EP-4321643-B1 - ZN-AL-MG PLATED CHECKERED STEEL PLATE

Inventors

• SAITO, MAMORU
• GOTO, YASUTO

Dates

Publication Date

20260513

Application Date

20220405

Claims (3)

1. A Zn-Al-Mg alloy coated checkered steel sheet, comprising: a substrate checkered steel sheet having a convex part and a flat part on one sheet surface; and a coating layer including a Zn-Al-Mg alloy layer disposed on the sheet surface of the substrate checkered steel sheet having the convex part and the flat part, wherein the coating layer has a chemical composition containing, in % by mass: Zn: greater than 65.0%, Al: from greater than 1.0% to less than 25.0%, Mg: from greater than 1.0% to less than 12.5%, Sn: from 0% to 5.0%, Bi: from 0% to less than 5.0%, In: from 0% to less than 2.0%, Ca: from 0% to 3.00%, Y: from 0% to 0.5%, La: from 0% to less than 0.5%, Ce: from 0% to less than 0.5%, Si: from 0% to less than 2.5%, Cr: from 0% to less than 0.25%, Ti: from 0% to less than 0.25%, Zr: from 0% to less than 0.25%, Mo: from 0% to less than 0.25%, W: from 0% to less than 0.25%, Ag: from 0% to less than 0.25%, P: from 0% to less than 0.25%, Ni: from 0% to less than 0.25%, Co: from 0% to less than 0.25%, V: from 0% to less than 0.25%, Nb: from 0% to less than 0.25%, Cu: from 0% to less than 0.25%, Mn: from 0% to less than 0.25%, Li: from 0% to less than 0.25%, Na: from 0% to less than 0.25%, K: from 0% to less than 0.25%, Fe: from 0% to 5.0%, Sr: from 0% to less than 0.5%, Sb: from 0% to less than 0.5%, Pb: from 0% to less than 0.5%, B: from 0% to less than 0.5%, and impurities, with the upper limit of the Zn concentration being a remnant concentration excluding the elements other than Zn and impurities; wherein the Zn concentration is the remnant concentration; the chemical composition being measured according to the description; wherein, when observing a cross section of cutting edge orthogonal to a longitudinal direction of the convex part and taken along a sheet thickness direction at a central part in the longitudinal direction of the convex part, a layer thickness ratio of the coating layer of the flat part on left and right sides of the convex part (layer thickness of left coating layer/layer thickness of right coating layer) is from 0.2 to 5.0, and wherein a convex height T-t, where T is a sheet thickness of the substrate checkered steel sheet at the convex part and t is a sheet thickness of the substrate checkered steel sheet at the flat part, and a gap height x between a horizontal surface and a sheet surface of the coated checkered steel sheet opposing the horizontal surface in a case in which the coated checkered steel sheet is placed on a horizontal surface, satisfy the following Formulae 1 and 2 below: x / T - t ≤ 1.5 0.5 ≤ T - t ≤ t wherein, in Formula 1 and Formula 2, units of the sheet thickness T, t, and the gap height x of the substrate checkered steel sheet are millimeters; wherein the layer thickness ratio, the convex height T-t and the gap height x are measured according to the description.
2. The Zn-Al-Mg alloy coated checkered steel sheet according to claim 1, wherein the Al concentration is greater than 5.0% and less than 25.0%, and the Mg concentration is greater than 3.0% and less than 12.5%.
3. The Zn-Al-Mg alloy coated checkered steel sheet according to claim 1 or 2, wherein the coating layer includes an Al-Fe alloy layer between the substrate checkered steel sheet and the Zn-Al-Mg alloy layer.

Description

Technical Field The present disclosure relates to a Zn-Al-Mg alloy coated checkered steel sheet. Background Art A checkered steel sheet is a steel sheet having continuous non-slip convex part (that is, protrusions) on surface by rolling. In general, convex part having a constant width, a constant length, and a constant height are provided at a constant angle and a constant pitch with respect to a rolling direction. Typically, checkered steel sheets are manufactured by hot rolling. Checkered steel sheets are used for floor boards or steps of large vehicles (bus, track, etc.), floor boards of multistory parking lots, floor boards of factories, decks of ships, temporary scaffoldings or stairs in construction sites, and the like. For example, Patent Literature 1 discloses "A hot-dip coated checkered steel sheet including: a substrate material steel sheet; a Ni coating layer disposed on a surface of the substrate material steel sheet; and a hot-dip coating layer disposed on a surface of the Ni coating layer, the hot-dip coated checkered steel sheet having a convex part and a flat surface part on a sheet surface, wherein a film thickness of the Ni coating layer of the convex part is from 0.07 µm to 0.4 µm per one surface, a film thickness of the Ni coating layer of the flat surface part is from 0.05 µm to 0.35 µm per one surface, the film thickness of the Ni coating layer of the convex part is greater than 100% and 400% or less with respect to the film thickness of the Ni coating layer of the flat surface part, a deposited amount of the hot-dip coating layer is from 60 g/m2 to 400 g/m2 per one surface, and the hot-dip coating layer contains, % by mass, Al: greater than 1.0% and 26% or less, Mg: from 0.05% to 10%, Si: from 0% to 1.0%, Sn: from 0% to 3.0%, and Ca: from 0% to 1.0% as a chemical composition, the hot-dip coated checkered steel sheet including Zn and impurities as a remnant." In addition, Patent Literature 2 discloses "A continuous hot-dip metal coating method for a strip-shaped checkered steel sheet, the method including: subjecting the strip-shaped checkered steel sheet to a pickling treatment; and then continuously subjecting the strip-shaped checkered steel sheet to hot-dip metal coating under conditions that satisfy the requirements of an annealing temperature of from 450°C to 850°C, a steel strip tension in an annealing furnace of from 0.3 kg/mm2 to 2.0 kg/mm2, a steel strip tension in a coating line of from 0.3 kg/mm2 to 3.0 kg/mm2, and a gas pressure for hot-dip metal wiping of from 0.02 kg/cm2 to 1.5 kg/cm2." Cited Documents Patent Literature Patent Literature 1: WO 2019/054483 APatent Literature 2: Japanese Patent No. 2743774 SUMMARY OF INVENTION Technical Problem Since a checkered steel sheet is often used outdoors, corrosion resistance is required. Therefore, as disclosed in Patent Document 1 to 2, in order to improve corrosion resistance, hot-dip coating is applied to the checkered steel sheet. On the other hand, since the checkered steel sheet is used for scaffolding, anti-slip, and the like, flatness is also required. However, the checkered steel sheet is a steel sheet having a local difference of sheet thickness due to a convex part and a flat part. Therefore, in order to improve corrosion resistance, when hot-dip coating is performed on the checkered steel sheet, a difference occurs in an expansion amount and a shrinkage amount due to a temperature change between the convex part and the flat part of the checkered steel sheet, and the checkered steel sheet is deformed. In a case in which the deformed coated checkered steel sheet is formed into a product, flatness is deteriorated. In addition, when the flatness is deteriorated, variations in the layer thickness of the coating layer occur, and corrosion resistance and formability are deteriorated. In particular, since a Zn-Al-Mg alloy coating bath has a lower viscosity than a Zn-based coating bath, when the flatness of the checkered steel sheet is deteriorated, the layer thickness of the coating layer tends to vary, and corrosion resistance and formability are deteriorated. Therefore, the Zn-Al-Mg alloy coated checkered steel sheet is required to have further improved flatness. Thus, an object of the present disclosure is to provide a Zn-Al-Mg alloy coated checkered steel sheet having excellent flatness, corrosion resistance, and formability. Solution to Problem The above object is achieved by the Zn-Al-Mg alloy coated checkered steel sheet defined in claim 1. Preferred embodiments are defined in dependent claims. Advantageous Effects of Invention According to the present disclosure, it is possible to provide a Zn-Al-Mg alloy coated checkered steel sheet excellent in flatness, corrosion resistance, and formability. BRIEF DESCRIPTION OF DRAWINGS Fig. 1A is a SEM photograph (500 times) showing an example of a cross section of cutting edge of a Zn-Al-Mg alloy coated checkered steel sheet according to the present disclosure.Fig. 1B is a SEM p