Plated steel sheet and method for manufacturing same

Abstract

Provided, according to exemplary embodiments of the present invention, may be a plated steel sheet having excellent surface appearance and image clarity, and a method for manufacturing same.

Description

galvanized steel sheet and method of manufacturing the same

[0001] The present invention relates to a plated steel sheet and a method for manufacturing the same.

[0002] Steel sheets can be exposed to various environments from the storage stage after manufacturing to the point where they are applied to and formed into products and used. Due to these external environments, oxidation and corrosion may occur, leading to a deterioration in the quality of the steel sheets. To prevent this, a plating layer can be formed on the surface of the steel sheet. This plating layer can provide a physical barrier against external oxygen, moisture, and salt, and the materials within the plating layer can act as an electrochemical sacrificial anode to prevent corrosion or oxidation of the steel sheet.

[0003] Various studies are being conducted to improve the quality of such galvanized steel sheets. In particular, Zn-Mg-Al galvanized steel sheets containing large amounts of Mg and Al, intended for further improvement in corrosion resistance, have limitations in their application as architectural exterior materials due to their poor surface appearance. Furthermore, they suffer from the disadvantage of poor linearity, making it difficult to secure aesthetically pleasing surface characteristics. Therefore, there is a need to develop technologies capable of improving the surface appearance of galvanized steel sheets.

[0004] [Prior Art Literature]

[0005] [Patent Literature]

[0006] (Patent Document 1) Japanese Published Patent Application No. 2001-323355.

[0007] The problem that the technical concept of the present invention aims to solve is to provide a plated steel sheet with excellent surface appearance and linearity, and a method for manufacturing the same.

[0008] The problems of the present invention are not limited to those described above. A person skilled in the art will have no difficulty understanding additional problems of the present invention from the overall contents of this specification.

[0009] According to exemplary embodiments for solving the problems of the present invention, a plated steel sheet is provided. The plated steel sheet comprises a base steel sheet; and a plating layer located on the surface of the base steel sheet, wherein the plating layer comprises, in weight percent, Mg: 4.0~10.0%, Al: 11.0~20.0%, Si: 0.10~0.50%, and the remainder being Zn and other unavoidable impurities, and the surface of the plating layer may satisfy an average roughness Ra: greater than 1.00㎛ and less than or equal to 1.50㎛, and a linearity index Wsa: 0.30~0.50㎛.

[0010] The above plating layer may further contain Ca in weight% of 0.200% or less (including 0%).

[0011] The above plating layer may further include one or more of the following groups (a) to (h).

[0012] (a) Ni: 0.5% or less

[0013] (b) At least one of the following: La: 0.1% or less, Ce: 0.1% or less, Y: 0.1% or less, Sr: 1.0% or less

[0014] (c) Ti: 0.1% or less

[0015] (d) W: 0.5% or less

[0016] (e) Cu: 2.0% or less

[0017] (f) At least one of Cr: 0.5% or less, Mn: 0.5% or less, V: 0.5% or less

[0018] (g) B: 0.1% or less, P: 0.1% or less

[0019] (h) At least one of Sn: 1.0% or less, Sb: 1.0% or less, Bi: 1.0% or less

[0020] (a) Ni: 0.5% or less

[0021] The thickness of the plating layer may be 10 to 50 μm.

[0022] According to other exemplary embodiments of the present invention, a method for manufacturing a plated steel sheet is provided. The method for manufacturing the plated steel sheet comprises the steps of: immersing a substrate steel sheet in a plating bath containing Mg: 4.0~10.0%, Al: 11.0~20.0%, Si: 0.10~0.50%, the remainder being Zn and other unavoidable impurities to perform plating treatment; and, after plating treatment, controlling the amount of plating by gas wiping treatment using a mixed gas, wherein the mixed gas comprises, in volume %, 1~5% air and the remainder being an inert gas, and the step of plating treatment may satisfy the following equation 1.

[0023] [Relationship 1]

[0024] (T B )℃ ≤ A ≤ (T B +50)℃

[0025] In the above relationship 1, TB is the temperature of the plating bath (°C), and A is the inlet temperature of the base steel sheet (°C).

[0026] The above plating bath may further contain Ca in weight percent of 0.200% or less (including 0%).

[0027] The temperature (TB) of the above plating bath may be 450 to 510°C.

[0028] According to exemplary embodiments of the present invention, a plated steel sheet with excellent surface appearance and linearity and a method for manufacturing the same can be provided.

[0029] The various and beneficial advantages and effects of the present invention are not limited to those described above and will be more easily understood in the process of explaining specific embodiments of the present invention.

[0030] FIG. 1 is an image photograph showing the surfaces of (a) Invention Example 5 and (b) Comparative Example 5, respectively.

[0031] Figure 2 shows the results of comparing and evaluating the surface shape characteristics of (a) Invention Example 5 and (b) Comparative Example 5, respectively.

[0032] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Prior to this, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings. Instead, based on the principle that the inventor can appropriately define the concepts of terms to best describe his invention, they should be interpreted in a meaning and concept consistent with the technical spirit of the present invention.

[0033] In the following descriptions with reference to the drawings, identical or corresponding components are assigned the same reference numerals, and redundant descriptions thereof will be omitted.

[0034] In the following embodiments, the terms first, second, etc. are used not in a limiting sense, but for the purpose of distinguishing one component from another component.

[0035] In the following embodiments, the singular expression includes the plural expression unless the context clearly indicates otherwise.

[0036] In the following embodiments, terms such as "include" or "have" mean that the features or components described in the specification are present, and do not preclude the possibility that one or more other features or components may be added.

[0037] In the drawings, the size of components may be exaggerated or reduced for convenience of explanation. For example, the size and thickness of each component shown in the drawings are depicted arbitrarily for convenience of explanation, so the present invention is not necessarily limited to what is illustrated.

[0038] Where an embodiment can be implemented differently, a specific process sequence may be performed differently from the order described. For example, two processes described consecutively may be performed substantially simultaneously or proceed in the reverse order of the description.

[0039] In addition, in describing the present invention, if it is determined that a detailed description of related known components or functions may obscure the essence of the invention, such detailed description is omitted.

[0040] The present invention will be described in detail below through each embodiment. It should be noted that each embodiment described in this specification is not limited to a single embodiment but may also be combined with other embodiments. Accordingly, the citation of claims in the patent claims is merely an example of an embodiment, and the technical concept of the present invention should not be interpreted as being limited only to a combination with the cited claims; rather, combinations with various claims are also included within the scope of the technical concept of the present invention.

[0041] The present invention will be described in detail below through examples. However, it should be noted that the following examples are intended merely to illustrate and embody the present invention and are not intended to limit the scope of the present invention. This is because the scope of the present invention is determined by the matters described in the patent claims and matters reasonably inferred therefrom.

[0042] [Galded Steel Sheet]

[0043] A plated steel sheet according to exemplary embodiments may include a base steel sheet and a plating layer.

[0044] Any steel suitable for manufacturing galvanized steel sheets may be used as the base steel sheet. To give a non-limiting example, the base steel sheet may be carbon steel containing a certain amount of carbon (C), and various steels such as stainless steel and aluminum sheets may be applied. As an example, if the base steel sheet is carbon steel, it may be ultra-low carbon steel, medium-low carbon steel, low carbon steel, general carbon steel, high carbon steel, etc., which are well known in the steel industry, and all of these can exhibit similar effects when used as the base steel sheet for alloy galvanized steel sheets. Therefore, the alloy composition of the carbon steel is not specifically limited. In particular, since there is almost no influence from elements such as manganese (Mn), silicon (Si), titanium (Ti), niobium (Nb), and boron (B), which are actively added to obtain carbon steel with high or ultra-high strength, no restrictions are placed on the alloy composition of the carbon steel.

[0045] The base steel sheet may be a hot-rolled steel sheet manufactured through a series of hot rolling processes, or it may be a cold-rolled steel sheet manufactured through a series of cold rolling processes on the hot-rolled steel sheet. Additionally, the cold-rolled steel sheet may be an annealed steel sheet that has undergone an annealing process performed after the cold rolling, or it may be an unanesthetized steel sheet that has not undergone the annealing process.

[0046] The plating layer may be located on the surface of the substrate steel sheet. As a result, the improvement of corrosion resistance may be contributed to by a sacrificial electrode method on the surface of the substrate steel sheet, but the present invention is not necessarily limited thereto.

[0047] As a non-limiting example, the thickness of the plating layer may be 10 to 50 μm. More specifically, the thickness of the plating layer may be 15 to 35 μm. In the present invention, the thickness of the plating layer refers to the average thickness. If the thickness of the plating layer is less than 10 μm, the plating layer may become excessively thin locally due to errors resulting from variations in the thickness of the plating layer, and corrosion resistance may be reduced as the plating layer may not naturally heal damage caused by external impact. If the thickness of the plating layer exceeds 50 μm, the cooling of the molten plating layer may be delayed, and there is a risk that solidification defects, such as flow patterns, may occur on the surface of the plating layer during the plating layer formation process. In addition, the time required to solidify the plating layer increases, which may reduce the productivity of the steel sheet.

[0048] According to exemplary embodiments, the plating layer may comprise, in weight percent, Mg: 4.0–10.0%, Al: 11.0–20.0%, Si: 0.10–0.50%, the remainder being Zn and unavoidable impurities. Additionally, the plating layer may further comprise Ca 0.200% or less (including 0%).

[0049] Magnesium (Mg): 4.0~10.0%

[0050] Magnesium (Mg) can contribute to improving the corrosion resistance of galvanized steel sheets. In particular, Mg within the plating layer leaches out in neutral, weakly acidic, or weakly alkaline corrosive environments such as saltwater or rainwater, forming LDH (Layered Double Hydroxide; (Zn,Mg)6Al2(OH)2) 16It can contribute to the uniform formation of (CO3)·4H2O). As this further contributes to the improvement of corrosion resistance, the Mg content may be 4.0% or more. More specifically, the Mg content may be 3.5% or more. More specifically, the Mg content may be 5.0% or more. However, in acidic corrosive environments, Mg leaching is too rapid, so if Mg is added excessively, there is a concern that corrosion resistance in acidic environments may deteriorate. In addition, if Mg is added excessively, there is a possibility that dross in the form of MgO may be generated in the plating bath. Therefore, the Mg content may be 10.0% or less. More specifically, the Mg content may be 0.07% or less. More specifically, the Mg content may be 6.0% or less.

[0051] Aluminum (Al): 11.0~20.0%

[0052] Aluminum (Al) is a component that improves corrosion resistance along with Mg. Since Al is resistant to acids, corrosion resistance in acidic conditions can significantly increase as the Al content increases. Additionally, Al has the effect of inhibiting the oxidation of Mg in the plating bath; therefore, the formation of MgO-based dross can be suppressed as the amount of Al added increases. Consequently, a relatively excess amount of Mg can be included, which can further contribute to the improvement of corrosion resistance. Thus, the Al content may be 11.0% or more. More specifically, the Al content may be 12.0% or more. Even more specifically, the Al content may be 14.0% or more. On the other hand, corrosiveness in alkaline environments may increase as the amount of Al added increases. Furthermore, if the amount of Al added is too high, excessive energy may be required to maintain the plating bath due to an excessive rise in the melting point. Additionally, there is a concern that the erosion of structures within the plating bath may intensify. In addition, if the Al content becomes excessive, the reaction between Al and Zn occurs rapidly, leading to the excessive formation of lump-shaped outburst phases, which may actually worsen corrosion resistance. In this regard, the Al content may be 20% or less. More specifically, the Al content may be 17.5% or less. Even more specifically, the Al content may be 16.0% or less.

[0053] Silicon (Si): 0.10~0.50%

[0054] Silicon (Si) can prevent the formation of Mg-based oxides by forming Mg2Si through a complex reaction with Mg. At this time, the generated Mg2Si phase can contribute to improving wear resistance, such as corrosion resistance and hardness, of the plated steel sheet. In addition, it can contribute to forming a plating layer with a beautiful surface by lowering the viscosity of the plating bath to improve fluidity and enhance wettability. To this end, the Si content may be 0.10% or more. More specifically, the Si content may be 0.15% or more. More specifically, the Si content may be 0.20% or more. However, if Si is added excessively to the plating layer, the temperature of the plating bath may rise excessively, which may reduce operability. Therefore, the Si content may be 0.50% or less. More specifically, the Si content may be 0.40% or less. More specifically, the Si content may be 0.30% or less.

[0055] Ca: 0.200% or less (including 0%)

[0056] Although it is not strictly necessary to add Ca, adding up to 0.200% can suppress the formation of MgO oxides in the plating bath. Additionally, since a small amount is sometimes added for ease of handling during the production of ingots for plating bath manufacturing, a small amount may be present in the plating bath produced from those ingots. However, if the amount of Ca added exceeds 0.200%, a problem may arise where the color of the steel sheet darkens. Therefore, the Ca content may be 0.200%. More specifically, the Ca content may be 0.180% or less.

[0057] In addition to the composition of the plating layer described above, the remainder may be Zn and other unavoidable impurities. The unavoidable impurities may include all those that may be unintentionally incorporated during the manufacturing process of conventional molten zinc-based or zinc alloy-based plated steel sheets, and since those skilled in the art can easily understand the meaning thereof, the present invention does not specifically limit them.

[0058] Optionally, according to exemplary embodiments, the plating layer may further comprise one or more of the following groups (a) to (h).

[0059] However, since the elements of each of the following groups are not essential for achieving the objectives of the present invention, the lower limit of their content is not restricted. Therefore, the lower limit of the content of each element may be 0%, even if not specifically mentioned below.

[0060] (a) Ni: 0.5% or less

[0061] (b) At least one of the following: La: 0.1% or less, Ce: 0.1% or less, Y: 0.1% or less, Sr: 1.0% or less

[0062] (c) Ti: 0.1% or less

[0063] (d) W: 0.5% or less

[0064] (e) Cu: 2.0% or less

[0065] (f) At least one of Cr: 0.5% or less, Mn: 0.5% or less, V: 0.5% or less

[0066] (g) B: 0.1% or less, P: 0.1% or less

[0067] (h) At least one of Sn: 1.0% or less, Sb: 1.0% or less, Bi: 1.0% or less

[0068] (a) Ni: 0.5% or less

[0069] Although Ni has the effect of preventing Fe diffusion by forming an Al-Ni alloy phase, if its content exceeds 0.5%, there may be a problem of excessive increase in auxiliary material costs.

[0070] (b) At least one of the following: La: 0.1% or less, Ce: 0.1% or less, Y: 0.1% or less, Sr: 1.0% or less

[0071] La, Ce, Y, and Sr have the effect of preventing Mg oxidation in the plating bath by forming an oxide film, but if their content exceeds 0.1%, 0.1%, 0.1%, and 1.0%, respectively, there may be a problem of increased Dross due to increased Ca oxide, and La, Ce, Y, and Sr may cause a problem of reduced plating performance due to increased viscosity of the plating bath.

[0072] (c) Ti: 0.1% or less

[0073] Although Ti acts as a nucleation site for Ti-Al intermetallic compounds and has a grain (spangle) refinement effect, if its content exceeds 0.1%, the melting point of the plating bath increases and there may be a problem with an increase in Dross.

[0074] (d) W: 0.5% or less

[0075] W forms W oxide on the surface, which improves corrosion resistance, but if the content exceeds 0.5%, there may be a problem where the melting point of the plating bath increases.

[0076] (e) Cu: 2.0% or less

[0077] Although Cu has the effect of lowering the hardness of the plating layer by forming an Al-Cu eutectic structure, if its content exceeds 2.0%, there may be a problem of spangles becoming coarse.

[0078] (f) At least one of Cr: 0.5% or less, Mn: 0.5% or less, V: 0.5% or less

[0079] Cr, Mn, and V have the effect of preventing electrode degradation by suppressing alloying between zinc and the welding electrode due to rapid liquid phase loss, but if their content exceeds 0.5%, 0.5%, and 0.5% respectively, there may be a problem where the melting point of the plating bath rises excessively.

[0080] (g) B: 0.1% or less, P: 0.1% or less

[0081] B and P have the effect of suppressing LME cracks in the weldment, but if their content exceeds 0.1% each, there may be a problem of increased Dross generation.

[0082] (h) At least one of Sn: 1.0% or less, Sb: 1.0% or less, Bi: 1.0% or less

[0083] Sn, Sb, and Bi have the effect of homogenizing spangles and improving pot durability by lowering the plating bath temperature, but if their content exceeds 1.0% each, there may be a problem with the coarsening of spangles.

[0084] According to exemplary embodiments, the surface of the plated steel sheet can satisfy an average surface roughness Ra: greater than 1.00㎛ and less than or equal to 1.50㎛, and Wsa: 0.30 to 0.50㎛.

[0085] Average surface roughness Ra: Greater than 1.00㎛ and less than or equal to 1.50㎛

[0086] When the above average surface roughness is 1.00㎛ or less, there is a high risk of the plating layer slipping during processing, and processability may deteriorate. On the other hand, when the average surface roughness exceeds 1.50㎛, the surface is rough, so the surface appearance may not be excellent. In addition, there is a concern that it may reduce linearity, making it difficult to apply as an exterior building material.

[0087] Accordingly, the average surface roughness Ra of the galvanized steel sheet can satisfy greater than 1.00㎛ and less than or equal to 1.50㎛. More specifically, the average surface roughness of the galvanized steel sheet can be 1.10 to 1.40㎛. Even more specifically, the average surface roughness of the galvanized steel sheet can be 1.20 to 1.30㎛.

[0088] Linearity Index Wsa: 0.30~0.50㎛

[0089] In the present invention, the linearity index Wsa value indicates how clearly an image reflected on the plating layer appears, and the linearity index Wsa value can affect the surface appearance characteristics of the plated steel sheet. As such, the present invention can further improve the surface appearance by controlling the linearity index within a specific range, in addition to the surface roughness. If the linearity index Wsa value is less than 0.30㎛, the degree of image clarity is too strong, making it unsuitable for use as an interior or exterior building material. On the other hand, if the linearity index Wsa value exceeds 0.50㎛, the surface shape appears inappropriate for image clarity, making it difficult to use as an exterior material. Therefore, the Wsa value of the surface of the plated steel sheet may be 0.30 to 0.50㎛, and more specifically, the Wsa value may be 0.35 to 0.45.

[0090] [Method for manufacturing galvanized steel sheets]

[0091] As described above, the galvanized steel sheets according to the exemplary embodiments have relatively high Mg and Al content. Although this improves corrosion resistance, it causes the roughness of the galvanized steel sheets to increase and reduces linearity, making it difficult to apply to architectural exteriors.

[0092] Accordingly, the inventors of the present invention, having conducted a thorough examination, discovered that by controlling the composition of the gas used to control the inlet temperature of the base steel sheet and the plating amount, not only the surface roughness but also the linearity of the plated steel sheet can be improved, and thus completed the present invention.

[0093] Hereinafter, the manufacturing method of the present invention will be described in detail.

[0094] According to exemplary embodiments, a method for manufacturing a plated steel sheet may include a step of plating; and a step of controlling the amount of plating.

[0095] plating step

[0096] The plating step may be a step of immersing the base steel plate in a plating bath.

[0097] Regarding the base steel sheet, one may refer to the description of the base steel sheet of the galvanized steel sheet described above. That is, the base steel sheet may be a hot-rolled steel sheet or a cold-rolled steel sheet, but is not necessarily limited thereto.

[0098] The plating bath may contain Mg: 4.0~10.0%, Al: 11.0~20.0%, Si: 0.10~0.50%, the remainder being Zn and unavoidable impurities. For a description of the plating bath composition, refer to the description of the plating layer composition described above. That is, the plating bath may further contain Ca at 0.200% or less (including 0%) and may further contain other additives.

[0099] To prepare a plating bath of the composition described above, as a non-limiting example, a composite ingot containing a predetermined amount of Zn, Al, and Mg, or a Zn-Mg or Zn-Al ingot containing individual components, may be used. To replenish the plating bath consumed by molten plating, the ingot may be additionally melted and supplied. In this case, a method of directly immersing the ingot in the plating bath to melt it may be chosen, or a method of melting the ingot in a separate pot and then replenishing the plating bath with the molten metal may be chosen.

[0100] According to exemplary embodiments, the plating step may satisfy the following relationship 1.

[0101] [Relationship 1]

[0102] (T B )℃ ≤ A ≤ (T B +50)℃

[0103] In the above relationship 1, T B is the temperature of the plating bath (°C), and A is the inlet temperature of the base steel sheet (°C).

[0104] The inlet temperature of the base steel plate is T BIf it is less than T, a problem may arise where the crystalline phase of the plating layer is not dense, and the inlet temperature of the base steel sheet is T B If it exceeds +50℃, plating adhesion may decrease. Therefore, the inlet temperature of the substrate steel sheet can satisfy the range of the above-described Equation 1, and more specifically, the range of the above Equation 1 is (T B )℃ to (T B It can be +30)℃. More specifically, the range of the above relationship 1 is, (T B +20)℃ to (T B It can be +10)℃.

[0105] According to exemplary embodiments, the temperature of the plating bath may be 450 to 510°C. More specifically, the temperature of the plating bath may be 450 to 510°C. Even more specifically, the temperature of the plating bath may be 460 to 500°C.

[0106] Step to control the plating amount

[0107] The step of controlling the plating amount may be a step of gas wiping after plating. That is, it may be a step of controlling the plating amount by spraying gas onto the surface of the plated steel sheet.

[0108] According to exemplary embodiments, a mixture of inert gas and air can be used for the gas wiping process. This allows for further improvement in the surface appearance and linearity of the plated steel sheet.

[0109] The mixed gas may comprise 1 to 5% air and the remainder being an inert gas in volume percent. If the air content is less than 1 volume percent, it may be difficult to improve the linearity of the steel sheet. On the other hand, if the air content exceeds 5 volume percent, it may cause uneven oxidation defects on the surface of the plating layer during the process of controlling the plating amount. Therefore, the air content of the mixed gas can be controlled to 1 to 5 volume percent. More specifically, the air content of the mixed gas can be controlled to 2 to 4 volume percent.

[0110] The residual inert gas may be any one of argon (Ar), nitrogen (N2), and mixtures thereof, although not specifically limited. More specifically, the residual inert gas may be nitrogen gas.

[0111] [Example]

[0112] The present invention will be explained in more detail below through examples. However, it should be noted that the following examples are intended only to illustrate and explain the present invention in more detail, and are not intended to limit the scope of the present invention.

[0113] A plated steel sheet was obtained by plating a substrate steel sheet having the composition shown in Table 1 below under the conditions shown in Table 2 below and adjusting the plating amount.

[0114] Classification Base Steel Composition (wt%), remainder Fe and impurities Thickness (mm) Width (mm) CSI Mn PS Al Nb Cr Ti B Base Steel 0.018 0.010 0.20 0.009 0.005 0.10.02 0.20 0.02 0.015 1.512 00

[0115] No. Plating Conditions Wiping Gas Plating Bath Composition [wt%] Plating Bath Temperature [°C] Substrate Iron Inlet Temperature [°C] Air Content in Mixed Gas [vol%] MgAlSiCa Invention Example 14.0 11.0 0.10 4554651 Invention Example 24.4 11.4 0.15 0.0 154604802 Invention Example 34.9 12.2 0.2 0.0 34654853 Invention Example 45.4 14.4 0.24 0.0 64704904 Invention Example 55.7 17.5 0.3 10.0 84754955 Invention Example 66.1 19.2 0.35 0.10 4805002 Invention Example 77.2 19.4 0.4 20.12 4855353 Invention Example 88.319.50.460.144905254 Invention Example 99.820.00.500.25005305 Comparative Example 13.910.20.040.054404407 Comparative Example 210.512.70.080.34504509 Comparative Example 35.79.80.150.247047011 Comparative Example 411.018.00.260.3549049013 Comparative Example 512.317.00.320.444043015 Comparative Example 67.516.00.2504604700

[0116] Subsequently, surface roughness and linearity index Wsa were measured for each obtained steel plate. The surface roughness and linearity index Wsa were measured in accordance with JIS 2013 standards using a contact-type roughness meter, KOSAKA product.

[0117] No. Surface Roughness Linearity Index WsaRa(μm)Wsa(μm) Invention Example 11.08 0.35 Invention Example 21.21 0.37 Invention Example 31.27 0.32 Invention Example 41.31 0.40 Invention Example 51.19 0.45 Invention Example 61.40 0.47 Invention Example 71.35 0.41 Invention Example 81.48 0.48 Invention Example 91.35 0.46 Comparative Example 10.87 0.28 Comparative Example 22.24 0.53 Comparative Example 32.32 0.55 Comparative Example 42.78 0.60 Comparative Example 53.02 0.52 Comparative Example 62.54 0.58

[0118] Referring to Tables 1 to 3, in the case of Comparative Examples 1 to 5, one or more of the plating composition and manufacturing conditions specified in the present invention were not satisfied, so the surface roughness and linearity index Wsa fell outside the range proposed in the present invention, and as a result, the surface appearance of the plated steel sheets of Comparative Examples 1 to 5 was poor. On the other hand, in the case of Inventive Examples 1 to 9, excellent surface appearance quality and excellent linearity were exhibited as the plating composition and manufacturing conditions specified in the present invention were satisfied.

[0119] FIG. 1 is an image photograph showing the surfaces of (a) Invention Example 5 and (b) Comparative Example 5, respectively.

[0120] Figure 2 shows the results of comparing and evaluating the surface shape characteristics of (a) Invention Example 5 and (b) Comparative Example 5, respectively.

[0121] Referring to FIGS. 1 and 2, it can be seen that the aesthetic quality of Inventive Example 5 is superior to that of Comparative Example 5 in terms of surface quality appearance. Additionally, it can be seen that Comparative Example 5 has a higher surface roughness than Inventive Example 5, and that Comparative Example 5 has lower linearity than Inventive Example 5. Therefore, Inventive Example 5 can secure surface quality with excellent surface appearance and superior linearity.

[0122] Although the present invention has been described in detail through embodiments above, other forms of embodiments are also possible. Therefore, the technical concept and scope of the claims described below are not limited to the embodiments.

Claims

1. Base steel plate; and It includes a plating layer located on the surface of the above-mentioned base steel plate, and The above plating layer comprises, in weight percent, Mg: 4.0~10.0%, Al: 11.0~20.0%, Si: 0.10~0.50%, and the remainder being Zn and other unavoidable impurities, and A plated steel sheet in which the surface of the plating layer satisfies an average roughness Ra: greater than 1.00㎛ and less than or equal to 1.50㎛, and a linearity index Wsa: 0.30~0.50㎛.

2. In Paragraph 1, The above plating layer is a plated steel sheet further containing 0.200% or less (including 0%) of Ca in weight%.

3. In Paragraph 1, The above plating layer is a plated steel sheet further comprising one or more of the following groups (a) to (h). (a) Ni: 0.5% or less (b) At least one of the following: La: 0.1% or less, Ce: 0.1% or less, Y: 0.1% or less, Sr: 1.0% or less (c) Ti: 0.1% or less (d) W: 0.5% or less (e) Cu: 2.0% or less (f) At least one of Cr: 0.5% or less, Mn: 0.5% or less, V: 0.5% or less (g) B: 0.1% or less, P: 0.1% or less (h) At least one of Sn: 1.0% or less, Sb: 1.0% or less, Bi: 1.0% or less (a) Ni: 0.5% or less 4. In Paragraph 1, A plated steel sheet having a plating layer thickness of 10 to 50 μm.

5. A step of plating a substrate steel plate by immersing it in a plating bath containing Mg: 4.0~10.0%, Al: 11.0~20.0%, Si: 0.10~0.50%, the remainder being Zn and other unavoidable impurities; and The method includes a step of controlling the amount of plating by gas wiping using a mixed gas after plating treatment, and The above mixed gas comprises, in volume percent, 1 to 5 percent air and the remainder being an inert gas, and The above plating step is a method for manufacturing a plated steel sheet satisfying the following relationship 1. [Relationship 1] (T B )℃ ≤ A ≤ (T B +50)℃ (In the above relationship 1, T B is the temperature of the plating bath (°C), and A is the inlet temperature of the base steel sheet (°C).

6. In Paragraph 5, A method for manufacturing a plated steel sheet in which the above plating bath further contains 0.200% or less (including 0%) of Ca in weight%.

7. In Paragraph 5, The temperature of the plating bath (T B ) is a method for manufacturing galvanized steel sheets at 450~510℃.

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