Aluminum-plated steel material, hot-formed member, and manufacturing method therefor

Abstract

The present invention relates to aluminum-plated steel material for hot-formed members used in automotive parts and a manufacturing method therefor.

Description

Aluminum-based plated steel, hot-formed member and manufacturing method thereof

[0001] The present invention relates to an aluminum-based plated steel for hot-formed parts used in automobile parts, etc., and a method for manufacturing the same.

[0002] Recently, the use of high-strength steel has been increasing to reduce the weight of automobiles. However, high-strength steel presents challenges in forming complex and precise shapes due to material fracture during processing and springback after processing. To address these issues, a method known as hot forming or hot press forming (HPF) has recently been expanding its use.

[0003] The above hot forming process is advantageous in that the steel is easily formed by heating it to a temperature of typically 800-900°C and then processing (press forming) while it is heated, and the strength of the formed product can be increased by rapidly cooling it through a mold. However, when the steel is heated to a high temperature, surface oxidation of the steel surface cannot be avoided. This requires an additional process to remove the oxide on the steel surface after press forming, which increases costs. To prevent this, plated steel (Patent Documents 1 and 2) with an aluminum plating layer formed on the steel surface is used as a material for hot forming.

[0004] However, during the heating process for hot forming of the above-mentioned plated steel, the plating layer with a low melting point turns into a liquid phase, and when the liquid phase comes into contact with the air, the moisture (H2O) contained in the air dissociates into oxygen (O2) and hydrogen (H), leaving the oxygen as an oxide on the surface and the hydrogen dissolved in the plating layer and accumulating. In this state, the plating layer that has become a solid after rapid cooling after forming processing remains with a lot of hydrogen. However, since the solid plating layer has a lower solubility of hydrogen than the liquid, hydrogen diffuses and moves from the plating layer to the surroundings, and some of this hydrogen enters the steel, and the hydrogen that has entered the steel gathers in the bonds and causes hydrogen brittleness, which causes the problem of hydrogen embrittlement.

[0005] Therefore, a solution to the above hydrogen embrittlement problem is required.

[0006] (Patent Document 1) U.S. Patent No. 6,296,805

[0007] (Patent Document 2) Japanese Patent No. 3845271

[0008] One aspect of the present invention is to provide an aluminum-based plated steel material having improved hydrogen embrittlement resistance of a hot-formed member and a method for manufacturing the same.

[0009] The objectives of the present invention are not limited to the above-described matters. Additional objectives of the present invention are described throughout the specification, and those skilled in the art will have no difficulty understanding the additional objectives of the present invention from the contents described in the specification.

[0010] An example of the present invention includes a base steel and an aluminum-based plating layer formed on the base steel,

[0011] A metal layer is included on the above aluminum-based plating layer,

[0012] The above metal layer relates to an aluminum-based plated steel material including a metal having a Gibbs free energy greater than Al when reducing with gaseous moisture at a temperature of 700°C or higher.

[0013] The above metal may be one or more of Fe, Zn, Ni and Mg.

[0014] If the above metal is Fe, the adhesion amount is 0.7 to 3.5 g / m 2 It could be.

[0015] When the above metal is Ni, the adhesion amount is 2.0 to 10.0 g / m 2 It could be.

[0016] When the above metal is Zn, the adhesion amount is 1.0 to 40 g / m 2 It could be.

[0017] The above-mentioned steel contains, in wt%, C: 0.02 to 0.6%, Si: 0.001 to 2%, Al: 0.001 to 1%, Mn: 0.1 to 4%, P: 0.05% or less, S: 0.02% or less, N: 0.02% or less, Ti: 0 to 0.1%, B: 0.0001 to 0.01%, Cu: 0 to 1.00%, Mo: 0 to 1.00%, Cr: 0 to 1.00%, Ni: 0 to 1.00%, V: 0 to 1.00%, Ca: 0 to 0.01%, Nb: 0 to 0.1%, Sn: 0 to 1%, W: 0 to 1%, Sb: 0 to 1%, Mg: 0 to 0.1%, Co: 0 to 1%, As: 0 to 1%, Zr: 0 to 1%, Bi: 0 to 1%, REM: 0 to 0.3%, the remainder may include Fe and unavoidable impurities.

[0018] The above aluminum-based plating layer may contain 15 wt% or less of Si, the remainder being Al and unavoidable impurities.

[0019] The above aluminum-based plating layer may contain 10 to 35 wt% of Zn, 15 wt% or less of Si, and the remainder being Al and unavoidable impurities.

[0020] Another example of the present invention comprises the steps of forming an aluminum-based plating layer on a steel substrate; and

[0021] The present invention relates to a method for manufacturing a plated steel sheet, including a step of forming a metal layer including a metal having a Gibbs free energy greater than Al when subjected to a reduction reaction with gaseous moisture at a temperature of 700°C or higher on the aluminum-based plated layer.

[0022] The step of providing the above aluminum-based plated steel sheet is:

[0023] A step of forming the aluminum-based plating layer by immersing the above-mentioned steel plate in a plating bath containing 15 wt% or less of Si, the remainder being Al and unavoidable impurities;

[0024] A step of cooling the aluminum-based plating layer to a solidification point at an average rate of 20°C / s or more; and

[0025] It may include a step of cooling from the above freezing point to 350°C at an average rate of less than 20°C / s.

[0026] The above plating bath may contain 10 to 35 wt% of Zn.

[0027] The above plating bath may contain 4 wt% or less of Fe.

[0028] The above plating bath may contain 4.5 wt% or less of one or more of Mg, Mn, Cr, and Ca.

[0029] Another example of the present invention comprises a substrate and an aluminum alloy layer on the substrate,

[0030] The above-mentioned material relates to a hot-formed member having a diffusible hydrogen content of 0.50 ppm or less.

[0031] The above hot-formed member may have a maximum bending angle of 49° or more when evaluated by three-point bending.

[0032] According to the aluminum-based plated steel of the present invention, the inhibition of hydrogen diffusion in the plated layer during the hot forming process is minimized, and hydrogen flowing into the steel is suppressed, thereby improving resistance to hydrogen embrittlement, and when applied to automobile parts, resistance to collision characteristics can be improved.

[0033] The various advantageous and beneficial advantages and effects of the present invention are not limited to the above-described contents, and will be more easily understood in the course of explaining specific embodiments of the present invention.

[0034] The terminology used herein is for the purpose of describing the present invention and is not intended to limit the present invention. Furthermore, the singular forms used herein also include the plural forms, unless the context clearly dictates otherwise.

[0035] The meaning of "comprising" as used in the specification is to specify a configuration and not to exclude the presence or addition of other configurations.

[0036] Unless otherwise defined, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by a person of ordinary skill in the art to which this invention pertains. Terms defined in the dictionary are to be interpreted to have meanings consistent with the relevant technical literature and the present disclosure.

[0037] Hydrogen adsorbed into the steel of hot-formed parts can cause serious problems with the material, including strength, ductility, rigidity, and bendability. Most hot-formed parts are composed of a martensite phase, which is highly susceptible to hydrogen embrittlement. This is because residual stress remains after rapid cooling after heating during the manufacturing process of hot-formed parts, and the amount of diffusible hydrogen entering the steel through the plating layer during the hot forming process increases. As higher-strength steels are used to reduce the weight of automobiles, problems such as hydrogen delayed fracture and reduced ductility due to hydrogen become more important as the strength of hot-formed parts increases.

[0038] The inventors of the present invention have discovered that reducing the amount of diffusible hydrogen within the steel is the most effective way to reduce hydrogen-delayed fracture. Most of the diffusible hydrogen contained in hot-formed parts is generated during the hot forming process, particularly in furnaces that heat the blanks to high temperatures. During the heating process of a steel blank with a plating layer made of aluminum or an aluminum alloy, moisture present in the air comes into contact with the surface of the plating layer. At high temperatures, moisture dissociates into oxygen and hydrogen at the surface of the plating layer. The oxygen reacts with the metallic components of the plating layer to form oxides, and hydrogen enters the plating layer. The hydrogen in the plating layer diffuses into the steel, which has a high hydrogen solubility in the austenitic phase, thereby increasing the hydrogen content in the steel. Furthermore, as the blank temperature continues to rise, the surface of the plating layer, which has not yet been alloyed, transforms into a liquid phase, increasing the hydrogen solubility and accelerating hydrogen absorption. Afterwards, due to rapid cooling of the mold, the austenite phase of the steel changes to martensite, which has low hydrogen solubility, and the plating layer becomes a solid alloy phase, making it difficult for the hydrogen trapped in the steel to escape from the steel. This trapped hydrogen becomes the cause of hydrogen retardation fracture.

[0039] Accordingly, the inventors of the present invention confirmed that if moisture is dissociated from the surface of the plating layer and absorbed into the plating layer, the amount of hydrogen entering the steel through the plating layer can be effectively reduced, thereby improving hydrogen embrittlement resistance, leading to the present invention.

[0040] Aluminum-plated steel undergoes hot forming at high temperatures, where atmospheric moisture reacts with the metal atoms in the plating layer to form oxides and hydrogen. At around 900°C, the temperature for hot forming, aluminum exists in a liquid state, and this liquid metal reacts with moisture to produce aluminum oxide and hydrogen. The hydrogen dissociates into atoms and is adsorbed on the plating layer. If the surface is iron (Fe), it exists in a solid state at 900°C, and the solid iron atoms react with gaseous moisture to form iron oxide (Fe2O3, Fe3O4, etc.). The driving force of this reaction can be determined by the Gibbs free energy (△G), and the lower the Gibbs free energy, the more likely this reaction is to occur.

[0041] Table 1 below shows the Gibbs free energies when iron (Fe), aluminum (Al), zinc (Zn), magnesium (Mg), and nickel (Ni) metals react with gaseous moisture (H2O) at 700°C and 900°C.

[0042] The reaction between the above gaseous moisture and metal atoms can occur significantly from 700°C or higher, and when the reduction reaction occurs with gaseous moisture at 700°C or higher, the metal having a higher Gibbs free energy than aluminum (Al) can have reduced hydrogen adsorption.

[0043] Classification700℃, △G(kJ)900℃, △G(kJ)Fe(s) + H2O(g) → FeO(s) + H2(g)-7.428-5.6842Fe(s) + 3H2O(g) → Fe2O3(s) + 3H2(g)-12.763-28.8343Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g)-22.497-6.9052Al(l) + 3H2O(g) → Al2O3(s) + 3H2(g)-787.937-755.070Zn(l) + H2O(g) → ZnO(s) + H2(g)-56.857-46.490Mg(l)+H2O(g) → MgO(s) + H2(g)-302.236-290.256Ni(s)+H2O(g) → NiO(s) + H2(g)-42.641-48.481

[0044] Based on the above, the present invention was conceived, and the present invention is described in detail below.

[0045] First, an example of the aluminum-based plated steel of the present invention will be described in detail.

[0046] The above-mentioned plated steel includes a base steel, an aluminum-based plating layer formed on the surface of the base steel, and a metal layer on the surface of the aluminum plating layer, and the metal layer includes a metal having a Gibbs free energy (△G, unit kJ) greater than Al when subjected to a reduction reaction with moisture in a gaseous state at a temperature of 700°C or higher, preferably 700 to 950°C. As a specific example, the Gibbs free energy (△G, unit kJ) when subjected to a reduction reaction with moisture in a gaseous state at the above-mentioned temperature may be -350 kJ or greater.

[0047] As previously explained, the metal layer prevents hydrogen from being adsorbed onto the plating layer, as aluminum in the aluminum-based plating layer dissociates into moisture, oxides, and hydrogen in the air at high temperatures for hot forming. Since the metal of the metal layer has a higher Gibbs free energy (△G, unit: kJ) than Al during a high-temperature reduction reaction, it can suppress hydrogen adsorption onto the plating layer.

[0048] The above metal may be zinc (Zn), iron (Fe), magnesium (Mg), nickel (Ni), etc.

[0049] Meanwhile, the metal of the metal layer is preferably a metal that releases a small amount of hydrogen per unit mass when reducing with gaseous moisture at a temperature of 700°C or higher.

[0050] In Table 1 above, in the case of aluminum (Al), the hydrogen generated by 1 g of aluminum is 0.056 mol.

[0051] From this point of view, it is desirable that the amount of adhesion of the metal layer be different for each metal.

[0052] As a specific example, for Fe, 0.7 to 3.5 g / m 2 It can be 2.0~10.0 g / m for Ni. 2 It can be 1.0~40 g / m for Zn. 2 It could be.

[0053] The above Fe content is 0.7 g / m 2 If it is less than 3.5 g / m, it is difficult to expect sufficient hydrogen adsorption inhibition effect because continuous layers cannot be formed. 2 If it exceeds this, a thick Fe-based oxide is formed on the plating layer through a reaction with atmospheric oxygen, and in this case, a separate process is required to remove this layer for electrodeposition coating after hot forming, which may increase manufacturing costs.

[0054] The above Ni content is 2.0 g / m 2 If it is less than 10.0 g / m, it is difficult to form a continuous layer on the surface. 2 When the hydrogen adsorption effect is saturated, the cost of plating increases, which may reduce the utility.

[0055] The above Zn content is 1.0 g / m 2 If it is less than 40.0 g / m, it is difficult to form a continuous layer on the surface. 2When heat treatment for hot forming is performed in excess, excessive zinc oxide is formed on the surface, which requires a separate process to remove it, and the cost for plating increases, which is not desirable.

[0056] The present invention does not specifically limit the above-mentioned base steel, and as long as it can be used in the technical field to which the present invention belongs, its type, composition, etc. are not specifically limited. The above-mentioned base steel may be a hot-rolled steel sheet, a cold-rolled steel sheet, annealed steel sheet, etc., and its form does not distinguish between steel sheet, wire rod, bar, etc.

[0057] The composition of the above-mentioned steel is not particularly limited, and it is sufficient if it can be used as a hot-formed member. As a preferred example, the above-mentioned iron contains, in wt%, C: 0.02 to 0.6%, Si: 0.001 to 2%, Al: 0.001 to 1%, Mn: 0.1 to 4%, P: 0.05% or less, S: 0.02% or less, N: 0.02% or less, Ti: 0 to 0.1%, B: 0.0001 to 0.01%, Cu: 0 to 1.00%, Mo: 0 to 1.00%, Cr: 0 to 1.00%, Ni: 0 to 1.00%, V: 0 to 1.00%, Ca: 0 to 0.01%, Nb: 0 to 0.1%, Sn: 0 to 1%, W: 0 to 1%, Sb: 0 to 1%, Mg: 0 to 0.1%, Co: 0 to 1%, As: 0 to 1%, Zr: 0 to 1%, Bi: 0 to 1%, REM: 0 to 0.3%, the remainder may contain Fe and unavoidable impurities.

[0058] The above aluminum-based plating layer refers to a plating layer containing Al as a main component, and the composition of the aluminum-based plating layer may include, for example, 15 wt% or less of Si, and the remainder being Al and unavoidable impurities. As another example, it may include 10 to 35 wt% of Zn, 15 wt% or less of Si, and the remainder being Al and unavoidable impurities, preferably 15 to 30 wt% of Zn, 12 wt% or less of Si, and the remainder being Al and unavoidable impurities, and more preferably 20 to 28 wt% of Zn, 9 wt% or less of Si, and the remainder being Al and unavoidable impurities.

[0059] Meanwhile, the aluminum-based plating layer may additionally contain Fe at 4 wt% or less. In addition, to improve corrosion resistance, it may contain one or more of Mg, Mn, Cr, and Ca at 4.5 wt% or less.

[0060] Next, the method for manufacturing the aluminum-based plated steel of the present invention will be described in detail.

[0061] The above manufacturing method comprises the steps of forming an aluminum-based plating layer on a base steel; and

[0062] It includes a step of forming a metal layer including a metal having a Gibbs free energy greater than Al when reduced with gaseous moisture at a temperature of 700°C or higher on the aluminum-based plating layer.

[0063] The above-mentioned Sojigang is no different from what was previously explained.

[0064] The method for forming the above aluminum-based plating layer is not particularly limited to a method such as hot-dip plating or electroplating.

[0065] For example, a cold-rolled steel sheet for hot forming can be annealed, immersed in a molten galvanizing bath, and then the plating amount can be adjusted and cooled to manufacture a plated steel sheet. Specifically, the composition of the molten galvanizing bath can include, for example, 15 wt% or less of Si, and the remainder being Al and unavoidable impurities. As another example, it can include 10 to 35 wt% of Zn, 15 wt% or less of Si, and the remainder being Al and unavoidable impurities, preferably 15 to 30 wt% of Zn, 12 wt% or less of Si, and the remainder being Al and unavoidable impurities, and more preferably 20 to 28 wt% of Zn, 9 wt% or less of Si, and the remainder being Al and unavoidable impurities.

[0066] Meanwhile, the aluminum-based plating layer may additionally contain Fe at 4 wt% or less. In addition, to improve corrosion resistance, it may contain one or more of Mg, Mn, Cr, and Ca at 4.5 wt% or less.

[0067] Among the plating bath components, silicon (Si) prevents the formation of an Al-Fe alloy layer by combining with aluminum and the Fe of the base steel plate, and protects the plating equipment immersed in the plating bath from erosion. However, if the content exceeds 15 wt%, the growth of the Al-Fe alloy layer may be excessively suppressed, potentially leading to liquid metal embrittlement (LME).

[0068] The above Zn suppresses the diffusion of Si into the surface layer as the solid phase grows during heat treatment to produce a hot-formed part, thereby controlling the position of the second alloy layer. In order to secure the corrosion resistance of the hot-formed part, it may be included in an amount of 10 wt% or more. However, if it exceeds 35 wt%, the melting point of the plating layer decreases and the fluidity increases, which increases the possibility of causing liquid metal embrittlement. Meanwhile, it may be preferably 15 to 30 wt%.

[0069] Meanwhile, Fe in the plating bath is dissolved from the base steel sheet over time during the continuous plating process and exists cumulatively, and can be managed to be less than 4 wt% to prevent dross defects.

[0070] The above metal layer can be formed through a molten plating method, an electroplating method, a PVD deposition method, etc.

[0071] Next, a hot-formed member manufactured using the above aluminum-plated steel sheet is described in detail.

[0072] It is preferable that the above hot-formed member have a diffusible hydrogen content of 0.50 ppm or less.

[0073] It is preferable that the above hot-formed member have a maximum bending angle of 49° or more when evaluated by three-point bending.

[0074] The above hot-formed member is obtained by hot-forming an aluminum-plated steel for hot forming, and the base steel, which is the parent material of the member, occupies most of the thickness of the cross-section of the hot-formed member. The base steel is the parent material of the hot-formed member obtained after hot-forming the base steel, which is the parent material of the steel for hot forming. At this time, the base steel can usually have a mainly martensite structure through hot forming and cooling.

[0075] Meanwhile, hot-formed parts are made by heating aluminum-plated steel at room temperature in a furnace for a certain period of time until it undergoes austenitic transformation. Over time, the aluminum-plated layer changes from a solid to a liquid state, then transforms into an intermetallic compound due to diffusion of iron from the base metal, ultimately transforming into a solid state. During this process, the iron from the base metal and the plating layer form an intermetallic compound, and the aluminum-plated layer transforms into an aluminum alloy layer.

[0076] The above hot-formed member can be manufactured by heating, processing, forming, and cooling the above aluminum-based plated steel, and for effective manufacturing, the plated steel can be manufactured in a blank form.

[0077] The above heating can be performed at a temperature of Ac3 or higher and 970°C or lower, preferably 850 to 950°C. For example, the aluminum-plated steel sheet can be placed in a heat treatment furnace set to the above temperature and heated for 180 to 600 seconds so that the steel structure can be completely transformed into austenite. If the temperature is too low, it is difficult for the steel material to completely transform into a single austenite phase, and if the temperature is too high, the surface may be oxidized or the hydrogen content in the steel may increase, and in the case of the plating layer, volatilization in the liquid phase is severe, so the plating layer cannot remain sufficiently, which may result in poor corrosion resistance.

[0078] Aluminum-plated steel sheets, transformed into a single austenite phase by heating, are transported from the furnace and placed in a mold. The mold then cools them while simultaneously processing them. Ideally, the transfer time from the furnace to the mold should be within 15 seconds. If this time elapses, the material may naturally cool before being cooled in the mold, potentially leading to ferrite formation and material deterioration.

[0079] The critical cooling rate to obtain martensite transformation in the mold may vary depending on the steel composition, but for example, considering that cooling occurs until it is transferred from the furnace to the mold, an effective average cooling rate from 700°C, which is the initial temperature of the material placed in the mold, to 350°C is a cooling rate of 20 to 50°C / s.

[0080] Hereinafter, embodiments of the present invention will be described. It should be apparent to those skilled in the art that various modifications to the following embodiments may be made without departing from the scope of the present invention. The following embodiments are intended to facilitate understanding of the present invention, and the scope of the present invention should not be limited to the following embodiments, but should be determined not only by the claims set forth below but also by their equivalents.

[0081] (Example)

[0082] A cold-rolled steel sheet having the composition shown in Table 2 below (unit, wt%, the remainder being Fe and unavoidable impurities) was prepared, and for plating, the temperature was increased from room temperature to 780°C in an annealing furnace in a nitrogen atmosphere containing 5% hydrogen, and maintained at the annealing temperature of 780°C for 80 seconds, and then immersed in an Al plating bath containing 9 wt.% Si to produce an aluminum-based plated steel sheet. After the plating, the plating amount was controlled using an air knife.

[0083] A metal layer was formed on the surface of the aluminum-based plated steel sheet manufactured above by electroplating the metals in Table 3. The entire plating layer of the metal layer and the aluminum-based plating layer was dissolved, and ICP analysis was performed, and the resulting component contents are shown in Table 3.

[0084] Classification CSiMnPAlCrBTiN Content (weight%) 0.210.211.10.010.030.20.00270.0300.004

[0085] Specimen numberMetal layerTotal plating layer adhesion amount and composition (wt.%)Metal adhesion amount (g / m 2 ) Adhesion amount (g / m) 2)AlSiFeZnMnNi1--709190.000.000.000.002Fe0.56781.668.319.900.000.13 0.003Fe15881.378.0110.480.000.140.004Fe56774.237.5018.150.000.120. 005Ni0.58180.049.349.630.000.170.816Ni18980.189.729.030.000.150.91 7Ni38477.359.848.670.000.124.028Zn0.55780.988.979.110.790.140.009Zn 16678.959.319.681.850.220.0010Zn1.56480.678.538.721.950.130.0011Zn 2.08079.208.619.142.920.130.0012Zn2.55677.838.799.243.940.190.0013Z n105071.328.457.7312.380.120.0014Zn204262.739.026.6321.510.110.001 5Zn305757.396.256.1030.150.110.0016Zn407352.015.385.3637.140.110.00

[0086] For the above specimens, in order to confirm the hydrogen embrittlement resistance and bendability after hot forming, hot forming conditions were simulated, and each specimen was heated in a furnace at 900°C for 5 minutes, and then cooled at a cooling rate of 20°C / s.

[0087] The above diffusible hydrogen amount was measured using a G8 Galileo (Bruker) after heat treatment of the specimen, shearing the specimen to a size of 3 cm x 8 cm. This is the result of measuring the amount of hydrogen released by heating the specimen from room temperature to 500°C, and the bendability was measured as the maximum bending angle using a 3-point bending tester according to the VDA standard. The results are shown in Table 4.

[0088] Specimen number Diffusive hydrogen content (ppm) Maximum bending angle (°) Classification 10.5248.0 Conventional example 20.5254.3 Comparative example 30.4752.4 Invention example 40.5255.5 Comparative example 50.5249.1 Comparative example 60.4752.6 Comparative example 70.4049.8 Invention example 80.5152.5 Comparative example 90.3553.6 Invention example 100.3755.3 Invention example 110.2955.2 Invention example 120.2854.7 Invention example 130.3255.9 Invention example 140.3951.5 Invention example 150.3553.4 Invention example 160.4255.5 Invention example

[0089] The invention examples according to the present invention were confirmed to have a reduced amount of diffusible hydrogen and an increased amount of bendability compared to the prior art examples. Meanwhile, the results confirmed through the invention examples and comparative examples confirmed that the amount of diffusible hydrogen and bending characteristics varied depending on the type of metal and the amount of plating attached.

Claims

1. Comprising a substrate and an aluminum-based plating layer formed on the substrate, A metal layer is included on the above aluminum-based plating layer, The above metal layer is an aluminum-based plated steel, which contains a metal having a Gibbs free energy greater than Al when reducing with moisture in a gaseous state at a temperature of 700°C or higher.

2. In claim 1, The above metal is an aluminum-based plated steel having at least one of Fe, Zn, Ni and Mg.

3. In claim 2, When the above metal is Fe, the adhesion amount is 0.7 to 3.5 g / m 2 Aluminum-based coated steel.

4. In claim 2, When the above metal is Ni, the adhesion amount is 2.0 to 10.0 g / m 2 Aluminum-based coated steel.

5. In claim 2, When the above metal is Zn, the adhesion amount is 1.0 to 40 g / m 2 Aluminum-based coated steel.

6. In claim 1, The above-mentioned steel contains, in wt%, C: 0.02 to 0.6%, Si: 0.001 to 2%, Al: 0.001 to 1%, Mn: 0.1 to 4%, P: 0.05% or less, S: 0.02% or less, N: 0.02% or less, Ti: 0 to 0.1%, B: 0.0001 to 0.01%, Cu: 0 to 1.00%, Mo: 0 to 1.00%, Cr: 0 to 1.00%, Ni: 0 to 1.00%, V: 0 to 1.00%, Ca: 0 to 0.01%, Nb: 0 to 0.1%, Sn: 0 to 1%, W: 0 to 1%, Sb: 0 to 1%, Mg: 0 to 0.1%, Aluminum-based plated steel containing Co: 0 to 1%, As: 0 to 1%, Zr: 0 to 1%, Bi: 0 to 1%, REM: 0 to 0.3%, and the remainder being Fe and unavoidable impurities.

7. In claim 1, The above aluminum-based plating layer is an aluminum-based plating steel material containing 15 wt% or less of Si, the remainder being Al and unavoidable impurities.

8. In claim 1, The above aluminum-based plating layer is an aluminum-based plating steel material containing 10 to 35 wt% of Zn, 15 wt% or less of Si, and the remainder being Al and unavoidable impurities.

9. Step of forming an aluminum-based plating layer on the steel sheet; and A method for manufacturing a plated steel sheet, comprising the step of forming a metal layer including a metal having a Gibbs free energy greater than Al when subjected to a reduction reaction with gaseous moisture at a temperature of 700°C or higher on the aluminum-based plating layer.

10. In claim 9, The step of providing the above aluminum-based plated steel sheet is: A step of forming the aluminum-based plating layer by immersing the above-mentioned steel plate in a plating bath containing 15 wt% or less of Si, the remainder being Al and unavoidable impurities; A step of cooling the aluminum-based plating layer to the solidification point at an average speed of 20°C / s or more; and A method for manufacturing a hot-formed member, comprising a step of cooling from the above-mentioned solidification point to 350°C at an average rate of less than 20°C / s.

11. In claim 10, The above plating bath is a method for manufacturing a hot-formed member containing 10 to 35 wt% of Zn.

12. In claim 10, A method for manufacturing a hot-formed member, wherein the above plating bath contains Fe of 4 wt% or less.

13. In any one of claims 10 to 12, A method for manufacturing a hot-formed member, wherein the above plating bath contains one or more of Mg, Mn, Cr, and Ca at 4.5 wt% or less.

14. Comprising a steel substrate and an aluminum alloy layer on the steel substrate, The above-mentioned material is a hot-formed material having a diffusible hydrogen content of 0.50 ppm or less.

15. In the above claim 14, The above hot-formed member is a hot-formed member with a maximum bending angle of 49° or more when evaluated by three-point bending.