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

Abstract

The present invention relates to a plated steel sheet for hot-press forming, suitable for automobile materials and, more specifically, to a composition for surface-treating the plated steel sheet for hot-press forming, and a plated steel sheet that is surface-treated using the composition, and a method for manufacturing same. In addition, provided is a hot-press-formed member obtained using the surface-treated plated steel sheet.

Description

Composition for surface treatment of hot-formed galvanized steel sheet, aluminum-based galvanized steel sheet surface-treated using the same, manufacturing method thereof, and hot-formed member

[0001] The present invention relates to a hot-forming galvanized steel sheet suitable as an automobile material, and more specifically, to a composition for surface treatment of the hot-forming galvanized steel sheet, an aluminum-based galvanized steel sheet surface-treated using the composition, a method for manufacturing the same, and a hot-forming member.

[0002] Recently, automakers have been conducting ongoing research into lightweight vehicle construction to improve fuel efficiency and meet CO2 emission regulations. As part of this effort, they are incorporating various alloying elements into steel alloy designs to enhance strength at a given weight. However, this incorporation of various alloying elements in steel leads to increased hardenability and defects such as springback, which impairs workability.

[0003] To address these issues, a hot press forming method was proposed. This method involves forming steel of a given strength within the austenitic single-phase region, then rapidly cooling the formed steel to a low temperature to form low-temperature structures such as martensite. This method dramatically improves product strength, thereby minimizing the problem of reduced workability when manufacturing high-strength (ultra-high-strength) components.

[0004] Meanwhile, efforts to achieve carbon neutrality nationwide are ongoing, and automobile and steel companies are jointly researching various technologies that can reduce the amount of CO2 generated during hot press forming.

[0005] As a result, the following method was proposed. From a metallurgical perspective, this is a technology that lowers the Ac3 point temperature by changing the composition of the steel by adding manganese (Mn), thereby enabling forming (warm stamping) at lower temperatures than conventional materials (Patent Document 1). This warm stamping has the advantage of securing productivity and extending the life of the mold because it does not require rapid cooling. However, issues such as reduced corrosion resistance of the steel sheet due to increased manganese content and productivity issues in the continuous casting and hot rolling processes during the manufacturing process remain to be resolved.

[0006] Meanwhile, as another method, a technique for coating a steel sheet surface with a polymer has been proposed to shorten the heating time to the target temperature during high-temperature heating for hot forming (Patent Document 2). Coating the surface of a steel sheet with a hydrocarbon-based polymer can increase the heating rate during hot forming. However, hot forming a coated steel sheet can lead to the generation of surface residues after forming, which can reduce weldability.

[0007] To address these issues, a surface treatment composition combining a polymer and carbon, excluding silicon (Patent Document 3), and a polymer coating agent (Patent Document 4) that does not contain phosphorus (P) have been developed. However, some compounds containing silicon, such as silane coupling agents, are important substances that affect the adhesion between the metal surface and the polymer coating film, and therefore their complete removal is not desirable. Furthermore, the phosphorus component is necessary for ensuring corrosion resistance, and therefore, it must be included within a range that does not impair weldability.

[0008] (Patent Document 1) Korean Patent Publication No. 10-2020-0051129

[0009] (Patent Document 2) Chinese Patent Publication No. 10616418

[0010] (Patent Document 3) Korean Patent Publication No. 2016-7026841

[0011] (Patent Document 4) Chinese Patent Publication No. 116219271

[0012] One aspect of the present invention is to provide a composition for surface treatment of a hot-forming plated steel sheet suitable as a material for automobiles, which can shorten the heating time during high-temperature heating for hot-forming of the plated steel sheet.

[0013] In addition, one aspect of the present invention is to provide a surface-treated aluminum-based plated steel sheet capable of shortening the heating time during high-temperature heating by surface-treating with the surface treatment composition, and a method for manufacturing the same.

[0014] As another aspect of the present invention, it is intended to provide a hot-formed member obtained by hot-forming a surface-treated aluminum-based plated steel sheet.

[0015] Meanwhile, 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 knowledge in the technical field to which the present invention belongs from the description below.

[0016] According to one aspect of the present invention, a composition for surface treatment of a hot-forming galvanized steel sheet is provided, which is a composition in which graphite is dispersed in a polymer binder resin.

[0017] In one embodiment of the present invention, a composition can be provided in which the weight ratio of the polymer binder resin and graphite is 1:0.25 or less.

[0018] In one embodiment of the present invention, the graphite may have an average particle size of 0.2 to 5.0 μm, and the composition may include carbon (C), hydrogen (H), oxygen (O), nitrogen (N), silicon (Si), and phosphorus (P).

[0019] In one embodiment of the present invention, the polymer binder resin may include 6 to 20% of acrylic resin, 0.01 to 1.00% of Teflon wax, 0.01 to 0.50% of silane coupling agent, 0.01 to 2.00% of phosphoric acid corrosion improvement agent, and the remainder of solvent, based on 100 wt%.

[0020] According to another aspect of the present invention, a surface-treated aluminum-based plated steel sheet is provided, comprising: a base steel sheet; an aluminum-based plated layer formed on at least one surface of the base steel sheet; and a surface-treated film layer formed on the aluminum-based plated layer.

[0021] In one embodiment of the present invention, the surface treatment film layer can be formed from a composition according to one aspect of the present invention.

[0022] In one embodiment of the present invention, the surface treatment film layer has a Si content of 8.00 wt% or less (excluding 0%) and an adhesion amount of 100.00 mg / m 2 It may be below. In addition, the surface treatment film layer has a P content of 0.70 wt% or less (excluding 0%) and an adhesion amount of 10.00 mg / m 2 It could be as follows:

[0023] In one embodiment of the present invention, the surface treatment film layer may have a graphite content of 0.1 to 60.0%.

[0024] In one embodiment of the present invention, the surface treatment film layer may have a thickness of 1.50 ㎛ or less based on the dry thickness, and may have an emissivity of 0.8 or more.

[0025] In one embodiment of the present invention, the aluminum-based plating layer may include, in weight %, 0 to 27% zinc (Zn), 7.0 to 10.0% silicon (Si), the remainder Al, and unavoidable impurities.

[0026] According to another aspect of the present invention, a method for manufacturing a surface-treated aluminum-plated steel sheet is provided, comprising the steps of: preparing an aluminum-plated steel sheet having an aluminum-plated layer formed on at least one surface of a base steel sheet; applying a surface treatment composition on the aluminum-plated layer; and applying the composition and then drying and curing to form a surface treatment film layer.

[0027] In one embodiment of the present invention, the composition for surface treatment may be a composition according to one aspect of the present invention.

[0028] In one embodiment of the present invention, the coating treatment may be performed by any one method selected from the group consisting of bar coating, roll coating, spraying, dipping, spray squeezing, and dipping squeezing.

[0029] In one embodiment of the present invention, the drying and curing steps can be performed at a temperature range of 80 to 150°C based on the final temperature (PMT) of the galvanized steel sheet.

[0030] According to another aspect of the present invention, a hot-formed member including a film layer on a plating layer of a surface-treated aluminum-plated steel sheet is provided.

[0031] In one embodiment of the present invention, the film layer can be formed from a composition according to one aspect of the present invention.

[0032] According to the present invention, in providing a steel sheet suitable for hot forming, a steel sheet with improved emissivity, particularly an aluminum-based coated steel sheet, can be provided. In manufacturing parts and the like using such an aluminum-based coated steel sheet with improved emissivity, the heating time during high-temperature heat treatment of the steel sheet can be reduced, resulting in economic and environmental benefits.

[0033] In addition, the present invention has the effect of providing a surface treatment composition that is advantageous in obtaining an aluminum-based plated steel sheet with improved emissivity.

[0034] 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.

[0035] The inventors of the present invention have conducted in-depth research into methods for providing a hot-formable galvanized steel sheet, which can reduce CO2 emissions during the manufacturing process while satisfying the properties required in the automotive field to which the hot-formable galvanized steel sheet is applied. In particular, they have examined methods for increasing the heating rate during high-temperature heating for forming the hot-formable galvanized steel sheet.

[0036] Accordingly, the present invention aims to provide a composition suitable for coating (surface treatment) the surface of a plating layer of a hot-forming galvanized steel sheet. In particular, it has been confirmed that a composition can be provided that secures the required properties of a surface treatment layer of a hot-forming galvanized steel sheet, such as corrosion resistance and weldability, while reducing the time required for heating to a target temperature for high-temperature forming, thereby improving productivity and reducing CO2 emissions. This has led to the completion of the present invention.

[0037] According to the present invention, not only a composition for surface treatment of a hot-formed galvanized steel sheet, but also an aluminum-based galvanized steel sheet surface-treated using the composition and a method for manufacturing the same, and a hot-formed member obtained from the surface-treated aluminum-based galvanized steel sheet are provided.

[0038] Hereinafter, the present invention will be described in detail.

[0039] A composition for surface treatment of a hot-forming galvanized steel sheet according to one aspect of the present invention includes a polymer binder resin as a main component, and may also include graphite dispersed in the polymer binder resin.

[0040] In one embodiment of the present invention, by including graphite in addition to a polymer binder resin as a surface treatment composition, the emissivity of a hot-formable plated steel sheet surface-treated with the composition can be increased. Here, emissivity refers to the rate at which an object re-radiates external energy (e.g., heat, light, etc.) after absorbing it, or re-radiates it when a surface reflection phenomenon occurs. A higher emissivity can be understood as an improved energy absorption rate. As an example, when the emissivity of a hot-formable plated steel sheet is high, the amount of radiant heat absorbed when the plated steel sheet is heated at a high temperature in a heating furnace for hot forming increases. As a result, the effect of shortening the time required for heating to a target temperature can be obtained.

[0041] In one embodiment of the present invention, the graphite contained in the composition may have an average particle size of 0.2 to 5.0 μm. If the average particle size of the graphite is less than 0.2 μm, the content of graphite to be dispersed in the polymer binder resin may need to be excessively increased, and in this case, there is a concern that the content of other components may be relatively reduced. On the other hand, if the average particle size of the graphite exceeds 5.0 μm, the particle size becomes too large, which may prevent sufficient dispersion in the polymer binder resin and may cause the graphite to easily settle.

[0042] In one embodiment of the present invention, the composition may have a weight ratio of the polymer binder resin and graphite of 1:0.25 or less. Here, the weight ratio refers to the ratio of weight parts (weight ratio). If the weight ratio of the graphite to the polymer binder resin exceeds 0.25, the content of the polymer binder resin as a composition component may decrease, and thus the physical properties of the surface-treated plated steel sheet, such as corrosion resistance and weldability, may be deteriorated. Meanwhile, the lower limit of the weight ratio of the graphite is not particularly limited, but in consideration of the effect of improving emissivity by graphite, it may be included at a weight ratio of 0.01 or more.

[0043] Meanwhile, in one embodiment of the present invention, a polymer binder resin composition in which graphite is dispersed can be obtained by adding graphite powder to a polymer binder resin and then stirring, as a non-limiting example.

[0044] A composition according to one embodiment of the present invention is a polymer composition, which may include a polymer binder resin as a main component, and the polymer binder resin may include various additives and a solvent in the resin component.

[0045] As an example, the polymer binder resin may contain, based on 100 wt% of the total, 6 to 20% of acrylic resin, 0.01 to 1.00% of Teflon wax, 0.01 to 0.50% of silane coupling agent, 0.01 to 2.00% of phosphoric acid corrosion resistance improver, and the remainder of solvent.

[0046] The above acrylic resin is a component that acts as a binder in the composition, and by adding it in a certain amount, the physical properties of the surface treatment layer, such as chemical resistance and alkali resistance, can be secured. The content of the acrylic resin may be included in an amount of 6 to 20% based on 100 wt% of the total polymer binder resin. If the content of the acrylic resin is less than 6%, the viscosity of the composition may be low, making it difficult to control the thickness of the surface treatment layer during surface treatment of a plated steel sheet. On the other hand, if the content exceeds 20%, the storage stability of the composition in a solution state may be reduced. There is no particular limitation on the type of the acrylic resin, and any material generally used in the field of surface treatment of steel sheets may be used.

[0047] The above Teflon-based wax may be added to provide lubricity to the surface treatment layer. The content of the Teflon-based wax may be 0.01 to 1.00% based on 100 wt% of the total polymer binder resin. If the content of the Teflon-based wax is less than 0.01%, the lubricity of the surface treatment layer may be insufficient, and thus, destruction may occur in the surface treatment layer and / or the material during processing of the surface-treated plated steel sheet. On the other hand, if the content exceeds 1.00%, lubricant particles may be excessively distributed in the surface treatment layer, which may actually lower corrosion resistance. The Teflon-based wax may be, but is not limited to, a polyethylene-Teflon-based wax or a polyTeflon-based wax.

[0048] The above silane coupling agent may be included to firmly maintain the bond between the organic resin and the inorganic compound contained in the composition and to induce a coupling bond reaction by modifying the maintenance resin. The silane coupling agent may be included in an amount of 0.01 to 0.50% based on 100% by weight of the total polymer binder resin. If the content of the silane coupling agent is less than 0.01%, the adhesion of the surface treatment layer formed on the surface of the plating layer of the plated steel sheet may be reduced. On the other hand, if the content exceeds 0.50%, the above-described effect is saturated, and may rather cause an increase in manufacturing costs. The above silane coupling agent may be at least one selected from the group consisting of vinyl triethoxy silane, 3-glycidoxypropyl trimethoxysilane, 3-glycidoxypropyl triethoxysilane, 3-glycidoxypropylmethyl dimethoxy silane, N-2-(aminoethyl)-3-aminopropyl triethoxy silane, 3-aminopropyl trimethoxy silane, 3-aminopropyl triethoxy silane, and 2-perfluorooctyl ethyl trimethoxy silane.

[0049] The above-mentioned phosphate-based corrosion-resistant improving agent can be added to provide corrosion resistance to the surface-treated layer. In addition, when a certain amount of P component remains on the surface of the surface-treated plated steel sheet, the effect of preventing hydrogen absorption generated during the subsequent heat treatment process can be obtained. As a result, the occurrence of hydrogen-induced embrittlement, etc. can be suppressed. The above-mentioned phosphate-based corrosion-resistant improving agent can be included in an amount of 0.01 to 2.00% based on 100 wt% of the total polymer binder resin. If the content of the above-mentioned phosphate-based corrosion-resistant improving agent is less than 0.01%, the corrosion resistance of the surface-treated layer may be reduced, and there is a concern that the surface-treated plated steel sheet may become vulnerable to hydrogen embrittlement after heat treatment. On the other hand, if the content exceeds 2.00%, the content of P contained in the surface-treated layer becomes excessive, which may result in poor weldability of the surface-treated plated steel sheet. The above-mentioned phosphate-based corrosion improvement agent may be at least one selected from a group of phosphate compounds having at least one element selected from among Zn, Cr, Si, Al, Mo, Mg, and Ca as a counter cation.

[0050] The polymer binder resin in the composition according to one embodiment of the present invention may include a solvent as the remainder excluding the aforementioned components. At this time, the solvent may be added to disperse the components constituting the polymer binder resin and to prepare a solution composition for surface treatment of a plated steel sheet. The solvent may be a mixed solvent of water and an organic solvent. At this time, the water may be deionized water or distilled water, and the organic solvent may be at least one selected from alcohol, ether, and acetone. As one example, the mixed solvent may be obtained by adding an organic solvent to water in an amount of 0.1 to 10.0%, and the content of the organic solvent here refers to the content relative to 100 wt% of the total solvent.

[0051] In this way, a composition according to one embodiment of the present invention may include carbon (C), hydrogen (H), oxygen (O), nitrogen (N), silicon (Si), and phosphorus (P) by including a polymer binder resin composed of the above-described components and graphite. At this time, the carbon (C) may be derived from the components of the graphite and the binder resin, the silicon (Si) may be derived from a silane coupling agent which is a component of the polymer binder resin, and the phosphorus (P) may be derived from a phosphate-based corrosion-resistant improving agent. Meanwhile, hydrogen (H) and oxygen (O) in the composition are components that naturally exist in the composition due to the components constituting the above-described composition.

[0052] Meanwhile, according to one embodiment of the present invention, a composition comprising a polymer binder resin and graphite can be used in a surface treatment process of a plated steel sheet for hot forming, and below, a plated steel sheet surface-treated with a composition according to one embodiment of the present invention will be described in detail.

[0053] According to one embodiment of the present invention, the plated steel sheet for surface treatment is a steel sheet that is hot-formed, for example, a plated steel sheet suitable for press-forming by a die or the like at a high temperature to obtain a part of a certain shape, and may be, for example, an aluminum-based plated steel sheet.

[0054] An aluminum-based plated steel sheet according to one embodiment of the present invention may include a base steel sheet and an aluminum-based plated layer formed on at least one surface of the base steel sheet.

[0055] In one embodiment of the present invention, the base steel sheet may be any material that is a high-strength steel suitable for automotive use and can be used to obtain a plated steel sheet through hot-dip galvanizing. Accordingly, there are no particular limitations on the alloy composition of the base steel sheet.

[0056] However, as a non-limiting example, the above-mentioned steel plate is carbon steel containing a certain amount of carbon (C), for example, in wt%, carbon (C): 0.02 to 0.60%, silicon (Si): 0.001 to 2.000%, aluminum (Al): 0.001 to 1.000%, manganese (Mn): 0.1 to 4.0%, phosphorus (P): 0.05% or less, sulfur (S): 0.02% or less, nitrogen (N): 0.02% or less, titanium (Ti): 0 to 0.1%, boron (B): 0.0001 to 0.0100%, copper (Cu): 0 to 1.00%, molybdenum (Mo): 0 to 1.00%, chromium (Cr): 0 to 1.00%, nickel (Ni): 0 to 1.00%, vanadium (V): 0~1.00%, Calcium (Ca): 0~0.01%, Niobium (Nb): 0~0.1%, Tin (Sn): 0~1.0%, Tungsten (W): 0~1.0%, Antimony (Sb): 0~1.0%, Magnesium (Mg): 0~1.0%, Cobalt (Co): 0~1.0%, Arsenic (As): 0~1.0%, Zirconium (Zr): 0~1.0%, Bismuth (Bi): 0~1.0%, Rare Earth Elements (REM): 0~0.3%, and the remainder may contain Fe and unavoidable impurities.

[0057] Among the alloy compositions described above, C, Mn, etc. can be added to secure the strength of the steel, Si can greatly contribute to stabilizing the strength, and Al has a deoxidation effect. P, S, N, etc. may be elements that are inevitably introduced during the steel manufacturing process, but it is to be noted that they are not limited thereto. In addition, it will be apparent to those skilled in the art that Ti, B, Cu, Mo, Cr, Ni, V, Ca, Nb, Sn, W, Sb, Mg, Co, As, Zr, Bi, REM, etc. may be additionally included in addition to the aforementioned composition, taking into account the target properties of the final product, etc.

[0058] According to one embodiment of the present invention, an aluminum-based plating layer may be included on at least one surface of the steel plate.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] In one embodiment of the present invention, a surface treatment film layer may be included on the aluminum-based plating layer. That is, a film layer having a certain thickness may be formed on the aluminum-based plating layer.

[0064] In this way, a plated steel sheet including a surface treatment film layer on an aluminum-based plating layer can have excellent corrosion resistance and high emissivity.

[0065] In one embodiment of the present invention, in order to obtain a plated steel sheet having the above-described properties, a surface treatment film layer provided on an aluminum-based plating layer may be formed from a composition for surface treatment of a plated steel sheet for hot forming according to one embodiment of the present invention. That is, the film layer formed according to one embodiment of the present invention can provide a plated steel sheet having the intended properties by being formed from a composition in which graphite having a certain size is dispersed in a certain amount in a polymer binder resin.

[0066] The surface treatment film layer according to one embodiment of the present invention may contain 0.1 to 60.0% of graphite, and the content at this time is based on 100 wt% of the entire dry film layer. If the content of graphite contained in the film layer is less than 0.1%, the emissivity of the surface treatment film layer cannot be increased. On the other hand, if the content exceeds 60.0%, the weldability may be reduced due to carbon remaining in the film layer after high-temperature heating for hot forming of the surface-treated aluminum-based plated steel sheet.

[0067] In one embodiment of the present invention, the thickness of the surface treatment film layer may be 1.50 μm or less based on the dry thickness. If the thickness of the film layer exceeds 1.50 μm, the film layer may be formed too thick, thereby deteriorating workability and weldability. There is no particular limitation on the lower limit of the thickness of the surface treatment film layer, but it may have a thickness of 0.30 μm or more in order to impart an effect by the film layer.

[0068] In one embodiment of the present invention, the surface treatment film layer may be formed from a composition according to one embodiment of the present invention, and the film layer may include carbon (C), hydrogen (H), oxygen (O), nitrogen (N), silicon (Si), and phosphorus (P). Among these, carbon (C) may be mainly derived from graphite, silicon (Si) may be derived from a silane coupling agent, and phosphorus (P) may be derived from a phosphoric acid-based corrosion resistance improving agent.

[0069] In one embodiment of the present invention, the Si contained in the film layer may be 8.00 wt% or less (excluding 0%), and the P may be 0.70 wt% or less (excluding 0%). The content at this time is based on 100 wt% of the entire dry film layer. If the content of Si contained in the film layer exceeds 8.00%, there is a concern that the content of Si remaining on the surface without being burned during the high-temperature heating (heat treatment) process for hot forming of the surface-treated plated steel sheet may become excessive. This remaining Si tends to have high electrical resistance, which may hinder the weldability of the product (e.g., a hot-formed member). In addition, if the content of P contained in the film layer exceeds 0.70%, the amount of P remaining in the film layer becomes excessive, which may significantly impair the weldability of a member obtained by hot forming a surface-treated aluminum-based plated steel sheet.

[0070] Meanwhile, in one embodiment of the present invention, the surface treatment film layer containing Si and P as described above has an adhesion amount of Si of 100.00 mg / m 2 It may be less than or equal to 10.00 mg / m of the above P adhesion amount. 2 It can be as follows. That is, the content of Si and P per unit area within the surface treatment film layer can be controlled as above. Here, the amount of adhesion of each element refers to the value of the relative proportion occupied by each element within the film layer.

[0071] Even if the content of Si and P within the film layer obtained through surface treatment is within a limited amount, if the absolute adhesion amount of Si and P also increases due to excessive adhesion amount of the coating composition, there is a concern that it may have a negative effect on weldability and workability of subsequent processes. In consideration of this, in one embodiment of the present invention, the adhesion amounts of Si and P within the film layer can be limited as described above.

[0072] In one embodiment of the present invention, the adhesion amount of Si in the surface treatment film layer is 100.00 mg / m 2 If it exceeds, Si may remain excessively on the surface even after high-temperature heating for hot forming of the surface-treated galvanized steel sheet. In this case, the surface electrical resistance of the hot-formed member increases, which ultimately inhibits the welding current in the welding process or deteriorates the weldability by generating spatter. In addition, if the adhesion amount of P in the surface-treated film layer is 10.00 mg / m 2 If it exceeds , it can also impair the weldability of hot-formed parts. In particular, P derived from phosphate compounds has a strong tendency to remain in a solid state, so if it remains excessively on the surface, it causes an increase in the electrical resistance of the surface, similar to Si.

[0073] According to another embodiment of the present invention, the adhesion amount of Si in the surface treatment film layer is 98.00 mg / m 2 may be less than or equal to 95.00 mg / m 2 It may be less than or equal to 9.00 mg / m. According to another embodiment, the amount of P deposited in the surface treatment film layer is 9.00 mg / m. 2 may be less than or equal to 8.50 mg / m 2 It could be as follows:

[0074] Meanwhile, the lower limit of the content of Si and P contained in the surface treatment film layer and the amount of adhesion of these elements is not particularly limited, and it is to be noted that it will be naturally determined according to the content of the silane coupling agent and the phosphoric acid-based corrosion-improving agent contained in the composition for forming the film layer.

[0075] Meanwhile, the content of Si and P contained in the surface treatment film layer and the adhesion amount of these elements can be measured using an X-ray fluorescence analysis method, a wet resin coating adhesion amount measuring method, a non-destructive coating thickness measuring device, etc. However, the present invention is not limited thereto.

[0076] X-ray fluorescence analysis is a method that can quantitatively obtain the content of each element using an X-ray fluorescence analyzer. Alternatively, the film layer can be separated from the surface-treated plated steel sheet by dissolving the film layer in an acid solution, and the weight of the separated coating film can be measured to obtain the resin coating adhesion amount per area. Another method is to obtain the thickness information of the film layer using a non-destructive coating thickness gauge (e.g., Betascope®), and then obtain the density of the film layer by taking a weighted sum of the densities of the known resin and graphite according to the content ratio. Then, the adhesion amount per unit area can be calculated by multiplying the film layer thickness and film layer density. According to the above, the adhesion amount of each element can be calculated from the obtained content of each element and the adhesion amount of the film layer.

[0077] Meanwhile, it is noted that the contents of graphite, Si and P in the film layer are based on the contents in the dry film layer.

[0078] As such, according to one embodiment of the present invention, the surface treatment film layer provided on the surface of the aluminum-based plating layer can improve the adhesion and corrosion resistance of the film layer by containing a certain amount of Si and P together with graphite, and can have excellent emissivity characteristics. As one example, the surface treatment film layer according to one embodiment of the present invention can have an emissivity of 0.8 or more. Here, the description of the emissivity can be replaced with the aforementioned content. Meanwhile, considering that the emissivity of an aluminum-based plating steel sheet is generally about 0.5, the aluminum-based plating steel sheet having a surface treatment film layer according to one embodiment of the present invention has an effect of improving the emissivity to 0.8 or more.

[0079] In this way, the aluminum-based coated steel sheet with improved emissivity exhibits high heat absorption during the process of heating to a high temperature for hot forming, thereby shortening the heating time (heating time) to the target temperature. Therefore, when manufacturing a hot-formed part suitable as an automotive material, by using the aluminum-based coated steel sheet according to an embodiment of the present invention, not only can CO2 emissions be effectively reduced, but also productivity can be improved.

[0080] Hereinafter, a method for manufacturing a plated steel sheet, i.e., a surface-treated aluminum-based plated steel sheet, according to another aspect of the present invention will be described. However, it should be noted that the following manufacturing method is only one example for manufacturing a surface-treated aluminum-based plated steel sheet.

[0081] 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.

[0082] In one embodiment of the present invention, the base steel sheet for forming an aluminum-based plating layer on at least one surface is a high-strength steel suitable as an automotive material, and its alloy composition is not particularly limited. In addition, the content of the base steel sheet mentioned above may be replaced.

[0083] 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.

[0084] In one embodiment of the present invention, the plating can be performed in an aluminum-based plating bath at 600 to 680°C.

[0085] In one embodiment of the present invention, the step of coating a surface treatment composition on an aluminum-based plating layer may use any one coating method selected from the group consisting of bar coating, roll coating, spraying, dipping, spray squeezing, and dipping squeezing.

[0086] In one embodiment of the present invention, the surface treatment composition coated on the aluminum-based plating layer may be a surface treatment composition of a hot-forming plated steel sheet according to one embodiment of the present invention.

[0087] In one embodiment of the present invention, the composition coated on the aluminum-based plating layer may include graphite dispersed in a polymer binder resin composed of an organic resin, a lubricant, a silane coupling agent, a rust inhibitor (corrosion improvement agent), etc. The surface treatment film layer formed by surface-treating the aluminum-based plating layer using such a composition may have excellent physical properties such as corrosion resistance and weldability, and may have high emissivity.

[0088] When applying the above-mentioned composition to an aluminum-plated steel plate, as an example, 400 to 1800 mg / m 2 The coating amount can be applied. After applying the composition with such an adhesion amount, a subsequent drying process is performed to obtain a surface treatment film layer having a thickness of 1.50 μm or less, preferably 0.30 to 1.50 μm. Here, the thickness of the film layer refers to the thickness after drying. In one embodiment of the present invention, the adhesion amount of the composition is 400 mg / m. 2 If it is less than 1800mg / m, the corrosion resistance may be reduced due to the composition being thinly applied to the acidic part of the aluminum plating layer, while if the thickness is less than 1800mg / m, 2 If it exceeds , the film layer may become too thick after drying, which may deteriorate properties such as weldability and processability.

[0089] In one embodiment of the present invention, a surface treatment composition is applied to the surface of a plating layer of an aluminum-based plated steel sheet, and then the plated steel sheet is dried and cured to obtain a surface treatment film layer. In one embodiment of the present invention, the drying and curing steps may be performed at a temperature range of 80 to 150°C based on the PMT (Peak Metal Temperature), which is the final temperature reached by the plated steel sheet. If the temperature during the drying is lower than 80°C based on the PMT, drying may not be completed completely, and thus the physical properties of the surface-treated plated steel sheet, such as corrosion resistance and alkali resistance, may be deteriorated. On the other hand, if the drying temperature exceeds 150°C based on the PMT, the organic components in the applied composition may be carbonized, making it impossible to secure physical properties such as corrosion resistance and heat resistance. In addition, the hardness of the surface treatment layer may increase excessively, which may cause the surface treatment layer to break during processing.

[0090] As described above, an aluminum-based plated steel sheet surface-treated using a composition for surface treatment of a plated steel sheet for hot forming according to an embodiment of the present invention can have excellent corrosion resistance and weldability, and a higher emissivity than an aluminum-based plated steel sheet that has not been surface-treated. This is due to optimization of the types and contents of components forming the composition, and in particular, by including graphite in addition to a polymer binder resin, and controlling the contents of Si and P present in the surface treatment film layer.

[0091] Meanwhile, when surface-treating a plated steel sheet for hot forming according to an embodiment of the present invention with a composition for surface treatment, it should be noted that this does not necessarily mean that the surface treatment is only possible for an aluminum-based plated steel sheet manufactured through hot-dip galvanizing. That is, the surface-treating composition according to an embodiment of the present invention can be applied to any plated steel sheet having an aluminum-based plated layer on at least one surface of the base steel sheet.

[0092] Hereinafter, a hot-formed member and a manufacturing method thereof according to another aspect of the present invention will be described.

[0093] In one embodiment of the present invention, a hot-formed member can be obtained by hot-forming a steel plate for hot forming, and the steel plate for hot forming at this time can be an aluminum-based plated steel plate according to one embodiment of the present invention.

[0094] An aluminum-based plated steel sheet according to one embodiment of the present invention comprises a base steel sheet; an aluminum-based plated layer on at least one surface of the base steel sheet, and a surface treatment film layer may be included on the aluminum-based plated layer. In this case, the surface treatment film layer may be formed from a surface treatment composition according to one embodiment of the present invention.

[0095] According to one embodiment of the present invention, an aluminum-based plated steel sheet can have improved emissivity characteristics by having a certain film layer on the plating layer. In this way, when an aluminum-based plated steel sheet with improved emissivity is applied to a hot forming process, it can have excellent properties in various physical properties. For example, compared to a general aluminum-based plated steel sheet that has not been surface treated, the heating time required for high-temperature heating for hot forming can be reduced. In addition, in terms of weldability, the welding current can be secured at an equivalent level or higher, and corrosion resistance can be further improved. Furthermore, in terms of hydrogen absorption, it can effectively suppress hydrogen intrusion, and is effective in preventing hydrogen-induced embrittlement during the automobile manufacturing process.

[0096] Meanwhile, it is disclosed that the steel plate and aluminum plating layer constituting the hot-formed member can be replaced with the above-mentioned contents.

[0097] Meanwhile, a method for manufacturing a hot-formed member according to one embodiment of the present invention is not particularly limited, and can be manufactured through a process of heating a steel plate for hot forming to a temperature higher than the austenitizing temperature, maintaining the temperature, and then rapidly cooling and forming the steel plate at the same time, as is widely known in the art.

[0098] As an example of the present invention, after obtaining a blank using a hot forming steel sheet according to one embodiment of the present invention, a step of heating the blank to a temperature range of 900 to 970°C and then maintaining it for 3 to 15 minutes can be performed. After hot press forming the blank heated and maintained in this manner, a step of cooling it at a cooling rate higher than the critical cooling rate can be performed, thereby manufacturing an intended hot press formed part. As a non-limiting example, the cooling can be performed at a cooling rate of 30°C / s or higher.

[0099] However, according to one embodiment of the present invention, an aluminum-based plated steel sheet having a predetermined film layer on a plating layer can be used as a hot-forming steel sheet, thereby reducing the heating time during the heating process of a blank manufactured using the aluminum-based plated steel sheet. Accordingly, a more economically advantageous manufacturing method can be provided compared to the existing manufacturing process for obtaining hot-formed parts.

[0100] Hereinafter, the present invention will be described in more detail through examples. However, it should be noted that the following examples are intended only to illustrate and further illustrate the present invention and are not intended to limit the scope of the invention. This is because the scope of the invention is determined by the matters set forth in the patent claims and matters reasonably inferred therefrom.

[0101] (Example)

[0102] An aluminum-plated steel sheet having an aluminum-plated layer composed of 9% silicon by weight, the remainder Al, and unavoidable impurities on both sides of the base steel sheet was prepared. Thereafter, a surface treatment composition in which graphite was dispersed was coated on the aluminum-plated layer using a roll coating method, and then dried and cured at 120°C based on the PMT. From this, a film layer having a thickness of 0.40 to 1.50 μm based on the dry film thickness was formed. Meanwhile, for comparison, the aluminum-plated steel sheet without surface treatment was used as a control steel.

[0103] At this time, the composition for surface treatment is a composition in which graphite is dispersed so that the weight ratio of the polymer binder resin solution and graphite is 1:0.25 or less, and the polymer binder resin contains 8% acrylic resin, 0.50% Teflon-based wax, silane coupling agent (content in Table 1), and phosphoric acid-based corrosion improvement agent (content in Table 1) with respect to the total 100 wt%, and the remainder is a solvent (water + 10% alcohol). Graphite powder having an average particle size of 0.2 to 5.0 ㎛ was added to the polymer binder resin thus composed at each weight ratio, and then stirred at 450 rpm for 15 minutes or more using a stirrer to obtain a composition for the final surface treatment.

[0104] According to the above, the Si and P contents and adhesion amount in each film layer formed on the plating layer were measured and calculated.

[0105] At this time, the content and adhesion amount of each element in the film layer were measured using the X-ray fluorescence analysis method and a non-destructive coating thickness meter (Betascope®). First, the content of each element was quantitatively obtained using the X-ray fluorescence analyzer. Then, after securing the thickness of the film layer using the non-destructive coating thickness meter, the density of the film layer was obtained, and then the adhesion amount per unit area was calculated by multiplying the coating thickness and the film layer density. Then, the adhesion amount of each element was calculated from the content of each element obtained previously and the adhesion amount of the film layer.

[0106] And, as described above, emissivity was measured for a hot-forming plated steel sheet having a film layer formed on the plating layer. At this time, emissivity was measured in the wavelength range of 2.5 to 50.0 ㎛ according to KS L 2514 and then calculated according to KS L 2525.

[0107] Meanwhile, each plated steel sheet having a film layer formed on the plating layer according to the above was heated to 900°C and then heat-treated for 5 minutes, then pressed (formed) using a mold and cooled simultaneously to obtain a hot-formed part. Thereafter, the corrosion resistance, weldability, and hydrogen absorption of the hot-formed part were measured. The results are shown in Table 2.

[0108] At this time, the time required to raise the temperature to the target heating temperature was also measured. Specifically, the time required to raise the temperature was expressed as a value converted to 100, with 100 being the time required to raise the temperature of an untreated aluminum-plated steel sheet to the target temperature.

[0109] In addition, the weldability was expressed as a value converted based on the maximum welding current of the untreated aluminum-plated steel sheet as 100 when tested according to the ISO18278-2 (2016) and RNES-B-00010v3 (2016) standards. The hydrogen absorption was expressed as a value converted based on the hydrogen absorption field of the untreated aluminum-plated steel sheet as 100 after leaving each hot-formed member in the air for one week. The corrosion resistance was evaluated according to the ISO 14993:2018 standard.

[0110] Specimen No. Composition Dry film layer Emissivity Steel grade Silane coupling agent (wt%) Phosphoric acid compound (wt%) Solution adhesion (mg / m 2 ) Thickness (㎛) Si content (weight %) P content (weight %) G content (weight %) Si adhesion amount (mg / m 2 )P attachment amount (mg / m 2) Control specimen--00000000.7 Control steel 10.400.825310.457.840.35041.631.860.80 Comparison steel 120.400.825311.407.840.35041.631.860.81 Comparison steel 230.4305770.456.4801037.3800.82 Comparison steel 340.4308060.452.8806023.2200.88 Comparison steel 450.420.425770.456.770.151039.040.880.83 Invention steel 160.420.428060.453.010.076024.260.550.88Inventive steel 270.400.825770.457.060.321040.711.820.83Inventive steel 380.400.828060.453.140.146025.291.130.87Inventive steel 490.401.185770.457.340.481042.372.750.85Inventive steel 5100.401.188060.453.260.216026.321.710.87Inventive steel 6110.391.545770.457.630.641044.033.690.84Inventive steel 7120.391.548060.453.390.286027.352.290.89Inventive steel 8130.43016671.406.48010108.0000.88Comparative steel 5140.43023301.402.8806067.0900.88Comparative steel 6150.420.4216671.406.770.1510112.802.550.87Comparative steel 7160.420.4223301.403.010.076070.071.580.90Comparative steel 8170.400.8216671.407.060.3210117.605.250.88Comparative steel 9180.400.8223301.403.140.146073.063.260.89Comparative steel 10190.401.1816671.407.340.4810122.407.950.87Comparative steel 11200.401.1823301.403.260.216076.044.940.90Comparative steel 12210.391.5416671.407.630.6410127.1910.650.88Comparison class 13220.391.5423301.403.390.286079.026.620.In Table 1 of the 90 Comparative Steel, the G content refers to the content of graphite. In Table 1, the representative specimen and the control steel refer to aluminum-plated steel sheets that have not undergone a surface treatment process.

[0111]

[0112] Steel type Target temperature Time required for heating Weldability Hydrogen absorption Corrosion resistance Classification Control steel 100 100 100 × Control Preliminary Comparison steel 19 19 590 ○ Comparison example 1 Comparison steel 293 < 90 90 ○ Comparison example 2 Comparison steel 38 3100 > 140 △ Comparison example 3 Comparison steel 47 29 5115 △ Comparison example 4 Invention steel 18 5 10 0 80 ○ Invention example 1 Invention steel 26 39 570 ○ Invention example 2 Invention steel 38 11 0 0 70 ○ Invention example 3 Invention steel 46 39 560 ○ Invention example 4 Invention steel 58 5 10 0 65 ○ Invention example 5 Invention steel 66 89 555 ○ Invention example 6 Invention steel 78 49 0 60 ○ Invention example 7 Invention steel 8629055○Invention example 8Comparative steel 584< 90130△Comparative example 5Comparative steel 661< 90110△Comparative example 6Comparative steel 784< 9080○Comparative example 7Comparative steel 865< 9065○Comparative example 8Comparative steel 982< 9070○Comparative example 9Comparative steel 1061< 9055○Comparative example 10Comparative steel 1183< 9060○Comparative example 11Comparative steel 1263< 9050○Comparative example 12Comparative steel 1382< 9060○Comparative example 13Comparative steel 1462< 9050○Comparative example 14

[0113]

[0114] As shown in Tables 1 and 2, it can be confirmed that the aluminum-plated steel sheet surface-treated using the surface treatment composition according to one embodiment of the present invention exhibits improved physical properties such as weldability, hydrogen absorption, and corrosion resistance compared to the plated steel sheet (control example) that has not been surface-treated. In particular, the higher the content of graphite present in the film layer, the better the physical properties are exhibited.

[0115] Furthermore, it was confirmed that the heating time for hot forming the surface-treated aluminum-plated steel sheet can be significantly reduced compared to the control example during high-temperature heating. These results suggest that the efficiency of the hot forming process can be increased and environmental pollutants generated during the manufacturing of parts and other products through hot forming can be reduced.

[0116] Meanwhile, in the case of Comparative Examples 1 and 2, in which graphite was not contained in the surface treatment composition, the time required for heating to the target temperature was somewhat reduced due to the formation of a film layer, but the hydrogen absorption property was inferior.

[0117] In addition, it can be confirmed that Comparative Examples 3 to 6, which contained graphite but did not contain P in the composition, had significantly inferior hydrogen absorption properties and also had reduced corrosion resistance. Among these, Comparative Example 3 had a higher Si content in the film layer than Comparative Example 4, which resulted in a relatively higher surface electrical resistance and inferior weldability. These results were also observed in Comparative Examples 5 and 6.

[0118] Similarly, although graphite, Si, and P were all contained in the surface treatment composition, Comparative Examples 7, 9, 11, and 13, in which the Si adhesion amount of the dry film layer was excessive, and Comparative Examples 5, 10, 12, and 14, in which the composition adhesion amount was excessive, generated excessive surface electrical resistance, resulting in poor weldability.

[0119] As such, it can be confirmed that the aluminum-plated steel sheet surface-treated using the composition for surface treatment of steel sheets according to one embodiment of the present invention has improved emissivity due to the film layer. This allows for a reduction in the heating time required to reach a target temperature during the manufacturing process of hot-formed parts, which is advantageous not only in terms of productivity and economy, but also reduces environmental pollutants such as CO2 generated during the manufacturing process of parts, thereby providing an eco-friendly product.

Claims

1. A composition in which graphite is dispersed in a polymer binder resin, wherein the weight ratio of the polymer binder resin and the graphite is 1:0.25 or less. The above graphite has an average particle size of 0.2 to 5.0 μm, The above composition is a composition for surface treatment of a hot-forming galvanized steel sheet containing carbon (C), hydrogen (H), oxygen (O), nitrogen (N), silicon (Si), and phosphorus (P).

2. In paragraph 1, The above polymer binder resin is 100 wt%, A composition for surface treatment of a hot-forming galvanized steel sheet, comprising 6 to 20% of acrylic resin, 0.01 to 1.00% of Teflon-based wax, 0.01 to 0.50% of a silane coupling agent, 0.01 to 2.00% of a phosphoric acid-based corrosion-resistant improving agent, and a residual solvent.

3. In paragraph 2, The above Teflon-based wax is a composition for surface treatment of a hot-forming galvanized steel sheet, which is a polyethylene-Teflon-based wax or a polyTeflon-based wax.

4. In paragraph 2, A composition for surface treatment of a hot-formed plated steel sheet, wherein the silane coupling agent is at least one selected from the group consisting of vinyl triethoxy silane, 3-glycidoxypropyl trimethoxysilane, 3-glycidoxypropyl triethoxysilane, 3-glycidoxypropylmethyl dimethoxy silane, N-2-(aminoethyl))-3-aminopropyl triethoxy silane, 3-aminopropyl trimethoxy silane, 3-aminopropyl triethoxy silane, and 2-perfluorooctyl ethyl trimethoxy silane.

5. In paragraph 2, The above solvent is a mixed solvent of water and an organic solvent. The above water is deionized water or distilled water, A composition for surface treatment of a hot-formed galvanized steel sheet, wherein the organic solvent is at least one selected from alcohol, ether and acetone.

6. 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 surface-treated aluminum-based plated steel sheet, wherein the surface treatment film layer is formed using a composition according to any one of claims 1 to 5.

7. In paragraph 6, The above surface treatment film layer has a Si content of 8.00 wt% or less (excluding 0%) and an adhesion amount of 100.00 mg / m 2 Aluminum-based galvanized steel sheet with surface treatment as follows:

8. In paragraph 6, The above surface treatment film layer has a P content of 0.70 wt% or less (excluding 0%) and an adhesion amount of 10.00 mg / m 2 Aluminum-based galvanized steel sheet with surface treatment as follows:

9. In paragraph 6, The above surface treatment film layer is a surface-treated aluminum-based galvanized steel sheet having a graphite content of 0.1 to 60.0%.

10. In paragraph 6, The above surface treatment film layer is a surface-treated aluminum-based galvanized steel sheet having a dry thickness of 1.50 ㎛ or less.

11. In paragraph 6, The above surface treatment film layer is a surface-treated aluminum-based plated steel sheet having an emissivity of 0.8 or higher.

12. In paragraph 6, The above steel plate contains, in weight %, carbon (C): 0.02 to 0.60%, silicon (Si): 0.001 to 2.000%, aluminum (Al): 0.001 to 1.000%, manganese (Mn): 0.1 to 4.0%, phosphorus (P): 0.05% or less, sulfur (S): 0.02% or less, nitrogen (N): 0.02% or less, titanium (Ti): 0 to 0.1%, boron (B): 0.0001 to 0.0100%, copper (Cu): 0 to 1.00%, molybdenum (Mo): 0 to 1.00%, chromium (Cr): 0 to 1.00%, nickel (Ni): 0 to 1.00%, vanadium (V): 0 to 1.00%, calcium (Ca): 0 to 0.01%, niobium (Nb): Surface-treated aluminum-based galvanized steel sheet containing carbon steel containing 0~0.1% tin (Sn): 0~1.0% tungsten (W): 0~1.0% antimony (Sb): 0~1.0% magnesium (Mg): 0~1.0% cobalt (Co): 0~1.0% arsenic (As): 0~1.0% zirconium (Zr): 0~1.0% bismuth (Bi): 0~1.0% rare earth elements (REM): 0~0.3%, the remainder iron and unavoidable impurities.

13. In paragraph 6, The above aluminum-based plating layer is a surface-treated aluminum-based plated steel sheet which is an aluminum alloy plating layer containing, in weight %, 0 to 27% zinc (Zn), 7.0 to 10.0% silicon (Si), the remainder Al, and unavoidable impurities.

14. A step for preparing an aluminum-plated steel sheet having an aluminum-plated layer formed on at least one surface of the steel sheet; A step of applying a surface treatment composition on the aluminum-based plating layer; and It includes a step of forming a surface treatment film layer by applying the above composition and then drying and curing it. A method for manufacturing a surface-treated aluminum-based plated steel sheet, wherein the surface treatment composition is a composition according to any one of claims 1 to 5.

15. In paragraph 14, A method for manufacturing a surface-treated aluminum-based galvanized steel sheet, wherein the above coating treatment is performed by any one method selected from the group consisting of bar coating, roll coating, spraying, dipping, spray squeezing, and dipping squeezing.

16. In paragraph 14, A method for manufacturing a surface-treated aluminum-based galvanized steel sheet, wherein the above drying and curing steps are performed at a temperature range of 80 to 150°C based on the final temperature (PMT) of the galvanized steel sheet.

17. A hot-formed member including a film layer on the plating layer of the aluminum-plated steel sheet having a surface treatment according to any one of claims 6 to 13.

18. In paragraph 17, A hot-formed member, wherein the film layer is formed from a composition according to any one of claims 1 to 5.