Composition for surface treating steel sheet, plated steel sheet surface treated using same, manufacturing method therefor, and hot press-formed member

Abstract

The present invention relates to a surface-treated steel sheet suitable as a material for an automotive sheet material and, more specifically, to a composition for surface treatment of a plated steel sheet, a plated steel sheet surface-treated with the composition, a manufacturing method therefor, and a hot press-formed member.

Description

Composition for surface treatment of steel plate, plated steel plate surface-treated using the same, method for manufacturing the same, and hot-formed member

[0001] The present invention relates to a surface-treated steel sheet suitable as a material for automobile panels, and more specifically, to a composition for surface treatment of a plated steel sheet, a plated steel sheet surface-treated with the composition, a method for manufacturing the same, and a hot-formed member.

[0002] Typically, galvanized steel sheets are used as the material for automobile panels. These galvanized steel sheets are inexpensive, have excellent corrosion resistance (pitting corrosion), and have a beautiful surface appearance, so their use for interior and exterior automobile panels is gradually increasing.

[0003] The steel sheets used for automotive panels undergo press forming, assembly processes such as welding and bonding during the automobile manufacturing process, and then degreasing, phosphating, and painting. Consequently, galvanized steel sheets used for automotive panels require properties such as lubricity, weldability, adhesion, film removal, and paintability.

[0004] Meanwhile, the required physical properties of galvanized steel sheets with a zinc-based plating layer vary depending on the type of plating, and relatively inferior physical properties require supplementation.

[0005] For example, hot-dip galvanized (GI) and electrogalvanized (EG) steel sheets have soft plating layers that, when subjected to high-pressure, high-speed friction during press forming, can detach and adhere to the bead portion of the die. This can cause defects such as scratches and dents to appear on the steel sheet surface.

[0006] As another example, in the case of galvanized steel (GA), there is a problem that the material itself is broken or a powdering phenomenon occurs in which a light plating layer is peeled off due to low lubrication characteristics during press forming due to the high surface friction coefficient.

[0007] To solve this type of friction problem, a post-treatment process is being performed on the surface of galvanized steel sheets and zinc-based alloy-coated steel sheets used as automobile panels.

[0008] Related technologies include technologies for forming a phosphate film on the surface of a zinc-plated layer (Patent Documents 1 and 2) and technologies for forming a metal oxide layer (Patent Documents 3 and 4). However, these technologies have complex processes and are limited in the types of zinc-plated steel sheets to which they can be applied.

[0009] Among these, Patent Documents 1 and 2 require surface conditioning, phosphate treatment, washing, and drying, and have drawbacks such as requiring significant equipment space and solution management during actual operation. Furthermore, because these methods rely on reactivity with the plating layer, they also present the inconvenience of having to adjust the solution composition depending on the type of zinc-plated steel sheet.

[0010] In the case of patent documents 3 and 4, there is a limitation in that they cannot be applied to all zinc-plated steel sheets because they are limited in the composition of the plating layer (metal components).

[0011] Accordingly, there is a need for a method that can effectively improve the lubricity (friction characteristics) of various zinc-coated steel sheets while enabling post-treatment (surface treatment) of zinc-coated steel sheets without going through multiple processes.

[0012] Furthermore, automobile manufacturers have been conducting ongoing research on lightweight vehicle bodies to improve fuel efficiency and meet CO2 emission regulations. As part of this effort, hot press forming has been proposed to improve the strength of steel materials while maintaining the same weight. Hot press forming involves forming steel materials of a certain strength in the austenitic single-phase region and then rapidly cooling the processed steel to a low temperature, thereby forming low-temperature structures such as martensite within the steel. This method can dramatically improve product strength, thereby minimizing the problem of reduced workability when manufacturing high-strength (ultra-high-strength) components.

[0013] Meanwhile, as efforts to achieve carbon neutrality continue nationwide, automobile and steel companies are jointly researching various technologies that can reduce the amount of CO2 generated during hot press forming.

[0014] To achieve this, a technology has been proposed to shorten the heating time to the target temperature during high-temperature heating for hot forming, and as a related technology, Patent Document 5 discloses a method of coating a polymer on the surface of a steel plate. In this way, if a hydrocarbon-based polymer is coated on the surface of a steel plate, the effect of increasing the heating rate during hot forming can be obtained, but when a steel plate with a coated surface is hot formed, residues may be generated on the surface after forming, which may cause problems such as reduced weldability.

[0015] Accordingly, there is a need for a method to improve the heating rate during hot forming without deteriorating the physical properties of steel plates (coated steel plates) suitable for hot forming, even if the surface is treated.

[0016] (Patent Document 1) Korean Patent Publication No. 2001-0074527

[0017] (Patent Document 2) Japanese Patent Publication No. 2003-206106

[0018] (Patent Document 3) Japanese Patent Publication No. 1990-190483

[0019] (Patent Document 4) Japanese Patent Publication No. 2014-185381

[0020] (Patent Document 5) Chinese Patent Publication No. 10616418

[0021] One aspect of the present invention is to provide a composition for surface treatment of a galvanized steel sheet, which can not only improve the lubricity of a zinc-based galvanized steel sheet to be surface treated, but also shorten the heating time during high-temperature heating for hot forming of a galvanized steel sheet to be surface treated.

[0022] In addition, a plated steel sheet surface-treated using a surface treatment composition according to one aspect of the present invention and a method for manufacturing the same are provided.

[0023] As another aspect of the present invention, it is intended to provide a hot-formed member obtained by hot-forming a surface-treated plated steel sheet.

[0024] The technical problems to be achieved in the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present invention belongs from the description below.

[0025] According to one aspect of the present invention, a composition for surface treatment of a steel sheet is provided, which comprises an inorganic compound, an organic compound, and a residual solvent, wherein the organic compound is a fatty acid-based organic compound or a dicarboxylic acid-based organic compound having a molecular weight of 1000 or less.

[0026] In one embodiment of the present invention, the organic compound may be included in an amount of 0.15 to 7.50% based on 100 wt% of the total solid content of the composition.

[0027] In this way, by including an organic compound as a composition for surface treatment of a steel plate, and particularly including a fatty acid-based organic compound, the lubricity of a steel plate to be surface treated (particularly, a plated steel plate) can be improved.

[0028] In one embodiment of the present invention, the inorganic compound may be at least one selected from the group consisting of phosphorus (P), boron (B), and zirconium (Zr), and may further include at least one selected from the group consisting of nickel (Ni), manganese (Mn), molybdenum (Mo), zinc (Zn), and silicon (Si).

[0029] According to another aspect of the present invention, a surface-treated zinc or aluminum-based plated steel sheet is provided, comprising: a base steel sheet; a zinc or aluminum-based plated layer formed on at least one surface of the base steel sheet; and a surface-treated film layer formed on the zinc or aluminum-based plated layer.

[0030] In one embodiment of the present invention, a surface treatment film layer formed on a zinc or aluminum-based plating layer can be formed using a composition according to one embodiment of the present invention.

[0031] In one embodiment of the present invention, the surface treatment film layer is composed of two layers, an upper layer and a lower layer, and the carbon (C) distribution of the upper layer and the lower layer can satisfy the following relationship 1.

[0032] [Relationship 1]

[0033] (upper layer carbon) / (lower layer carbon) > 1.0

[0034] In this way, a surface-treated zinc or aluminum-based plated steel sheet according to one embodiment of the present invention has a surface-treated film layer containing an organic compound, and the surface-treated film layer can achieve a content distribution of the organic compound in the thickness (depth) direction, thereby improving lubricity.

[0035] In one embodiment of the present invention, the surface treatment film layer formed on the zinc or aluminum-based plating layer may have a thickness of 0.1 to 1.0 μm.

[0036] According to another aspect of the present invention, a method for manufacturing a surface-treated plated steel sheet is provided, comprising the steps of: preparing a plated steel sheet having a zinc or aluminum-based plated layer formed on at least one surface of a base steel sheet; coating a surface treatment composition on the plated layer; and drying the plated steel sheet coated with the surface treatment composition to form a surface treatment film layer.

[0037] In one embodiment of the present invention, the step of coating a surface treatment composition on a plating layer can be performed using a solution composition according to one embodiment of the present invention.

[0038] In one embodiment of the present invention, the step of coating the surface treatment composition is 100 to 1000 mg / m 2 It can be done with the amount of attachment.

[0039] In one embodiment of the present invention, the step of drying after coating can be performed at a temperature range of 70 to 150°C based on the PMT of the plated steel sheet.

[0040] According to another aspect of the present invention, a hot-formed member is provided, comprising: a steel plate; an aluminum-based plating layer formed on at least one surface of the steel plate; and a surface treatment film layer formed on the aluminum-based plating layer.

[0041] According to the present invention, a composition for surface treatment of a steel plate comprising an inorganic compound and an organic compound can be provided, and the composition can be coated using a simple coating method, thereby having an economical effect of reducing process costs.

[0042] In addition, when surface-treating a zinc or aluminum-based plated steel sheet using the composition provided in the present invention, the lubricity of the surface-treated zinc or aluminum-based plated steel sheet can be increased, thereby significantly improving cold or hot press formability.

[0043] In particular, when processing surface-treated zinc or aluminum-based plated steel sheets into parts with complex shapes or requiring severe drawing processing, or when applying conditions with high press loads, such as cold forming of high-strength steel materials, cracks in the steel sheets can be prevented and formability can be improved.

[0044] Furthermore, when surface-treating a hot-formable galvanized steel sheet using the composition provided by the present invention, formability can be improved when working with blanks for processing into specific automobile component shapes. In particular, when manufacturing a surface-treated hot-formable galvanized steel sheet into components, etc., there are economically and environmentally advantageous effects, such as reducing the heating time during high-temperature heating for hot forming.

[0045] Figure 1 is a diagram illustrating a cross-sectional shape of a surface-treated steel plate according to one embodiment of the present invention.

[0046] Fig. 2 is a side view of a test piece for measuring adhesive strength according to one embodiment of the present invention.

[0047] Hereinafter, preferred embodiments of the present invention will be described with reference to various examples. However, the embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

[0048] The present invention provides a composition capable of surface-treating a steel plate, a plated steel plate surface-treated using the composition, and a method for manufacturing the same. The present invention will be described in detail below.

[0049] The inventors of the present invention recognized problems that arise when zinc-plated steel sheets are used as materials for automobile panels due to insufficient lubrication properties, and conducted in-depth research to solve these problems.

[0050] In addition, the inventors of the present invention have conducted in-depth research on a method for providing a hot-forming galvanized steel sheet, which can reduce CO2 emissions during the hot-forming process of the galvanized steel sheet while satisfying the properties required in the automotive field to which the hot-forming galvanized steel sheet is applied. In particular, a method for increasing the heating rate during high-temperature heating for forming the hot-forming galvanized steel sheet was examined.

[0051] As a result, it was confirmed that a composition for surface treatment of steel sheets can be provided that can not only significantly improve cold press formability by increasing lubricity in the case of zinc-plated steel sheets, but also secure the properties required as a surface treatment layer of a hot-forming plated steel sheet, such as corrosion resistance and bendability, while reducing the time required for heating to the target temperature for high-temperature forming, thereby improving productivity and achieving a CO2 reduction effect. Thus, the present invention has been completed.

[0052] According to one aspect of the present invention, a composition for surface treatment of a steel sheet is provided, comprising an inorganic compound, an organic compound, and a residual solvent. Hereinafter, each component constituting the composition will be described in detail. Furthermore, the content of components within a film layer obtained by treatment with the composition will be described. Unless otherwise specified, the content of each component is based on 100 wt% of the entire composition (solution composition) or 100 wt% within the film layer after drying.

[0053] Inorganic compounds

[0054] When forming a surface treatment film layer by coating (applying) a surface treatment composition on the plating layer of a plated steel sheet, it is necessary to improve the adhesion between the plating layer and the film layer. Accordingly, a composition for surface treatment of a steel sheet according to one embodiment of the present invention includes an inorganic compound.

[0055] In one embodiment of the present invention, the inorganic compound may be at least one selected from the group consisting of phosphorus (P), boron (B), and zirconium (Zr), and may further include at least one selected from the group consisting of nickel (Ni), manganese (Mn), molybdenum (Mo), zinc (Zn), and silicon (Si).

[0056] In one embodiment of the present invention, the inorganic compound may be at least one selected from materials composed of acetate, carbonate, alkali salt, ammonium salt of the aforementioned metal, or oxides or hydroxides thereof.

[0057] In one embodiment of the present invention, the content of the inorganic compound contained in the composition is not particularly limited. That is, it is preferable that the inorganic compound be contained at a level such that the surface treatment film layer does not detach or peel off during the processing, forming, etc. of the surface-treated plated steel sheet and is maintained until the final component is manufactured. As an example, the inorganic compound may be contained at 5 to 15 wt% with respect to 100 wt% of the total composition, and the content at this time refers to the content in the solution composition.

[0058] organic compounds

[0059] A composition for surface treatment of a steel sheet according to one embodiment of the present invention may include an organic compound in order to obtain desired properties during surface treatment on a plated steel sheet.

[0060] In one embodiment of the present invention, the inorganic compound may be present in the form of a highly hard oxide or a hydroxide with low shear resistance within the surface treatment film layer obtained by coating (applying) the composition, thereby contributing to lubricity. However, this is not at a level advantageous for molding. Therefore, the composition according to one embodiment of the present invention is technically significant in that it further comprises an organic compound in addition to the aforementioned inorganic compound.

[0061] In this way, when processing for forming a plated steel sheet surface-treated with a composition containing an inorganic compound and an organic compound, for example, when press-forming (cold forming) a zinc-plated steel sheet surface-treated using a die, significantly improved lubricity can be provided to the plated steel sheet. This can prevent phenomena such as peeling off of the plating layer or fracture of the steel sheet material during press-forming of the plated steel sheet. In addition, when processing a high-strength steel plated steel sheet into a component, even better lubrication performance can be exhibited under high-load press conditions.

[0062] In addition, when a hot-forming plated steel sheet, for example, an aluminum-based plated steel sheet, is subjected to high-temperature heating for hot forming, surface-treated with the aforementioned composition, the time required for heating to a target temperature can be shortened due to the composition having a high combustion heat. As one example, when a substance having a high combustion heat is contained in the solution used for surface treatment, the surface temperature rise rate becomes faster due to the combustion heat of the substance in the solution applied when the plated steel sheet is subjected to high-temperature heating in a heating furnace for hot forming. As a result, the time required for heating to a target temperature can be shortened.

[0063] Thus, the present invention aims to improve the lubrication properties of a surface-treated galvanized steel sheet, and to reduce the heating time during high-temperature heating of a surface-treated galvanized steel sheet for hot forming. To achieve this, it is preferable to include, as the organic compound, a monocarboxylic acid-based organic compound such as a fatty acid-based organic compound or a dicarboxylic acid-based organic compound having carboxyl groups at both terminals.

[0064] In one embodiment of the present invention, the organic compound preferably has a molecular weight of 1000 or less, as it is advantageous for the organic compound to have a melting point of 50°C or higher, be in a solid phase at room temperature, and have low viscosity in a molten state. If the molecular weight exceeds 1000 and the viscosity is high (sticky) in a molten state, there is a risk of contaminating equipment during the production process and parts processing process.

[0065] In one embodiment of the present invention, the organic compound may be a fatty acid organic compound such as a fatty acid, a fatty acid salt, or a fatty acid amide, and may be a dicarboxylic acid, a dicarboxylic acid salt, or the like.

[0066] As a non-limiting example, the fatty acid may be at least one selected from the group consisting of stearic acid, 12-hydroxy stearic acid, 12-oxo stearic acid, palmitic acid, and oleic acid. In addition, the fatty acid salt may be sodium stearate, sodium laurate, sodium oleate, etc., and the fatty acid amide may be stearamide. In addition, the dicarboxylic acid may be at least one selected from the group consisting of adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, and dodecanedioic acid, and the dicarboxylic acid salt may be at least one selected from the group consisting of disodium adipate, diammonium adipate, disodium decanedioate, and diammonium decanedioate.

[0067] Meanwhile, the fatty acid-based organic compound may further include an ether of a fatty acid and polyoxyethylene(n), an ester of a fatty acid and polyoxyethylene(n), or a fatty acid ester. As a non-limiting example, the ether of a fatty acid and polyoxyethylene(n) may be polyoxyethylene(n) stearyl ether where n is 10 or less, and the ester of a fatty acid and polyoxyethylene(n) may be polyoxyethylene(n) stearate where n is 10 or less. And, the fatty acid ester may be at least one of ethylene glycol monostearate, sorbitan monostearate, and glycerol monostearate.

[0068] In one embodiment of the present invention, the organic compound may be included in an amount of 0.15 to 7.50% based on 100% by weight of the entire composition. A higher content of the organic compound is advantageous in terms of improving the lubricity and combustion heat of the surface-treated plated steel sheet.

[0069] The content of these organic compounds in the surface treatment film layer (dry film layer) obtained by surface treatment with the composition according to one embodiment of the present invention is important, and may be present at 2 to 50% with respect to 100 wt% of the film layer. When the content of the organic compound in the film layer is 2% or more, the effect of adding the organic compound can be obtained. However, when the content exceeds 50%, the resistance to shear is excessively lowered, which greatly reduces the sealer adhesion and may cause other problems such as equipment contamination. In another embodiment of the present invention, the organic compound may be present at 2 to 30% with respect to 100 wt% of the film layer, and in another embodiment, it may be present at 5 to 20%.

[0070] Meanwhile, in cases where the organic compound contained in the composition for surface treatment of steel sheets according to one embodiment of the present invention is a poorly soluble substance or has low dispersibility in a solution when contained in a high content, an additive such as an emulsifier may be further included. This is to ensure that the organic compound is sufficiently dispersed in a solvent such as water when the composition is prepared as a solution composition for coating treatment. At this time, the emulsifier may be appropriately selected depending on the type and amount of the organic compound and added in a certain amount.

[0071] Meanwhile, the composition for surface treatment of steel sheets according to one embodiment of the present invention is a solution composition, and the solvent used in this case is not particularly limited, but may be water. In this case, the water may be distilled water or deionized water. When preparing a solution composition in this way, it may be prepared by adding and dissolving an inorganic compound and an organic compound to the solvent as described above. In one embodiment of the present invention, the solution composition may have a solids content of 8 to 15 wt%.

[0072] Hereinafter, a plated steel sheet according to another aspect of the present invention, specifically a surface-treated zinc-based plated steel sheet and a surface-treated plated steel sheet for hot forming, will be described in detail.

[0073] A surface-treated zinc-plated steel sheet according to one aspect of the present invention may include a base steel sheet; a zinc-plated layer formed on at least one surface of the steel sheet; and a surface-treated film layer formed on the plating layer.

[0074] According to another aspect of the present invention, a surface-treated hot-forming galvanized steel sheet may include: a base steel sheet; an aluminum-based plating layer formed on at least one surface of the steel sheet; and a surface-treated film layer formed on the plating layer.

[0075] In one embodiment of the present invention, the base steel sheet may be any steel sheet capable of obtaining a plated steel sheet through plating treatment, and there are no particular limitations on its type or alloy composition. The plated steel sheet in this case applies not only to a zinc-based plated steel sheet, but also to an aluminum-based plated steel sheet having an aluminum-based plating layer.

[0076] As a non-limiting example, the above-mentioned steel plate may be carbon steel containing a certain amount of carbon (C), manganese (Mn), silicon (Si), phosphorus (P), sulfur (S), etc., and such carbon steel is widely known in the art, and thus there is no particular limitation on the composition of alloy elements.

[0077] In one embodiment of the present invention, a zinc-based plating layer may be included on at least one surface of the base steel sheet. The zinc-based plating layer may be a layer containing zinc (Zn) as a main component, for example, a plating layer containing Zn at 50 wt% or more. In addition, the plating layer may be a zinc-based alloy plating layer containing one or more elements, such as aluminum (Al), magnesium (Mg), and silicon (Si), in addition to zinc (Zn). Such a plating layer may be provided on not only one surface but also both surfaces of the base steel sheet.

[0078] In one embodiment of the present invention, the type of zinc-based coated steel sheet including a zinc-based plating layer on at least one surface of the base steel sheet is not particularly limited. However, as a non-limiting example, it may be a hot-dip galvanized steel sheet or an alloyed hot-dip galvanized steel sheet manufactured by hot-dip galvanizing, and it may also be an electro-galvanized steel sheet or a zinc-based electro-alloy coated steel sheet manufactured by electro-galvanizing.

[0079] In addition, in another embodiment of the present invention, the base steel sheet may include an aluminum-based plating layer on at least one surface. It should be noted that this is distinct from the base steel sheet having the aforementioned zinc-based plating layer formed thereon. In other words, this does not mean that the base steel sheet includes a zinc-based plating layer on one surface and an aluminum-based plating layer on the other surface.

[0080] In one embodiment of the present invention, the aluminum-based plating layer may be a plating layer containing aluminum (Al) as a main element, and as one example, the aluminum-based plating layer may include, in weight %, 0 to 27% zinc (Zn), 7.0 to 10.0% silicon (Si), the remainder aluminum (Al), and unavoidable impurities. This plating layer may also be provided on not only one side but also both sides of the base steel sheet.

[0081] In one embodiment of the present invention, the aluminum-based plating layer can be formed by immersing the base steel sheet in an aluminum-based molten plating bath, as will be described in detail later, and it is well known that the composition of the aluminum-based plating layer is determined according to the composition of the aluminum-based molten plating bath.

[0082] In one embodiment of the present invention, zinc (Zn) among the alloy compositions constituting the aluminum-based plating layer is an element advantageous in securing the corrosion resistance of the plating layer, and a sacrificial corrosion protection effect can be obtained by Zn. As one example, if the content of Zn exceeds 27%, there is a problem in that the Zn diffuses into the base steel sheet during hot forming of the base steel sheet on which the plating layer is formed, causing cracks to occur due to LME. Therefore, it is to be noted that the Zn may be included up to 27%, and even if it is 0%, there is no problem in securing the physical properties of the aluminum-based plating layer.

[0083] In one embodiment of the present invention, silicon (Si) among the alloy compositions forming the aluminum-based plating layer can play a role in suppressing diffusion of aluminum present in the plating bath into the interior of the base steel sheet during plating of the base steel sheet. As an example, in order to obtain the above-described effect, the content of Si may be 7% or more. On the other hand, if the content exceeds 10%, there is a concern that the melting point of the plating bath may rapidly increase, and in this case, there is a problem that the amount of ash generated from the plating bath rapidly increases.

[0084] In one embodiment of the present invention, a surface treatment film layer may be included on the zinc-based plating layer. That is, a coating layer having a certain thickness may be formed on the zinc-based plating layer.

[0085] Additionally, in one embodiment of the present invention, a surface treatment film layer may be included on the aluminum-based plating layer, and the film layer may also have a certain thickness.

[0086] In one embodiment of the present invention, a surface treatment film layer provided on a zinc-based plating layer or an aluminum-based plating layer can be formed from a composition for surface treatment of a steel sheet according to one embodiment of the present invention. That is, the film layer formed from the composition according to one embodiment of the present invention includes an inorganic compound and an organic compound.

[0087] This allows the surface-treated galvanized steel sheet to possess the desired properties. In particular, zinc-based galvanized steel sheets can achieve significantly improved lubricity, and aluminum-based galvanized steel sheets, an example of galvanized steel sheets for hot forming, can shorten the heating time during high-temperature heating for hot forming, as well as improve bendability and hydrogen embrittlement resistance (hydrogen absorption).

[0088] In one embodiment of the present invention, the surface treatment film layer may be composed of two layers, an upper layer and a lower layer. That is, the film layer formed from the surface treatment composition according to one embodiment of the present invention has a content distribution of organic compounds in the depth direction, and the carbon (C) distribution of the upper layer and the lower layer may satisfy the following relationship 1.

[0089] [Relationship 1]

[0090] (upper layer carbon) / (lower layer carbon) > 1.0

[0091] As mentioned above, the surface treatment film layer according to one embodiment of the present invention is formed from a composition composed of an inorganic compound and an organic compound, wherein the inorganic compound is composed of a metal such as P, B, or Zr, and the organic compound may include a fatty acid-based organic compound, and the type thereof may be replaced with the aforementioned content.

[0092] As an example, when a composition according to an embodiment of the present invention is coated (applied) on the surface of a plating layer of a zinc-based galvanized steel sheet, the plating components (e.g., Zn, etc.) in the plating layer are etched and oxidized by the etching action, and the inorganic compounds in the composition are precipitated on the surface (interface) of the plating layer to form a film. Meanwhile, the organic compounds contained in the composition do not react with the plating layer, and are therefore mainly distributed on the upper portion of the surface treatment film layer rather than at the interface adjacent to the plating layer. As a result, the surface treatment film layer formed on the plating layer according to an embodiment of the present invention may be composed of a lower layer in which mainly inorganic compounds exist near the interface with the plating layer, a relatively small amount of organic compounds, and an upper layer in which a relatively large amount of organic compounds is present compared to the lower layer. Such a structure of the upper and lower layers may appear not only in a zinc-based galvanized steel sheet, but also in an aluminum-based galvanized steel sheet, which is a galvanized steel sheet for hot forming.

[0093] In particular, a composition according to one embodiment of the present invention includes a fatty acid-based organic compound as an organic compound, so that the carbon distribution of the upper and lower layers of the surface treatment film layer can satisfy equation 1. As a result, the lubrication properties of the surface-treated zinc-based and aluminum-based plated steel sheets can be improved.

[0094] In one embodiment of the present invention, a case where the above relational expression 1 is not met may correspond to a case where the organic compound is not mainly distributed within the upper layer of the surface treatment film layer. In this case, the lubricity of the plated steel sheet is reduced compared to a case where relational expression 1 is satisfied under the condition that the organic compound is added in the same amount. In addition, due to the organic compound existing in a large amount in the lower layer, the adhesion at the interface between the surface treatment film layer and the plated layer is reduced, which may cause other problems such as reduced sealer adhesion.

[0095] In one embodiment of the present invention, the carbon distribution in the thickness (depth) direction of the surface treatment film layer can be confirmed by measuring the carbon amount of the upper and lower layers constituting the film layer using a glow discharge spectrometer (GDS) or by measuring the cross-section in the thickness direction of the film layer using an energy dispersive spectrometer (EDS, for example, SEM-EDS equipment) analysis.

[0096] According to one embodiment of the present invention, the surface treatment film layer may have a thickness of 0.1 to 1.0 μm. The thickness at this time is based on the thickness after drying. If the thickness of the film layer is less than 0.1 μm, there is a problem that lubricity, corrosion resistance, bendability, hydrogen embrittlement resistance, etc. are inferior because the solution composition is thinly applied to the rough acid portion existing on the surface of the plating layer of the plated steel sheet. On the other hand, if the thickness of the film layer exceeds 1.0 μm, it is formed too thick, which deteriorates the sealer adhesion, etc., and increases the processing cost of the solution composition, which is economically disadvantageous.

[0097] Meanwhile, in one embodiment of the present invention, the surface treatment film layer having an upper layer and a lower layer structure can be divided into an upper layer from the extreme surface to an area in the thickness (depth) direction where the value of relational expression 1 exceeds 1.0, and a lower layer for the remaining area. In other words, based on the value of relational expression 1, the area from the point where the value becomes 1.0 or less to the surface (interface) in contact with the plating layer can be considered as the lower layer.

[0098] Hereinafter, a method for manufacturing a zinc-plated steel sheet, i.e., a surface-treated zinc-plated steel sheet, according to another aspect of the present invention will be described.

[0099] In addition, a method for manufacturing a hot-forming plated steel sheet according to another aspect of the present invention, i.e., a surface-treated hot-forming plated steel sheet, is described.

[0100] However, it should be noted that the manufacturing methods below are each one example for manufacturing surface-treated zinc-based galvanized steel sheets and surface-treated galvanized steel sheets for hot forming.

[0101] First, in one embodiment of the present invention, a surface-treated zinc-plated steel sheet can be manufactured through the steps of preparing a zinc-plated steel sheet having a zinc-plated layer formed on at least one surface of a base steel sheet; coating a composition for surface treatment on the zinc-plated layer of the zinc-plated steel sheet; and drying the zinc-plated steel sheet after the coating.

[0102] In one embodiment of the present invention, a surface-treated aluminum-based plated steel sheet can be manufactured through the steps of: preparing a plated steel sheet having an aluminum-based plated layer formed on at least one surface of a base steel sheet; applying a surface treatment composition on the aluminum-based plated layer of the plated steel sheet; and drying and curing the plated steel sheet after applying the composition to form a surface treatment film layer.

[0103] In one embodiment of the present invention, any steel sheet capable of producing a plated steel sheet by plating can be used as the base steel sheet for forming a zinc-based plating layer or an aluminum-based plating layer on at least one surface, and thus, there is no particular limitation on its type. In addition, the content of the base steel sheet mentioned above can be replaced.

[0104] In one embodiment of the present invention, the zinc-based plating layer is a plating layer containing zinc (Zn) as a main component, and the addition of elements other than zinc is not excluded. As one example, the elements other than zinc may be at least one selected from aluminum (Al), magnesium (Al), and silicon (Si), and a plating layer containing a mixture of these elements and zinc may be referred to as a zinc-based alloy plating layer. In addition, the content of the zinc-based plating layer mentioned above may be replaced.

[0105] In one embodiment of the present invention, an aluminum-based plating layer can be formed by plating a base steel sheet, and as one example, can be obtained through a process of immersing the base steel sheet in an aluminum-based plating bath containing inevitable impurities including Si, Zn, and Fe in addition to Al. As a non-limiting example, the aluminum-based plating bath can contain 7.0 to 10.0% of silicon (Si), and by adding the Si, the effect of suppressing the fluidity of the molten metal and the diffusion of Al into the base steel sheet during plating can be obtained. In addition, the aluminum-based plating bath can further contain 0 to 27% of zinc (Zn) and 3% or less of iron (Fe), and it is to be noted that these contents are replaced with the contents described above.

[0106] In one embodiment of the present invention, the surface treatment composition can be applied to the surface, regardless of the type of plating layer, by a solution application method in which the surface is simply applied and then dried. For example, any one coating method selected from the group consisting of bar coating, roll coating, spraying, dipping, spray squeegeeing, and dipping squeegeeing can be used. When such a coating method is used, the process is simple and the process operation cost is low, so an economic effect can be achieved.

[0107] In one embodiment of the present invention, the surface treatment composition coated on the zinc-based plating layer or the aluminum-based plating layer may be a steel sheet surface treatment composition according to one embodiment of the present invention. In this case, the composition may be a solution composition, and the solution composition may be, for example, a surface treatment composition containing water as a solvent and having a solid content of 8 to 15 wt%. Here, the water may be deionized water or distilled water.

[0108] In coating treatment of the above-mentioned solution composition, as an example, 100 to 1000 mg / m 2 It can be done with an adhesion amount of . The amount of the solution composition coated is 100 mg / m 2If it is less than 1000 mg / m, the lubricity may be reduced due to the composition being thinly applied to the acidic areas of the plating layer. On the other hand, if the adhesion amount of the solution composition is less than 1000 mg / m 2 If it exceeds , the surface treatment film layer after drying may become too thick, which may deteriorate physical properties such as sealer adhesion. More advantageously, the solution composition is 150 to 500 mg / m 2 It can be applied with an adhesive amount of .

[0109] In one embodiment of the present invention, the step of drying the plated steel sheet coated with the surface treatment composition can be performed at a temperature range of 70 to 150°C. If the temperature during the drying is lower than 70°C, complete drying may not occur, and thus the physical properties of the surface-treated plated steel sheet, such as corrosion resistance, film adhesion, and lubricity, may deteriorate. On the other hand, if the drying temperature exceeds 150°C, the ratio of hydroxide / oxide of the inorganic compound in the composition may decrease, resulting in deterioration of lubricity, sealer adhesion, film removal, and phosphate treatment properties.

[0110] By doing this, a plated steel sheet having a surface treatment film layer formed thereon can be obtained, and the plated steel sheet at this time can be not only a zinc-based plated steel sheet but also an aluminum-based plated steel sheet suitable as a plated steel sheet for hot forming. At this time, the surface treatment film layer can be formed by a composition containing an inorganic compound and an organic compound, and a surface treatment film layer having a structure in which the organic compound has a content distribution in the thickness (depth) direction can be obtained.

[0111] Meanwhile, the surface treatment film layer having a content distribution in the thickness (depth) direction can be formed by a chemical reaction occurring during the coating treatment and drying process of a solution composition containing both inorganic compounds and organic compounds.

[0112] However, it should be noted that in order to obtain such a surface treatment film layer, a method of first coating and drying a solution composition containing an inorganic compound, and then second coating and drying a solution composition containing an organic compound is not excluded.

[0113] Hereinafter, the present invention will be described in more detail through examples. However, the description of these examples is merely intended to illustrate the implementation of the present invention and is not intended to limit the present invention. This is because the scope of the present invention is determined by the matters set forth in the claims and matters reasonably inferred therefrom.

[0114] (Example)

[0115] Experimental Example 1. Surface-treated zinc-plated steel sheet

[0116] The thickness including the zinc-plated layer is 0.8 mm, the elongation is 36-37%, and the plating weight is 45 g / m. 2 A galvanized steel sheet (GA) with an alloying composition was prepared. Thereafter, a surface treatment composition in a solution state was coated (applied) on the plating layer of the galvanized steel sheet with an alloying composition.

[0117] The surface treatment composition in the above solution state contained boric acid (B) and ammonium molybdate (Mo) as inorganic compounds, and contained organic compounds as shown in Table 1 below. At this time, each composition was prepared so that the content of the organic compound in the film layer formed by subsequent drying had the content shown in Table 1. For example, when the content of the organic compound in the film layer was 20 wt%, the inorganic compound was composed at 9 wt% and the organic compound was composed at 1 wt% in the solution composition having a solid content of 10 wt%. Water (distilled water) was used as the solvent.

[0118] After drying the surface treatment composition in each solution state on the plating layer using the bar coating method, the adhesion amount of the film layer is 400 mg / m 2After coating (applying) this, it was dried at 90℃ to obtain an alloyed hot-dip galvanized steel sheet with each surface treatment film layer formed.

[0119] Meanwhile, for some alloyed hot-dip galvanized steel sheets, an inorganic compound solution and an organic compound solution were prepared separately, and then one of the two solutions was coated first, and then the other solution was coated second to form a surface treatment film layer.

[0120] Friction tests and sealer adhesion evaluations were conducted on the alloyed hot-dip galvanized steel sheets on which each surface treatment film layer was formed, and the results are shown in Table 1 below.

[0121] Friction tests were conducted using a pin-on-disk method. A 3-mm-diameter steel ball was used as the fixed pin. Friction (mN) was measured under conditions of a 50-g load, a 10-mm rotational radius, and a 20-mm / s linear speed. The average value was taken from the measurement interval of 5 to 100 seconds. Consequently, lower friction indicates better lubricity (frictional properties).

[0122] The sealer adhesion evaluation was performed by manufacturing two specimens of 25×100mm in size, and then applying mastic sealer (adhesive strength Spec: 4.0 kgf / cm) in size of 25mm (width)×25mm (length)×3mm (height) 10mm inside from the end of one specimen. 2 ) adhesive was applied. Afterwards, another specimen was wrapped as shown in Fig. 2, and baked at 170°C for 20 minutes, and the adhesive shear strength of the upper and lower specimens was measured. At this time, the shear strength was measured at a speed of 50 mm / min, and the maximum shear force measured was 6.25 cm of the bonded area. 2 The adhesive strength (kgf / cm) is derived by dividing by 2 ) was indicated.

[0123] Meanwhile, in order to confirm the carbon distribution in the thickness direction of the surface treatment film layer, the carbon amounts of the upper and lower layers constituting the surface treatment film layer were measured using SEM-EDS surface analysis. Thereafter, the carbon distribution was calculated according to Equation 1. At this time, the carbon amount (wt%) obtained by surface analysis from the outermost surface of the surface treatment film layer to a point t / 2 in the thickness direction (where t corresponds to the thickness of the film layer) was set as the carbon amount of the upper layer, and the carbon amount (wt%) obtained by surface analysis from the point t / 2 to the interface of the film layer and the plating layer was set as the carbon amount of the lower layer.

[0124] Type of organic compound Content of organic compound in film layer Characteristics of film layer Content (wt%) Carbon distribution (Relationship 1) Friction force (mN) Adhesive strength (kgf / cm) 2) Comparative Example 1 - (Uncoated) - 58.55.3 Comparative Example 2 - (No organic compound added) 0041.65.5 Comparative Example 3 Sodium stearate 601.317.33.5 Comparative Example 4 Sodium stearate 701.517.12.6 Comparative Example 5 12-Hydroxy stearic acid 701.419.83.3 Comparative Example 6 Polyoxyethylene(2) stearyl ether 551.415.32.2 Comparative Example 7 12-Hydroxy stearic acid*200.0220.93.0 Comparative Example 8 Sodium stearate 11.540.05.6 Comparative Example 9 12-Hydroxy stearic acid 11.238.75.7 Inventive Example 1 Sodium stearate 21.5 25.45.0 Invention Example 2 Sodium stearate 201.3 19.25.3 Invention Example 3 Sodium stearate 501.6 19.14.4 Invention Example 4 Stearic acid 101.5 19.85.1 Invention Example 5 12-Hydroxy stearic acid 21.3 28.85.7 Invention Example 6 12-Hydroxy stearic acid 501.3 21.64.5 Invention Example 7 12-Hydroxy stearic acid** 2077.0 20.24.7 Invention Example 8 Stearamide 51.9 20.05.7 Invention Example 9 Adipic acid 201.3 25.5 5.2 Invention Example 10 Sebacic acid 301.4 25.35.0 Invention Example 11 Sebacic acid401.421.54.5Invention example 12Sebacic acid501.321.44.7Invention example 13Sebacic acid**2053.020.44.3Invention example 14Polyoxyethylene(2) stearyl ether101.216.54.6Invention example 15Polyoxyethylene(2) stearyl ether401.316.54.0Except for the content of organic compounds in the film layer, the remainder is inorganic compounds.*Comparative Example 7 is an example in which coating is performed sequentially, in which an organic compound solution is coated first and then an inorganic compound solution is coated second.**Invention examples 7 and 13 are also examples of sequential coating, in which an inorganic compound solution is coated first and then an organic compound solution is coated second.

[0125]

[0126] As shown in Table 1, in the case of Comparative Example 1, which did not undergo surface treatment, and Comparative Example 2, which was surface treated with a composition composed only of inorganic compounds even after undergoing surface treatment, it can be confirmed that the lubricity is relatively poor with a frictional force of 40 mN or more.

[0127] On the other hand, it can be confirmed that the surface-treated examples 1 to 15 using a composition containing a certain amount of an organic fatty acid compound together with an inorganic compound have significantly lower frictional force compared to comparative examples 1 and 2. This can be attributed to the fact that the surface-treated film layer is formed with a structure having a content distribution of the organic compound in the thickness (depth) direction due to the inclusion of an organic fatty acid compound in the film layer, thereby having a carbon distribution satisfying equation 1.

[0128] Meanwhile, Comparative Examples 3 to 6, which included an organic compound in the surface treatment composition but had an excessive content, satisfied the carbon distribution of Equation 1, but had inferior adhesive strength due to the excessive fatty acid organic compound.

[0129] In addition, in the case of Comparative Examples 8 and 9 where the content of organic compounds in the composition was insufficient, the adhesive strength was excellent due to the relatively high content of inorganic compounds, but the frictional force increased and the lubricity decreased.

[0130] Meanwhile, Comparative Example 7 is a case where the carbon distribution in the surface treatment film layer is excessively high in the lower layer compared to the upper layer. It can be seen that if the organic compound is excessive in the lower layer of the film layer, the adhesion between the film layer and the base steel sheet decreases, which can cause problems with sealer adhesion.

[0131] In contrast, in invention examples 7 and 13, the carbon distribution in the surface treatment film layer is excessively less in the lower layer than in the upper layer, and thus excellent lubricity can be confirmed. This is due to the organic compounds present in large quantities in the upper layer. In addition, it can be predicted that the excellent adhesive strength characteristics are due to the organic compounds in the upper layer within the film layer melting at the sealer firing temperature and becoming fluid, which is then absorbed toward the sealer.

[0132] Experimental Example 2. Surface-treated aluminum-based galvanized steel sheet

[0133] An aluminum-plated steel sheet having an aluminum-plated layer composed of 9% silicon, the remainder Al, and unavoidable impurities by weight was prepared on both sides of the base steel sheet. Thereafter, a surface treatment composition in a solution state was coated (applied) on the plating layer of the aluminum-plated steel sheet. At this time, the surface treatment composition in a solution state was the same composition as that used in Experimental Example 1.

[0134] Each solution-state surface treatment composition is dried on the plating layer using the bar coating method, and the adhesion amount of the film layer is 400 mg / m 2 After coating (applying) to this, the aluminum-based plated steel sheet was dried at 90°C to obtain each surface treatment film layer.

[0135] Thereafter, each aluminum-based plated steel sheet having a film layer formed on the plating layer according to the above was heated to 900°C, heat-treated for 5 minutes, and then pressed (formed) using a mold and cooled simultaneously to obtain a hot-formed part. Thereafter, the corrosion resistance, bendability, and hydrogen absorption of the hot-formed part were measured, and the results are shown in Table 2 below.

[0136] Corrosion resistance was evaluated according to the ISO 14993:2018 standard, and was also evaluated as the relative red rust area compared to untreated aluminum-plated steel sheets.

[0137] The bendability (C direction and L direction) was measured five times each through a three-point bending test (VDA238-100), and was recorded as the average value of the bending outer angle converted from the maximum bending strength.

[0138] The amount of diffusible hydrogen was evaluated by quantifying the amount of hydrogen released while heating the specimen from room temperature to 400°C using Bruker's G8 GALILEO. Considering that hydrogen contained in the material naturally releases to the outside over time, specimens that had been manufactured for the same amount of time were used for the hydrogen measurement.

[0139] Meanwhile, even if the aforementioned properties are excellent, practical application is difficult if the film detaches and contaminates equipment during handling processes such as coil-state steel sheet manufacturing, transportation, and blanking. Therefore, a taping test was conducted prior to hot forming, in which a strong tape was attached to the surface of a galvanized steel sheet specimen and then removed. Based on the increase in tape weight, specimens expected to contaminate equipment were identified. The results are presented in Table 2 below.

[0140] Additionally, the time required to raise the temperature to the target heating temperature was measured. Specifically, the time required for raising the temperature was expressed as a relative shortening rate (%) based on the time required to raise the temperature of an untreated aluminum-plated steel sheet to the target temperature.

[0141] Classification Organic compound type Target temperature Reduction rate Equipment contamination Corrosion resistance Bending property Hydrogen storage amount Comparative example a-(Uncoated)--×600.234 Comparative example b-(No organic compound added) 3-×600.292 Comparative example c Sodium stearate 35○○ 66 0.125 Comparative example d Sodium stearate 40○○ 67 0.099 Comparative example e 12-Hydroxy stearic acid 40○○ 67 0.144 Comparative example f Polyoxyethylene(2) stearyl ether 33○○ 65 0.187 Comparative example g 12-Hydroxy stearic acid* 16○○ 62 0.197 Comparative example h Sodium stearate 6-×600.250 Comparative example i 12-Hydroxy stearic acid 6-×600.248 Invention example aSodium stearate 7-△610.209 invention example bSodium stearate 16-○620.176 invention example cSodium stearate 30-○650.167 invention example dStearic acid 11-○610.195 invention example e12-Hydroxy stearic acid 7-△610.201 invention example f12-Hydroxy stearic acid 30-○650.156 invention example g12-Hydroxy stearic acid**16-○620.172 invention example hStearamide 8-△610.197 invention example iAdipic acid 16-○620.196 invention example jSebacic acid 21-○630.179 invention example kSebacic acid 26-○640.163 invention example lSebacic acid30-○650.149 Invention example mSebacic acid**16-○620.196 Invention example nPolyoxyethylene(2) stearyl ether11-△630.214 Invention example oPolyoxyethylene(2) stearyl ether26-○650.163 The content of each organic compound is set to the same as in Table 1, and the rest except for the organic compounds are inorganic compounds (the content of each compound at this time is based on the content in the film layer on the plating layer of the plating steel sheet before hot forming).*Comparative example g is an example in which coating is performed sequentially, in which an organic compound solution is coated first and then an inorganic compound solution is coated second. **Inventive examples g and m are also examples in which coating is performed sequentially, in which an inorganic compound solution is coated first and then an organic compound solution is coated second.

[0142]

[0143] As shown in Table 2, it can be confirmed that the hot-formed parts (Invention Examples a to o) obtained by hot-forming an aluminum-plated steel sheet surface-treated using a surface treatment composition according to one embodiment of the present invention have improved properties of corrosion resistance, bendability, and hydrogen absorption compared to the hot-formed parts (Comparative Example a) that are not surface-treated.

[0144] In particular, it was confirmed that the heating time for hot forming the surface-treated aluminum-plated steel sheet can be significantly reduced compared to Comparative Example a when heated at high temperatures. These results suggest that the efficiency of the hot forming process can be increased, and energy costs can be reduced when manufacturing parts, etc., through hot forming.

[0145] Meanwhile, Comparative Examples c to f, which contain organic compounds in their surface treatment compositions but have excessive amounts thereof, and Comparative Example g, which has excessive carbon distribution in the lower layer compared to the upper layer within the film layer, were judged difficult to apply to actual products due to the anticipated contamination of equipment during the material handling process. In addition, Comparative Examples h and i, which do not contain sufficient amounts of organic compounds in their compositions, exhibited poor corrosion resistance and failed to improve hydrogen absorption.

[0146] [Explanation of symbols]

[0147] 1...Steel plate

[0148] 2...zinc-based plating layer or aluminum-based plating layer

[0149] 3...Surface treatment film layer

[0150] 4...lower layer

[0151] 5...upper floor

Claims

1. Contains inorganic compounds, organic compounds and residual solvents; A composition for surface treatment of a steel plate, wherein the organic compound is a fatty acid-based organic compound or a dicarboxylic acid-based organic compound having a molecular weight of 1000 or less.

2. In paragraph 1, A composition for surface treatment of a steel plate, wherein the organic compound is contained in an amount of 0.15 to 7.50% based on 100 wt% of the total composition.

3. In paragraph 1, The above organic compounds are Stearic Acid, 12-Hydroxy Stearic Acid, 12-Oxo Stearic Acid, Palmitic Acid, Oleic Acid, Sodium Stearate, Sodium Laurate, Sodium Oleate, Stearamide, Adipic Acid, Pimelic Acid, Suberic Acid, Azelaic Acid, Sebacic Acid, Undecanedioic Acid, Dodecanedioic Acid, Disodium Adipate, Diammonium Adipate, A composition for surface treatment of a steel sheet, comprising at least one selected from the group consisting of disodium decanedioate, diammonium decanedioate, ethers of fatty acids and polyoxyethylene(n), esters of fatty acids and polyoxyethylene(n), and fatty acid esters.

4. In paragraph 1, A composition for surface treatment of a steel plate, wherein the above inorganic compound is at least one selected from the group consisting of phosphorus (P), boron (B), and zirconium (Zr).

5. In paragraph 4, A composition for surface treatment of a steel sheet, wherein the above inorganic compound further comprises at least one selected from the group consisting of nickel (Ni), manganese (Mn), molybdenum (Mo), zinc (Zn), and silicon (Si).

6. Steel plate; A plating layer formed on at least one surface of the above steel plate; and Includes a surface treatment film layer formed on the above plating layer, A surface-treated plated steel sheet, wherein the surface treatment film layer is formed using a surface treatment composition according to any one of claims 1 to 5.

7. In paragraph 6, The surface-treated plated steel sheet having the above surface-treated film layer containing an organic compound at 2 to 50% by weight based on the total 100% by weight.

8. In paragraph 6, The above surface treatment film layer is composed of two layers: an upper layer and a lower layer. A surface-treated galvanized steel sheet in which the carbon (C) distribution of the upper and lower layers satisfies the following relationship 1. [Relationship 1] (Amount of carbon in upper layer) / (Amount of carbon in lower layer) > 1.0 9. In paragraph 6, The above surface treatment film layer is a surface-treated plated steel sheet having a thickness of 0.1 to 1.0 ㎛.

10. In paragraph 6, The above plating layer is a surface-treated plated steel sheet which is a zinc-based plating layer or an aluminum-based plating layer.

11. A step for preparing a plated steel sheet having a plated layer formed on at least one surface of the steel sheet; A step of coating a surface treatment composition on the above plating layer; and It includes a step of drying a plated steel sheet coated with the above surface treatment composition to form a surface treatment film layer. A method for manufacturing a surface-treated plated steel sheet, wherein the surface treatment composition is a composition according to any one of claims 1 to 5.

12. In paragraph 11, The step of coating the above surface treatment composition is 100 to 1000 mg / m 2 A method for manufacturing a surface-treated galvanized steel sheet by attaching a coating amount.

13. In paragraph 11, A method for manufacturing a surface-treated galvanized steel sheet, wherein the coating step is performed by any one method selected from the group consisting of bar coating, roll coating, spraying, dipping, spray squeezing, and dipping squeezing.

14. In paragraph 11, A method for manufacturing a surface-treated galvanized steel sheet, wherein the drying step is performed at a temperature range of 70 to 150°C based on the PMT of the galvanized steel sheet.

15. In paragraph 11, A method for manufacturing a surface-treated plated steel sheet, wherein the above-mentioned plating layer is a zinc-based plating layer or an aluminum-based plating layer.

16. Steel plate; An aluminum-based plating layer formed on at least one surface of the above steel plate; and It includes a surface treatment film layer formed on the above aluminum plating layer, A hot-formed member, wherein the film layer is formed from a composition according to any one of claims 1 to 5.

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