm (preferably 4 to 7 mm) D: Minimum width of the protrusions = 0.5 to 6 mm (preferably 1 to 4 mm) E: Arrangement pitch of the protrusions (distance between the positions of the center of the protrusions in the lengthwise direction and the center of the protrusions in the widthwise direction along the rolling direction) = 15 to 50 mm (preferably 20 to 40 mm) Area occupation ratio of the protrusions = 10 to 70% (preferably 15 to 60%)

[0016] The convex shape of the bare checkered steel plate is usually imparted by hot rolling. The steel type of the bare checkered steel plate is not particularly limited. Examples of the bare checkered steel plate include steel types corresponding to general structural rolled steel materials specified in JIS G3101:2015. The convex shape of the bare checkered steel plate is imparted, for example, by transferring a concave shape formed on a working roll to the steel plate surface during the finishing stage of hot rolling. The opposite surface of the plate facing the thickness direction from the surface having the convex and flat portions has the surface texture of a normal steel plate. Specifically, the opposite surface of the plate facing the thickness direction from the surface having the convex and flat portions is the surface imparted by a normal rolling roll (i.e., a roll with normal roughness) facing the working roll on which the convex and flat portions are formed during the finishing hot rolling stage.

[0017] The base checkered steel sheet may be a pre-plated checkered steel sheet. Pre-plated checkered steel sheet can be obtained, for example, by an electrolytic treatment method or a displacement plating method. In the electrolytic treatment method, the base checkered steel sheet is immersed in a sulfate bath or chloride bath containing metal ions of various pre-plating components for electrolytic treatment to obtain a pre-plated checkered steel sheet. In the displacement plating method, the base checkered steel sheet is immersed in an aqueous solution containing metal ions of various pre-plating components and the pH of which is adjusted with sulfuric acid to cause displacement precipitation of the metal to obtain a pre-plated checkered steel sheet. A typical example of a pre-plated checkered steel sheet is a pre-Ni-plated checkered steel sheet.

[0018] (Plating layer) The plating layer includes a zinc-based alloy layer. The coating weight of the plating layer is 60 to 500 g / m per side. ２ The coating weight of the plating layer is preferably 60 g / m ２ On the other hand, if the coating weight of the plating layer is 500 g / m or more, corrosion resistance can be more reliably ensured. ２ If the coating weight is less than this, it is possible to suppress poor appearance such as sagging of the plating layer. Therefore, the coating weight of the zinc-based plating layer is set to the above range. From the viewpoint of improving corrosion resistance, the coating weight of the plating layer is set to 90 to 460 g / m ２ More preferably, 100 to 400 g / m ２ is more preferable.

[0019] The coating weight of the plating layer is measured as follows. A 50 mm x 50 mm sample is cut from the plated checkered steel sheet to be measured, and the sheet surface opposite the sheet surface with the convex and flat portions in the thickness direction is sealed with tape. The sample is then immersed in hydrochloric acid containing an inhibitor that suppresses iron dissolution, dissolving the plating on the sheet surface with the convex and flat portions. The difference in weight before and after dissolution is divided by the area of ​​the sample (50 mm x 50 mm) to calculate the coating weight. This is performed three times and the average is taken.

[0020] The zinc-based alloy layer is an alloy layer containing zinc and aluminum. It may also contain one or more elements selected from the group consisting of magnesium and silicon. Specific examples of the zinc-based alloy layer include well-known zinc-based alloy layers such as a zinc-aluminum alloy layer, a zinc-aluminum-magnesium alloy layer, a zinc-aluminum-magnesium-silicon alloy layer, and a zinc-aluminum-silicon alloy layer.

[0021] The zinc-based alloy layer may be a plated layer containing small amounts of cobalt, molybdenum, tungsten, nickel, titanium, calcium, chromium, manganese, iron, lead, bismuth, antimony, tin, copper, cadmium, arsenic, etc. as additive elements or impurities.

[0022] In particular, the zinc-based alloy layer is preferably an alloy layer containing zinc, aluminum, and magnesium from the viewpoint of corrosion resistance.

[0023] The plating layer may include an Al—Fe alloy layer in addition to the zinc-based alloy layer, and the Al—Fe alloy layer is disposed between the base checkered steel sheet and the zinc-based alloy layer.

[0024] That is, the plating layer may have a single-layer structure of a zinc-based alloy layer, or a laminated structure including a zinc-based alloy layer and an Al—Fe alloy layer. In the case of a laminated structure, the zinc-based alloy layer is a layer that constitutes the surface of the plating layer. However, although an oxide film of the plating layer constituent elements is formed on the surface of the plating layer with a thickness of about 50 nm, it is considered to be thin compared to the overall thickness of the plating layer and does not constitute the main part of the plating layer.

[0025] The Al-Fe alloy layer may be formed on the surface of the checkered steel sheet (specifically, between the checkered steel sheet and the zinc-based coating layer), and the Al-Fe alloy layer may have a structure similar to that of the checkered steel sheet. ５ The Fe phase is the main phase layer. The Al-Fe alloy layer is formed by mutual atomic diffusion between the base checkered steel sheet and the coating bath. In the checkered steel sheet of the present disclosure, the coating layer is formed by hot-dip coating, so that an Al-Fe alloy layer is easily formed in the coating layer containing Al element. Since the coating bath contains Al at a certain concentration or more, Al ５ The Fe phase is formed in the largest amount. However, atomic diffusion takes time, and there are also areas where the Fe concentration is high near the base checkered steel sheet. Therefore, the Al-Fe alloy layer is partially composed of AlFe phase, Al ３ Fe phase, Al ５ Fe ２ In addition, since the plating bath contains a certain concentration of Zn, the Al-Fe alloy layer also contains a small amount of Zn.

[0026] When the coating layer contains Si, Si is particularly likely to be incorporated into the Al-Fe alloy layer, forming an Al-Fe-Si intermetallic compound phase. Identified intermetallic compound phases include the AlFeSi phase, with isomers such as α-, β-, q1-, and q2-AlFeSi phases. Therefore, these AlFeSi phases may be detected in the Al-Fe alloy layer. An Al-Fe alloy layer containing these AlFeSi phases is also referred to as an Al-Fe-Si alloy layer. Since the Al-Fe-Si alloy layer is thinner than the coating layer, its impact on the corrosion resistance of the entire coating layer is minimal. Furthermore, when various pre-plated checkered steel sheets are used as base checkered steel sheets, the structure of the Al-Fe alloy layer may change depending on the amount of pre-plating applied. Specifically, there are cases where a pure metal layer used in pre-plating remains around the Al-Fe alloy layer, cases where an intermetallic compound phase (e.g., an Al3Ni phase when pre-Ni plated checkered steel sheet is used) in which the constituent components of the plating layer and the pre-plating components combine to form an alloy layer, cases where an Al-Fe alloy layer is formed in which some Al atoms and Fe atoms are substituted, cases where an Al-Fe-Si alloy layer is formed in which some Al atoms, Fe atoms, and Si atoms are substituted, etc. In any case, these alloy layers are also thinner than the Zn-Al-Mg alloy layer, and therefore have little effect on the corrosion resistance of the entire plating layer.

[0027] The plating layer has, for example, the following composition by mass: Al: more than 0.1% and less than 25.0%, Mg: 0% to less than 12.5%, Sn: 0% to 5.0%, Bi: 0% to less than 5.0%, In: 0% to less than 2.0%, Ca: 0% to 3.00%, Y: 0% to 0.5%, La: 0% to less than 0.5%, Ce: 0% to less than 0.5%, Si: 0% to less than 2.5%, Cr: 0% to less than 0.25%, Ti: 0% to less than 0.25%, Zr: 0% to less than 0.25%, Mo: 0% to less than 0.25%, W: 0% to less than 0.25%, Ag: 0% to less than 0.25%, P: 0% to less than 0.25%, A preferred chemical composition is Ni: 0% to less than 0.25%, Co: 0% to less than 0.25%, V: 0% to less than 0.25%, Nb: 0% to less than 0.25%, Cu: 0% to less than 0.25%, Mn: 0% to less than 0.25%, Li: 0% to less than 0.25%, Na: 0% to less than 0.25%, K: 0% to less than 0.25%, Fe: 0% to 5.0%, Sr: 0% to less than 0.5%, Sb: 0% to less than 0.5%, Pb: 0% to less than 0.5%, B: 0% to less than 0.5%, and the balance: Zn and impurities. With this chemical composition, corrosion resistance is improved.

[0028] In the chemical composition of the plating layer, Mg, Sn, Bi, In, Ca, Y, La, Ce, Si, Cr, Ti, Zr, Mo, W, Ag, P, Ni, Co, V, Nb, Cu, Mn, Li, Na, K, Fe, Sr, Sb, Pb, and B are optional components, meaning that these elements do not have to be contained in the plating layer.

[0029] Here, the chemical composition of the plating layer is the average chemical composition of the entire plating layer (when the plating layer has a single-layer structure of a zinc-based alloy layer, the average chemical composition of the zinc-based alloy layer; when the plating layer has a laminated structure of a zinc-based alloy layer and an Al—Fe alloy layer, the average chemical composition of the sum of the zinc-based alloy layer and the Al—Fe alloy layer).

[0030] Typically, in hot-dip galvanizing, the chemical composition of the zinc-based alloy layer is almost identical to the chemical composition of the plating bath, since the reaction for forming the plating layer is almost always completed within the plating bath. Furthermore, in hot-dip galvanizing, the Al-Fe alloy layer is instantaneously formed and grows immediately after immersion in the plating bath. The reaction for forming the Al-Fe alloy layer is already completed within the plating bath, and its thickness is often sufficiently smaller than that of the zinc-based alloy layer. Therefore, unless special heat treatment such as a thermal alloying treatment is performed after plating, the average chemical composition of the entire plating layer is substantially identical to the chemical composition of the zinc-based alloy layer, and the components of the Al-Fe alloy layer can be ignored.

[0031] The chemical composition of the plating layer is measured by the following method. First, the plating layer is stripped and dissolved using an acid containing an inhibitor that suppresses corrosion of the base checkered steel sheet to obtain an acid solution. Next, the obtained acid solution is measured by ICP analysis to obtain the chemical composition of the plating layer (if the plating layer has a single-layer structure of a zinc-based alloy layer, the chemical composition of the zinc-based alloy layer; if the plating layer has a laminate structure of an Al-Fe alloy layer and a zinc-based alloy layer, the combined chemical composition of the Al-Fe alloy layer and the zinc-based alloy layer). There are no particular restrictions on the type of acid, as long as it can dissolve the plating layer. The chemical composition is measured as an average chemical composition. In ICP analysis, the Zn concentration is calculated using the formula: Zn concentration = 100% - concentration of other elements (%).

[0032] Here, when a pre-plated checkered steel sheet is used as the base checkered steel sheet, the components of the pre-plating are also detected. For example, when a pre-Ni plated checkered steel sheet is used, ICP analysis detects not only Ni in the plating layer but also Ni in the pre-Ni plating. Specifically, for example, when the Ni deposition amount is 1 g / m ２ ~3g / m ２When the pre-plated checkered steel sheet is used as a base checkered steel sheet, even if the Ni concentration in the plating layer is 0%, the Ni concentration is detected as 0.1 to 15%. On the other hand, when a pre-Ni-plated checkered steel sheet is used as a base checkered steel sheet, a small amount of Ni in the pre-Ni plating layer dissolves in the plating bath when the base checkered steel sheet is immersed in the plating bath. As a result, the Ni concentration in the plating bath is 0.02 to 0.03% higher than the Ni concentration in the prepared plating bath. Therefore, when a pre-Ni-plated checkered steel sheet is used, the Ni concentration in the plating layer is increased by up to 0.03%. The method for determining whether a base checkered steel sheet is a pre-plated checkered steel sheet is as follows. A sample is taken from the target plated checkered steel sheet, with the cross section cut along the plate thickness direction of the plated checkered steel sheet serving as the measurement surface. The measurement surface of the sample is subjected to line analysis near the interface between the plating layer and the base checkered steel sheet in the plated checkered steel sheet using an electron probe microanalyzer (FE-EPMA) to measure the Ni concentration. The measurement conditions are an acceleration voltage of 15 kV, a beam diameter of approximately 100 nm, an irradiation time per point of 1000 ms, and a measurement pitch of 60 nm. The measurement distance may be any distance that allows confirmation of whether or not the Ni concentration is enriched at the interface between the plating layer and the base checkered steel sheet in the plated checkered steel sheet. If the Ni concentration is enriched at the interface between the plating layer and the base checkered steel sheet in the plated checkered steel sheet, the base checkered steel sheet is determined to be a pre-plated checkered steel sheet.

[0033] Furthermore, when a pre-Ni-plated checkered steel sheet is used as the base checkered steel sheet, the Ni concentration of the plating layer is defined as the value measured as follows. First, the Ni emission intensity is measured for three or more standard samples (BAS Zn alloy standard samples IMN ZH1, ZH2, and ZH4) with different Ni concentrations using a high-frequency glow discharge optical emission surface analyzer (GDS: manufactured by HORIBA, Ltd., model number: GD-Profiler2). A calibration curve is prepared from the relationship between the obtained Ni emission intensity and the Ni concentration of the standard samples. Next, the high-frequency glow discharge optical emission surface analyzer (GDS: manufactured by HORIBA, Ltd., model number: GD-Profiler2) is used to measure the Ni emission intensity at a position halfway through the thickness of the plating layer of the plated checkered steel sheet to be measured (the sheet surface opposite the sheet surface on which the convex and flat portions are provided in the thickness direction). The Ni concentration at the position halfway through the plating layer is determined from the obtained Ni emission intensity and the prepared calibration curve. The Ni concentration at the obtained half position of the plating layer is defined as the Ni concentration of the plating layer. When a pre-Ni-plated checkered steel sheet is used as the base checkered steel sheet, the Zn concentration of the plating layer is defined as the Zn concentration calculated from the following formula: Zn concentration = 100 - (concentration of elements other than Zn and Ni determined by ICP analysis + Ni concentration determined by GDS) The measurement conditions for the high-frequency glow discharge optical emission surface analyzer are as follows: H.V.: 630 V Anode diameter: φ4 mm Gas: Ar Gas pressure: 600 Pa Output: 35 W

[0034] (Chemical Conversion Coating) The thickness of the chemical conversion coating layer on the flat portions of the base checkered steel sheet is 0.10 to 5.00 μm per side. If the thickness of the chemical conversion coating layer on the flat portions is thin, white rust will occur locally, resulting in poor primary rust prevention. If the thickness of the chemical conversion coating layer on the flat portions is thick, cracks will occur in the chemical conversion coating layer, resulting in poor primary rust prevention. Therefore, the thickness of the chemical conversion coating layer on the flat portions of the base checkered steel sheet is set to the above range. From the viewpoint of improving primary rust prevention, the thickness of the chemical conversion coating layer on the flat portions of the base checkered steel sheet is preferably 0.20 to 4.00 μm, more preferably 0.30 to 3.00 μm. Here, the thickness of the chemical conversion coating layer on the flat portions is the thickness of the chemical conversion coating layer on the flat portions 3 mm away from the convex portions (the thickness of the chemical conversion coating layer at the position indicated by F2 in FIG. 1A).

[0035] The thickness ratio of the chemical conversion coating layer between the flat and convex portions of the base checkered steel sheet (thickness of the chemical conversion coating layer between the flat and convex portions / thickness of the chemical conversion coating layer between the convex portions) is 0.2 to 5.0. If the thickness ratio of the chemical conversion coating layer between the flat and convex portions is too low, the convex portions will be thick and the flat portions will be thin, which will make the flat portions more prone to coating defects, resulting in localized white rust and poor primary rust prevention. If the thickness ratio of the chemical conversion coating layer between the flat and convex portions is too high, the thickness unevenness of the chemical conversion coating layer will increase, resulting in localized white rust and poor primary rust prevention. Therefore, the thickness ratio of the chemical conversion coating layer between the flat and convex portions is set to the above range. From the viewpoint of improving primary rust prevention, the thickness ratio of the chemical conversion coating layer between the flat and convex portions is preferably 0.3 to 4.0, more preferably 0.4 to 3.0.

[0036] Here, in the use of the plated checkered steel sheet of the present disclosure, it is advantageous to control the film thickness of the chemical conversion coating layer formed on the convex and flat portions. The chemical conversion coating layer is typically a transparent coating layer several micrometers thick and located on the surface of a light-reflecting metal layer. Therefore, interference colors may be exhibited due to the refraction of light caused by the thickness of the chemical conversion coating layer. Interference colors, such as red, yellow, or green, appear as patterns in various parts of the plated checkered steel sheet, causing poor appearance. To ensure the appearance quality of the plated checkered steel sheet as consistent as possible, making the film thickness of the chemical conversion coating layer on the convex and flat portions as similar as possible results in a uniform appearance and eliminates pattern-like phenomena such as color spots. Therefore, from the viewpoint of suppressing pattern-like phenomena such as color spots, the film thickness ratio of the chemical conversion coating layer on the flat portions to the convex portions is most preferably 1.0, more preferably 0.4 to 1.5, and even more preferably 0.8 to 1.1. When the film thickness ratio of the chemical conversion coating layer on the flat portion and the convex portion is set as described above, the color will be of the same color family.

[0037] On the other hand, the plated checkered steel sheet of the present disclosure may be cut, bent, and arc-welded to various components to be made into structures such as parking lot pallets and stair steps. In particular, controlling the film thickness of the chemical conversion coating layer affects arc welding. Generally, plated checkered steel sheet requires a higher welding current than hot-rolled checkered steel sheet without a plated layer, which can lead to welding defects. In particular, when a chemical conversion coating layer is formed on a plated layer, the following problems can occur: (1) Current flow becomes unstable, resulting in an unstable bead formed during arc welding. (2) Spatter marks caused by a large current become severe. (3) Damage to the chemical conversion coating layer causes the weld to expand more than necessary. (4) Gas vaporized from the chemical conversion coating layer causes intense welding fumes. (5) Foreign matter is generated within the bead.

[0038] In particular, the shape of the bead significantly affects the strength of structures obtained from plated checkered steel sheet. Therefore, it is important to properly release the bead shape, specifically, the fume gases generated during welding, preventing their entrapment within the bead. From this perspective, plated checkered steel sheet requires a higher current value than hot-rolled steel sheet, making it more difficult to weld. A uniformly formed chemical conversion coating generally makes current application difficult. On the other hand, when the film thickness ratio between the flat and convex portions is large, there are regions where the chemical conversion coating layer is partially thin. This relatively stabilizes the arc and the bead shape. Therefore, a film thickness ratio between the flat and convex portions of the chemical conversion coating layer of 1.0 is least suitable for arc welding. From the viewpoint of stabilizing the bead shape during welding, the film thickness ratio between the flat and convex portions of the chemical conversion coating layer is preferably less than 0.8 or 1.5 or more, and more preferably less than 0.6 or 1.9 or more. In other words, from the viewpoint of suppressing primary rust prevention defects and stabilizing the shape of the bead during welding, the film thickness ratio of the chemical conversion coating layer on the flat portion to the convex portion is preferably 0.2 or more and less than 0.8, or 1.5 or more and 5.0 or less, and more preferably 0.2 or more and less than 0.6, or 1.9 or more and 5.0 or less.

[0039] Here, the film thickness of the chemical conversion coating layer on the convex portion is the film thickness of the chemical conversion coating layer at the center in the length direction and the center in the width direction of the convex portion (the film thickness of the chemical conversion coating layer at the position indicated by F1 in FIG. 1A).

[0040] The thickness of the chemical conversion coating layer is measured as follows. A sample is taken from a plated checkered steel sheet to be measured by cutting it in the thickness direction at the center of the length of the convex portion and along the width of the convex portion. Specifically, the plated checkered steel sheet is cut at a position corresponding to the F-F cross section in Figure 1A to obtain a sample. A gold film is then vapor-deposited onto the surface of the chemical conversion coating layer of the sample. The sample is then embedded in epoxy resin and polished to the observation position. The polished cut cross section of the sample is then observed at 10,000x magnification using a scanning electron microscope (SEM). The thickness of the chemical conversion coating layer at each position on the observed cross section is then measured as follows. The thickness of the chemical conversion coating layer at each position is measured by measuring the thickness of the layer between the plating layer and the gold film. (1) The thickness of the chemical conversion coating layer at the center of the length and width of the convex portion (the thickness of the chemical conversion coating layer at the position indicated by F1 in Figure 1A). (2) The film thickness of the chemical conversion coating layer at a flat portion 3 mm away from the convex portion (the film thickness of the chemical conversion coating layer at the position indicated by F2 in FIG. 1A).

[0041] The above operation is then carried out three times, and the average film thickness of the chemical conversion coating layer at each position is determined.

[0042] The components of the chemical conversion coating layer are not particularly limited, and well-known components can be used. Examples of the chemical conversion coating layer include well-known chemical conversion coating layers whose main components are silane coupling agents (organosilicon compounds), zirconium compounds, titanium compounds, phosphate compounds, fluorine compounds, vanadium compounds, cobalt compounds, ammonium zirconium carbonate, acrylic resins, vanadium compounds, and phosphorus compounds. The term "main component" refers to the component that is most abundant in the layer. However, from the perspective of reducing environmental impact, the chemical conversion coating layer should preferably be a chemical conversion coating layer other than a chromate chemical conversion coating layer.

[0043] From the viewpoint of suppressing primary rust prevention failure, the following specific examples of the chemical conversion coating layer are preferred: (1) A silane coupling agent containing one amino group in the molecule and a silane coupling agent containing one glycidyl group in the molecule, which has a group of the formula -SiR １ R ２ R (wherein, R １ , R ２ and R ３ (1) A coating layer comprising an organic silicon compound containing two or more functional groups (a) represented by the formula (a) (each independently represents an alkoxy group or a hydroxyl group, and at least one represents an alkoxy group), one or more hydrophilic functional groups (b) selected from hydroxyl groups (other than those that may be contained in the functional groups (a)) and amino groups, at least one fluoro compound selected from titanium hydrofluoric acid or zirconium hydrofluoric acid, phosphoric acid, and a vanadium compound. (2) A coating layer comprising one or two of an organic silicon compound, a zirconium compound, and a titanium compound, a phosphoric acid compound, a fluorine compound, and a vanadium compound. (3) A coating layer comprising an acrylic resin, zirconium, vanadium, phosphorus, and cobalt. (4) A coating layer comprising an acrylic resin obtained by copolymerizing a zirconium carbonate compound with monomer components containing at least styrene, (meth)acrylic acid, a (meth)acrylic acid alkyl ester, and acrylonitrile; a divalent to tetravalent vanadium compound; a phosphorus compound; and a cobalt compound (E).

[0044] (Method for manufacturing plated checkered steel sheet) An example of a method for manufacturing a plated checkered steel sheet according to the present disclosure will be described below. The method for manufacturing a plated checkered steel sheet according to the present disclosure, which will be described below as an example, is particularly suitable for manufacturing a plated checkered steel sheet using a base checkered steel sheet having the shape shown in Figures 1A to 1C and having the convex portion arrangement angle A, convex portion length B, convex portion maximum width C, convex portion minimum width D, convex portion arrangement pitch E, convex portion height H, and convex portion area occupancy ratio within the above-mentioned ranges.

[0045] The method for manufacturing a plated checkered steel sheet according to the present disclosure includes a plating layer forming step and a chemical conversion coating forming step.

[0046] - Plating layer forming step - In the plating layer forming step, a base checkered steel sheet is provided with convex portions and flat portions each having a height of 3 mm or less on one sheet surface, and a plating layer is formed on the sheet surface on which the convex portions and flat portions are provided in a coating weight of 60 to 500 g / m per side. ２ A plating layer including a zinc-based alloy layer is formed.

[0047] The method for forming the coating layer is not particularly limited, and well-known methods can be used. For example, the base checkered steel sheet is heated to and maintained at a temperature between 20°C above the coating bath temperature and 850°C below the coating bath temperature, and then cooled to a temperature between the coating bath temperature and 10°C above the coating bath temperature. The cooled base checkered steel sheet is immersed in the coating bath and removed from the coating bath. If the coating bath temperature is above 500°C, the coating layer is formed on the base checkered steel sheet at a cooling rate of 1 to 20°C / s to 500°C. Here, the coating is performed using a continuous hot-dip metal coating method such as the Sendzimir process. Furthermore, the base checkered steel sheet may be pre-plated (e.g., Ni pre-plated) after pickling and before heating.

[0048] - Chemical conversion coating formation process - In the chemical conversion coating formation process, a grooved applicator roll is used, which has a plurality of circumferential grooves arranged in the axial direction on its outer peripheral surface, with the grooves having a groove pitch of 0.2 to 1.0 mm, a groove height of 0.05 to 0.5 mm, and a ratio of groove pitch to groove height (groove pitch / groove height) of 2 to 8, and a chemical conversion coating layer is formed by applying a chemical conversion coating solution (hereinafter also referred to as "chemical solution") to the surface of the plating layer, with the circumferential direction of the grooved applicator roll at an angle within a range of 45±10° with respect to the longitudinal direction of the convex portions of the base checkered steel sheet.

[0049] Specifically, in the chemical conversion coating formation step, a chemical conversion coating layer is formed by applying a chemical conversion treatment solution to the surface of the plating layer using, for example, an applicator shown in Fig. 2. However, the applicator may be a well-known applicator equipped with a grooved applicator roll.

[0050] The coating device shown in Figure 2 includes a grooved applicator roll that transfers chemical solutions onto the surface of the plating layer of a base checkered steel sheet on which a plating layer has been formed, and a backup roll that is positioned opposite the base checkered steel sheet and supports the base checkered steel sheet as it passes through. An applicator roll on the opposite side may be placed instead of the backup roll. In this case, from the perspective of coating the opposite side, the base checkered steel sheet is made to travel straight without changing its direction of travel by the roll. Around the grooved applicator roll, a storage pan that stores the chemical solution is placed, and a pickup roll that picks up the chemical solution from the storage pan and then supplies the chemical solution to the grooved applicator roll. A transfer roll may be placed between the pickup roll and the applicator roll. In FIG. 2 , 101 denotes an application device, 10 denotes a grooved applicator roll, 12 denotes a backup roll, 14 denotes a storage pan, 14A denotes a chemical conversion treatment solution, 16 denotes a pickup roll, M1 denotes a base checkered steel plate on which a plating layer is formed, M2 denotes a base checkered steel plate on which a chemical conversion treatment film and a plating layer are formed, and A denotes the sheet passing direction of the base checkered steel plate on which a plating layer is formed.

[0051] The grooved applicator roll may be, for example, an applicator roll having a metal roll and a rubber coating layer provided on the outer circumferential surface of the metal roll.

[0052] The grooved applicator roll has a plurality of circumferential grooves arranged in the axial direction on its outer peripheral surface. In the grooved applicator roll, the groove pitch (see 10P in FIG. 3) is 0.2 to 1.0 mm, the groove height (see 10H in FIG. 3) is 0.05 to 0.5 mm, and the ratio of the groove pitch to the groove height (groove pitch / groove height) is 2 to 8. Here, the groove pitch refers to both the groove width and the width of the convex portion formed between adjacent grooves. Usually, in a grooved applicator roll, the groove width and the width of the convex portion formed between adjacent grooves are often the same. In FIG. 3, 10 denotes the grooved applicator roll, 10A denotes the groove, 10P denotes the groove pitch, and 10H denotes the groove height.

[0053] When the groove pitch is 0.2 mm or more and 1.0 mm or less, the amount of chemical solution carried out is appropriate. When the groove height is 0.05 mm or more, the amount of chemical solution carried out is appropriate. When the groove height is 0.5 mm or less, air entrapment by the grooves is suppressed.

[0054] Furthermore, by setting the ratio of groove pitch to groove height in the grooved applicator roll to between 2 and 8, the amount of chemical solution carried over is guaranteed, and the chemical solution can be uniformly applied to the convex portions, flat portions, and the boundaries between the convex and flat portions (i.e., the bases of the convex portions) of the base checkered steel sheet. By using such a grooved applicator roll, the film thickness of the chemical conversion coating layer on the flat portions of the base checkered steel sheet and the film thickness ratio of the chemical conversion coating layer on the flat portions to the convex portions of the base checkered steel sheet are within the above-mentioned ranges. As a result, white rust is less likely to occur, and primary rust prevention defects are suppressed.

[0055] In the grooved applicator roll, the ratio of the maximum width of the convex portions of the base checkered steel plate (see C in Figure 1A) to the pitch of the grooves (maximum width of the convex portions of the base checkered steel plate / groove pitch) is preferably, for example, 3.0 to 40.0.

[0056] When the ratio of the maximum width of the convex portions of the base checkered steel plate to the groove pitch is 3.0 or more, the groove pitch is not too large relative to the maximum width of the convex portions of the base checkered steel plate. Therefore, the grooves that hold the chemical solution are also close to the boundaries between the convex portions and flat portions of the base checkered steel plate (i.e., the base of the convex portions), making it easier for the chemical solution to spread. When the ratio of the maximum width of the convex portions of the base checkered steel plate to the groove pitch is 40.0 or less, the groove pitch is not too small relative to the maximum width of the convex portions of the base checkered steel plate. Therefore, the grooves that hold the chemical solution are prevented from being difficult to approach the boundaries between the convex portions and flat portions of the base checkered steel plate (i.e., the base of the convex portions), and the amount of chemical solution carried over is also ensured. As a result, insufficient application of the chemical solution is suppressed. Therefore, it is preferable that the ratio of the maximum width of the convex portions of the base checkered steel plate to the groove pitch be within the above range in a grooved applicator roll. This ensures that the amount of chemical solution carried over is consistent, making it easier to apply the solution uniformly to the convex portions, flat portions, and the boundaries between the convex and flat portions (i.e., the bases of the convex portions) of the base checkered steel sheet. This makes it easier for the film thickness of the chemical conversion coating layer on the flat portions of the base checkered steel sheet and the film thickness ratio of the chemical conversion coating layer on the flat portions to the convex portions of the base checkered steel sheet to fall within the above-mentioned ranges. As a result, white rust is less likely to occur, further suppressing primary rust prevention defects.

[0057] In the chemical conversion coating formation process, the grooved applicator roll is rotated, and the chemical conversion solution is picked up by a pickup roll from a storage pan containing the chemical conversion solution, and then the chemical conversion solution is supplied to the grooved applicator roll. After or simultaneously with the start of supplying the chemical conversion solution to the grooved applicator roll, the base checkered steel sheet begins to be passed, and the chemical conversion solution supplied by the grooved applicator roll is transferred and applied to the plating layer surface of the base checkered steel sheet as it passes through.

[0058] In the chemical conversion coating layer formation process, the circumferential direction of the grooved applicator roll is angled within a range of 45±10° relative to the longitudinal direction of the convex portions of the base checkered steel sheet, and the chemical conversion solution is applied to the surface of the coating layer. By setting the circumferential direction of the grooved applicator roll at an angle within a range of 45±10° relative to the longitudinal direction of the convex portions of the base checkered steel sheet, the height of the convex portions (i.e., the stripe height) can be made uniform in the width direction of the base checkered steel sheet (i.e., the direction perpendicular to the sheet passing direction of the base checkered steel sheet). Therefore, the contact area between the convex portions and the roll is constant in the width direction of the grooved applicator roll, the rolling force of the grooved applicator roll against the base checkered steel sheet is uniform, and the chemical solution can be uniformly applied to the convex portions, flat portions, and the boundaries between the convex portions and flat portions (i.e., the skirts of the convex portions) of the base checkered steel sheet. As a result, the thickness of the chemical conversion coating layer on the flat portions of the base checkered steel sheet and the ratio of the thickness of the chemical conversion coating layer on the flat portions to the thickness of the convex portions of the base checkered steel sheet fall within the above ranges, making it difficult for white rust to occur and suppressing primary rust prevention failure.

[0059] Here, from the viewpoint of ensuring that the film thickness of the chemical conversion coating layer on the flat portions of the base checkered steel sheet and the film thickness ratio of the chemical conversion coating layer on the flat portions and the convex portions of the base checkered steel sheet fall within the above-mentioned ranges, the linear pressure of the grooved applicator roll applied to the base checkered steel sheet is preferably 1000 to 3000 (g / mm).

[0060] The rotation direction of the grooved applicator roll may be the same as the running direction of the base checkered steel plate, or the opposite direction to the running direction of the base checkered steel plate. However, it is better if the rotation direction of the grooved applicator roll is the opposite direction to the running direction of the base checkered steel plate. If the rotation direction of the grooved applicator roll is the opposite direction to the running direction of the base checkered steel plate, unevenness in the application of the chemical solution during application of the chemical solution is suppressed, and unevenness in the film thickness of the chemical conversion coating layer is suppressed. Note that the rotation direction of the grooved applicator roll refers to the direction at the position facing the base checkered steel plate (i.e., paint application position P1 in Figure 2).

[0061] The amount of chemical solution supplied to the grooved applicator roll is set appropriately depending on the film thickness of the chemical conversion coating layer. The rotation speed of the grooved applicator roll is also set appropriately depending on the film thickness of the chemical conversion coating layer to be formed on the plating layer surface of the base checkered steel sheet. The sheet passing speed LS of the base checkered steel sheet is set to, for example, 20 to 200 m / min.

[0062] A chemical solution coating is formed on the surface of the plating layer on the base checkered steel sheet, and the coating is then dried and / or cured to form a chemical conversion coating layer. The drying and curing conditions for the chemical solution coating may be set appropriately depending on the chemical solution used.

[0063] Hereinafter, post-treatments that can be applied to the plated checkered steel sheet of the present disclosure will be described.

[0064] The plated checkered steel sheet of the present disclosure may have one or more organic resin coating layers on the chemical conversion coating layer. The organic resin is not limited to a specific type, and examples include polyester resin, polyurethane resin, epoxy resin, acrylic resin, polyolefin resin, fluororesin, and modified versions of these resins. Here, the term "modified version" refers to a resin in which a reactive functional group contained in the structure of the resin is reacted with another compound (such as a monomer or a crosslinking agent) containing a functional group capable of reacting with the reactive functional group.

[0065] Such organic resins may be a mixture of one or more unmodified organic resins, or a mixture of one or more organic resins obtained by modifying at least one other organic resin in the presence of at least one organic resin. The organic resin film may also contain any coloring pigment or anti-rust pigment. Water-based organic resins obtained by dissolving or dispersing them in water may also be used.

[0066] Although examples of the present disclosure will be described, the conditions in the examples are merely examples adopted to confirm the feasibility and effects of the present disclosure, and the present disclosure is not limited to these examples. Various conditions may be adopted in the present disclosure as long as they do not deviate from the gist of the present disclosure and the object of the present disclosure is achieved.

[0067] (Example) A predetermined amount of pure metal ingot was used and melted to prepare a plating bath in the atmosphere so as to obtain a plating layer having the chemical composition shown in Table 1. A batch-type hot-dip plating apparatus was used to form the plating layer.

[0068] Then, a plating layer was formed on both sides of the base checkered steel sheet as follows. ２ -H ２ (5%) (dew point -40°C or less, oxygen concentration less than 25 ppm) environment, the temperature was raised from room temperature by electrical heating, and after holding for 60 seconds, N ２ The plate was cooled to a temperature 10°C above the plating bath temperature by gas blowing and immediately immersed in the plating bath. ２ The gas wiping pressure was adjusted to control the coating weight of the plating layer. The coating weight of the plating layer on the plate surface having the convex portions and flat portions was set as shown in Table 2.

[0069] The base checkered steel sheet used was hot-rolled Al-killed steel, and the shape of the base checkered steel sheet was the same as that shown in Figures 1A to 1C. However, various hot-rolled checkered steel sheets with different shapes (protrusion height H, maximum protrusion width C) were used as the base checkered steel sheet. The specific shapes were as follows: - Protrusion arrangement angle A = 45° - Protrusion length B = 25.3 mm - Protrusion maximum width C = width shown in Table 2 - Protrusion minimum width D = 2.5 mm - Protrusion arrangement pitch E = 28.6 mm - Protrusion height (i.e., fringe height) H = height shown in Table 2. The area occupancy rate of the protrusions was 40%.

[0070] In some examples, a pre-Ni-plated checkered steel sheet obtained by pre-plating the above-mentioned hot-rolled checkered steel sheet was used as the base checkered steel sheet. ２ ~3g / m ２ In addition, examples in which a pre-Ni plated checkered steel sheet was used as the base checkered steel sheet are indicated as "Pre-Ni" in the "Base checkered steel sheet" and "Type" columns in Table 2.

[0071] Next, a chemical conversion coating layer was formed by applying a chemical conversion treatment solution to the surface of the plating layer using the coating device shown in Figure 2 equipped with a grooved applicator roll under the conditions shown in Table 2. In Table 2, "angle" indicates the angle formed by the circumferential direction of the grooved applicator roll with respect to the longitudinal direction of the convex portion of the base checkered steel sheet. Also, "linear pressure" indicates the pressing force of the grooved applicator roll against the base checkered steel sheet.

[0072] The chemical conversion treatment solutions used were as follows:

[0073] Chemical solution A: Chemical solution containing 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, vanadium oxysulfate, phosphoric acid, and fluorozirconic acid

[0074] Chemical solution B: A chemical solution containing ammonium zirconium carbonate, acrylic resin, vanadium oxyoxalate, phosphoric acid, 1-hydroxyethane-1,1-diphosphonic acid, and cobalt nitrate.

[0075] - Various measurements - The following items were measured for the obtained plated checkered steel sheets according to the methods described above: - Thickness of the chemical conversion coating layer on the flat portions of the base checkered steel sheet (in the table, this is indicated as "flat portion thickness T1") - Thickness of the chemical conversion coating layer on the convex portions of the base checkered steel sheet (in the table, this is indicated as "convex portion thickness T2")

[0076] - Primary rust prevention - The obtained plated checkered steel sheet was cut to obtain 100 mm x 50 mm samples. Next, the backside and edge surfaces of the sheet surface having the convex and flat portions were sealed. Next, the samples were subjected to an accelerated corrosion test (SST JIS Z 2371:2015) for 24 hours to examine the white rust occurrence area ratio of the convex and flat portions. The white rust occurrence area ratio was evaluated as "A" if it was 10% or less, "B" if it was more than 10% and 20% or less, "C" if it was more than 20% and 30% or less, and "D" if it was more than 30%.

[0077] - Appearance - The appearance of the obtained plated checkered steel sheets was observed. Specifically, the following procedure was carried out. First, a Panasonic white fluorescent light source (straight fluorescent light highlight 6 type FL6W) was placed at a distance of 1 m from each checkered surface. Next, with white light irradiating the checkered surface from the light source, photographs were taken of the checkered surface in an area of ​​1200 mm in width and 1000 mm in length every 100 x 100 mm. The reduced photographs were used to measure the color difference ΔE within a 100 x 100 mm range. Specifically, the color difference ΔE was measured in accordance with CIE 1976L ＊ a ＊ b ＊ Color coordinate value (L ＊ Value, a ＊ value and b ＊ Then, the color difference ΔE was calculated from the measurement point where the color difference ΔE was maximum with respect to the average value of the L* value, a* value, and b* value. The color difference ΔE was calculated using the formula ΔE = ((Δa ＊ ) ２ + (Δb ＊ ) ２ + (ΔL ＊ ) ２ ) １／２ The average color difference ΔE over the entire range (i.e., the striped surface in an area of ​​1200 mm in width and 1000 mm in length) was measured and evaluated according to the following criteria: A: The average color difference ΔE is 0.6 or less; B: The average color difference ΔE is more than 0.6 and less than 1.2; C: The average color difference ΔE is 1.2 or more.

[0078] - Welding - Two 100 mm x 50 mm steel plates were cut from the obtained plated checkered steel plate and extracted. One of the obtained steel plates was placed vertically in the center of the other steel plate, and a weld bead was formed by arc welding on the side sandwiched between the checkered surfaces. Specifically, the two steel plates were arranged such that the other steel plate was placed vertically in the center of one steel plate so that the pattern of the base checkered steel plate shown in Figure 1A was connected. In the arc welding, a weld bead was formed in a direction perpendicular to the rolling direction (direction C) from the intersection of four lines of the protrusions of the checkered steel plate, with a length of 90 mm and a width of 10 mm (build-up width (side x √2 = 10 mm) when viewed from a 45-degree welding angle). Arc welding was performed using welding wire: YM-28Z, welding speed: 40 cm / min, CO ２The test was carried out under the following conditions: shielding gas flow rate: 20 liters / min, extension length: 15 mm, welding wire diameter: 1.2 mm, lamination pass: 1, welding current: 170 A, arc voltage: 23 V. The obtained weld bead was projected with an X-ray, and the quality of the weld was judged based on the blowhole opening rate of the fillet weld, using the following criteria: A: Blowhole opening rate: less than 3%, no wave pattern or pit holes visible in the bead B: Blowhole opening rate: 3 to less than 10%, pit holes less than 1 mm visible, but no wave pattern visible in the bead C: Blowhole opening rate: 10% or more, pit holes of 1 mm or larger, or wave pattern visible in the bead

[0079] Examples are listed in Tables 1 and 2.

[0080]

[0081]

[0082]

[0083] The above results show that the Examples corresponding to the plated checkered steel sheets of the present disclosure suppress primary rust prevention defects in both flat and convex portions compared to the Comparative Examples.

[0084] Although the preferred embodiments and examples of the present disclosure have been described in detail above, the present disclosure is not limited to such examples. It is clear that a person skilled in the art to which the present disclosure pertains can conceive of various modified or altered examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally fall within the technical scope of the present disclosure.

[0085] The disclosure of Japanese Patent Application No. 2022-138733 is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A base checkered steel plate having a convex portion and a flat portion having a height of 3.0 mm or less on one plate surface; A plating layer including a zinc-based alloy layer arranged on the plate surface on which the convex portion and the flat portion of the base checkered steel plate are provided; A chemical conversion coating layer provided on a surface of the plating layer; having The film thickness of the chemical conversion coating layer on the flat portion of the base checkered steel sheet is 0.10 to 5.00 μm per side, a thickness ratio of the chemical conversion coating layer between the flat portion and the convex portion of the base checkered steel sheet (thickness of the chemical conversion coating layer on the flat portion / thickness of the chemical conversion coating layer on the convex portion) is 0.2 to 5.0; Galvanized checkered steel sheet.

2. 2. The plated checkered steel sheet according to claim 1, wherein a thickness ratio of the chemical conversion coating layer between the flat portions and the protruding portions of the base checkered steel sheet is 0.4 or more and 1.5 or less.

3. 2. The plated checkered steel sheet according to claim 1, wherein a film thickness ratio of the chemical conversion coating layer between the flat portions and the protruding portions of the base checkered steel sheet is 0.2 or more and less than 0.8, or 1.5 or more and 5.0 or less.