Hot stamping part

Abstract

The invention relates to a hot stamping component and a manufacturing method thereof. According to the hot-pressed part and the manufacturing method thereof, the hot-pressed part with suppressed hydrogen embrittlement and ultrahigh strength can be obtained.

Description

Technical Field

[0001] The present invention relates to a hot stamping component and a method for manufacturing the same. Background Art

[0002] Currently, environmental and fuel efficiency regulations, as well as safety standards, are tightening in the automotive industry. Consequently, the application rate of ultra-high-strength steel and hot stamping steel is steadily increasing. In particular, hot stamping steels, including conventional 1.5 GPa hot stamping steels, are being explored in the research and development of high toughness and high strength.

[0003] The hot stamping process is a technology that achieves ultra-high strength by using a microstructure based on the phase transformation of the material during processing, and generally consists of a heating step, a forming step, a cooling step, and a finishing step.

[0004] Unlike conventional press forming, which is performed in a cold state, hot stamping processes are primarily performed at temperatures of 900°C or higher. Therefore, plated steel sheets coated with aluminum (Al) alloys are often used to ensure high-temperature stability and surface treatment of vehicle body components. Among Al alloys, Al-Si, Al-Cu, and Al-Zn alloys have excellent mechanical properties, such as fluidity, shrinkage during solidification, and corrosion resistance. Therefore, they are widely used as structural castings and coating materials for aircraft, automobiles, and other applications, and are also widely used as materials for hot stamping.

[0005] On the other hand, when a high-temperature heat treatment is performed in a heating step using a heating furnace during the hot stamping process, a reaction occurs in which moisture in the air decomposes and produces hydrogen. In this case, as described in Patent Document 1 (Korean Patent Application Publication No. 2012-0134709), a plated steel sheet obtained by plating hot stamping steel with aluminum-silicon (Al-Si) transforms into a liquid phase due to its low melting point during the high-temperature heat treatment, and a large amount of hydrogen flows in from the surface. Subsequently, when cooled through the cooling step, the hydrogen flowing into the material is captured because the coating is transformed into an Al-Fe intermetallic compound layer. At this time, the inflowing hydrogen gathers in one place over time, which can cause hydrogen embrittlement. Therefore, in order to solve this problem, a hot stamping component that can suppress hydrogen embrittlement and has ultra-high strength is needed. Summary of the Invention

[0006] Technical goals

[0007] An object of the present invention is to provide a hot stamping component having suppressed hydrogen embrittlement and ultra-high strength and a method for manufacturing the same.

[0008] Technical Solution

[0009] To achieve the above object, a hot stamping component of the present invention includes a steel plate; and a plating layer formed on at least one surface of the steel plate, the plating layer satisfying the following General Formula 1 and containing zinc.

[0010] [General formula 1]

[0011]

[0012] (In the above general formula 1, when the plating layer consists of n layers with different structures, L k is the average thickness (μm) measured along the short axis at 10 random positions in the kth layer of the coating observed in the SEM image, D k is the value obtained by the electrochemical hydrogen permeation test method shown below (m 2 / s), t is the total heating time during hot stamping (s), and n is an integer greater than or equal to 2.

[0013] <Electrochemical Hydrogen Permeation Experimental Method>

[0014] - The sample formed by the kth layer is placed between two cells, hydrogen is electrogenerated in one cell and allowed to permeate into the other cell.

[0015] -Measure the time it takes for hydrogen to permeate into the other cell.

[0016] - The value calculated by the following general formula 2 using the measurement time and the thickness of the sample is defined as D k .

[0017] [Formula 2]

[0018]

[0019] (In the above general formula 2, L 样品 is the thickness of the sample (m), t 样品 is the time required to penetrate the sample (s).

[0020] In addition, the plating layer may satisfy the following general formula 3.

[0021] [Formula 3]

[0022]

[0023] (In the above general formula 3, when the coating is composed of n layers with different structures, L k is the average thickness (μm) measured along the short axis at 10 random positions in the kth layer of the coating observed in the SEM image, D k is the value obtained by the following electrochemical hydrogen permeation test method (m 2 / s), t is the total heating time during hot stamping (s), and n is an integer greater than or equal to 2.

[0024] <Electrochemical Hydrogen Permeation Experimental Method>

[0025] - The sample formed by the kth layer is placed between two cells, hydrogen is electrogenerated in one cell and allowed to permeate into the other cell.

[0026] -Measure the time it takes for hydrogen to permeate into the other cell.

[0027] - The value calculated by the following general formula 2 using the measurement time and the thickness of the sample is defined as D k .

[0028] [Formula 2]

[0029]

[0030] (In the above general formula 2, L 样品 is the thickness of the sample (m), t 样品 is the time required to penetrate the sample (s).

[0031] In addition, the plating layer may satisfy the following general formula 4.

[0032] [Formula 4]

[0033]

[0034] (In the above general formula 4, when the coating is composed of n layers with different structures, L k is the average thickness (μm) measured along the short axis at 10 random positions in the kth layer of the coating observed in the SEM image, D k is the value obtained by the following electrochemical hydrogen permeation test method (m 2 / s), t is the total heating time during hot stamping (s), and n is an integer greater than or equal to 2.

[0035] <Electrochemical Hydrogen Permeation Experimental Method>

[0036] - The sample formed by the kth layer is placed between two cells, hydrogen is electrogenerated in one cell and allowed to permeate into the other cell.

[0037] -Measure the time it takes for hydrogen to permeate into the other cell.

[0038] - The value calculated by the following general formula 2 using the measurement time and the thickness of the sample is defined as D k .

[0039] [Formula 2]

[0040]

[0041] (In the above general formula 2, L 样品 is the thickness of the sample (m), t 样品 is the time required to penetrate the sample (s).

[0042] Furthermore, the hot stamped component may be a component manufactured by hot stamping a plated steel sheet having a plating layer containing zinc formed on at least one surface of the steel sheet.

[0043] In addition, hot stamping may include a heating step of preparing a plated steel sheet having a coating layer containing zinc formed on at least one surface of the steel sheet and heating the prepared plated steel sheet; a forming step of stamping the heated plated steel sheet using a stamping die and forming a formed body; and a cooling step of cooling the formed body.

[0044] Furthermore, when the plated steel sheet prepared in the heating step is heated, the plated steel sheet may be heated at an average heating rate of 3° C. / s to 8° C. / s within a temperature range of 600° C. to 700° C.

[0045] Furthermore, when the plated steel sheet prepared in the heating step is heated, the plated steel sheet may be heated at an average heating rate of 0.5°C / s to 3°C / s within a temperature range of 800°C to X°C. In this case, X°C is equal to the maximum heating temperature of the plated steel sheet in the heating step minus 10°C.

[0046] Furthermore, the total heating time during the hot stamping process may be 150 seconds to 450 seconds.

[0047] In addition, the thickness of the plating layer may be 10 μm to 30 μm.

[0048] In addition, the method of manufacturing a hot stamping component of the present invention relates to a manufacturing method for a hot stamping component, wherein the hot stamping component includes a steel plate and a coating formed on at least one surface of the steel plate, the coating satisfying the following general formula 1 and containing zinc, the manufacturing method including a heating step of preparing a plated steel plate having a coating containing zinc formed on at least one surface of the steel plate and heating the prepared plated steel plate; a forming step of stamping the heated plated steel plate using a stamping die to form a formed body; and a cooling step of cooling the formed body.

[0049] [General formula 1]

[0050]

[0051] (In the above general formula 1, when the plating layer consists of n layers with different structures, L kis the average thickness (μm) measured along the short axis at 10 random positions in the kth layer of the coating observed in the SEM image, D k is the value obtained by the following electrochemical hydrogen permeation test method (m 2 / s), t is the total heating time during hot stamping (s), and n is an integer greater than or equal to 2.

[0052] <Electrochemical Hydrogen Permeation Experimental Method>

[0053] - The sample formed by the kth layer is placed between two cells, hydrogen is electrogenerated in one cell and allowed to permeate into the other cell.

[0054] -Measure the time it takes for hydrogen to permeate into the other cell.

[0055] - The value calculated by the following general formula 2 using the measurement time and the thickness of the sample is defined as D k .

[0056] [Formula 2]

[0057]

[0058] (In the above general formula 2, L 样品 is the thickness of the sample (m), t 样品 is the time required to penetrate the sample (s).

[0059] Furthermore, when the plated steel sheet prepared in the heating step is heated, the plated steel sheet may be heated at an average heating rate of 3° C. / s to 8° C. / s within a temperature range of 600° C. to 700° C.

[0060] Furthermore, when the plated steel sheet prepared in the heating step is heated, the plated steel sheet may be heated at an average heating rate of 0.5°C / s to 3°C / s within a temperature range of 800°C to X°C. In this case, X°C is equal to the maximum heating temperature of the plated steel sheet in the heating step minus 10°C.

[0061] Furthermore, the plating layer formed on the plated steel sheet prepared in the heating step may include a ζ layer, a δ layer, and a γ layer.

[0062] Effects of the Invention

[0063] According to the hot pressed component and the manufacturing method thereof of the present invention, a hot pressed component in which hydrogen embrittlement is suppressed and which has ultrahigh strength can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 A schematic diagram illustrating a hot stamping assembly according to one embodiment of the present invention as an example;

[0065] Figure 2 An image of the hot stamped component manufactured in Example 2 taken at the highest heating temperature using a scanning electron microscope; and

[0066] Figures 3 to 5 The images are obtained by photographing the fracture test evaluation results of the hot stamping components manufactured in Example 2, Comparative Example 1, and Comparative Example 2, respectively, using a camera. DETAILED DESCRIPTION

[0067] Hereinafter, the hot stamping assembly of the present invention will be described with reference to the accompanying drawings, which are illustrative and the hot stamping assembly of the present invention is not limited to the accompanying drawings.

[0068] Figure 1 Schematic diagram showing a hot stamping assembly according to one embodiment of the present invention as an example. Figure 1 As shown, the hot stamping component 10 of the present invention includes a steel plate 11 and a coating 12. According to the hot stamping component 10 of the present invention, hydrogen embrittlement can be suppressed and ultrahigh strength can be achieved.

[0069] The steel plate 11 represents a plate made of steel used for automobile bodies. For example, the steel plate 11 may contain carbon (C), silicon (Si), manganese (Mn), phosphorus (P), sulfur (S), boron (B), and the balance iron (Fe), along with other unavoidable impurities. Specifically, the steel plate 11 may contain 0.1 to 0.5% by weight of carbon (C), 0.1 to 0.8% by weight of silicon (Si), 0.3 to 3.0% by weight of manganese (Mn), greater than 0 to 0.05% by weight of phosphorus (P), greater than 0 to 0.03% by weight of sulfur (S), 0.0005 to 0.005% by weight of boron (B), and the balance iron (Fe), along with other unavoidable impurities.

[0070] In addition, the steel plate 11 may further include one or more selected from titanium (Ti) and / or niobium (Nb), chromium (Cr), molybdenum (Mo), and nickel (Ni). Specifically, the steel plate 11 may further include 0.01 to 0.1% by weight of titanium (Ti) and / or niobium (Nb), 0.01 to 1.0% by weight of chromium (Cr), 0.01 to 1.0% by weight of molybdenum (Mo), and 0.001 to 1.0% by weight of nickel (Ni).

[0071] Carbon (C) is a main element that determines the strength and hardness of steel and can be added after the hot stamping process or hot pressing process to ensure the tensile strength of the steel material. In addition, carbon (C) can be added to ensure the hardenability properties of the steel material. If carbon (C) is contained in the steel plate 11 in an amount less than the above content, it may be difficult to achieve the required mechanical strength. On the other hand, if carbon (C) is contained in the steel plate 11 in an amount exceeding the above content, problems such as reduced toughness or brittleness control of the steel plate may occur.

[0072] Silicon (Si) can act as a ferrite stabilizing element in the steel plate 11. The role of silicon (Si) can be to improve ductility by purifying ferrite and to improve carbon enrichment in austenite by suppressing the formation of low-temperature carbides. In addition, silicon (Si) can be a key element for homogenization of hot-rolled, cold-rolled and hot-stamped structures (control of pearlite and manganese segregation zones) and fine dispersion of ferrite. If silicon (Si) is contained in the steel plate 11 in an amount less than the above content, the above effects may not be fully exerted. On the other hand, if silicon (Si) is contained in the steel plate 11 in an amount exceeding the above content, the hot rolling load and the cold rolling load may increase, the hot-rolled red oxide scale may become excessive, and the bonding may decrease.

[0073] Manganese (Mn) may be added to improve hardenability and strength during heat treatment. If manganese (Mn) is included in the steel plate 11 in an amount less than the above-mentioned content, the material quality after hot stamping may be insufficient (for example, the hard phase fraction may be insufficient) due to insufficient hardenability. On the other hand, if manganese (Mn) is included in the steel plate 11 in an amount exceeding the above-mentioned content, ductility and toughness may be reduced due to manganese segregation or pearlite bands, which may lead to a decrease in bending properties and the occurrence of an uneven microstructure.

[0074] Phosphorus (P) is an element that easily segregates and can affect the toughness of steel. If the steel plate 11 contains phosphorus (P) at the above-mentioned content, a decrease in the toughness of the steel can be prevented. On the other hand, if the steel plate 11 contains phosphorus (P) at a content exceeding the above-mentioned content, cracks may occur during processing and iron phosphide compounds may be formed, resulting in a decrease in the toughness of the steel.

[0075] Sulfur (S) may be an element that affects workability and physical properties. If sulfur (S) is contained in the steel plate 11 in an amount exceeding the above, hot workability may be reduced and surface defects such as cracks may occur due to the formation of larger inclusions.

[0076] Boron (B) can be added to ensure the hardenability and strength of the steel material by ensuring a martensitic structure, and can have a grain refinement effect as the austenite grain growth temperature increases. If boron (B) is included in the steel plate 11 in the above-mentioned content, the occurrence of hard phase grain boundary embrittlement can be prevented, and high toughness and bendability can be ensured.

[0077] Titanium (Ti) can be added to enhance hardenability and improve material quality by forming precipitates after hot stamping heat treatment. In addition, titanium (Ti) can effectively promote austenite grain refinement by forming precipitates such as Ti(C,N) at high temperatures.

[0078] Niobium (Nb) may be added to improve strength and toughness by reducing the size of the martensite lath bundles.

[0079] Chromium (Cr) may be added to improve the hardenability and strength of steel. If chromium (Cr) is included in the steel plate 11 in the above-mentioned content, the hardenability and strength of the steel can be improved, an increase in production cost can be prevented, and a decrease in the toughness of the steel material can be prevented.

[0080] Molybdenum (Mo) can contribute to improving strength by suppressing the coarsening of precipitates during hot rolling and hot stamping and improving hardenability. By including molybdenum (Mo) in the steel plate 11 at the above-mentioned content, the effects of suppressing the coarsening of precipitates and improving hardenability during hot rolling and hot stamping can be excellent.

[0081] Nickel (Ni) may be added to ensure hardenability and strength. Furthermore, nickel (Ni) can contribute to improving elongation by controlling austenite transformation as an austenite stabilizing element. If the steel plate 11 contains nickel (Ni) in an amount less than the above-mentioned content, it may be difficult to properly achieve the above-mentioned effects. Furthermore, if the steel plate 11 contains nickel (Ni) in an amount exceeding the above-mentioned content, toughness may decrease, cold workability may deteriorate, and the manufacturing cost of the product may increase.

[0082] In one example, the steel plate 11 may have a microstructure comprising 90% or greater martensite. Specifically, the steel plate 11 may have a microstructure comprising 90% or greater martensite with a remainder of less than 10% for other unavoidable structures and other precipitates. Preferably, the steel plate 11 may be fully martensite. This microstructure ensures ultrahigh strength for the steel plate 11.

[0083] In addition, the steel plate 11 may have a tensile strength (TS) of 1350 MPa or more, for example, 1680 MPa to 2300 MPa, a yield stress (YP) of 900 MPa to 1300 MPa, for example, 1150 MPa to 1300 MPa, and an elongation (EL) of 4% to 15%.

[0084] The coating 12 is a layer to be plated on the surface of the steel sheet 11. It is formed on at least one surface of the steel sheet 11, satisfies the following general formula 1, and contains zinc. In this specification, the term "surface" refers to an outer surface located on one, both, or all sides of the steel sheet. For example, one surface of the steel sheet 11 may be the top surface of the steel sheet 11.

[0085] [General formula 1]

[0086]

[0087] (In the above general formula 1, when the plating layer consists of n layers with different structures, L k is the average thickness (μm) measured along the short axis at 10 random positions in the kth layer of the coating observed in the SEM image, D k is the value obtained by the following electrochemical hydrogen permeation test method (m 2 / s), t is the total heating time during hot stamping (s), and n is an integer greater than or equal to 2.

[0088] <Electrochemical Hydrogen Permeation Experimental Method>

[0089] - The sample formed by the kth layer is placed between two cells, hydrogen is electrogenerated in one cell and allowed to permeate into the other cell.

[0090] -Measure the time it takes for hydrogen to permeate into the other cell.

[0091] - The value calculated by the following general formula 2 using the measurement time and the thickness of the sample is defined as D k .

[0092] [Formula 2]

[0093]

[0094] (In the above general formula 2, L 样品 is the thickness of the specimen (m), t 样品 is the time required to penetrate the specimen (s).

[0095] By satisfying the above general formula 1, the coating 12 can suppress the amount of diffusible hydrogen to less than 0.5 ppm, thereby suppressing hydrogen embrittlement of the hot stamping component and having ultra-high strength. On the other hand, if the coating 12 does not satisfy the above general formula 1, the amount of hydrogen flowing into the steel sheet of the hot stamping component (i.e., the amount of diffusible hydrogen) may increase, resulting in higher hydrogen embrittlement.

[0096] In this specification, the term "kth layer of the coating" refers to the layer corresponding to the kth layer in the thickness direction from the surface of the coating toward the steel sheet. For example, if n = 3, the kth layer of the coating can be the first layer, the second layer, or the third layer. Furthermore, in this specification, the term "minor axis direction" refers to the stacking direction of the steel sheets and coatings based on the hot stamping assembly.

[0097] In another example, the plating layer 12 may satisfy the following general formula 3.

[0098] [Formula 3]

[0099]

[0100] (In the above general formula 3, when the coating is composed of n layers with different structures, L k is the average thickness (μm) measured along the short axis at 10 random positions in the kth layer of the coating observed in the SEM image, D k is the value obtained by the following electrochemical hydrogen permeation test method (m 2 / s), t is the total heating time during hot stamping (s), and n is an integer greater than or equal to 2.

[0101] <Electrochemical Hydrogen Permeation Experimental Method>

[0102] - The sample formed by the kth layer is placed between two cells, hydrogen is electrogenerated in one cell and allowed to permeate into the other cell.

[0103] -Measure the time it takes for hydrogen to permeate into the other cell.

[0104] - The value calculated by the following general formula 2 using the measurement time and the thickness of the sample is defined as D k .

[0105] [Formula 2]

[0106]

[0107] (In the above general formula 2, L 样品 is the thickness of the specimen (m), t 样品 is the time required to penetrate the specimen (s).

[0108] By satisfying the above general formula 3, the coating 12 can suppress the amount of diffusible hydrogen to less than 0.1 ppm, thereby further suppressing hydrogen embrittlement of the hot stamped component and providing ultra-high strength. On the other hand, if the coating 12 exceeds the upper limit of the above general formula 3, the amount of hydrogen flowing into the steel sheet of the hot stamped component may increase, resulting in higher hydrogen embrittlement.

[0109] In another example, the plating layer 12 may satisfy the following general formula 4.

[0110] [Formula 4]

[0111]

[0112] (In the above general formula 4, when the coating is composed of n layers with different structures, L k is the average thickness (μm) measured along the short axis at 10 random positions in the kth layer of the coating observed in the SEM image, D k is the value obtained by the following electrochemical hydrogen permeation test method (m 2 / s), t is the total heating time during hot stamping (s), and n is an integer greater than or equal to 2.

[0113] <Electrochemical Hydrogen Permeation Experimental Method>

[0114] - The sample formed by the kth layer is placed between two cells, hydrogen is electrogenerated in one cell and allowed to permeate into the other cell.

[0115] -Measure the time it takes for hydrogen to permeate into the other cell.

[0116] - The value calculated by the following general formula 2 using the measurement time and the thickness of the sample is defined as D k .

[0117] [Formula 2]

[0118]

[0119] (In the above general formula 2, L 样品 is the thickness of the specimen (m), t 样品 is the time required to penetrate the specimen (s).

[0120] By satisfying the above general formula 4, the coating 12 can further suppress hydrogen embrittlement of the hot stamped component and exhibit ultrahigh strength. On the other hand, if the coating 12 exceeds the upper limit of the above general formula 4, the amount of hydrogen flowing into the steel sheet of the hot stamped component may increase, resulting in higher hydrogen embrittlement. Furthermore, if the coating 12 is less than the lower limit of the above general formula 4, the total heating time may be significantly shortened, or the thickness of the coating 12 may be significantly thinned, resulting in the inability to ensure the target material quality or a decrease in corrosion resistance.

[0121] The coating 12 may be a zinc-based coating as described above containing zinc. For example, the galvanized steel sheet having a zinc-based coating formed on the steel sheet may be at least one or more of a galvanized iron (GI) sheet, an electrogalvanized iron (EGI) sheet, and a galvannealed iron (GA) sheet. Specifically, the coating 12 may contain iron (Fe), aluminum (Al), manganese (Mn), a balance of zinc (Zn), and other unavoidable impurities. More specifically, the coating 12 may contain 10% to 70% by weight of iron (Fe), 0% to 5% by weight of aluminum (Al), 0% to 1% by weight of manganese (Mn), a balance of zinc (Zn), and other unavoidable impurities. Since the coating 12 is formed by the zinc-based coating comprising the above composition, the hot stamping component can have ultra-high strength.

[0122] The thickness of the coating 12 may be 10 μm to 30 μm. By having the above thickness, the coating 12 can protect the surface of the steel plate 11 while preventing or minimizing the decrease in toughness of the hot stamping component 10, and can satisfy the above general formula 1, general formula 3, or general formula 4, and thus can suppress hydrogen embrittlement of the hot stamping component 10 and make the hot stamping component 10 have ultra-high strength. If the thickness of the coating 12 is less than the above lower limit, the effectiveness of the zinc-specific sacrificial method may be reduced, and the hot stamping component 10 may not satisfy the above general formula 1, general formula 3, or general formula 4. In addition, if the thickness of the coating 12 exceeds the above upper limit, the toughness of the hot stamping component 10 including the coating 12 may be reduced.

[0123] In one example, the hot stamped component 10 may be a component manufactured by hot stamping a plated steel sheet (not shown) having a plating layer including zinc formed on at least one surface.

[0124] Specifically, hot stamping may appropriately include a heating step, a forming step, and a cooling step.

[0125] The heating step may be a step of preparing a plated steel sheet having a zinc-containing plating layer formed on at least one surface of the steel sheet 11 and heating the prepared plated steel sheet, and may be performed by a heating furnace having a specific temperature range. For example, the temperature range of the heating furnace may be Ac1 to 950°C, specifically Ac3 to 950°C or 860°C to 920°C.

[0126] In one example, when the plated steel sheet prepared in the heating step is heated, the plated steel sheet may be heated at an average heating rate of 3°C / s to 8°C / s within a temperature range of 600°C to 700°C. Specifically, the plated steel sheet may be heated at an average heating rate of 4°C / s to 7°C / s or 5°C / s to 6°C / s within the above temperature range. By heating the plated steel sheet at the above average heating rate within the above temperature range, the plated steel sheet can satisfy the above general formula 1, general formula 3, or general formula 4, thereby obtaining a hot stamping component with suppressed hydrogen embrittlement and ultra-high strength.

[0127] In another example, when the plated steel sheet prepared in the heating step is heated, the plated steel sheet may be heated at an average heating rate of 0.5°C / s to 3°C / s within a temperature range of 800°C to X°C. In this case, X°C is equal to the maximum temperature at which the plated steel sheet is heated in the heating step minus 10°C. For example, if the maximum temperature at which the plated steel sheet is heated is 860°C to 920°C, X°C may be 850°C to 910°C. By heating the plated steel sheet at the average heating rate within the temperature range, the plated steel sheet may satisfy Formula 1, Formula 3, or Formula 4, thereby obtaining a hot stamping component having suppressed hydrogen embrittlement and ultra-high strength.

[0128] The total heating time during the hot stamping process (i.e., the total heating time of the heating step) can be 150 seconds to 450 seconds. Specifically, the total heating time during the hot stamping process can be 165 seconds to 410 seconds, 180 seconds to 370 seconds, 195 seconds to 330 seconds, 210 seconds to 290 seconds, or 225 seconds to 240 seconds. By heating the plated steel sheet with the above heating time during the hot stamping process, the above-mentioned general formula 1, general formula 3, or general formula 4 can be satisfied, and thus a hot stamped component with suppressed hydrogen embrittlement and ultra-high strength can be obtained.

[0129] The forming step may be a step of forming the plated steel sheet heated in the heating step into a formed body, and may be performed by stamping using a stamping die. For example, in the forming step, the forming start temperature may be 500°C to 700°C. If the forming start temperature in the forming step satisfies the above range, the formability of the plated steel sheet can be improved, the manufactured hot stamping component 10 can have the target structure and physical properties, and wrinkles or bends on the surface of the manufactured hot stamping component 10 can be prevented or minimized. On the other hand, if the forming start temperature in the forming step is lower than the above range, the formability of the plated steel sheet may be reduced, and the manufactured hot stamping component 10 may not have the target structure and physical properties. In addition, if the forming start temperature in the forming step exceeds the above range, wrinkles or bends may appear on the surface of the manufactured hot stamping component 10, and the coating 12 may adhere to the die.

[0130] The cooling step is a step of cooling the formed body formed in the forming step. The cooling step can be performed in a press die used to press the plated steel sheet.

[0131] Specifically, the formed body can be cooled while being formed into the final component shape in the stamping die, thereby forming the final product. The die can be provided with cooling channels through which a refrigerant circulates. The circulation of the refrigerant supplied through the cooling channels within the die allows for rapid cooling of the formed body. To prevent springback of the sheet and maintain the desired shape, rapid cooling can be performed while the die is closed for pressing. During the forming and cooling operations of the formed body, the average cooling rate can be maintained at 10°C or higher, down to the martensitic transformation end temperature Mf. If the cooling end temperature during the cooling step falls within the above-mentioned range, the productivity of the manufacturing process can be improved, and the occurrence of warping in the manufactured hot stamped component 10 can be prevented or minimized. On the other hand, the cooling end temperature at the end of the cooling step can be between 25°C and 200°C. If the cooling end temperature during the cooling step falls below the above-mentioned range, the productivity of the manufacturing process may be reduced. Furthermore, if the cooling end temperature during the cooling step exceeds the above-mentioned range, the hot stamped component 10 may warp, and ensuring the target material quality may be difficult.

[0132] The present invention also relates to a method for manufacturing a hot stamping component. The method for manufacturing a hot stamping component relates to the method for manufacturing the hot stamping component described above, and since the contents described in the hot stamping component can be applied in a similar manner, the specific details of the hot stamping component described below will be omitted.

[0133] The present invention relates to a method for manufacturing a hot stamping component, wherein the hot stamping component includes a steel plate and a coating formed on at least one surface of the steel plate, wherein the coating satisfies the following general formula 1 and contains zinc. The method includes a heating step, a forming step, and a cooling step.

[0134] [General formula 1]

[0135]

[0136] (In the above general formula 1, when the plating layer consists of n layers with different structures, L k is the average thickness (μm) measured along the short axis at 10 random positions in the kth layer of the coating observed in the SEM image, D k is the value obtained by the following electrochemical hydrogen permeation test method (m 2 / s), t is the total heating time during hot stamping (s), and n is an integer greater than or equal to 2.

[0137] <Electrochemical Hydrogen Permeation Experimental Method>

[0138] - The sample formed by the kth layer is placed between two cells, hydrogen is electrogenerated in one cell and allowed to permeate into the other cell.

[0139] -Measure the time it takes for hydrogen to permeate into the other cell.

[0140] - The value calculated by the following general formula 2 using the measurement time and the thickness of the sample is defined as D k .

[0141] [Formula 2]

[0142]

[0143] (In the above general formula 2, L 样品 is the thickness of the specimen (m), t 样品 is the time required to penetrate the specimen (s).

[0144] The hot stamping component manufactured by the method of manufacturing the hot stamping component can suppress hydrogen embrittlement and have ultrahigh strength by satisfying the above general formula 1.

[0145] The overall plating layer formed on the plated steel sheet prepared in the heating step may contain 10 to 70 wt % of iron (Fe) and the balance of zinc (Zn) and other inevitable impurities.

[0146] The thickness of the coating formed on the plated steel sheet prepared in the heating step may be 5 μm to 20 μm, specifically 8 μm to 18 μm or 10 μm to 15 μm. By having the above thickness, the coating formed on the plated steel sheet prepared in the heating step can protect the surface of the steel sheet while preventing or minimizing the decrease in toughness of the hot stamping component manufactured according to the above manufacturing method. If the thickness of the coating formed on the plated steel sheet prepared in the heating step is less than the above range, the effectiveness of the zinc specific sacrificial method may be reduced. In addition, if the thickness of the coating formed on the plated steel sheet prepared in the heating step exceeds the above range, the toughness of the hot stamping component manufactured according to the above manufacturing method and including the coating may be reduced.

[0147] In one example, after alloying by including the above-mentioned composition, the plating layer formed on the plated steel sheet prepared in the heating step may include a ζ layer, a δ layer, and a γ layer.

[0148] Since the plated steel sheet prepared in the heating step includes the above-mentioned layers, the hot stamping component manufactured by the method for manufacturing a hot stamping component can satisfy the above-mentioned general formula 1, general formula 3, or general formula 4, and thus can suppress hydrogen embrittlement and have ultra-high strength. The stacking order of the ζ layer, δ layer, and γ layer in the coating formed on the plated steel sheet prepared in the heating step is not particularly limited. For example, the coating formed on the plated steel sheet prepared in the heating step can include a ζ layer, a δ layer, and a γ layer in this order along the thickness direction from the surface toward the steel sheet.

[0149] The ζ layer is a layer showing a ζ phase, and may contain 3 to 8 wt % of iron (Fe) and the balance of zinc (Zn) and other inevitable impurities.

[0150] The thickness of the ζ layer may be greater than 0 μm to 4 μm, specifically greater than 0 μm to 3 μm or greater than 0 μm to 2 μm. Due to the aforementioned thickness of the ζ layer, it may be more advantageous for the hot stamping component to satisfy Formula 1, Formula 3, or Formula 4.

[0151] The δ layer is a layer showing a δ phase, and may contain 8 to 12 wt % of iron (Fe) and the balance of zinc (Zn) and other inevitable impurities.

[0152] The thickness of the δ layer may be greater than 3 μm to 10 μm, specifically greater than 6 μm to 10 μm or greater than 8 μm to 9 μm. Due to the aforementioned thickness of the δ layer, it may be more advantageous for the hot stamping component to satisfy Formula 1, Formula 3, or Formula 4.

[0153] The γ layer is a layer showing a γ phase, and may contain 19 to 32 wt % of iron (Fe) and the balance of zinc (Zn) and other inevitable impurities.

[0154] The thickness of the γ layer may be 1 μm to 6 μm, specifically 1 μm to 5 μm or 1 μm to 4 μm. Since the γ layer has the aforementioned thickness, it may be more advantageous for the hot stamping component to satisfy the aforementioned Formula 1, Formula 3, or Formula 4.

[0155] In one example, a method for manufacturing a plated steel sheet having a coating layer comprising a layer composed of the above-described structure on a steel sheet can be used to manufacture a galvanized steel sheet having a coating layer formed on the steel sheet comprising the above-described structure by immersing the steel sheet in a coating bath, and the galvanized steel sheet can be alloyed to manufacture a galvannealed steel sheet. In this case, the coating bath can contain the following components: less than 0.3% by weight of aluminum, less than 0.1% by weight of iron, the remainder of zinc, and other unavoidable impurities. The coating layer can be attached to both sides of the steel sheet, with a thickness of 10 μm to 15 μm. In addition, the difference between the temperature of the steel sheet before alloying and the alloying temperature can be 80°C or greater. Since the difference between the temperature of the steel sheet before alloying and the alloying temperature satisfies the above-described range, the ζ layer, δ layer, and γ layer can be ensured in the coating layer formed on the steel sheet, the thickness of the coating layer can be satisfied, and thus, General Formula 1, General Formula 3, or General Formula 4 can be satisfied, thereby achieving a hot stamped component with suppressed hydrogen embrittlement and ultra-high strength.

[0156] In one example, when the plated steel sheet prepared in the heating step is heated, the steel sheet may be heated at an average heating rate of 3°C / s to 8°C / s within a temperature range of 600°C to 700°C. A detailed description of the average heating rate of the steel sheet within the temperature range when the plated steel sheet prepared in the heating step is heated is the same as that described above for hot stamping and will therefore be omitted.

[0157] Furthermore, when the plated steel sheet prepared in the heating step is heated, the plated steel sheet may be heated at an average heating rate of 0.5° C. / s to 3° C. / s within a temperature range of 800° C. to 900° C. When the plated steel sheet prepared in the heating step is heated, a detailed description of the average heating rate of the plated steel sheet within the above temperature range is the same as that described above in the hot stamping process and will therefore be omitted.

[0158] Hereinafter, the present invention will be described in more detail through various Examples and Comparative Examples, but the scope of the present invention is not limited to the Examples presented below.

[0159] Example 1

[0160] Manufacturing of hot stamped components

[0161] A galvannealed steel sheet was prepared by immersing a steel sheet (having a sheet thickness of 1.2 mm and composed of 0.29% by weight of carbon, 0.2% by weight of silicon, 1.5% by weight of manganese, 0.02% by weight or less of phosphorus, 0.015% by weight or less of sulfur, 0.2% by weight of chromium, 0.0025% by weight of boron, 0.035% by weight of titanium, and the balance of iron and other inevitable impurities) in a plating bath. A plating layer consisting of a ζ layer, a δ layer, and a γ layer was formed on the upper and lower surfaces of the steel sheet along the thickness direction from the surface to the steel sheet. The galvannealing was performed by adjusting the coating adhesion using an air knife after immersing the steel sheet in the plating bath, followed by alloying, so that the average thickness of the plating layer was 12 μm. Specifically, the plating bath composition contained 0.13% by weight of aluminum, 0.06% by weight of iron, and the balance of zinc and other inevitable impurities, and the temperature of the plating bath was set to 450°C. Furthermore, the steel sheet was passed through a plating bath at a speed of 120 mpm, causing molten zinc to adhere to the upper and lower surfaces of the steel sheet. The sheet was then placed in a 530°C galvanizing annealing furnace, where the iron atoms constituting the steel sheet diffused into the coating layer, thereby alloying the steel sheet with the molten zinc to produce a galvanized annealed steel sheet. The position of the galvanizing annealing furnace was adjusted so that the temperature of the steel sheet immediately before placement in the galvanizing annealing furnace was 420°C, and the temperature difference between the steel sheet and the galvanizing annealing furnace was set to 80°C or greater. The duration of the alloying temperature (i.e., the alloying time) was set to 30 seconds.

[0162] The produced plated steel sheets were then prepared and heated for 450 seconds in a heating furnace at a maximum temperature of 900°C. A multi-stage temperature-increasing type heating furnace was used as the heating furnace. The multi-stage temperature-increasing type heating furnace was configured to include multiple heating zones, wherein the temperature gradually increased from the inlet side, where the plated steel sheets were charged, toward the outlet side, where the heated plated steel sheets were removed. The temperature in each heating zone of the heating furnace was controlled so that the plated steel sheets were heated at an average temperature-increasing rate of 7.20°C / s within the temperature range from 600°C to 700°C, and at an average temperature-increasing rate of 2.22°C / s within the temperature range from 800°C to 890°C.

[0163] The heated plated steel sheet was then stamped using a press to form a formed body while rapidly cooling it to 300°C or lower at an average cooling rate of 10°C / s, thereby producing a hot stamped component. The physical properties of the produced hot stamped component are shown in Table 1 below.

[0164] Example 2

[0165] Manufacturing of hot stamped components

[0166] A hot stamped component was manufactured in the same manner as in Example 1, except that the average heating rate in the temperature range from 600°C to 700°C was 5.20°C / s, and the average heating rate in the temperature range from 800°C to 890°C was 1.21°C / s. The physical properties of the manufactured hot stamped component are shown in Table 1 below.

[0167] Example 3

[0168] Manufacturing of hot stamped components

[0169] A hot stamped component was manufactured in the same manner as in Example 1, except that the average heating rate in the temperature range from 600°C to 700°C was 4.10°C / s, and the average heating rate in the temperature range from 800°C to 890°C was 0.86°C / s. The physical properties of the manufactured hot stamped component are shown in Table 1 below.

[0170] Example 4

[0171] Manufacturing of hot stamped components

[0172] A hot stamped component was manufactured in the same manner as in Example 1, except that the average heating rate in the temperature range from 600°C to 700°C was 3.00°C / s, and the average heating rate in the temperature range from 800°C to 890°C was 0.53°C / s. The physical properties of the manufactured hot stamped component are shown in Table 1 below.

[0173] Comparative Example 1

[0174] Manufacturing of hot stamped components

[0175] A hot stamped component was manufactured in the same manner as in Example 1, except that the average heating rate in the temperature range from 600°C to 700°C was 3.50°C / s, and the average heating rate in the temperature range from 800°C to 890°C was 0.30°C / s. The physical properties of the manufactured hot stamped component are shown in Table 1 below.

[0176] Comparative Example 2

[0177] Manufacturing of hot stamped components

[0178] A hot stamped component was manufactured in the same manner as in Example 1, except that the average heating rate in the temperature range from 600°C to 700°C was 2.91°C / s, and the average heating rate in the temperature range from 800°C to 890°C was 0.52°C / s. The physical properties of the manufactured hot stamped component are shown in Table 1 below.

[0179] Comparative Example 3

[0180] Manufacturing of hot stamped components

[0181] A hot stamped component was manufactured in the same manner as in Example 1, except that the average heating rate in the temperature range from 600°C to 700°C was 2.98°C / s, and the average heating rate in the temperature range from 800°C to 890°C was 0.45°C / s. The physical properties of the manufactured hot stamped component are shown in Table 1 below.

[0182] Evaluation Example 1. Analysis and evaluation of the shape of the coating

[0183] The coating layers of the hot stamping components manufactured in the examples and comparative examples were photographed using a scanning electron microscope (SEM), and the results are shown in Table 1. Specifically, Figure 2 Shown is an image obtained by photographing, using a scanning electron microscope, the plating layer of the hot stamped component manufactured in Example 2. In this case, structures formed in the plating layer are marked in order from the surface toward the thickness direction of the steel sheet.

[0184] Evaluation Example 2. Evaluation of electrochemical hydrogen permeation experiment

[0185] The structure of each layer (n layers) formed in the plating of the hot stamping components manufactured in the examples and comparative examples was identified, and each sample consisting of each structure was manufactured. Each manufactured sample was placed between two cells, hydrogen was electrically generated in one cell, and the hydrogen was allowed to permeate into the other cell. Then, the time required for hydrogen to permeate into the other cell was measured. The measured time and the thickness of the sample were used to obtain D calculated by the following general formula 2 k value.

[0186] The D of the samples of Examples and Comparative Examples was calculated by the following formula 2: k The values ​​are 8×10 -14 m 2 / s to 8×10 -11 m 2 / s.

[0187] [Formula 2]

[0188]

[0189] (In the above general formula 2, L 样品 is the thickness of the sample (m), t 样品 is the time required to penetrate the sample (s).

[0190] Evaluation Example 3. Evaluation of whether the general formula 3 is satisfied

[0191] By using the results of Evaluation Examples 1 and 2 described above, it was evaluated whether the hot stamped components produced in Examples and Comparative Examples satisfied the following General Formula 3, and the results are shown in Table 1 below.

[0192] [Formula 3]

[0193]

[0194] (In the above general formula 3, when the coating is composed of n layers with different structures, L k is the average thickness (μm) measured along the short axis at 10 random positions in the kth layer of the coating observed in the SEM image, D k is the value obtained by the following electrochemical hydrogen permeation test method (m 2 / s), t is the total heating time during hot stamping (s), and n is an integer greater than or equal to 2.

[0195] [Table 1]

[0196]

[0197]

[0198] As shown in Table 1 above, it was confirmed that the hot stamping components manufactured in Examples 1 to 4 all satisfied General Formula 3. In contrast, it was confirmed that the hot stamping components manufactured in Comparative Examples 1 to 3 all did not satisfy General Formula 3.

[0199] Evaluation Example 4. Hydrogen Embrittlement Evaluation

[0200] The amount of diffusible hydrogen in the hot stamped components manufactured in each Example and Comparative Example was measured using thermal desorption spectroscopy. Specifically, the amount of hydrogen released from the hot stamped components manufactured in each Example and Comparative Example was measured at a temperature of 350°C or less while increasing the temperature of the hot stamped components manufactured in each Example and Comparative Example from room temperature (±20°C) to 500°C at a heating rate of 20°C. The results are shown in Table 2 below.

[0201] [Table 2]

[0202] Amount of diffusible hydrogen (ppm) Example 1 0.025 Example 2 0.034 Example 3 0.059 Example 4 0.058 Comparative Example 1 0.423 Comparative Example 2 0.412 Comparative Example 3 0.497

[0203] As shown in Table 2 above, it was confirmed that the amount of diffusible hydrogen of the hot stamping components manufactured in Examples 1 to 4 was less than 0.1 ppm, which was significantly lower than that of the hot stamping components manufactured in Comparative Examples 1 to 3, and thus hydrogen embrittlement could be suppressed.

[0204] Evaluation Example 5. Fracture Test Evaluation

[0205] The fracture experiments of the hot stamping components manufactured in Example 2 and Comparative Examples 1 and 2 were evaluated using a four-point bending test. Specifically, in the four-point bending test, a stress level below the elastic limit (specifically, 1000 MPa in air) was applied to a specific point of each manufactured specimen for 100 hours, while the hot stamping components manufactured in each Example and Comparative Example were exposed to a corrosive environment, and the occurrence of stress corrosion cracking (i.e., the occurrence of fracture) was examined. The results are shown in FIG. Figures 3 to 5 In this context, stress corrosion cracking refers to cracks that occur when both corrosion and sustained tensile stresses are applied simultaneously.

[0206] like Figure 3 As shown in , it was confirmed that the hot stamping components manufactured in Example 2 did not break. On the contrary, it was confirmed that Figure 4 and Figure 5 As shown in , the hot stamped components manufactured in Comparative Examples 1 and 2 fractured. In other words, it was confirmed that the hot stamped component manufactured in Example 2 had hydrogen embrittlement suppressed by satisfying the above general formula 3, compared with the hot stamped components manufactured in Comparative Examples 1 and 2 that did not satisfy the above general formula 3.

[0207] <Description of Reference Numerals>

[0208] 1: α iron layer

[0209] 2: Gamma layer

[0210] 10: Hot stamping components

[0211] 11: Steel Plate

[0212] 12: Plating

Claims

1. A hot stamping component, comprising: Steel plates; and A coating layer formed on at least one surface of the steel sheet satisfies the following general formula 1 and contains zinc: [General formula 1] (In general formula 1, when the coating consists of n layers with different structures, L k is the average thickness (μm) measured along the short axis at 10 random positions in the kth layer of the coating observed in the SEM image, D k is the value obtained by the following electrochemical hydrogen permeation test method (m 2 / s), t is the total heating time during hot stamping (s), n is an integer greater than or equal to 2), <Electrochemical Hydrogen Permeation Experimental Method> - placing a sample formed of the kth layer between two cells, electrogenerating hydrogen in one cell and allowing it to permeate into the other cell, - measure the time it takes for hydrogen to permeate into the other cell, and - The value calculated by the following general formula 2 using the measurement time and the thickness of the sample is defined as D k : [Formula 2] (In general formula 2, L 样品 is the thickness of the sample (m), t 样品 is the time required to penetrate the sample (s).

2. The hot stamping component according to claim 1, wherein The coating satisfies the following general formula 3: [Formula 3] (In general formula 3, when the coating consists of n layers with different structures, L k is the average thickness (μm) measured along the short axis at 10 random positions in the kth layer of the coating observed in the SEM image, D k is the value obtained by the following electrochemical hydrogen permeation test method (m 2 / s), t is the total heating time during hot stamping (s), n is an integer greater than or equal to 2), <Electrochemical Hydrogen Permeation Experimental Method> - placing a sample formed of the kth layer between two cells, electrogenerating hydrogen in one cell and allowing it to permeate into the other cell, - measure the time it takes for hydrogen to permeate into the other cell, and - The value calculated by the following general formula 2 using the measurement time and the thickness of the sample is defined as D k : [Formula 2] (In general formula 2, L 样品 is the thickness of the sample (m), t 样品 is the time required to penetrate the sample (s).

3. The hot stamping component according to claim 1, wherein The coating satisfies the following general formula 4: [Formula 4] (In general formula 4, when the coating consists of n layers with different structures, L k is the average thickness (μm) measured along the short axis at 10 random positions in the kth layer of the coating observed in the SEM image, D k is the value obtained by the following electrochemical hydrogen permeation test method (m 2 / s), t is the total heating time during hot stamping (s), n is an integer greater than or equal to 2), <Electrochemical Hydrogen Permeation Experimental Method> - placing a sample formed of the kth layer between two cells, electrogenerating hydrogen in one cell and allowing it to permeate into the other cell, - measure the time it takes for hydrogen to permeate into the other cell, and - The value calculated by the following general formula 2 using the measurement time and the thickness of the sample is defined as D k : [Formula 2] (In general formula 2, L 样品 is the thickness of the sample (m), t 样品 is the time required to penetrate the sample (s).

4. The hot stamping component according to claim 1, wherein The hot stamped component is a component manufactured by hot stamping a plated steel sheet having a plating layer containing zinc formed on at least one surface of the steel sheet.

5. The hot stamping component according to claim 4, wherein The hot stamping comprises: a heating step of preparing a plated steel sheet having a plating layer containing zinc formed on at least one surface of the steel sheet and heating the prepared plated steel sheet; a forming step of punching the heated plated steel sheet using a punching die to form a formed body; and A cooling step of cooling the molded body.

6. The hot stamping component according to claim 5, wherein When heating the plated steel sheet prepared in the heating step, the plated steel sheet is heated at an average heating rate of 3° C. / s to 8° C. / s within a temperature range of 600° C. to 700° C.

7. The hot stamping assembly according to claim 5, wherein: When heating the plated steel sheet prepared in the heating step, the plated steel sheet is heated at an average heating rate of 0.5°C / s to 3°C / s within a temperature range of 800°C to X°C, and X°C is equal to the maximum temperature at which the plated steel sheet is heated in the heating step minus 10°C.

8. The hot stamping assembly according to claim 4, wherein The total heating time during the hot stamping process ranges from 150 seconds to 450 seconds.

9. The hot stamping assembly according to claim 1, wherein: The thickness of the coating is 10 μm to 30 μm.

10. A method for manufacturing a hot stamping component, the hot stamping component comprising a steel plate and a coating formed on at least one surface of the steel plate, the coating satisfying the following general formula 1 and containing zinc, the method comprising: a heating step of preparing a plated steel sheet having a plating layer containing zinc formed on at least one surface of the steel sheet and heating the prepared plated steel sheet; a forming step of punching the heated plated steel sheet using a punching die to form a formed body; and A cooling step of cooling the molded body: [General formula 1] (In general formula 1, when the coating consists of n layers with different structures, L k is the average thickness (μm) measured along the short axis at 10 random positions in the kth layer of the coating observed in the SEM image, D k is the value obtained by the following electrochemical hydrogen permeation test method (m 2 / s), t is the total heating time during hot stamping (s), n is an integer greater than or equal to 2), <Electrochemical Hydrogen Permeation Experimental Method> - placing a sample formed of the kth layer between two cells, electrogenerating hydrogen in one cell and allowing it to permeate into the other cell, - measure the time it takes for hydrogen to permeate into the other cell, and - The value calculated by the following general formula 2 using the measurement time and the thickness of the sample is defined as D k : [Formula 2] (In general formula 2, L 样品 is the thickness of the sample (m), t 样品 is the time required to penetrate the sample (s).

11. The method according to claim 10, wherein: When heating the plated steel sheet prepared in the heating step, the plated steel sheet is heated at an average heating rate of 3° C. / s to 8° C. / s within a temperature range of 600° C. to 700° C.

12. The method according to claim 10, wherein: When heating the plated steel sheet prepared in the heating step, the plated steel sheet is heated at an average heating rate of 0.5°C / s to 3°C / s within a temperature range of 800°C to X°C, and X°C is equal to the maximum temperature at which the plated steel sheet is heated in the heating step minus 10°C.

13. The method according to claim 10, wherein: The plated layer formed on the plated steel sheet prepared in the heating step includes a ζ layer, a δ layer, and a γ layer.

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