Plated steel sheet exhibiting excellent coating adhesion and corrosion resistance after hot press forming, method for manufacturing plated steel sheet, and hot press formed part

Abstract

To provide a plated steel sheet for hot press forming which exhibits excellent coating adhesion and corrosion resistance after hot press forming, to provide a method for producing the plated steel sheet, and to provide a hot press formed member.SOLUTION: According to an aspect of the present disclosure, a plated steel sheet may include a base steel sheet and a plating layer formed of an Al-Fe alloy on the base steel sheet, wherein a sum of contents of Al and Fe in the plating layer may be 80% or more by weight, an average content of Fe in the plating layer may be 20% or more by weight, and a product of Ra and RPc of a surface of the plating layer may be 60 to 150 μm / cm. Here, Ra means the arithmetic average roughness and the unit is μ m, and RPc means the number of peaks per unit length and the unit is / cm.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a plated steel sheet for hot press forming, a method for producing the plated steel sheet, and a method for hot press forming. This relates to shaped members. [Background technology]

[0002] Recently, with the depletion of petroleum energy resources and growing concern about the environment, the fuel efficiency of automobiles has Regulations on fuel economy are becoming stronger every day. One method for achieving this is to reduce the thickness of the steel plate used. If the strength of the steel plate is reduced, it may cause problems with the safety of the automobile. Improvement in quality needs to be ensured.

[0003] For these reasons, there is a continuous demand for high-strength steel plates, and various types of steel plates are being developed. However, such steel sheets have high strength and are therefore difficult to work. In other words, the product of strength and elongation rate is always constant depending on the grade of steel sheet. Therefore, when the strength of the steel sheet increases, the workability index tends to have a higher value. There was a problem that the stretching ratio was reduced.

[0004] In order to solve this problem, a hot press forming method has been proposed. is a method of processing steel sheets at high temperatures that make them easier to process, and then quenching them at low temperatures to make the steel sheets This method increases the strength of the final product by forming low-temperature structures such as martensite within the steel. This method minimizes workability problems when manufacturing high strength components. The advantage is that it can be suppressed.

[0005] However, in the above-mentioned hot press forming method, the steel sheet is heated to a high temperature, and the surface of the steel sheet is oxidized. Therefore, an additional process is required to remove oxides from the steel sheet surface after press forming. As a method for solving this problem, Patent Document 1 has been proposed. In the above Patent Document 1, an aluminum-plated steel sheet is subjected to hot press forming or uses a process of heating and quenching after cold forming (i.e., "post-heat treatment"), Since the aluminum plating layer is present on the surface of the steel sheet, the steel sheet does not oxidize when heated. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Patent No. 6,296,805 Summary of the Invention [Problem to be solved by the invention]

[0007] According to one embodiment of the present invention, it is possible to improve the paint adhesion of a hot press-formed part. Hot press-forming plated steel sheets that can be used for hot press forming and also ensure corrosion resistance, and the manufacturing method of the plated steel sheets A method of manufacturing is provided.

[0008] According to another embodiment of the present invention, a hot press-formed part having excellent paint adhesion and corrosion resistance is provided. Provided.

[0009] The object of the present invention is not limited to the above-mentioned scope. Anyone skilled in the art will be able to appreciate the full scope of the invention from the overall disclosure herein. There is no difficulty in understanding the problem. [Means for solving the problem]

[0010] The plated steel sheet according to one embodiment of the present invention comprises a base steel sheet and an A formed on the base steel sheet. The total content of Al and Fe in the plating layer is The average content of Fe in the plating layer is 80% or more by weight. and the product of Ra and RPc on the surface of the plating layer may be 60 to 150 μm / cm. .

[0011] Here, Ra means the arithmetic mean roughness, and its unit is μm, and RPc means the peaks per unit length. The unit is / cm.

[0012] According to another embodiment of the present invention, there is provided a plated steel sheet comprising a base steel sheet and a coating layer formed on the base steel sheet. The total content of Al and Fe in the plating layer is is 80% or more by weight, and the average content of Fe in the plating layer is 20% by weight. The surface of the plating layer was observed under a scanning electron microscope at a magnification of 100 times. The field of view is divided into 10 equal parts horizontally and vertically, and the number of cracks in each area is calculated based on the number of cracks per square meter. m 2 The ratio of the area occupied by the indentations on the surface of the plating layer is 5. It may be up to 50%.

[0013] Here, the indentation is the highest point measured in the area observed under an optical microscope at 100x magnification. This refers to an area that has a brightness of 70% or more of the original brightness.

[0014] According to yet another embodiment of the present invention, a method for producing a plated steel sheet is provided in which Al and F are added to a base steel sheet. obtaining an Al-Fe alloy-plated steel sheet on which a plating layer made of an alloy of e is formed; and For the Al-Fe alloy plated steel sheet, the SPMI represented by the following relational formula 1 is 5000 to 8 The method may include a step of skin pass rolling under conditions whereby the rolling temperature is 500°C or lower.

number

[0015] According to another embodiment of the present invention, a hot press-formed member includes a base steel sheet and a and a plating layer made of an Al-Fe alloy formed on the surface of the substrate, The total content is 70% or more by weight, and the Fe content in the plating layer is and the product of Ra and RPc on the surface of the plating layer is 60 to 150 μm / cm It may be.

[0016] Here, Ra means the arithmetic mean roughness, and its unit is μm, and RPc means the peaks per unit length. The unit is / cm.

[0017] According to another embodiment of the present invention, a hot press-formed member includes a base steel sheet and a and a plating layer made of an Al-Fe alloy formed on the surface of the substrate, The total content is 70% or more by weight, and the average content of Fe in the plating layer is The surface of the plating layer was observed under a scanning electron microscope at 100x magnification. The field of view obtained when the cracks were measured was divided into 10 equal parts horizontally and vertically. The number is 1 mm 2 The area occupied by the indentations on the surface of the plating layer is 15 to 220 per The ratio may be 5 to 50%.

[0018] Here, the indentation is the highest point measured in the area observed under an optical microscope at 100x magnification. This refers to an area that has a brightness of 70% or more of the original brightness. [Effects of the Invention]

[0019] As described above, the plated steel sheet of the present invention has surface Ra and RPc controlled to appropriate levels. Therefore, even if a large increase in illuminance does not occur during the hot press forming process, sufficient coating of the parts can be achieved. Adhesion can be ensured. [Brief explanation of the drawings]

[0020] [Figure 1] 1 shows photographs of the surfaces of aluminum-iron-based plated steel sheets produced by Comparative Example 1(a) and Inventive Example 2(b), observed with a scanning electron microscope (SEM). [Figure 2] 1 shows photographs of the surfaces of the aluminum-iron-based plated steel sheets produced by Comparative Example 1(a) and Inventive Example 2(b) observed with an optical microscope, and the images were processed accordingly. [Figure 3] 1 is a graph showing the relationship between the number of cracks generated on the surface of an aluminum-iron-plated steel sheet and skin-pass rolling conditions. DETAILED DESCRIPTION OF THE INVENTION

[0021] The terminology used herein is merely to refer to particular embodiments and is not intended to limit the scope of the present invention. The singular forms used herein are not intended to limit the scope of the invention unless the phrase clearly contradicts this. Unless otherwise indicated, plural expressions are also included.

[0022] As used in the specification, "comprises" means any specific properties, regions, integers, steps, acts, elements and and / or components, and other specific properties, regions, integers, steps, operations, elements, components, and The presence or addition of / or groups is not excluded.

[0023] All terms, including technical and scientific terms, used herein unless otherwise defined The meanings are the same as those generally understood by a person having ordinary skill in the technical field to which the present invention pertains. Commonly used predefined terms have the same meaning as those in the relevant technical literature and presently disclosed subject matter. Unless further construed and defined, the terms and conditions of the present invention shall have a meaning consistent with the content of the terms and conditions of the present invention. It is not always interpreted as a formal meaning.

[0024] In the present invention, the steel sheet is in the form of a coil or a sheet. It means something before it is processed into a specific shape, and a component is something that is not a plate-like shape due to the molding process. The plating layer in this invention refers to a layer formed in contact with the base steel sheet. The term "metallic layer" refers to a layer of a metal, alloy or intermetallic compound.

[0025] In the present invention, the content of each element is based on weight unless otherwise specified. It should be noted that the proportion of crystals and textures is based on the area unless otherwise specified. The gas content is based on volume unless otherwise specified.

[0026] The present invention will be described in detail below.

[0027] As mentioned above, when heating aluminum-plated steel sheets for hot press forming, However, depending on the heating speed, problems such as the aluminum plating layer melting and contaminating the equipment may occur. In addition, in the case of high-strength components, hydrogen trapped in the base steel sheet may In some cases, hydrogen accumulation can lead to the destruction of parts, resulting in the problem of so-called delayed hydrogen fracture.

[0028] One solution to this problem is to use an adhesive before heating for hot press forming. The aluminum-plated steel sheet is heated to form an aluminum-iron alloy layer on the steel sheet, and then the above There is a method in which a steel sheet on which an aluminum-iron alloy plating layer is formed is used for hot press forming. That is, the plating layer is alloyed at a relatively low temperature range before heating for hot press forming. By keeping the temperature at a relatively high rate, the aluminum is already alloyed. Therefore, even if it is heated to a temperature higher than the melting point of aluminum, This prevents problems caused by melting. In addition, in the case of pre-alloyed plated steel sheets, The alloy layer on the surface has a structure that allows hydrogen to be easily discharged, and hydrogen delayed fracture does not occur. This can have the effect of reducing the possibility of this happening.

[0029] On the other hand, when painting on a general plated steel sheet, it is not possible to fix the paint layer. There is no anchor that can be used, which causes problems such as insufficient adhesion between the paint and the steel plate surface. Therefore, to solve this problem, phosphate treatment is usually performed. However, the phosphate treatment increases the roughness of the steel surface, which reduces the adhesion between the steel and the paint. Sexuality becomes higher.

[0030] Incidentally, when a plated steel sheet having an aluminum-iron plated layer formed on its surface is hot-rolled, When press forming, there is a problem that it is difficult to increase the surface roughness of the part any further. The plating layer formed on the surface of the molded part is formed by an alloying reaction between aluminum and iron. In this way, the surface of the hot press formed part is Because it is chemically stable, it is difficult to further improve the roughness even if phosphate treatment is performed. When ordinary aluminum-plated steel sheets are heated and hot-pressed, The surface roughness increases during the heating process of the phosphated steel sheet, so the surface roughness is sufficient even without phosphate treatment. It is possible to ensure this, and there may be no major problems with paint adhesion.

[0031] On the other hand, aluminum-iron alloys, which have been subjected to alloying treatment in advance to form an aluminum-iron alloy layer, In the case of iron alloy plated steel sheets, the increase in surface roughness during heating for subsequent hot press forming is Therefore, even if the roughness increases in part during the pre-alloying heat treatment, Since the increase in roughness during the hot press forming process is not significant, aluminum-iron alloy plated steel sheet The surface roughness of the part obtained by hot press forming is the same as that of the aluminum-plated steel sheet after alloying heat treatment. The surface roughness of the parts obtained by hot press forming without any treatment is insufficient. This results in the problem of insufficient paint adhesion.

[0032] In addition, aluminum alloy plating layers are not as excellent in sacrificial corrosion protection as zinc-based plating layers. However, if the steel plate is exposed due to cracks, etc., corrosion may occur along with bristle formation. do.

[0033] Generally, increasing the surface roughness (Ra) improves paint adhesion, which results in a better finish after painting. Generally, corrosion resistance is also improved, but according to the inventor, simply increasing the surface roughness In addition, the product of the number of peaks per unit length (RPc) and the roughness (Ra) (Ra × RPc) Research has shown that increasing the value is effective in improving paint adhesion and corrosion resistance. This could be confirmed by the results.

[0034] The inventors of the present invention have also developed a so-called aluminum alloy that has already been alloyed before hot press forming. The paintability of hot press-formed parts manufactured using aluminum-iron alloy plated steel sheets is understood. As mentioned above, in the case of alloy-plated steel sheets, a considerable amount of iron has already diffused into the plating layer. Therefore, the surface roughness (Ra) and the number of peaks per unit length ( Since the increase in RPc is not large, the roughness (Ra) of the plated steel sheet before hot press forming Or increase the number of peaks per unit length (RPc), resulting in an increase in the Ra × RPc value. It was found that adding heat treatment is effective in increasing the Ra × RPc value of hot press formed parts. I put it out.

[0035] Therefore, in one embodiment of the present invention, a hot press molding is used to ensure high paint adhesion. Considering the surface Ra × RPc of the part obtained by the shape, R of the surface of the plating layer of the plated steel sheet a×RPc may be 60 μm / cm or more. In the formula, Ra is the arithmetic mean roughness. RPc has the unit of μm, and RPc is the reciprocal of cm as the peak count ( If the above Ra × RPc is not sufficient, sufficient paint adhesion will not be achieved. Therefore, the lower limit of Ra×RPc can be set at 60 μm / cm. Depending on the application, the lower limit of Ra×RPc may be set at 70 μm / cm. The higher the value of Ra × RPc, the better for improving the performance. However, if the value is too high, In the process of increasing Ra and RPc, excessive cracks are introduced on the surface of the plating layer. Therefore, in one embodiment of the present invention, the upper limit of Ra×RPc is can be set to 150 μm / cm, and in some cases the upper limit of the above Ra × RPc can be set to 14 It can also be set to 0 μm / cm.

[0036] In addition, the plated steel sheet according to another embodiment of the present invention has a surface crack count. By appropriately adjusting the area ratio of the indented part and the indented part, the obtained Therefore, the coating adhesion and corrosion resistance of the coated member can be improved. The surface area of ​​the plated steel sheet is 1mm 2 10 to 200 cracks per hit The proportion of the area occupied by the indentations on the surface of the plating layer may be 5 to 50%.

[0037] The cracks occur when the coating layer is anchored on the surface of the hot press-formed part. In one embodiment of the present invention, the unit of the plating layer can function as a fixing part. Area 1mm 2 Even if there are 10 or more cracks per hole, and in some cases 15 or more cracks The number of cracks is calculated by dividing the field of view of a microscope (magnification: 100x) into 10 equal parts vertically and horizontally. The number of cracks observed in the 100 obtained areas was calculated based on the observation area of ​​1 mm. 2 observed in In one embodiment of the present invention, the microscope is a ZEISS S A UPRA 55VP model scanning electron microscope may be used. If there are multiple areas where cracks are observed, the number of cracks is calculated based on the number of cracks observed. If multiple cracks are observed in one area, The number of cracks can be considered to be the total length of the cracks in the observation area. This is a concept that takes into consideration the overall length of the crack, which affects the fixing effect of the paint layer. However, unlike zinc-plated steel sheets, aluminum-plated steel sheets do not have a sacrificial corrosion protection function. Therefore, if cracks exist, corrosion may occur through the cracks. Therefore, excessive cracks may impair the corrosion resistance of the steel plate, so the above method Calculated 1mm 2 The maximum number of cracks per item can be limited to 200. Depending on the situation, you may be limited to 180 items.

[0038] In one embodiment of the present invention, the surface of the plating layer is When the above-mentioned indentations are present, the surface of the plating layer is In one embodiment of the present invention, the surface of the plating layer can be increased in Ra and RPc. The proportion of the indented portion may be 5% or more, and in some cases may be 8% or more. In one embodiment, the indentation is an area observed under an optical microscope at a magnification of 100 times. This can mean an area having a brightness of 70% or more relative to the highest brightness measured by In addition, although not necessarily limited to this, in one embodiment of the present invention, Surface images were taken at 100x magnification using a Leica DM6000M model optical microscope. The observation results were then analyzed using Clemex Vision PE software to calculate the color brightness. After dividing into 56 sections, the area with brightness equal to or greater than 70% of the highest brightness value is selected as the indentation area. If the proportion of the indented portion is too high, The load applied to the steel sheet to form the indentations is excessive, and the surface cracks increase. Therefore, the upper limit of the percentage of the indented portion can be set at 50%, and the upper limit can be set at 45%. In one embodiment of the present invention, the indented portion is formed by skin pass rolling. However, it is not necessarily limited to this.

[0039] In addition, since the subject of the present invention is an aluminum-iron alloy plated steel sheet, the content of Al and Fe The total content of these elements must be 80% or more by weight. does not need to be particularly defined, and a plating layer consisting of only 100% Al and Fe also falls under this category.

[0040] In addition, since one embodiment of the present invention is directed to a fully alloyed plated steel sheet, Therefore, the average Fe content is 20% or more by weight. If the content is less than 20%, problems such as melting of the aluminum plating layer when heated and hydrogen embrittlement may occur. Therefore, in the present invention, Fe is used in an amount of 20% or more by weight. In some cases, the Fe content may be 3 It may be 0% or more, or 40% or more.

[0041] There is no particular upper limit for the Fe content, but considering the Fe content in ordinary alloy-plated steel sheets, In this case, the upper limit of the Fe content can be set at 90%, and in some cases it can be set at 80% or less. Here, the average Fe content is the average Fe content in the entire coating layer. There are several methods for measuring this, but in this example, glow radiation Glow Discharge emission Spectromet The depth that appears when analyzing from the surface of the coating layer to the interface of the steel sheet using the GDS method. After integrating the Fe content curve according to the thickness (i.e., the surface The value obtained by dividing the thickness by the distance from the coating layer to the steel sheet interface can be used. There are various criteria for making the judgment, but in one embodiment, the curves of Al and Fe content intersect in the GDS results. The point where the contents of the two elements become similar is defined as the interface between the coating layer and the steel sheet. It is possible.

[0042] In one embodiment of the present invention, the plating layer contains, in addition to the above-mentioned Al and Fe, Examples of such elements include Mg, Zn, , Mn, Cr, Mo, Si, Ti, and These may be contained in the plating layer up to a total of 20% by weight or less.

[0043] In one embodiment of the present invention, the aluminum-iron alloy plating for hot press forming is The Fe content in the surface of the coated steel sheet is 50% of the average Fe content in the coating layer. % or more. That is, the Fe content on the surface may be the average Fe content in the plating layer. By making the content 50% or more, the plating layer is sufficiently alloyed up to the surface. In one embodiment of the present invention, the Fe content in the surface is In one embodiment of the present invention, the surface portion may be the outermost surface. It can mean a point 1 μm deep from the surface. The Fe content in the surface area was measured by EDS surface analysis at a magnification of 100 times using a scanning electron microscope. It can be measured.

[0044] The steel sheet of the present invention is a steel sheet for hot press forming, and is used for hot press forming. However, in one embodiment of the present invention, the composition is not particularly limited as long as it is Please note that unless otherwise specified, the compositions of the steel sheet and the plating layer of the present invention are based on weight. (It is necessary to add 0.01% to 0.5% of silicon), C: 0.01 to 0.5%, Si: 2.0% or less (excluding 0%), Mn :0.1~4.0%, P:0.05% or less, S:0.02% or less, Al:0.001~1 %, Cr: 5.0% or less (excluding 0%), N: 0.02% or less, Ti: 0.1% or less (0 %, B: 0.0001 to 0.01%, the balance Fe and unavoidable impurities. It's fine to do so.

[0045] C: 0.01 to 0.5% The above-mentioned C is an essential element for improving the strength of the heat-treated member, and when added in an appropriate amount, That is, in order to ensure sufficient strength of the heat-treated member, the above C is 0.0 In one embodiment, the lower limit of the C content may be 0.05%. However, if the content is too high, when producing cold-rolled material, the The strength of the hot-rolled material is too high, which not only significantly deteriorates cold rolling properties but also greatly reduces spot weldability. In order to significantly reduce the temperature, the content must be 0.5% or less to ensure sufficient cold rolling and spot weldability. The C content is limited to 0.45% or less or 0.4% or less. It can also be limited.

[0046] Si: 2.0% or less (excluding 0%) The above-mentioned Si is not only required to be added as a deoxidizer in steelmaking, but also in hot pressing. Not only does it suppress the generation of carbides, which have the greatest effect on the strength of formed parts, but it also After the formation of martensite in the forming process, carbon is deposited at the martensite lath grain boundaries. It may be added to steel to concentrate the austenite and secure the retained austenite. When performing aluminum plating, in order to ensure sufficient plating properties, the above Si content The upper limit can be set to 2% (excluding 0%). In one embodiment of the present invention, The content can be limited to 1.5% or less. The lower limit of the i content can be set at 0.01%.

[0047] Mn: 0.1 to 4.0% The above Mn is added not only to ensure the effect of solid solution strengthening, but also to improve the strength of hot press-formed parts. In order to reduce the critical cooling rate for securing martensite, a content of 0.1% or more is In addition, by maintaining the strength of the steel sheet appropriately, it is possible to improve the strength of the steel sheet during the hot press forming process. In order to ensure workability, reduce manufacturing costs, and improve spot weldability, The n content can be 4% or less, and in one embodiment of the present invention, 3.5% or less, or It can be reduced to 2.5% or less.

[0048] P:0.05% or less The above-mentioned P exists as an impurity in steel, and the lower its content, the more advantageous it is. Therefore, in one embodiment of the present invention, P is contained in a content of 0.05% or less. In another embodiment of the present invention, P may be limited to 0.03% or less. Since P is an impurity element that is more advantageous when it is reduced, there is no need to specifically set an upper limit for its content. However, excessive reduction of the P content may increase the manufacturing cost. When this is taken into consideration, the lower limit can be set at 0.001%.

[0049] S: 0.02% or less The above-mentioned S is an element that acts as an impurity in steel and impairs the ductility, impact properties, and weldability of the component. Therefore, the maximum content is set to 0.02% (preferably 0.01% or less). If the content is less than 0.0001%, the manufacturing cost may increase. In an embodiment, the lower limit of the content may be set to 0.0001%.

[0050] Al: 0.001 to 1% The above-mentioned Al, together with Si, acts as a deoxidizer during steelmaking, and can increase the cleanliness of steel. Therefore, it may be added at a content of 0.001% or more. Also, the Ac3 temperature should not be too high. In this way, the heating required for hot press forming can be performed within an appropriate temperature range. Therefore, the Al content can be set to 1% or less.

[0051] Cr: 5.0% or less (excluding 0%) The above-mentioned Cr plays a role in improving the hardening ability of steel and improving the strength of hot press formed parts. In some cases, the lower limit of the Cr content is set at 0.001%. However, if the content exceeds 5.0%, the effect will be It is difficult to expect an increase in Cr content, and costs may also increase. The upper limit can be set at 5.0%.

[0052] N: 0.02% or less The above-mentioned N is an element contained as an impurity in steel, and is used to cause cracks during continuous casting of slabs. To reduce the sensitivity to cracking and ensure impact properties, the lower the content, the better. It is not necessary to set a lower limit, but the manufacturing In consideration of rising costs, the N content in one embodiment is set to 0.001% or more. It can also be done as follows.

[0053] Ti: 0.1% or less (excluding 0%) The Ti reacts with nitrogen to help improve the hardening ability of B. In addition, the strength of hot press formed parts is improved by forming fine precipitates, and the grains are refined. It can be added in an amount of 0.1% or less because it is effective in thinning and improving impact toughness. In order to obtain the above-mentioned effect more reliably, in one embodiment of the present invention, The lower limit of the content can also be set at 0.0005%.

[0054] B: 0.0001 to 0.01% The above B not only improves hardening ability even with a small amount of addition, but also The grain boundary segregation of P and / or S causes brittleness of hot press-formed parts. Therefore, B is added at a concentration of 0.0001% or more. However, if the content exceeds 0.01%, not only will the effect saturate, but the steel may become brittle during hot rolling. Therefore, the upper limit can be set at 0.01%. The B content can be 0.005% or less.

[0055] In one embodiment of the present invention, Nb: 0.1% or less, Mo: 0.5% or less, One or two selected from Ni: 1% or less, Cu: 1% or less, and V: 0.5% or less The above elements may further be included.

[0056] Nb: 0.1% or less The above-mentioned Nb improves the steel sheet of heat-treated components by forming fine precipitates, and reduces residual austenite by refining the crystal grains. It can be added to steel because it is effective in stabilizing stenite and improving impact toughness. However, if the amount of addition exceeds 0.1%, not only does the effect saturate, but excessive alloying occurs. The addition of iron can increase costs. In one embodiment of the present invention, the Nb is 0. It can also be added in an amount of 0.01% or more.

[0057] Mo: 0.5% or less Mo improves hardening ability and ensures strength and grain refinement through the effect of precipitation strengthening. However, if added in excess, it may cause poor weldability. In consideration of this, it can be added in an amount of 0.5% or less. When Mo is added, the lower limit of the amount of addition can be set at 0.001%.

[0058] Ni: 1% or less The above-mentioned Ni is an element that forms fine precipitates to improve strength. Since exceeding 0.0% would result in excessive cost increases, the upper limit is set at 1%. In this embodiment, in order to reliably obtain the above-mentioned effects, the amount of Ni added is set to 0.005% or more. This can be done.

[0059] Cu: 1% or less The above Cu is an element that forms fine precipitates in the same way as Ni, thereby improving strength. If the value exceeds 1.0%, it will result in excessive cost increases, so the upper limit is set at 1%. To reliably obtain the above-mentioned effects, the amount of Cu added can be set to 0.005% or more. .

[0060] V: 0.5% or less The above V improves the steel sheet quality of heat-treated components by forming fine precipitates, and reduces the residual austenite by refining the crystal grains. It can be added to steel because it is effective in stabilizing stagnite and improving impact toughness. However, if the amount of addition exceeds 0.5%, not only does the effect saturate, but excessive alloying occurs. In one embodiment of the present invention, the addition of V as described above can increase costs. To ensure the effect, V can be added in an amount of 0.001% or more.

[0061] The balance other than the above-mentioned components includes iron and unavoidable impurities. There are no particular limitations on the components as long as they can be contained in the plate.

[0062] An example of a method for manufacturing a steel sheet for hot press forming according to an embodiment of the present invention will be described below. However, the manufacturing method of the steel sheet for hot press forming described below is only an example. The steel sheet for hot press forming of the present invention does not necessarily have to be manufactured by this manufacturing method. However, any manufacturing method may be used as long as it satisfies the scope of the present invention. It should be noted that there is no problem in implementing each embodiment of the present invention.

[0063] According to one embodiment of the present invention, the steel sheet has an aluminum-iron alloy plating layer on a base steel sheet. obtaining an aluminum-iron (Al-Fe) alloy plated steel sheet having the aluminum-iron (Al-Fe) alloy plated thereon; It is manufactured by skin-pass rolling aluminum-iron (Al-Fe) alloy plated steel sheet. It is possible.

[0064] In one embodiment of the present invention, the aluminum-iron alloy plated steel sheet is or a step of obtaining an aluminum-plated steel sheet plated with an aluminum alloy; and It can be obtained by a process including the step of heating and alloying an aluminized steel sheet. .

[0065] In this case, if the aluminum-plated steel sheet is industrially called aluminum-based, Any material can be used, and in one embodiment of the present invention, the Al content is 7% by weight. The remaining elements other than Al in the plating layer are The following elements are added to aluminum-based plating layers: Si, Mg, Zn, Mn, Cr, Mo, One or more components selected from Ti, Fe and / or other impurity elements Among them, Si may be contained in a proportion of 0.01 to 20%. To control the concentration to 0.01% or less, high purity raw materials are required, which significantly increases manufacturing costs. If it exceeds 20%, it will be difficult to maintain the equipment due to the increase in the plating bath melting temperature. Therefore, the alloying rate is reduced, making it difficult to obtain sufficient alloying. In this case, the Si content in the plating bath can be limited to 0.01 to 20%. One or more elements selected from Mg, Zn, Mn, Cr, Mo, and Ti are contained. The total amount of the elements contained in the plating layer may be 20% by weight or less.

[0066] The aluminum-based plating layer is formed on a steel plate that has been hot-rolled or cold-rolled and annealed. The plate is immersed in a hot-dip aluminum plating bath. It can be formed.

[0067] In one embodiment of the present invention, the amount of aluminum plating is 1 0-100g / m 2 The plating amount may be 10 g / m 2If it is less than this, corrosion resistance will decrease. In contrast, the plating amount is 100g / m 2 If it exceeds this limit, problems will arise with reduced weldability. Therefore, in the present invention, the amount of aluminum plating is 10 to 100 per side. 100g / m 2 On the other hand, in another embodiment of the present invention, The amount of aluminum plating per side is 20 to 90 g / m 2 It can also be.

[0068] In one embodiment of the present invention, the step of heating the aluminum-plated steel sheet to alloy it is The floor is directly connected to the line where steel sheets are coated with aluminum or aluminum alloy. The heating can be performed by online heating, in which the plated steel sheet is heated while it is traveling. In one embodiment of the present invention, the heating temperature range during the alloying is 670 to 900°C. In another embodiment of the present invention, the above The heating temperature may be in the range of 680 to 880°C, and the maintenance time may be 1 to 10 seconds. stomach.

[0069] In another embodiment of the present invention, the step of heating the aluminum-plated steel sheet to alloy it is The above-mentioned annealing can also be carried out by box annealing, in which the coiled plated steel sheet is heated in a box annealing furnace. At this time, the coil cooled to room temperature after aluminum plating is placed in a In a box annealing furnace in a hydrogen or hydrogen and nitrogen atmosphere, the temperature is 600 to 800°C, and the The alloying heat treatment can be carried out by heating for 10 hours (in the present invention, the furnace atmosphere temperature is set within the above temperature range). The maximum temperature reached by the temperature sensor is the heating temperature.

[0070] In each embodiment, the maintenance time is the time period after the ambient temperature reaches the target temperature and cooling begins. It means the time until

[0071] In one embodiment of the present invention, the skin pass rolling is performed by SPM represented by the following relational expression 1. It can be carried out under conditions where I is 5000 to 8500.

number

[0072] That is, the above SPMI can control the surface condition of the steel sheet, which is devised by the present inventor. The Ra and RPc of the steel sheet surface are of course the Ra and RPc of the roll surface, It is also affected by the pressing force applied by the roll, and as a result of quantitatively analyzing the degree of influence of these factors, Research results have shown that the relationship expressed by the above equation 1 is true. In order for the product of Ra and RPc of the surface to have a sufficient value, the SPMI value should be 500. 0 or higher, and in some cases, the above SPMI value may be limited to 5500 or higher. However, if the SPMI value is too high, the durability of the parts obtained after hot press forming will be reduced. Since feeding habits may be reduced, the value can be limited to 8500 or less. You can also limit it to 8000 or less.

[0073] Hereinafter, a hot press-formed part according to one embodiment of the present invention will be described. As a conventional method for producing a cold press-formed part, a steel sheet is heated to a temperature above the austenitizing temperature. This process involves heating and maintaining the temperature at the temperature, followed by rapid cooling and molding at the same time. There are no particular restrictions in the specification.

[0074] The hot press-formed member according to one embodiment of the present invention comprises a base steel sheet and a steel sheet formed on the base steel sheet. The plated layer is made of an Al-Fe alloy and has a surface roughness of 1000 nm. The product of Pc can be adjusted to provide both paint adhesion and corrosion resistance.

[0075] In one embodiment of the present invention, a porcelain sintered body obtained by hot press forming is used to ensure high paint adhesion. The Ra×RPc of the surface of the plated layer of the plated member can be 60 μm / cm or more. In the formula, Ra is the arithmetic mean roughness in μm, and RPc is the number of peaks (Pea The unit is the reciprocal of cm ( / cm) as k Count. If the ratio is not sufficient, it may be difficult to expect sufficient paint adhesion. The lower limit can be set to 60 μm / cm. can be set at 70 μm / cm. To improve paint adhesion, the value of Ra × RPc The higher the value, the more advantageous it is. However, if the value is too high, it may be possible to partially During the processing of plated steel sheets to increase the Ra and RPc of the material, excessive cracks are generated on the surface of the plated layer. In one embodiment of the present invention, the above Ra × R The upper limit of Pc can be set at 150 μm / cm, and in some cases, the above Ra × RPc The upper limit can also be set at 140 μm / cm.

[0076] In addition, the hot press-formed member according to another embodiment of the present invention includes an Al-Fe alloy plating layer. By appropriately adjusting the number of cracks formed on the surface and the area ratio of the indentation, The paint adhesion and corrosion resistance of the parts obtained by the hot press forming process can be improved. For this reason, the plated steel sheet according to one embodiment of the present invention has a surface area of ​​1 mm 2 Hit There are 15 to 220 cracks in the area of ​​the indentation on the surface of the plating layer. can be 5 to 50%.

[0077] The cracks occur when the coating layer is anchored on the surface of the hot press-formed part. In one embodiment of the present invention, the plating layer can be simply fixed. area 1mm 2 There are 15 or more cracks per square meter, and in some cases 20 or more cracks per square meter. The number of cracks was determined by dividing the field of view of a microscope (magnification 100x) into 10 equal parts vertically and horizontally. The number of cracks observed in the 100 areas obtained by the observation was counted as 1 mm2. 2 observed in In one embodiment of the present invention, the microscope is a ZEISS A SUPRA 55VP model scanning electron microscope may be used. If there are multiple cracks, the number of cracks is calculated based on the number of cracks observed. If multiple cracks are observed in one area, Of course, the number of racks will be the same as the number of cracks in the observation area. This is a concept that takes into account the overall length of the crack, and the overall length of the crack affects the fixing effect of the paint layer. However, aluminum-plated steel sheets (components) differ from zinc-plated steel sheets in that Since there is no sacrificial corrosion protection function, if cracks exist, corrosion may occur through the cracks. Therefore, excessive cracks may impair the corrosion resistance of the component. , 1mm 2 The maximum number of cracks per round can be limited to 220, and in some cases can be limited to 200.

[0078] In one embodiment of the present invention, the coating layer of the steel sheet is formed on the surface of the coating layer to increase the contact area of ​​the coating layer. A large number of indentations can be formed on the surface of the material, and these indentations remain on the material. When the above-mentioned indentations are present, the surface of the plating layer is Ra and RPc may increase, so in one embodiment of the present invention, The proportion of indentations on the surface may be 5% or more, and in some cases may be 8% or more. Although not necessarily limited thereto, one embodiment of the present invention includes a Leica The surface image was observed at 100x magnification using a DM6000M model optical microscope. The color intensity was divided into 256 values ​​using Clemex Vision PE software. Then, the part with a brightness equal to or greater than 70% of the highest brightness value is identified as the indentation part. When the proportion of the indented portion is too high, the area ratio of the indented portion is calculated. The load on the plating layer is excessive and surface cracks may increase, resulting in the above indentations. The upper limit of the division's percentage can be set at 50% or 45%.

[0079] According to one embodiment of the present invention, the aluminum-iron (Al-Fe) alloy plating layer is The plating layer can contain a total of 70% or more of Al and Fe by weight. Therefore, there is no need to set a specific upper limit for the total content of these elements. The total content may be 100%.

[0080] In the plating layer, Fe can diffuse into the plating layer during hot press forming, so It may contain 30% or more by quantity. If the Fe content in the plating layer is less than 30%, However, this method may not be very useful in solving problems such as hydrogen embrittlement during storage. The plating layer of the member may contain 30% or more Fe by weight, and in some cases, the above-mentioned F The e content may be 35% or more, or may be 40% or more.

[0081] There is no particular upper limit for the Fe content, but the F content in the plating layer of ordinary hot press-formed parts is When considering the e content, the upper limit of the Fe content can be set at 90%. The average Fe content can be set to 80% or less. The average of the e content can be measured by various methods. In this state, glow discharge spectroscopy (Glow Discharge Emission Spectroscopy) The analysis was carried out from the surface of the coating layer to the interface of the steel sheet using the GDS (Glass Deposition Spectroscopy) method. After integrating the curve of Fe content according to the depth (thickness) that appears when There are various criteria for determining the interface between the coating layer and the steel sheet. In this example, the curves of Al and Fe content intersect in the GDS results. The point where the contents of the two elements are equal can be defined as the interface between the coating layer and the steel sheet. .

[0082] According to one embodiment of the present invention, the plating layer of the hot press-formed member contains the above-mentioned Al and F. In addition to e, the plating layer may contain other elements that are commonly contained in the plating layer. Examples of the metal include one or more metals selected from Mg, Zn, Mn, Cr, Mo, Si, and Ti. Two or more of these may be included in the plating layer up to a total of 20% by weight or less.

[0083] The base steel sheet of the hot press formed member of the present invention can have various structures according to strength. If the tensile strength is 400 to 800 MPa, the area of ​​martensite is 5 to 50 % and the remainder selected from ferrite, pearlite, bainite and austenite It can have a microstructure consisting of one or more phases, and has a tensile strength of 800 to 130 At 0 MPa, the area ratio is 90% or more martensite and the remaining ferrite and pearlite. A microphase consisting of one or more phases selected from arsenite, bainite and austenite. It can have a fine structure, and when the tensile strength is 1300 MPa or more, it is Over 95% tensite, the rest ferrite, pearlite, bainite and austenite The microstructure may be composed of one or more phases selected from the following: [Example]

[0084] The present invention will be described in more detail below with reference to examples. However, the following examples are not intended to be limiting of the scope of the present invention. The following is for illustrative purposes only and is not intended to limit the scope of the present invention. It should be noted that the scope of the present invention is not limited to the matters described in the claims. This is because the matter is determined by matters that can be reasonably inferred from this.

[0085] (Example) As the base steel sheet, a cold-rolled steel sheet for hot press forming having the composition shown in Table 1 below was prepared. The base steel sheet was annealed and heat treated in the usual manner, and then hot-dip aluminum plating was performed. The bath has a composition consisting essentially of 9.5% Si by weight and the balance Al. The temperature was set to 660°C. After plating, the plating was performed using an air knife. Amount of coverage: 40g / m 2 was adjusted to.

[0086] After this, alloying was carried out by online or box annealing for each of the invention examples and comparative examples, and Al-F The alloyed steel sheet was obtained. The online alloying was carried out by reheating the steel sheet to 720°C and then The coil is then maintained at 650°C for 10 seconds and cooled to room temperature. The annealing was carried out in a box furnace for 10 hours.

[0087] After alloying, the rolls had the surface roughness (Ra) and peak count (RPc) shown in Table 2. The plated steel sheet was skin-pass rolled using the rolling force shown in Table 2. The surface condition of the plated layer was adjusted.

[0088] In all of the invention examples and comparative examples, the alloys obtained by the respective alloying methods and skin pass rolling were The total content of Al and Fe in the alloy plating layer and the Fe content were 90% and 43%, respectively. Therefore, no particular differences were observed between the Examples. The Fe content at the surface of the coating layer was 77% of the average Fe content in the coating layer. At this time, the surface of the plating layer was the outermost surface of the plating layer. This refers to a point 1 μm deep from the surface.

[0089] The skin-pass rolled coated steel sheet was heated at 930°C for 6 minutes in an air atmosphere. After heating, hot press forming and rapid cooling were carried out to obtain a hot press formed part. The internal structure of the cold press-formed part is essentially 100% martensite, and the strength is 150 However, the structure and strength of the steel may be changed as needed. It is possible to change the composition of the steel, cooling conditions, etc., and any ordinary engineer would be able to understand the manufacturing process. By changing the conditions, it is not difficult to manufacture components with the desired structure and strength. stomach.

[0090] In addition, in all the hot press formed parts obtained in the invention examples and comparative examples, the alloy plating The total content of Al and Fe in the layer and the Fe content were 83% and 44%, respectively. No particular differences were observed between the examples.

[0091] Surface roughness (Ra), peak of skin-pass rolled coated steel sheet and hot press formed parts The number of cracks (RPc), the number of cracks per unit area, and the percentage of indented areas were measured. The number of peaks was measured at five locations according to JIS B 0601 (2013) standard. The number of cracks was calculated by dividing the field of view of a microscope (magnification: 100x) vertically and horizontally. The total number of cracks observed in each of the 100 areas obtained by dividing the area into 10 equal parts is Observation area 1mm 2 The measurements were converted to those observed in the ZEISS SUPR A 55VP model scanning electron microscope was used to measure five areas, and the average value was calculated. The proportion of the indented area was measured using a Leica DM6000M model. Surface images observed with an optical microscope at 100x magnification were captured using Clemex Vision. Using PE software, the color brightness is divided into 256 values, and then 70% of the highest brightness value is used. The area having a brightness equal to or greater than the value was determined as the indented portion, and the area ratio of the indented portion was calculated. The area ratio was also the average value of the results of observing five locations. The results for the hot press formed parts are shown in Table 3, and those for the hot press formed parts are shown in Table 4.

[0092] The paint adhesion and corrosion resistance of the hot press formed parts were evaluated by the following methods. The results are shown in Table 4.

[0093] First, the paint adhesion grade was determined by painting the parts obtained by the GMW14829 method. Then, a lattice scratch was created with 1 mm intervals, and tape was peeled off. A grade was determined based on the evaluation. If the above grade is 1 or less, it can be considered as good.

[0094] Corrosion resistance is measured after phosphate treatment and painting of the above components according to the GMW14872 standard. After making a crosscut, the cyclic corr After 52 ossion tests, the blister width was measured. In this example, a width of 2 mm or less was determined to be good.

[0095] [Table 1]

[0096] [Table 2]

[0097] [Table 3]

[0098] [Table 4]

[0099] In Comparative Examples 1 to 3, the SPMI during skin pass rolling was less than 5000, As a result, the Ra × RPc of the alloyed plated steel sheet surface is not sufficiently secured, or the indentation The proportion of cracks and the number of cracks were not sufficient. The hot press formed parts obtained by this method also have insufficient Ra × RPc, or the number of cracks or pressure In such cases, the anchoring effect is insufficient and the paint layer is partially damaged. It may be difficult to bond firmly to the surface of the material, and as a result, the paint adhesion rating is always 2 or higher. On the other hand, in Comparative Examples 4 to 6, the SPMI value was too high. In such cases, the Ra × RPc of the plating layer, the proportion of indentations, and the number of cracks are determined by the coating of the component. Although this may be sufficient to ensure good adhesion, it may also cause damage to the plating layer. As shown in Table 4, the corrosion resistance of the components deteriorated. In this case, aluminum alloy-based materials that cannot provide the corrosion protection performance of the sacrificial anode method are used. The damaged coating may expose the base steel sheet and cause corrosion. The width of the blisters, which is an indicator of corrosion resistance, may exceed the allowable limit.

[0100] On the other hand, in Examples 1 to 7, which satisfy the conditions of the present invention, the skin pass rolling conditions were appropriately controlled to plate the steel. As a result of ensuring the surface properties of the coated steel sheet, the final component has excellent paint adhesion and corrosion resistance at the same time. I was able to secure it.

[0101] FIG. 1 shows the plated steel sheet (a) manufactured according to Comparative Example 1 and the plated steel sheet (b) manufactured according to Inventive Example 2. As can be seen from the drawing, the plated steel sheet manufactured according to Comparative Example 1 is In the case of Example 1, the surface unevenness is insufficient, whereas the plated steel sheet manufactured by Example 2 In this case, the surface is sufficiently roughened, and the product is then manufactured by hot press forming. The surface of the component may be adapted to secure a coating layer.

[0102] 2 shows the surfaces of the steel sheets manufactured in Comparative Example 1 and Inventive Example 2 under a 100x microscope (DM6 000M) and processed using Clemex Vision PE software. The results are shown in white in the areas with 70% or more of the maximum brightness (indented areas). In this invention, the SPMI is controlled within an appropriate range and skin pass rolling is performed. Example 2 had a much higher indentation than Comparative Example 1, which was skin-pass rolled under low SPMI conditions. It was possible to form a section.

[0103] The relationship between the SPMI value and the number of cracks is shown in the graph in Figure 3. If the value is between 5000 and 8000√Ton·μm / cm, the number of cracks is It can be confirmed that the temperature can be maintained within an appropriate range.

[0104] Therefore, the advantageous effects of the present invention were confirmed.

Claims

1. Base steel sheet and a plating layer made of an Al-Fe alloy formed on the base steel sheet, The total content of Al and Fe in the plating layer is 80% or more by weight, The average content of Fe in the plating layer is 20% or more by weight, The product of Ra and RPc of the surface of the plating layer is 60 to 150 μm / cm. Plated steel sheet for forming. Here, Ra means the arithmetic mean roughness, and its unit is μm, and RPc means the peaks per unit length. The unit is / cm.

2. Base steel sheet and a plating layer made of an Al-Fe alloy formed on the base steel sheet, The total content of Al and Fe in the plating layer is 80% or more by weight, The average content of Fe in the plating layer is 20% or more by weight, The field of view obtained when the surface of the plating layer is observed with a scanning electron microscope at a magnification of 100 times. The number of cracks in each area obtained by dividing the area into 10 equal parts horizontally and vertically is 1 mm. ２ Win 10 to 200 pieces, The hot press forming process is performed such that the area occupied by the indentations on the surface of the plating layer is 5 to 50%. Galvanized steel sheet. Here, the indentation is the highest point measured in an area observed under an optical microscope at 100 times magnification. It means an area having a brightness of 70% or more of the lightness of the original area.

3. The Fe content in the surface portion of the plating layer is 5% or more relative to the average Fe content in the plating layer. The plated steel sheet for hot press forming according to claim 1, wherein the Cr content is 0% or more. Here, the Fe content of the surface area is measured by a scanning electron microscope (SEM) at a magnification of 100 times. The value is measured through DS surface analysis, and the average Fe content is the value measured through GDS analysis. The curve of Fe content from the layer to the depth where the Fe and Al contents intersect is integrated and then displayed. It means the value obtained by dividing by the distance from the layer to the depth where the Fe and Al contents intersect.

4. 4. The method according to claim 3, wherein the surface portion of the plating layer has an Fe content of 15% or more by weight. Plated steel sheet for hot press forming.

5. The Fe content in the surface portion of the plating layer is The plated steel sheet for hot press forming according to claim 2, wherein the Cr content is 50% or more. Here, the Fe content of the surface area is measured by a scanning electron microscope (SEM) at a magnification of 100 times. The value is measured through DS surface analysis, and the average Fe content is the value measured through GDS analysis. The curve of Fe content from the layer to the depth where the Fe and Al contents intersect is integrated and then displayed. It means the value obtained by dividing by the distance from the layer to the depth where the Fe and Al contents intersect.

6. 6. The method according to claim 5, wherein the surface portion of the plating layer has an Fe content of 15% or more by weight. Plated steel sheet for hot press forming.

7. 7. The method according to claim 1, wherein the average content of Fe in the plating layer is 90% or less. Item 1. The plated steel sheet for hot press forming according to item 1.

8. The plating layer is made of one material selected from the group consisting of Mg, Zn, Mn, Cr, Mo, Si, and Ti. or two or more elements in a total content of 20 wt% or less according to any one of claims 1 to 6. Item 1. The plated steel sheet for hot press forming according to item 1.

9. The base steel sheet contains, by weight, C: 0.01 to 0.5%, Si: 2.0% or less (0% is excluding), Mn: 0.1 to 4.0%, P: 0.05% or less, S: 0.02% or less, Al: 0 .001-1%, Cr: 5.0% (excluding 0%), N: 0.02% or less, Ti: 0.1% or less (excluding 0%), B: 0.0001 to 0.01%, balance Fe and unavoidable impurities The plated steel sheet for hot press forming according to any one of claims 1 to 6, having a composition.

10. The base steel sheet contains Nb: 0.1% or less, Mo: 0.5% or less, Ni: 1% or less, Cu: and V: 0.5% or less. The plated steel sheet for hot press forming according to claim 9, comprising:

11. Al-Fe alloy plating, in which a plating layer made of an alloy of Al and Fe is formed on a base steel sheet Obtaining a steel plate; and The Al-Fe alloy plated steel sheet has an SPMI of 5000 to 10000 represented by the following relational expression 1: A step of skin pass rolling under conditions of 8500°C. Manufacturing method. [Equation 1] Here, P is the rolling force (unit: ton) during skin pass rolling, and Ra ｒｏｌｌ Has Arithmetic mean roughness (unit: μm) of the Kimpas rolling roll surface, said RPc ｒｏｌｌ Is Skinpa The SP refers to the number of peaks per unit length of the roll (unit: / cm). The unit of MI is √Ton·μm / cm.

12. The Al-Fe alloy plated steel sheet is A process for obtaining an aluminum-plated steel sheet plated with aluminum or an aluminum alloy. floor; and The aluminum-plated steel sheet is obtained by a process including a step of heating and alloying the aluminum-plated steel sheet. The method for producing a plated steel sheet for hot press forming according to claim 11.

13. The step of heating and alloying the aluminum-plated steel sheet comprises heating the steel sheet to aluminum or It is directly connected to the aluminum alloy plating line, and the plated steel sheet is running. The plating for hot press forming according to claim 12, which is carried out by online heating. Steel plate manufacturing method.

14. The step of heating and alloying the aluminum-plated steel sheet comprises heating the rolled aluminum-plated steel sheet. The hot press forming method according to claim 12, wherein the hot press forming method is carried out by box annealing in a box annealing furnace. Manufacturing method for coated steel sheets.

15. The base steel sheet contains, by weight, C: 0.01 to 0.5%, Si: 2.0% or less (0% is excluding), Mn: 0.1 to 4.0%, P: 0.05% or less, S: 0.02% or less, Al: 0 . 001 to 1%, Cr: 5.0% or less (excluding 0%), N: 0.02% or less, Ti:

0. 1% or less (excluding 0%), B: 0.0001 to 0.01%, balance Fe and inevitable impurities The plating for hot press forming according to any one of claims 11 to 14, having a composition comprising Steel plate manufacturing method.

16. The base steel sheet contains Nb: 0.1% or less, Mo: 0.5% or less, Ni: 1% or less, Cu: and V: 0.5% or less. The method for producing a plated steel sheet for hot press forming according to claim 15, comprising:

17. Base steel sheet and a plating layer made of an Al-Fe alloy formed on the base steel sheet, The total content of Al and Fe in the plating layer is 70% or more by weight, The content of Fe in the plating layer is 30% or more by weight, The product of Ra and RPc of the surface of the plating layer is 60 to 150 μm / cm. Molded parts. Here, Ra means the arithmetic mean roughness, and its unit is μm, and RPc means the peaks per unit length. The unit is / cm.

18. Base steel sheet and a plating layer made of an Al-Fe alloy formed on the base steel sheet, The total content of Al and Fe in the plating layer is 70% or more by weight, The average content of Fe in the plating layer is 30% or more by weight, The field of view obtained when the surface of the plating layer was observed with a scanning electron microscope at a magnification of 100 times was The number of cracks in each area obtained by dividing the area into 10 equal parts horizontally and vertically is 1 mm. ２ 1 Win 5 to 220 pieces, The hot press forming process is performed such that the area occupied by the indentations on the surface of the plating layer is 5 to 50%. Components. Here, the indentation is the highest point measured in an area observed under an optical microscope at 100 times magnification. It means an area having a brightness of 70% or more of the lightness of the original area.

19. The base steel sheet contains, by weight, C: 0.01 to 0.5%, Si: 2.0% or less (0% is excluding), Mn: 0.1 to 4.0%, P: 0.05% or less, S: 0.02% or less, Al: 0 . 001 to 1%, Cr: 5.0% or less (excluding 0%), N: 0.02% or less, Ti:

0. 1% or less (excluding 0%), B: 0.0001 to 0.01%, balance Fe and inevitable impurities 19. The hot-press-formed part according to claim 17 or 18, having a composition comprising:

20. The base steel sheet contains Nb: 0.1% or less, Mo: 0.5% or less, Ni: 1% or less, Cu: and V: 0.5% or less. The hot-press-formed part of claim 19, comprising:

21. The base steel sheet is made of 5 to 50% martensite on an area basis, with the remainder being ferrite and pearlite. A microphase consisting of one or more phases selected from arsenite, bainite and austenite. The sintered body according to claim 17 or 18, having a fine structure and a tensile strength of 400 to 800 MPa. Hot press formed parts.

22. The base steel sheet is made of 90% or more martensite on an area basis, with the remaining ferrite and pearlite. It consists of one or more phases selected from arsenite, bainite and austenite.

19. The method according to claim 17 or 18, wherein the steel sheet has a fine structure and a tensile strength of 800 to 1300 MPa. Hot press formed parts shown above.

23. The base steel sheet is composed of 95% or more martensite on an area basis, the remaining ferrite and perlite. It is composed of one or more phases selected from the group consisting of ferrite, bainite and austenite.

19. The steel sheet according to claim 17 or 18, having a microstructure of 1300 MPa or more and a tensile strength of 1300 MPa or more. Hot press formed parts.

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