Hot stamping parts and method for manufacturing the same

Abstract

The present invention includes the steps of cutting a plated steel sheet having a plating layer formed on at least one surface of a base material to form a blank, and heating the blank in a heating furnace having a plurality of sections with different temperature ranges. The step of heating the blank includes a multi-stage heating step of heating the blank step by step, and a soaking heating step of heating the multi-stage heated blank at a temperature of Ac3 to 910 °C. The temperature (a n ) of the soaking heating step and the total heating time (b n ) of the step of heating the blank satisfy the following relational expression, and a method for manufacturing a hot stamping part is provided. (Relational expression) 62 ≦ 91.81 + K - 0.022 × a n - 0.23 × b n (In the above relational expression, K is a material correction coefficient).

Description

Technical Field

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

Background Art

[0002] Worldwide, environmental regulations and fuel consumption regulations are being strengthened, and the need for lighter vehicle materials is increasing. As a result, research and development on ultra-high strength steel and hot stamping steel are being actively carried out.

[0003] The hot stamping process generally utilizes the phase transformation of the material and the change in the microstructure in a process consisting of heating / formning / cooling / trimming. In order to improve the toughness of hot stamping steel, research is being actively carried out by generally using alloy components to improve the toughness of the base material.

[0004] However, if the alloy components are changed or increased, there is a problem that the economic efficiency such as cost increase is reduced.

[0005] Related technologies include Republic of Korea Patent Publication No. 10-2021-0129902 (title of the invention: Hot Stamping Parts and a Method for Manufacturing the Same).

Summary of the Invention

Problems to be Solved by the Invention

[0006] Embodiments of the present invention can improve the bending characteristics of the manufactured hot stamping parts by satisfying a preset relational expression for the temperature in the soaking heating stage and the total heating time in the heating stage.

Means for Solving the Problems

[0007] One embodiment of the present invention includes cutting a plated steel sheet having a plating layer formed on at least one surface of a base material to form a blank, and heating the blank in a heating furnace having a plurality of sections with different temperature ranges. The step of heating the blank includes a multi-step heating step of heating the blank step by step, and a soaking heating step of heating the multi-step heated blank at a temperature of Ac3 to 910 ° C. The temperature (a n ), and the total heating time (b n ) of the step of heating the blank satisfy the following relational expression, and a method for manufacturing a hot stamping part is provided. (Relational expression) 62 ≦ 91.81 + K - 0.022 × a n -0.23 × b n (In the above relational expression, K is a material correction coefficient).

[0008] In this embodiment, the total heating time (b n ) of the step of heating the blank may be 2 minutes (min) to 20 minutes (min).

[0009] In this embodiment, the material correction coefficient (K) is 0.71 × c n -0.025 × d n where c n in the material correction coefficient (K) is the dew point temperature of the annealing furnace of the base material, and d n is also the line speed of the annealing furnace of the base material.

[0010] In this embodiment, the dew point temperature (c n ) of the annealing furnace of the base material may be -15 ° C to +15 ° C.

[0011] In this embodiment, the line speed (d n ) of the annealing furnace of the base material may be 30 mpm to 200 mpm.

[0012] In this embodiment, the annealing temperature of the base material may be 750 ° C to 900 ° C.

[0013] In this embodiment, annealing of the base material can be performed in an atmosphere composed of 0.5% to 25% by volume of hydrogen and the balance of nitrogen.

[0014] In this embodiment, it also further includes a decarburized layer formed on the base material.

[0015] In this embodiment, the thickness of the decarburized layer may be 10 μm to 100 μm.

[0016] In this embodiment, the average hardness of the decarburized layer is also 80% or less in comparison with the average hardness at a point 1 / 4 from the surface of the base material.

[0017] In this embodiment, the plating layer is also a zinc (Zn)-based plating layer or an aluminum (Al)-based plating layer.

[0018] In this embodiment, the thickness of the plating layer may be 5 μm to 30 μm.

[0019] In this embodiment, after the step of heating the blank, it further includes a step of transferring the heated blank, a step of pressing the transferred blank with a mold to form a molded body, and a step of cooling the formed molded body.

[0020] Another embodiment of the present invention is a hot stamping part, the hot stamping part includes a base material, a decarburized layer disposed on the base material, and a plating layer disposed on the decarburized layer, and the hot stamping part provides a hot stamping part having a tensile strength (TS) of 1,680 MPa to 2,000 MPa, a yield stress (YP) of 1,150 MPa to 1,500 MPa, and an elongation (EL) of 4% to 10%.

[0021] In this embodiment, the average hardness of the decarburized layer is also 70% or less in comparison with the average hardness at a point 1 / 4 from the surface of the base material.

[0022] In this embodiment, the carbon content included in the plating layer is also 50% or less of the carbon content included in the base material.

[0023] In this embodiment, the hot stamping part may have a microstructure containing 90% or more of the martensite fraction.

[0024] In this embodiment, the thickness of the decarburized layer may be 10 μm to 100 μm.

[0025] In this embodiment, the thickness of the plating layer may be 7 μm to 40 μm.

[0026] Other aspects, features, and advantages other than those described above will become apparent from the specific content, claims, and drawings for carrying out the following invention.

Effects of the Invention

[0027] According to one embodiment of the present invention made as described above, by satisfying the temperature in the soaking heating stage and the total heating time in the stage of heating the blank with a preset relational expression, the toughness of the manufactured hot stamping part can be improved.

[0028] Also, according to one embodiment of the present invention, by raising the dew point temperature of the annealing furnace so that a decarburized layer is formed on the surface of the base material, the toughness of the manufactured hot stamping part can be improved.

Brief Description of the Drawings

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MODE FOR CARRYING OUT THE INVENTION

[0030] The present invention can be subjected to various transformations and can have various embodiments. Specific embodiments are illustrated in the drawings and will be described in detail by a detailed description. The effects, features, and methods for achieving them of the present invention will become clear by referring to the embodiments described in detail later together with the drawings. However, the present invention is not limited to the embodiments disclosed below and can be embodied in various forms.

[0031] In the following embodiments, terms such as first and second are not used in a limiting sense and are used for the purpose of distinguishing one component from other components.

[0032] In the following embodiments, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0033] In the following embodiments, terms such as "comprising" or "having" mean that the features or components described in the specification are present, and do not preclude in advance the possibility of adding one or more other features or components.

[0034] In the following embodiments, when a part such as a film, region, or component is said to be on or above another part, it includes not only the case where it is directly above the other part, but also the case where still other films, regions, components, etc. are interposed in between.

[0035] In the drawings, for the sake of convenience of explanation, the sizes of components may be exaggerated or reduced. For example, since the sizes and thicknesses of each configuration shown in the drawings are arbitrarily shown for the convenience of explanation, the present invention is not necessarily limited to what is shown in the drawings.

[0036] In this specification, "A and / or B" indicates the case where it is A, B, or both A and B. Also, in this specification, "at least one of A and B" indicates the case where it is A, B, or both A and B.

[0037] In the following embodiments, the meaning of "extended in the first direction or the second direction" for a wiring includes not only being extended linearly, but also being extended in a zigzag or curved manner along the first direction or the second direction.

[0038] In the following embodiments, when it is "on a plane", it means when the target part is viewed from above, and when it is "in a cross-section", it means when the cross-section obtained by vertically cutting the target part is viewed from the side. In the following embodiments, when it is "superimposed", it includes "superimposition on a plane" and "superimposition in a cross-section".

[0039] Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described in detail. When describing with reference to the drawings, the same or corresponding components are given the same drawing reference numerals.

[0040] FIG. 1 is a cross-sectional view schematically showing a hot stamping part according to an embodiment of the present invention.

[0041] Referring to FIG. 1, a hot stamping part 1 according to an embodiment also includes a base material 100, a decarburized layer 200, and a plating layer 300. The base material 100, the decarburized layer 200, and the plating layer 300 can be sequentially laminated in the thickness direction of the hot stamping part 1.

[0042] In one embodiment, the base material 100 also contains carbon (C), silicon (Si), manganese (Mn), phosphorus (P), sulfur (S), boron (B), the balance iron (Fe), and other inevitable impurities. For example, the base material 100 contains about 0.25 wt% or more and about 0.5 wt% or less of carbon (C), about 0.1 wt% or more and about 0.8 wt% or less of silicon (Si), about 0.3 wt% or more and about 3.0 wt% or less of manganese (Mn), more than 0 and about 0.05 wt% or less of phosphorus (P), more than 0 and about 0.01 wt% or less of sulfur (S), about 0.0005 wt% or more and about 0.005 wt% or less of boron (B), the balance iron (Fe), and other inevitable impurities.

[0043] In addition, the base material 100 also further contains one or more components among titanium (Ti), niobium (Nb), and vanadium (V). Further, the base material 100 also further contains chromium (Cr), molybdenum (Mo), and nickel (Ni).

[0044] The base material 100 also further contains one or more components among titanium (Ti), niobium (Nb), and vanadium (V), and the total of one or more components among titanium (Ti), niobium (Nb), and vanadium (V) contained in the base material 100 is also about 0.01 wt% or more and about 0.1 wt% or less. For example, the base material 100 contains titanium (Ti) and niobium (Nb), and the total weight % of titanium (Ti) and niobium (Nb) contained in the base material 100 is also about 0.01 wt% or more and about 0.1 wt% or less.

[0045] Further, the base material 100 may further contain about 0.01% by weight or more and about 1.0% by weight or less of chromium (Cr), about 0.01% by weight or more and about 1.0% by weight or less of molybdenum (Mo), and about 0.001% by weight or more and about 1.0% by weight or less of nickel (Ni).

[0046] Carbon (C) is a major element that determines the strength and hardness of steel and can be added for the purpose of ensuring the tensile strength of the steel material after the hot stamping (or hot pressing) process. Also, carbon (C) can be added for the purpose of ensuring the hardenability characteristics of the steel material. In one embodiment, carbon (C) may be contained in an amount of about 0.25% by weight or more and about 0.5% by weight or less based on the total weight of the base material 100. If carbon (C) is contained in an amount of less than about 0.25% by weight based on the total weight of the base material 100, it is difficult to achieve the desired mechanical strength. On the other hand, if carbon (C) is contained in an amount exceeding about 0.5% by weight based on the total weight of the base material 100, problems such as a decrease in the toughness of the steel material or problems in controlling the brittleness of the steel may be caused.

[0047] Silicon (Si) can act as a ferrite stabilizing element within the base material 100. Silicon (Si) can perform the function of improving ductility by cleaning the ferrite and improving the carbon concentration in austenite by suppressing carbide formation in the low-temperature range. Furthermore, silicon (Si) is also a core element for hot rolling, cold rolling, hot stamping microstructure homogenization (pearlite, manganese segregation band control), and fine dispersion of ferrite. In one embodiment, silicon (Si) may be contained in an amount of about 0.1% by weight or more and about 0.8% by weight or less based on the total weight of the base material 100. If silicon (Si) is contained in an amount of less than about 0.1% by weight based on the total weight of the base material 100, the above-described functions cannot be fully exerted. On the other hand, if silicon (Si) is contained in an amount exceeding about 0.8% by weight based on the total weight of the base material 100, the hot rolling load and the cold rolling load increase, excessive hot rolling red scale occurs, and the joinability may be reduced.

[0048] Manganese (Mn) can be added for the purpose of hardenability and strength increase during heat treatment. In one embodiment, manganese (Mn) can be contained in an amount of about 0.3 wt% or more and about 3.0 wt% or less based on the total weight of the base material 100. If manganese (Mn) is contained in an amount of less than about 0.3 wt% based on the total weight of the base material 100, the material may become insufficient (insufficient hard phase fraction) after hot stamping due to insufficient hardenability. On the other hand, if manganese (Mn) is contained in an amount exceeding about 3.0 wt% based on the total weight of the base material 100, the ductility and toughness are reduced due to manganese segregation or pearlite banding, which may cause a decrease in bending performance and a non-uniform fine microstructure may occur.

[0049] Phosphorus (P) is an element that segregates and also an element that inhibits the toughness of steel. In one embodiment, phosphorus (P) can be contained in an amount exceeding 0 and about 0.05 wt% or less based on the total weight of the base material 100. When phosphorus (P) is contained within the above-mentioned range based on the total weight of the base material 100, a decrease in the toughness of the steel can be prevented. On the other hand, if phosphorus (P) is contained in an amount exceeding 0.05 wt% based on the total weight of the base material 100, cracks may occur during the process, iron phosphide compounds are formed, and the toughness of the steel may be reduced.

[0050] Sulfur (S) is also an element that inhibits workability and physical properties. In one embodiment, sulfur (S) can be contained in an amount exceeding 0 and about 0.01 wt% or less based on the total weight of the base material 100. If sulfur (S) is contained in an amount exceeding about 0.01 wt% based on the total weight of the base material 100, the hot workability is reduced, and surface defects such as cracks may occur due to the formation of large inclusions.

[0051] Boron (B) is added for the purpose of ensuring the hardenability and strength of the steel material by ensuring a martensite structure, and may have a grain refinement effect due to an increase in the austenite grain growth temperature. In one embodiment, boron (B) can be contained in an amount of about 0.0005 wt% or more and about 0.005 wt% or less based on the total weight of the base material 100. When boron (B) is contained within the above-mentioned range based on the total weight of the base material 100, the occurrence of hard phase grain boundary brittleness can be prevented, and high toughness and bendability can be ensured.

[0052] Titanium (Ti) can be added for the purpose of hardenability enhancement and material improvement by precipitate formation after hot stamping heat treatment. Also, titanium (Ti) can effectively contribute to austenite grain refinement by forming precipitate phases such as Ti(C,N) at high temperatures.

[0053] Niobium (Nb) can be added for the purpose of increasing strength and toughness by reducing the martensite packet size.

[0054] Vanadium (V) can be added for the purpose of increasing the strength of steel through the precipitation strengthening effect by precipitate formation.

[0055] In one embodiment, titanium (Ti), niobium (Nb), and vanadium (V) can be selectively included in the base material 100. At this time, when one or more of titanium (Ti), niobium (Nb), and vanadium (V) are included in the base material 100, the total of one or more components of titanium (Ti), niobium (Nb), and vanadium (V) is also about 0.01 wt% or more and about 0.1 wt% or less.

[0056] Chromium (Cr) can be added for the purpose of improving the hardenability and strength of steel. In one embodiment, chromium (Cr) can be included in an amount of about 0.01 wt% or more and about 1.0 wt% or less based on the total weight of the base material 100. When chromium (Cr) is included within the aforementioned range based on the total weight of the base material 100, 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.

[0057] Molybdenum (Mo) can contribute to strength improvement through suppression of precipitate coarsening and increase in hardenability during hot rolling and hot stamping. Molybdenum (Mo) can be included in an amount of about 0.01 wt% or more and about 1.0 wt% or less based on the total weight of the base material 100. When molybdenum (Mo) is included within the aforementioned range based on the total weight of the base material 100, the effects of suppressing precipitate coarsening and increasing hardenability during hot rolling and hot stamping are excellent.

[0058] Nickel (Ni) can be added for the purpose of ensuring hardenability and strength. Also, nickel (Ni) is an austenite stabilizing element and can contribute to improving elongation by controlling austenite transformation. In one embodiment, nickel (Ni) can be included in an amount of about 0.001 wt% or more and about 1.0 wt% or less based on the total weight of the base material 100. If the amount of nickel (Ni) included is less than about 0.001 wt% based on the total weight of the base material 100, it is difficult to properly embody the above-described effects. If the amount of nickel (Ni) included exceeds about 1.0 wt% based on the total weight of the base material 100, the toughness may be reduced, the cold workability may be reduced, and the manufacturing cost of the product may increase.

[0059] In one embodiment, the base material 100 can have a microstructure including a martensite fraction of about 90% or more. Specifically, the base material 100 can also be one that includes about 90% or more of martensite, the balance being other inevitable structures and less than about 10% of other precipitates.

[0060] In one embodiment, a decarburized layer 200 can be disposed on the base material 100. When the decarburized layer 200 is formed on the base material 100, the toughness of the hot stamping part 1 including the same can be improved.

[0061] A layer having a hardness of about 70% or less can be defined as the decarburized layer 200 in terms of the average hardness ratio at about 1 / 4 point from the surface of the base material 100. Alternatively, a layer having a hardness of about 70% or less can be defined as the decarburized layer 200 in terms of the average hardness ratio at about 1 / 4 point from the surface of the hot stamping part 1. That is, the average hardness of the decarburized layer 200 is also about 70% or less in terms of the average hardness ratio at about 1 / 4 point from the surface of the base material 100 or the surface of the hot stamping part 1. As another expression, the average hardness of the decarburized layer 200 is also about 70% or less of the average hardness at about 1 / 4 point from the surface of the base material 100 or the surface of the hot stamping part 1.

[0062] The decarburized layer 200 can be provided with a thickness (t1) of about 10 μm to about 100 μm in the thickness direction of the hot stamping part 1. When the thickness (t1) of the decarburized layer 200 is about 10 μm or less, the effect of improving toughness is negligible. When the thickness (t1) of the decarburized layer 200 is about 100 μm or more, the thickness of the decarburized layer 200 is excessively thick, and the strength of the hot stamping part 1 including the decarburized layer 200 can be reduced. Therefore, when the decarburized layer 200 is provided with a thickness (t1) of about 10 μm to about 100 μm, it is possible to prevent or minimize the reduction in the strength of the hot stamping part 1 while improving the toughness of the hot stamping part 1.

[0063] In one embodiment, a plating layer 300 can be disposed on the decarburized layer 200. The plating layer 300 can also be a zinc (Zn)-based plating layer or an aluminum (Al)-based plating layer. For example, the plating layer 300 can also contain zinc (Zn) and / or aluminum (Al).

[0064] In one embodiment, when the plating layer 300 is provided as a zinc (Zn)-based plating layer, the plating layer 300 can also contain iron (Fe), aluminum (Al), manganese (Mn), silicon (Si), the balance of zinc (Zn), and other inevitable impurities. For example, the plating layer 300 can also contain about 10 wt% or more and about 70 wt% or less of iron (Fe), more than 0 and about 5 wt% or less of aluminum (Al), more than 0 and about 1 wt% or less of manganese (Mn), more than 0 and about 1 wt% or less of silicon (Si), the balance of zinc (Zn), and other inevitable impurities. Also, the plating layer 300 can further contain carbon (C). At this time, the carbon (C) content contained in the plating layer 300 is also 50% or less of the carbon (C) content contained in the base material 100. For example, when the base material 100 contains about 0.25 wt% or more and about 0.5 wt% or less of carbon (C), the plating layer 300 can contain more than 0 and about 0.25 wt% or less of carbon (C).

[0065] The plating layer 300 can be provided with a thickness (t2) of about 7 μm to about 40 μm in the thickness direction of the hot stamping part 1. When the thickness (t2) of the plating layer 300 is about 7 μm or less, the sacrificial method effect peculiar to zinc is reduced. When the thickness (t2) of the plating layer 300 is about 40 μm or more, the thickness of the plating layer 300 is excessively thick, and the toughness of the hot stamping part 1 including the plating layer 300 can be reduced. Therefore, when the plating layer 300 is provided with a thickness (t2) of about 7 μm to about 40 μm, the surface of the base material (or steel material) can be protected, and at the same time, the reduction in toughness of the hot stamping part 1 can be prevented or minimized.

[0066] In one embodiment, the hot stamping part 1 can have a tensile strength (TS) of about 1,680 MPa to about 2,000 MPa, a yield stress (YP) of about 1,150 MPa to about 1,500 MPa, and an elongation (EL) of about 4% to about 10%. Also, the hot stamping part 1 can have a VDA bending angle of about 60° or more. At this time, the VDA bending angle can be measured in accordance with the VDA standard (VDA238 - 100).

[0067] Thereby, the inventor derived Relational Expression 1 for making the hot stamping part 1 have a VDA bending angle of about 60° or more through excessively repeated experiments. In one embodiment, the hot stamping part 1 can satisfy the following Relational Expression 1. (Relational Expression 1) 60≦176.92+1.25×c m -0.15×a m -0.52×b m In Relational Expression 1, a m is the temperature in the soaking heating stage, b m is the total heating time in the heating stage (for example, the total heating time in the stage of heating the blank), and c m is the thickness of the decarburized layer.

[0068] In Relational Expression 1, a m is the temperature in the soaking heating stage, and the temperature unit in the soaking heating stage is also °C, a mThe value of a may represent the temperature value in the soaking heating stage in °C. For example, when the temperature in the soaking heating stage is 900 °C, the value of a m is also 900.

[0069] In relational expression 1, b m is the total heating time in the stage of heating the blank, and the unit of the total heating time in the stage of heating the blank is also minutes (min), and b m may represent the value of the total heating time in the stage of heating the blank in minutes (min). For example, when the total heating time in the stage of heating the blank is 5 minutes (min), the value of b m is also 5.

[0070] In relational expression 1, c m is the thickness of the decarburized layer, and the unit of the thickness of the decarburized layer is also μm, and c m may represent the value in μm units. For example, when the thickness of the decarburized layer is 40 μm, the value of c m is also 40.

[0071] In one embodiment, the thickness of the decarburized layer 200 (c m ), the temperature in the soaking heating stage (a m ), and the total heating time in the stage of heating the blank (b m ) may satisfy the aforementioned relational expression 1. At this time, the thickness of the decarburized layer 200 (c m ) is also about 10 μm to about 100 μm, the temperature in the soaking heating stage (a m ) is also about Ac3 to about 910 °C, and the total heating time in the stage of heating the blank (b m ) is also about 2 minutes (min) to about 20 minutes (min).

[0072] When the thickness of the decarburized layer 200 (c m ), the temperature in the soaking heating stage (a m ), and the total heating time in the stage of heating the blank (b m ) satisfy the aforementioned relational expression 1, the toughness of the manufactured hot stamping part 1 can be improved. Specifically, the thickness of the decarburized layer 200 (c m ), the temperature in the soaking heating stage (am ) and the total heating time (b) of the step of heating the blank m ) When the above relational expression 1 is satisfied, the manufactured hot stamping part 1 can have a VDA bending angle of about 60° or more. Also, the thickness (c) of the decarburized layer 200 m ) the temperature (a) of the soaking heating step m ) and the total heating time (b) of the step of heating the blank m ) When the above relational expression 1 is satisfied, the manufactured hot stamping part 1 can have a tensile strength (TS) of about 1,680 MPa to about 2,000 MPa, a yield stress (YP) of about 1,150 MPa to about 1,500 MPa, and an elongation (EL) of about 4% to about 10%.

[0073] FIG. 2 is a flowchart schematically showing a method for manufacturing a hot stamping part according to an embodiment of the present invention, and FIGS. 3 to 5 are cross-sectional views schematically showing a method for manufacturing a hot stamping part according to an embodiment of the present invention.

[0074] Referring to FIGS. 2 to 5, a method for manufacturing a hot stamping part according to an embodiment also includes a hot rolling step (S100), a cooling / winding step (S200), a cold rolling step (S300), a tempering step (S400), a plating step (S500), and a hot stamping step (S600).

[0075] First, the reheating step of the base material 100 (e.g., steel slab) provided by the composition described in FIG. 1 can be advanced. In the steel slab reheating step, the steel slab secured through the continuous casting process is reheated to a predetermined temperature, whereby the components segregated during casting can be redissolved. In one embodiment, the slab reheating temperature (SRT) is also about 1,200°C to about 1,400°C. When the slab reheating temperature (SRT) is lower than about 1,200°C, the components segregated during casting are not sufficiently redissolved, it is difficult to see a great homogenization effect of alloying elements, and it is difficult to see a great solution effect of titanium (Ti). Although a higher slab reheating temperature (SRT) is more advantageous for homogenization, when the slab reheating temperature (SRT) exceeds about 1,400°C, the austenite crystal grain size increases, it is not only difficult to ensure strength, but also the manufacturing cost of the steel sheet can increase due to an excessive heating process.

[0076] In the hot rolling step (S100), the reheated base material 100 can be hot rolled at a predetermined finishing delivery temperature (FDT). Through the hot rolling step (S100), a hot rolled steel sheet can be manufactured. In one embodiment, the finishing delivery temperature (FDT) is also about 880°C to about 950°C. At this time, if the finishing delivery temperature (FDT) is lower than about 880°C, it is difficult to ensure the workability of the steel sheet due to the occurrence of a mixed grain structure caused by abnormal area rolling, and there are problems not only that the workability is reduced due to non-uniform fine structures, but also that a through-feedability problem can occur during hot rolling due to a rapid phase change. When the finishing delivery temperature (FDT) exceeds about 950°C, the austenite crystal grains are coarsened, the TiC precipitates are coarsened, and the performance of the hot stamping parts can be reduced.

[0077] In the cooling / winding-up stage (S200), the hot-rolled base material 100 can be cooled to a predetermined winding-up temperature (CT: coiling temperature) and then wound up. In one embodiment, the winding-up temperature in the cooling / winding-up stage (S300) is also about 550°C to about 800°C. This winding-up temperature affects the redistribution of carbon (C). When the winding-up temperature is less than about 550°C, the low-temperature phase fraction due to supercooling increases and the strength increases. During cold rolling, there is a concern that the rolling load will deepen, and the ductility may decrease rapidly. On the contrary, when the winding-up temperature exceeds about 800°C, deterioration of formability and strength may occur due to abnormal crystal grain growth or excessive crystal grain growth.

[0078] In the cold rolling stage (S300), the wound base material 100 can be uncoiled, pickled, and then cold rolled. At this time, the pickling can be carried out for the purpose of removing the scale of the wound steel sheet (or the base material), that is, the hot-rolled coil manufactured through the above-mentioned hot rolling process. Through the cold rolling stage (S300), cold-rolled steel sheets can be manufactured.

[0079] In the annealing stage (S400), annealing can be performed on the cold-rolled base material 100 at a temperature of about 700°C or higher. For example, the annealing stage (S400) also includes a stage of heating the cold-rolled base material 100 and cooling the heated base material 100 at a predetermined cooling rate.

[0080] In one embodiment, annealing can be performed on the base material in the annealing stage (S400). The annealing stage (S400) can be carried out in an annealing furnace.

[0081] The annealing of the base material 100 can be carried out in an atmosphere composed of about 0.5% by volume to about 25% by volume of hydrogen and the balance nitrogen. At this time, water can be injected into the annealing furnace together with hydrogen gas and nitrogen gas. When water is injected into the annealing furnace, the dew point temperature of the annealing furnace can be increased. Therefore, the amount of water injected into the annealing furnace can be adjusted to adjust the dew point temperature of the annealing furnace.

[0082] Also, when the dew point temperature of the annealing furnace rises, a decarburized layer 200 can be formed on the base material 100. For example, carbon can disappear from the surface of the base material 100, and the decarburized layer 200 can be formed. At this time, the thickness (t3) of the decarburized layer 200 formed on the surface of the base material 100 is also about 10 μm to about 100 μm in the thickness direction of the base material 100. When the thickness (t3) of the decarburized layer 200 is 10 μm or less, the thickness (t3) of the decarburized layer 200 is excessively thin, and the effect of improving the toughness of the manufactured hot stamping part is negligible. When the thickness (t3) of the decarburized layer 200 is 100 μm or more, the thickness of the decarburized layer 200 is excessively thick, and the strength of the manufactured hot stamping part can be reduced. Therefore, when the decarburized layer 200 is formed to have a thickness (t3) of about 10 μm to about 100 μm, the reduction in the strength of the manufactured hot stamping part 1 can be prevented or minimized while improving the toughness of the manufactured hot stamping part.

[0083] In one embodiment, a layer having a hardness of about 80% or less in terms of the average hardness ratio at about 1 / 4 point from the surface of the base material 100 can be defined as the decarburized layer 200. That is, the average hardness of the decarburized layer 200 is also about 80% or less in terms of the average hardness ratio at about 1 / 4 point from the surface of the base material 100.

[0084] In one embodiment, the dew point temperature of the annealing furnace in which the base material 100 is annealed is also about -15°C to about +15°C. When the dew point temperature of the annealing furnace is -15°C or lower, the thickness (t3) of the formed decarburized layer 200 is excessively thin, and the effect of improving the toughness of the manufactured hot stamping part is negligible. When the dew point temperature of the annealing furnace is +15°C or higher, the operability due to equipment oxidation can be reduced. For example, in order to raise the dew point temperature of the annealing furnace, a large amount of water must be supplied to the annealing furnace. However, when a large amount of water is supplied to the annealing furnace, the equipment of the annealing furnace is oxidized, and it takes a long time to clean it, and the operability can be reduced. Therefore, by satisfying that the dew point temperature of the annealing furnace in which the base material 100 is annealed is about -15°C to about +15°C, the efficiency of the manufacturing process can be improved while improving the toughness of the manufactured hot stamping part.

[0085] In one embodiment, the line speed of the annealing furnace in which the annealing of the base material 100 is performed is also about 30 mpm (meters per minute) to about 200 mpm. When the line speed of the annealing furnace is 30 mpm or less, the moving speed of the base material 100 is excessively slow, and the productivity decreases sharply. When the line speed of the annealing furnace is 200 mpm or more, the moving speed of the base material 100 is excessively fast, and the thickness of the decarburized layer 200 formed is reduced, whereby the effect of improving the toughness of the manufactured hot stamping parts is negligible. Therefore, when the line speed of the annealing furnace in which the annealing of the base material 100 is performed satisfies about 30 mpm to about 200 mpm, the productivity of the hot stamping parts can be improved, and at the same time, the toughness of the manufactured hot stamping parts can be improved.

[0086] In one embodiment, the annealing temperature of the base material 100 is also about 750°C to about 900°C. When the annealing temperature of the base material 100 is less than about 750°C, the desired structure cannot be obtained, and recrystallization is not sufficiently completed. On the other hand, when the annealing temperature of the base material 100 exceeds about 900°C, the annealing temperature is excessively high, and the efficiency of the manufacturing process may be reduced. Therefore, when the annealing temperature of the base material 100 satisfies about 750°C to about 900°C, the desired structure can be obtained, recrystallization is sufficiently completed, and the efficiency of the manufacturing process can be improved.

[0087] The plating step (S500) is also a step of forming a plating layer on the annealed base material 100. In one embodiment, a plating layer 300 can be formed on the annealed base material 100 through the plating step (S500). Specifically, through the plating step (S500), a plating layer 300 can be formed on the decarburized layer 200. At this time, the plating layer 300 also includes a zinc (Zn)-based plating layer or an aluminum (Al)-based plating layer.

[0088] Specifically, in the plating step (S500), the annealed base material 100 can be immersed in a plating bath. At this time, the plating bath can maintain a temperature of about 400°C to about 700°C. The plating layer can be formed by plating with about 40 g / m 2 to about 200 g / m 2 Thus, it can be formed by plating.

[0089] In one embodiment, the thickness (t4) of the plating layer 300 formed on the base material 100 or the decarburized layer 200 is also about 5 μm to about 30 μm. When the thickness (t4) of the plating layer 300 is less than or equal to about 5 μm, the sacrificial performance of the plating layer 300 is insufficient. When the thickness (t4) of the plating layer 300 is greater than or equal to about 30 μm, the cost of forming the plating layer 300 increases, and the economic efficiency can be reduced. Therefore, when the thickness (t4) of the plating layer 300 satisfies about 5 μm to about 30 μm, corrosion of the base material 100 of the hot stamping part can be prevented or minimized.

[0090] In one embodiment, the annealing step (S400) and the plating step (S500) can be performed on the same line. Therefore, the line speed at which the plating step (S500) is performed is also about 30 mpm to about 200 mpm. When the line speed is less than or equal to 30 mpm, the line speed is excessively slow, and the productivity can be reduced. An air knife is used to control the plating amount. When the line speed is greater than or equal to 200 mpm, the line speed is excessively fast, and it is very difficult to control the plating amount using the air knife. Therefore, when the line speed at which the plating step (S500) is performed satisfies about 30 mpm to about 200 mpm, the productivity can be improved, and at the same time, the plating amount can be easily controlled.

[0091] In one embodiment, through the plating step (S500), a plated steel sheet with a plating layer 300 formed on at least one surface of the base material 100 can be manufactured. At this time, the plated steel sheet also includes the base material 100, the decarburized layer 200 disposed on the base material 100, and the plating layer 300 disposed on the decarburized layer 200.

[0092] FIG. 6 is a flowchart schematically showing a hot stamping step according to an embodiment of the present invention, and FIG. 7 is a flowchart schematically showing a heating step according to an embodiment of the present invention.

[0093] Referring to FIGS. 3 and 6, after the plating step (S500), the hot stamping step (S600) can be performed. The hot stamping step (S600) also includes a heating step (S610), a transfer step (S620), a forming step (S630), and a cooling step (S640).

[0094] First, a plated steel sheet having a plating layer 300 formed on at least one surface of a base material 100 can be cut to form a blank. However, the present invention is not limited thereto.

[0095] In the heating step (S610), the blank can be heated in a heating furnace having a plurality of sections with different temperature ranges. As shown in FIG. 7, the heating step (S610) also includes a multi-stage heating step (S611) and a soaking heating step (S612). The multi-stage heating step (S611) and the soaking heating step (S612) are also steps in which the blank is heated as it passes through a plurality of sections provided in the heating furnace.

[0096] In one embodiment, the overall temperature of the heating furnace is also about 680°C to about 910°C. Specifically, the overall temperature of the heating furnace in which the multi-stage heating step (S611) and the soaking heating step (S612) are performed is also about 680°C to about 910°C. At this time, the temperature of the heating furnace in which the multi-stage heating step (S611) is performed is also about 680°C to Ac3, and the temperature of the heating furnace in which the soaking heating step (S612) is performed is also Ac3 to about 910°C.

[0097] In the multi-stage heating step (S611), the blank can pass through a plurality of sections provided in the heating furnace and be heated (or the temperature can be raised) step by step. In the plurality of sections provided in the heating furnace, there are a plurality of sections in which the multi-stage heating step (S611) is performed, and the temperature is set for each section so that the temperature increases from the inlet of the heating furnace where the blank is inserted to the outlet side of the heating furnace where the blank is taken out, and the blank can be heated (or the temperature can be raised) step by step.

[0098] After the multi-stage heating step (S611), a soaking heating step (S612) can be performed. In the soaking heating step (S612), the multi-stage heated blank can pass through a section of the heating furnace set at a temperature of Ac3 to about 910 °C and be heated (or soaked). Among the plurality of sections provided in the heating furnace, there is at least one section in which the soaking heating step (S612) is performed.

[0099] FIG. 8 is a drawing illustrated to explain a heating furnace having a plurality of sections in the heating step of the method for manufacturing a hot stamping part according to an embodiment of the present invention.

[0100] Referring to FIG. 8, a heating furnace according to an embodiment can include a plurality of sections having different temperature ranges. Specifically, the heating furnace has a first section P having a first temperature range T 1 a second section P having a second temperature range T 1 a third section P having a third temperature range T 2 a fourth section P having a fourth temperature range T 2 a fifth section P having a fifth temperature range T 3 a sixth section P having a sixth temperature range T 3 a seventh section P having a seventh temperature range T 4 a seventh section P having a seventh temperature range T 4 a fifth section P having a fifth temperature range T 5 a sixth section P having a sixth temperature range T 5 a seventh section P having a seventh temperature range T 6 a seventh section P having a seventh temperature range T 6 and a seventh section P having a seventh temperature range T 7 and can include a seventh section P having a seventh temperature range T 7 .

[0101] In one embodiment, in the multi-stage heating step (S611), the blank can pass through the first section P 1 to the fourth section P 4 and be heated step by step. Also, in the soaking heating step (S612), the blank heated in multiple stages in the first section P 1 to the fourth section P 4 can pass through the fifth section P 5 to the seventh section P 7 and be soaked heated.

[0102] The first section P 1 to the seventh section P 7 can be arranged in the heating furnace in order. The first section P 1 having the first temperature range T 1 is adjacent to the inlet of the heating furnace where the blank is introduced, and the seventh section P 7 having the seventh temperature range T 7 can be adjacent to the outlet of the heating furnace where the blank is discharged. Therefore, the first section P 1 having the first temperature range T 1 is also the first section of the heating furnace, and the seventh section P 7 having the seventh temperature range T 7 is also the last section of the heating furnace.

[0103] The temperatures of the multiple sections provided in the heating furnace, for example, the first section P 1 to the seventh section P 7 can rise from the inlet of the heating furnace where the blank is introduced to the outlet side of the heating furnace where the blank is taken out. However, the temperatures of the fifth section P 5 , the sixth section P 6 and the seventh section P 7 are the same. Also, among the multiple sections provided in the heating furnace, the temperature difference between two adjacent sections is greater than 0°C and at most about 100°C. For example, the temperature difference between the first section P 1 and the second section P 2 is greater than 0°C and at most about 100°C.

[0104] The heating furnace temperature in the soaking heating stage (S612) is also from Ac3 to about 910°C. When the heating furnace temperature in the soaking heating stage (S612) is below Ac3, the manufactured hot stamping parts do not have the desired material. On the other hand, when the heating furnace temperature in the soaking heating stage (S612) is about 910°C or higher, the zinc (Zn) contained in the plating layer 300 is vaporized, and loss of the plating layer 300 may occur. Therefore, when the heating furnace temperature in the soaking heating stage (S612) satisfies from Ac3 to about 910°C, the manufactured hot stamping parts can be formed of the desired material, and loss of the plating layer 300 can be prevented or minimized.

[0105] In FIG. 8, the heating furnace according to one embodiment is illustrated as including seven sections having different temperature ranges from each other, but the present invention is not limited thereto. The heating furnace may also include five, six, or eight such sections having different temperature ranges from each other.

[0106] In one embodiment, since the heating stage (S610) is constituted by the multi-stage heating stage (S611) and the soaking heating stage (S612), the temperature of the heating furnace can be set stepwise, and the energy efficiency of the heating furnace can be improved.

[0107] In one embodiment, the heating furnace may have a length of about 20 m to about 40 m along the transfer path of the blank. The heating furnace includes a plurality of sections having different temperature ranges, and in the plurality of sections, the ratio of the length of the section where the blank is multi-stage heated to the length of the section where the blank is soaking heated may satisfy about 1:1 to about 4:1. Inside the heating furnace, when the length of the section where the blank is soaking heated increases and the ratio of the length of the section where the blank is multi-stage heated to the length of the section where the blank is soaking heated exceeds about 1:1, the amount of hydrogen permeating into the blank in the soaking heating section increases, and delayed fracture may increase. On the other hand, when the length of the section where the blank is soaking heated is reduced and the ratio of the length of the section where the blank is multi-stage heated to the length of the section where the blank is soaking heated is less than about 4:1, the soaking heating section (or time) is not sufficiently ensured, and the strength of the hot stamping parts manufactured by the manufacturing process of the hot stamping parts may become non-uniform. For example, in the plurality of sections provided in the heating furnace, the length of the uniform heating section is also about 20% to about 50% of the total length of the heating furnace.

[0108] In one embodiment, the total heating time during which the heating step (S610) is performed is also about 2 minutes (min) to about 20 minutes (min). That is, the total time that the blank stays in the heating furnace is also about 2 minutes (min) to about 20 minutes (min). When the total heating time during which the heating step (S610) is performed is about 2 minutes (min) or less, the heating time is insufficient, and the manufactured hot stamping parts do not have the desired material. On the other hand, when the total heating time during which the heating step (S610) is performed is about 20 minutes (min) or more, the heating time is excessively long, the production speed is reduced, and the economic efficiency may be reduced. Therefore, when the total heating time during which the heating step (S610) is performed satisfies about 2 minutes (min) to about 20 minutes (min), the manufactured hot stamping parts have the desired material, and at the same time, the reduction of the economic efficiency of the manufacturing process can be prevented or minimized.

[0109] After the heating step (S610), a transfer step (S620), a forming step (S630), and a cooling step (S640) may be further performed.

[0110] In one embodiment, the transfer step (S620) is also a step of transferring the heated blank from the heating furnace to the mold. At this time, in the transfer step (S620), the heated blank can be cooled at the atmospheric temperature (or normal temperature). That is, the heated blank can be air-cooled during transfer. If the heated blank is not air-cooled, the mold entry temperature (e.g., the forming start temperature) will be high, and wrinkles (or buckling) may occur on the surface of the manufactured hot stamping part. Also, when using a refrigerant, it may affect the subsequent process (hot stamping). Therefore, it is desirable that the heated blank be air-cooled during transfer.

[0111] In one embodiment, the forming step (S630) is also a step of hot stamping the transferred blank to form a formed body. Specifically, in the forming step (S400), the blank can be pressed with a mold to form a formed body.

[0112] In one embodiment, the forming start temperature is also about 500°C or more and about 700°C or less. If the forming start temperature is less than 500°C, the forming start temperature is excessively low, the formability of the blank is reduced, and the manufactured hot stamping part may not have the target structure and physical properties. On the other hand, if the forming start temperature exceeds about 700°C, wrinkles (or buckling) may occur on the surface of the manufactured hot stamping part. Also, the plating layer may stick to the mold. Therefore, when the forming start temperature is about 500°C or more and about 700°C or less, the formability of the blank is improved, the manufactured hot stamping part has the target structure and physical properties, and the occurrence of wrinkles (or buckling) on the surface of the manufactured hot stamping part can be prevented or minimized.

[0113] In one embodiment, the cooling step (S500) is also a step of cooling the formed formed body. The cooling step (S500) can be performed in the mold that has pressed the blank.

[0114] Specifically, the molded article can be cooled simultaneously with molding the final part shape by a mold, and the final product can be formed. The mold can be provided with a cooling channel through which a refrigerant circulates inside. The refrigerant supplied through the cooling channel provided in the mold can rapidly cool the molded article by circulation. At this time, in order to maintain the desired shape while preventing the springback phenomenon of the plate material, rapid cooling can be performed while applying pressure with the mold closed. When performing the molding and cooling operations on the molded article, the average cooling rate can be cooled to at least about 10 °C / s or more until the martensite finish temperature.

[0115] In one embodiment, the cooling end temperature at the end of the cooling stage (S640) is also approximately room temperature or higher and about 200 °C or lower. If the cooling end temperature is less than room temperature, the productivity of the manufacturing process may be reduced. On the other hand, if the cooling end temperature exceeds about 200 °C, the manufactured hot stamping part is air-cooled at room temperature. At this time, the hot stamping part is bent, and it is also difficult to ensure the target material. Therefore, when the cooling end temperature at the end of the cooling stage (S500) satisfies the range of room temperature or higher and about 200 °C or lower, the productivity of the manufacturing process can be improved, and bending of the manufactured hot stamping part can be prevented or minimized.

[0116] In order to ensure the impact absorption performance of the hot stamping part, the hot stamping part needs to have a certain level or higher (or higher than a pre-set level) of toughness. At this time, the toughness of the hot stamping part can be improved by adding alloy components, but when adding the alloy components, the economy such as the manufacturing cost of the hot stamping part may be reduced. Therefore, it is necessary to control the process conditions for manufacturing the hot stamping part so that the hot stamping part has a certain level or higher (or higher than a pre-set level) of toughness. However, even when using various types of materials, process conditions are required to manufacture a hot stamping part having a certain level or higher (or higher than a pre-set level) of toughness.

[0117] Accordingly, the inventor of the present invention derived Relational Expression 2 that enables hot stamping parts manufactured through excessively repeated experiments to have a VDA bending angle of about 60° or more. In one embodiment, the method for manufacturing hot stamping parts may satisfy the following Relational Expression 2. Specifically, the temperature (a n ) in the soaking heating stage and the total heating time (b n ) in the heating stage of the method for manufacturing hot stamping parts may satisfy the following Relational Expression 2. (Relational Expression 2) 62 ≦ 91.81 + K - 0.022×a n - 0.23×b n In Relational Expression 2, K is a material correction coefficient. At this time, the material correction coefficient (K) is 0.71×c n - 0.025×d n and in the material correction coefficient (K), c n is the dew point temperature of the annealing furnace of the base material, and d n is the line speed of the annealing furnace of the base material.

[0118] In Relational Expression 2, a n is the temperature in the soaking heating stage, and the unit of the temperature in the soaking heating stage is also °C. The value of a n may represent the temperature value of the soaking heating stage in °C units. For example, when the temperature in the soaking heating stage is 900 °C, the value of a n is also 900.

[0119] In Relational Expression 2, b n is the total heating time in the heating stage (for example, the total heating time in the stage of heating the blank), and the unit of the total heating time in the heating stage is also minutes (min). The value of b n may represent the value of the total heating time in the heating stage in minutes (min) units. For example, when the total heating time in the heating stage is 5 minutes (min), the value of b n is also 5.

[0120] As described above, in Relational Expression 2, K is also a material correction coefficient. At this time, the material correction coefficient (K) is 0.71×c n - 0.025×dn is also the case. In the material correction coefficient (K), c n is the dew point temperature of the annealing furnace of the base material, and the unit of the dew point temperature of the annealing furnace of the base material is also °C, and c n may represent the value of the dew point temperature of the annealing furnace of the base material in °C units. For example, when the dew point temperature of the annealing furnace of the base material is +10 °C, c n has a value of 10. Also, in the material correction coefficient (K), d n is the line speed of the annealing furnace of the base material, and the unit of the line speed of the annealing furnace of the base material is also mpm, and d n may represent the value of the line speed of the annealing furnace of the base material in mpm units. For example, when the line speed of the annealing furnace of the base material is 100 mpm, d n has a value of 100.

[0121] In one embodiment, the temperature (a n ) in the soaking heating stage and the total heating time (b n ) in the heating stage may satisfy the aforementioned relational expression 2. At this time, since the material correction coefficient (K) is a coefficient based on the dew point temperature (c n ) of the annealing furnace of the base material and the line speed (d n ) of the annealing furnace of the base material, the temperature (a n ) in the soaking heating stage, the total heating time (b n ) in the heating stage, the dew point temperature (c n ) of the annealing furnace of the base material, and the line speed (d n ) of the annealing furnace of the base material can also be regarded as satisfying the aforementioned relational expression 2.

[0122] At this time, the temperature (a n ) in the soaking heating stage is also about Ac3 to about 910 °C, the total heating time (b n ) in the heating stage is also about 2 minutes (min) to about 20 minutes (min), the dew point temperature (c n ) of the annealing furnace of the base material is also about -15 °C to about +15 °C, and the line speed (d n ) of the annealing furnace of the base material is also about 30 mpm to about 200 mpm.

[0123] The temperature (a n), and the total heating time (b) of the heating stage n ), when the above-mentioned relational expression 2 is satisfied, the toughness of the hot stamping part 1 manufactured through the manufacturing method of the hot stamping part can be improved. Specifically, the temperature (a) of the soaking heating stage n ), and the total heating time (b) of the heating stage n ), when the above-mentioned relational expression 2 is satisfied, the hot stamping part 1 manufactured through the manufacturing method of the hot stamping part can have a VDA bending angle of about 60° or more. Further, the hot stamping part 1 manufactured through the manufacturing method of the hot stamping part can have a tensile strength (TS) of about 1,680 MPa to about 2,000 MPa, a yield stress (YP) of about 1,150 MPa to about 1,500 MPa, and an elongation (EL) of about 4% to about 10%.

[0124] As another expression, the temperature (a) of the soaking heating stage n ), the total heating time (b) of the heating stage n ), the dew point temperature (c) of the annealing furnace of the base material n ), and the line speed (d) of the annealing furnace of the base material n ), when the above-mentioned relational expression 2 is satisfied, the toughness of the hot stamping part 1 manufactured through the manufacturing method of the hot stamping part can be improved. Specifically, the temperature (a) of the soaking heating stage n ), the total heating time (b) of the heating stage n ), the dew point temperature (c) of the annealing furnace of the base material n ), and the line speed (d) of the annealing furnace of the base material n ), when the above-mentioned relational expression 2 is satisfied, the hot stamping part 1 manufactured through the manufacturing method of the hot stamping part can have a VDA bending angle of about 60° or more. Further, the hot stamping part 1 manufactured through the manufacturing method of the hot stamping part can have a tensile strength (TS) of about 1,680 MPa to about 2,000 MPa, a yield stress (YP) of about 1,150 MPa to about 1,500 MPa, and an elongation (EL) of about 4% to about 10%.

[0125] The present invention has been described with reference to the embodiments illustrated in the drawings, but they are merely exemplary, and those having ordinary knowledge in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention is defined by the technical idea of the appended claims.

Claims

1. Cutting a plated steel sheet with a plating layer formed on at least one surface of a base material to form a blank; Heating the blank in a heating furnace having a plurality of sections with different temperature ranges; The step of heating the blank includes: A multi-stage heating step of heating the blank step by step; A soaking heating step of heating the multi-stage heated blank at a temperature of Ac3 to 910 °C; The temperature (a ｎ ) of the soaking heating stage, and the total heating time (b ｎ ) of the stage of heating the blank satisfy the following relational expression, a method for manufacturing a hot stamping part: (Relational expression) 62 ≤ 91.81 + K - 0.022 × a ｎ - 0.23 × b ｎ (In the relational expression, K is a material correction coefficient).

2. The total heating time (b ｎ ) of the step of heating the blank is from 2 minutes (min) to 20 minutes (min). The method for manufacturing a hot stamping part according to claim 1.

3. The material correction coefficient (K) is 0.71 × c ｎ −0.025 × d ｎ and is In the material correction coefficient (K), c ｎ is the dew point temperature of the annealing furnace of the base material, and d ｎ is the line speed of the annealing furnace of the base material. The method for manufacturing a hot stamping part according to claim 1.

4. The dew point temperature (c ｎ ) of the annealing furnace for the base material is -15°C to +15°C. The method for manufacturing a hot stamping part according to claim 3.

5. The line speed (d ｎ ) of the annealing furnace for the base material is 30 mpm to 200 mpm. The method for manufacturing a hot stamping part according to claim 3.

6. The tempering temperature of the base material is 750 °C to 900 °C. The method for manufacturing a hot stamping part according to Claim 1.

7. The tempering of the base material is performed in an atmosphere composed of 0.5% to 25% by volume of hydrogen and the balance of nitrogen. The method for manufacturing a hot stamping part according to Claim 1.

8. Further including a decarburized layer formed on the base material. The method for manufacturing a hot stamping part according to Claim 1.

9. The thickness of the decarburized layer is 10 μm to 100 μm. The method for manufacturing a hot stamping part according to Claim 8.

10. The average hardness of the decarburized layer is 80% or less in comparison with the average hardness at a point 1 / 4 from the surface of the base material. The method for manufacturing a hot stamping part according to Claim 8.

11. The plating layer is a zinc (Zn)-based plating layer or an aluminum (Al)-based plating layer. The method for manufacturing a hot stamping part according to Claim 1.

12. The thickness of the plating layer is 5 μm to 30 μm. The method for manufacturing a hot stamping part according to Claim 1.

13. After the step of heating the blank, A step of transferring the heated blank; A step of pressing the transferred blank with a mold to form a molded body; A step of cooling the formed molded body. The method for manufacturing a hot stamping part according to Claim 1.

14. A hot stamping part, The hot stamping part includes: A base material, A decarburized layer disposed on the base material, A plating layer disposed on the decarburized layer. The hot stamping part is a hot stamping part having a tensile strength (TS) of 1,680 MPa to 2,000 MPa, a yield stress (YP) of 1,150 MPa to 1,500 MPa, and an elongation (EL) of 4% to 10%.

15. The hot stamping part according to claim 14, wherein the average hardness of the decarburized layer is 70% or less in comparison with the average hardness at a point 1 / 4 from the surface of the base material.

16. The hot stamping part according to claim 14, wherein the carbon content contained in the plating layer is 50% or less of the carbon content contained in the base material.

17. The hot stamping part according to claim 14, wherein the hot stamping part has a microstructure containing a martensite fraction of 90% or more.

18. The hot stamping part according to claim 14, wherein the thickness of the decarburized layer is 10 μm to 100 μm.

19. The hot stamping part according to claim 14, wherein the thickness of the plating layer is 7 μm to 40 μm.

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