Hot stamped component and manufacturing method therefor

Abstract

Disclosed is a hot stamped component, comprising Fe and inevitable impurities, and further comprising the following chemical elements in percentage by mass: 0.24-0.34% of C, 0.5-2.0% of Si, 2.0-4.0% of Mn, 0.05-1.0% of Al, and 0.03-0.1% of Nb. The microstructure of the hot stamped component comprises at least 60% of tempered martensite and 5-20% of austenite. Further disclosed is a method for manufacturing the hot stamped component, comprising the steps of: preparing a steel blank; hot stamping; first-stage quenching; second-stage quenching; and aging treatment. The hot-stamped component of the present invention effectively addresses and improves the problems of poor elongation and bending angle of 1300 MPa-grade hot-stamped components, and improves hot-stamped component crash performance.

Description

A hot-stamped component and its manufacturing method Technical Field

[0001] This invention relates to a steel forming part and its manufacturing method, and more particularly to a hot stamping forming part and its manufacturing method. Background Technology

[0002] The application of ultra-high strength steel can reduce vehicle weight while ensuring safety. Ultra-high strength steel applications in car bodies include two technical approaches: cold stamping and hot stamping. Hot stamping offers advantages such as ultra-high strength, ease of forming, and high dimensional accuracy. However, current hot stamping steels with strengths of 1300MPa and above suffer from insufficient plasticity and toughness, which can lead to cracking of the car body during a collision.

[0003] Existing hot-stamping steel, tested according to the national standard GB / T228 Metallic Materials, room temperature tensile testing method, uses P6 sample, A50 gauge length, with a typical elongation of 6%. The VDA bending angle is tested according to VDA238-100 Metallic Materials, plate bending test, with a typical thickness of 1.5mm and the indenter parallel to the rolling direction, measuring a typical bending angle of 50°. In existing technologies, there is limited research, both domestically and internationally, on ultra-high strength hot-stamping components that simultaneously improve plasticity and toughness. Among these:

[0004] For example, Chinese patent document CN108474081A, published on August 31, 2018, entitled "Steel for Stamping and Forming and Forming Components Thereof and Heat Treatment Method", discloses a steel for stamping and forming and forming components thereof and heat treatment method. The steel has a Mn content of 5-9.5% and contains 30-60% retained austenite in its microstructure. The purpose is to obtain steel with a yield strength of 0.5-1.2 GPa, a strength of 1.0-1.5 GPa, and a strength-ductility product ≥25 GPa%. The above patent document mainly obtains high strength-ductility product by introducing retained austenite through a higher manganese content. However, steel with a Mn content of more than 5% is more difficult to manufacture and has a higher cost.

[0005] For example, Chinese patent document CN114959514A, published on August 30, 2022, entitled "Method for producing high-strength steel parts with improved ductility and parts obtained by said method", discloses a method for producing high-strength steel parts with improved ductility and parts obtained by said method. The parts contain 0.25-2% Ni element, and the number of Ni element diffusion enrichment particles on the surface is controlled, with the aim of improving the ductility of hot stamping steel. Summary of the Invention

[0006] One of the objectives of this invention is to provide a hot-stamped component that, by controlling its chemical composition ratio and regulating its microstructure, can achieve ultra-high strength, plasticity, and toughness, and has excellent impact performance.

[0007] To achieve the above objectives, the present invention provides a hot-stamped component containing Fe and unavoidable impurities, and further containing the following chemical elements in the following mass percentages:

[0008] C: 0.24-0.34%, Si: 0.5-2.0%, Mn: 2.0-4.0%, Al: 0.05-1.0%, Nb: 0.03-0.1%;

[0009] The microstructure of the hot-stamped component comprises at least 60% tempered martensite and 5-20% austenite.

[0010] In this invention, when the proportion of tempered martensite in the microstructure is less than 60%, the tensile strength requirement of this invention cannot be met. The plasticity improvement of this invention mainly relies on austenite, which has high mechanical stability. During the tensile test of hot-stamped parts, the austenite in the microstructure undergoes a TRIP effect, increasing the material's work hardening rate and thus increasing plasticity, especially increasing the uniform elongation of the material. However, when the proportion of austenite in the microstructure is less than 5%, it affects the elongation and uniform elongation of the hot-stamped parts. When the proportion of austenite in the microstructure is greater than 20%, more alloying elements need to be added, and the stability of austenite will be affected.

[0011] Furthermore, in the hot-stamped component described in this invention, the mass percentage content of each chemical element is as follows:

[0012] C: 0.24-0.34%, Si: 0.5-2.0%, Mn: 2.0-4.0%, Al: 0.05-1.0%, Nb: 0.03-0.1%; balance Fe and unavoidable impurities.

[0013] The design principles of each chemical element in the hot-stamped component of this invention are as follows:

[0014] C: In the hot-stamped components described in this invention, carbon (C) is a key element for strength. When the mass percentage content of C is too low, it is difficult to achieve the target strength of 1300 MPa for the hot-stamped components. When the mass percentage content of C is too high, the plasticity, toughness, weldability, and resistance to delayed cracking of the hot-stamped components deteriorate. Therefore, in the hot-stamped components described in this invention, the mass percentage content of C is controlled between 0.24% and 0.34%.

[0015] Si: In the hot-stamped components of this invention, Si can suppress cementite precipitation and promote the distribution of C to austenite, thereby improving austenite stability. When the mass percentage content of Si is too low, the strengthening effect is not significant. When the mass percentage content of Si is too high, it will affect the weldability of the steel sheet and the plating applicability. Therefore, in the hot-stamped components of this invention, the mass percentage content of Si is controlled between 0.5% and 2.0%. In some embodiments, the mass percentage content of Si is 1.0% to 2.0%.

[0016] Mn: In the hot-stamped components of this invention, Mn is a highly stabilizing element in austenite structure, second only to Ni in its effect. It significantly increases the strength and hardness of steel while ensuring a certain degree of stability in austenite. When the mass percentage content of Mn is too low, its contribution to strength and austenite stability is low, failing to achieve the objectives of this invention. When the mass percentage content of Mn is too high, it deteriorates the manufacturability and weldability of the steel. Therefore, in the hot-stamped components of this invention, the mass percentage content of Mn is controlled between 2.0% and 4.0%. In some embodiments, the mass percentage content of Mn is 3.0% to 4.0%.

[0017] Al: In the hot-stamped parts described in this invention, Al acts as a deoxidizing element and also inhibits cementite precipitation and improves austenite stability, with effects similar to Si. However, when the mass percentage content of Al is too high, it can cause the formation of large inclusions in the steel and reduce manufacturability. Therefore, in the hot-stamped parts described in this invention, the mass percentage content of Al is controlled between 0.05% and 1.0%. In some embodiments, the mass percentage content of Al is 0.1% to 1.0% or 0.1% to 0.8%.

[0018] Nb: In the hot-stamped components described in this invention, Nb is an important microalloying element in steel, partially playing a role in solid solution strengthening. Furthermore, Nb has extremely strong binding affinity with C and N elements, precipitating stable carbides, nitrides, and carbonitrides, thus refining the grain size. Its precipitated phases also act as hydrogen traps, reducing susceptibility to hydrogen-induced delayed cracking. Therefore, considering both cost and effectiveness, the mass percentage content of Nb in the hot-stamped components described in this invention is controlled between 0.03% and 0.1%.

[0019] Furthermore, the hot-stamped component of the present invention also contains at least one of the following chemical elements:

[0020] 0 < Ti ≤ 0.15%;

[0021] 0 < V ≤ 1.0%;

[0022] 0 < Ni ≤ 1.0%;

[0023] 0 < Cr ≤ 2.0%;

[0024] 0 < Mo ≤ 1.0%;

[0025] 0 < Cu ≤ 1.0%;

[0026] 0 < Ca ≤ 0.01%;

[0027] 0 < REM ≤ 0.1%.

[0028] In the hot-stamped component of the present invention, the design principles of the above-mentioned chemical elements are specifically described as follows:

[0029] Ti and V: In the hot-stamped components of this invention, both Ti and V are microalloying elements. Adding small amounts can combine with C and N elements to precipitate stable carbides, nitrides, and carbonitrides, thus inhibiting austenite grain growth during hot stamping and refining the grain size. Therefore, in the hot-stamped components of this invention, the mass percentage content of Ti can be controlled to 0 < Ti ≤ 0.15%, and the mass percentage content of V can be controlled to 0 < V ≤ 1.0%.

[0030] Ni, Cr, Mo, Cu: In the hot-stamped parts described in this invention, Ni, Cr, Mo, and Cu elements all have an austenite-stabilizing effect, and some of these elements can also precipitate carbides to refine the grains. Considering cost, they can be added in small amounts to improve the plasticity and toughness of the hot-stamped parts. Therefore, in the hot-stamped parts described in this invention, the mass percentage content of Ni can be controlled to 0 < Ni ≤ 1.0%, the mass percentage content of Cr can be controlled to 0 < Cr ≤ 2.0%, the mass percentage content of Mo can be controlled to 0 < Mo ≤ 1.0%, and the mass percentage content of Cu can be controlled to 0 < Cu ≤ 1.0%.

[0031] Ca and REM: In the hot-stamped parts described in this invention, small amounts of Ca and REM elements can be added to the steel grade. These elements can be used to modify inclusions and improve the quality of the slab blanks used for hot-stamped parts. Therefore, in the hot-stamped parts described in this invention, the mass percentage content of Ca can be controlled to 0 < Ca ≤ 0.01%, and the mass percentage content of REM can be controlled to 0 < REM ≤ 0.1%.

[0032] Furthermore, in the unavoidable impurities of the hot-stamped parts described in this invention, each impurity element satisfies at least one of the following: P≤0.05%, S≤0.01%, N≤0.01%, B≤0.0005%.

[0033] In the above technical solution, P, S, N, and B are all unavoidable impurity elements in steel. Where technical conditions permit, to obtain strip steel with better performance and superior quality, the content of these impurity elements in the steel should be reduced as much as possible. Specifically:

[0034] P and S: In the hot-stamped components described in this invention, both P and S are harmful elements. P segregation leads to cold brittleness in steel; while S segregation, along with MnS and sulfides, reduces toughness and causes hot brittleness at high temperatures. Therefore, to improve the components' resistance to low-temperature brittleness, the mass percentage content of P in the hot-stamped components described in this invention can be controlled to P ≤ 0.05%, and the mass percentage content of S can be controlled to S ≤ 0.01%.

[0035] N: In the hot-stamped components described in this invention, nitrogen (N) is an impurity element in the hot-stamped steel, and its content during steelmaking needs to be strictly controlled. Therefore, in the hot-stamped components described in this invention, the mass percentage content of nitrogen can be controlled to N ≤ 0.01%.

[0036] B: In the hot-stamped component of this invention, element B can combine with nitrogen to form BN. Furthermore, element B significantly improves hardenability, leading to the formation of twinned martensite in the microstructure. Both BN and twinned martensite significantly deteriorate the material's plasticity and toughness. Therefore, in the hot-stamped component of this invention, the mass percentage content of element B can be controlled to B ≤ 0.0005%.

[0037] Furthermore, in the hot-stamped component of the present invention, its austenite shape factor K1 = γ1 / γ0, and K1 ≥ 0.7, where γ1 represents the austenite content with a length-to-short diameter ratio of not less than 4, and γ0 represents the total austenite content.

[0038] In this invention, austenite stability plays a crucial role in the plasticity and toughness of materials. The mechanical stability of austenite is related to its shape and alloy content. The inventors discovered that austenite with a length-to-diameter ratio below 4 is prone to the TRIP effect earlier during tensile testing, meaning it has poor mechanical stability. The TRIP effect occurs even in the elastic stage, resulting in a low contribution to the work hardening rate of hot-stamped parts and little improvement in uniform elongation and bending performance. Therefore, the austenite shape factor K1 is defined as γ1 / γ0, and K1 is controlled to be ≥0.7. In some embodiments, K1 is 0.7-1.0, such as 0.7-0.95.

[0039] Furthermore, in the hot-stamped component of the present invention, its austenite composition factor K2 = M1 / M2, and K2 ≥ 3.0, where M1 represents the mass percentage content of Mn element in austenite, and M2 represents the mass percentage content of Mn element in tempered martensite.

[0040] In this invention, the mass percentage of Mn in austenite affects the stability of austenite. Therefore, defining the austenite composition factor K2 = M1 / M2 and controlling K2 ≥ 3.0 can effectively control the elongation and VDA bending angle of hot-stamped parts. In some embodiments, K2 is 3.0-7.0, such as 3.0-6.5.

[0041] Furthermore, in the hot-stamped component of the present invention, its austenite stability factor K3 = V1 / V2, and K3 ≥ 1.5, where V1 represents the austenite transformation amount in the plastic stage of the tensile test at room temperature, and V2 represents the austenite transformation amount in the elastic stage of the tensile test at room temperature.

[0042] In this invention, austenite is a Mn-rich phase relative to the surrounding martensite, where the Mn content further affects stability. Therefore, the austenite composition factor K3 is defined as V1 / V2, and K3 is controlled to be ≥1.5, thereby giving the austenite good stability. In some embodiments, K3 is 1.5-4.0.

[0043] Furthermore, in the hot-stamped component of the present invention, the microstructure contains particulate precipitates dispersed in the matrix, the particulate precipitates including TiC and Nb(C,N), and the diameter of the particulate precipitates is less than or equal to 30 nm.

[0044] In this invention, Nb and Ti are both important microalloying elements in steel, playing a role in solid solution strengthening. Furthermore, Nb and Ti have extremely strong binding forces with C and N, precipitating stable carbides, nitrides, and carbonitrides, which can inhibit austenite grain growth during hot stamping and refine the grain size. The precipitated phases can also act as hydrogen traps, reducing the susceptibility to hydrogen-induced delayed cracking and significantly improving the toughness of the steel. The inventors have discovered that in hot-stamped components with an austenitic structure, controlling the grain size and precipitate size distribution can significantly improve the component's toughness. Therefore, in the hot-stamped component described in this invention, the TiC and Nb(C,N) precipitates can be controlled to be dispersed in the matrix in a granular manner, with the precipitate particle diameter controlled to be less than or equal to 30 nm.

[0045] Furthermore, in the hot-stamped component described in this invention, its surface is also covered with a plating layer and / or a coating layer.

[0046] In some embodiments, the surface of the hot-stamped part may be covered with a plating or chemical coating, including aluminum-based, zinc-based, or similar coatings, thereby improving the oxidation and corrosion resistance of the hot-stamped part.

[0047] Further, the hot-stamped component of the present invention has a tensile strength ≥1300MPa, an elongation A50 ≥10%, a uniform elongation ≥8%, and a VDA bending angle ≥60°. In some embodiments, the hot-stamped component of the present invention has a tensile strength ≥1380MPa, or ≥1420MPa, ≥1500MPa, or ≥1600MPa. In some embodiments, the tensile strength of the hot-stamped component of the present invention is between 1300 and 1900MPa, such as 1400 to 1900MPa. In some embodiments, the elongation A50 of the hot-stamped component of the present invention is 10 to 16%. In some embodiments, the uniform elongation of the hot-stamped component of the present invention is 8 to 12%. In some embodiments, the VDA bending angle of the hot-stamped component of the present invention is ≥65°; in some embodiments, the VDA bending angle of the hot-stamped component of the present invention is 60° to 75°, such as 65° to 75°.

[0048] Another object of the present invention is to provide a method for manufacturing a hot-stamped part, which, through process control, can obtain a hot-stamped part with ultra-high strength, high plasticity and high toughness.

[0049] To achieve the above objectives, the present invention provides a method for manufacturing a hot-stamped component, comprising the following steps:

[0050] Steel plates were produced;

[0051] Hot stamping: Heat the steel plate to (Ac1+50)-(Ac3+150)℃ and hold for 2-15 minutes, then complete the hot stamping process.

[0052] First stage of cooling: The hot-stamped parts are rapidly cooled to Ms-Mf and held at that temperature for 5-200 seconds;

[0053] Second stage cooling: Cooling the component to below 100°C;

[0054] Aging treatment: Reheat the component to 100-400℃, hold for 10-60 minutes, and then air cool to room temperature.

[0055] In the hot stamping forming step of the present invention, Ac1 and Ac3 are the start temperature and end temperature of the ferrite to austenite transformation during the heating process, respectively. By controlling the heating temperature and time, the degree of austenitization of the steel plate after heating can be ensured, so that martensite can be obtained in the subsequent cooling process, thus ensuring strength performance.

[0056] In the hot stamping process, after heat treatment, the steel sheet obtained from the heat treatment can be hot stamped using conventional hot stamping techniques. For example, the heated steel sheet can be transferred to a mold for die-cutting. The stamping process (speed and time, etc.) is conventional in the field.

[0057] In the first cooling step of this invention, Ms and Mf are the start and end temperatures of the austenite-to-martensite transformation during continuous cooling, respectively. When the cooling temperature is lower than Ms, sufficient austenite cannot be obtained; when the cooling temperature is higher than Mf, sufficient martensite cannot be obtained. Controlling the holding time between 5-200 seconds can regulate the ratio of martensite to austenite in the microstructure, thereby obtaining good performance.

[0058] In the aging process of this invention, by reheating the component to 100-400°C and holding it at that temperature for 10-60 minutes, followed by air cooling to room temperature, the martensite in the microstructure can be transformed into tempered martensite, softening the matrix microstructure. Furthermore, during the low-temperature aging process, the precipitation of Nb (Ti, V) alloying element carbides can be promoted. This improves the plasticity and toughness of the hot-stamped component.

[0059] Furthermore, in the manufacturing method described in this invention, a reheating step is provided between the first cooling step and the second cooling step: the hot-stamped part is reheated to Ms-500°C and held at that temperature for 10-300 seconds.

[0060] Between the first and second cooling steps of this invention, reheating can further regulate the microstructure ratio and austenite stability of the final component, and the reheating process is conducive to the enrichment of C and Mn elements in the microstructure into austenite.

[0061] Furthermore, in the first cooling step of the manufacturing method described in this invention, the cooling rate is 30-100°C / s.

[0062] In the first cooling step of the present invention, when the cooling rate is controlled at 30°C / s or higher, the cooling rate can meet the requirements of the critical transformation cooling rate of martensite, thereby obtaining sufficient martensite.

[0063] Furthermore, in the second cooling step of the manufacturing method described in this invention, the cooling rate is not higher than 30°C / s.

[0064] In the second cooling step of the present invention, when the cooling rate is higher than 30°C / s, the previously obtained austenite may be transformed into martensite, thus obtaining fresh martensite and reducing the austenite content of the final part.

[0065] Furthermore, in the manufacturing method described in this invention, after the aging treatment step, there is a step of plating a coating layer and / or applying a coating layer.

[0066] The hot-stamped component and its manufacturing method described in this invention have the following advantages and beneficial effects compared to the prior art:

[0067] The hot stamping component and its manufacturing method described in this invention can obtain a hot stamping component with high strength, high plasticity and high toughness by controlling its chemical composition ratio, microstructure and process design. It effectively solves and improves the problem of poor elongation and bending angle of 1300MP grade hot stamping components, and improves the impact performance of hot stamping components.

[0068] In some embodiments, the hot-stamped parts of the present invention have a tensile strength ≥1300MPa, an elongation A50 ≥10%, a uniform elongation ≥8%, and a VDA bending angle ≥60°, and can be widely used in the automotive, shipbuilding, and machinery industries. Detailed Implementation

[0069] The hot stamping component and its manufacturing method described in this invention will be further explained and described below with reference to specific embodiments. However, such explanation and description do not constitute an undue limitation on the technical solution of this invention.

[0070] Examples 1-10

[0071] The hot-stamped components of Embodiments 1-10 of the present invention are all manufactured using the following steps:

[0072] (1) Steel plates are obtained;

[0073] (2) Hot stamping: Heat the steel plate to (Ac1+50)~(Ac3+150)℃ and hold for 2~15min, then complete the hot stamping.

[0074] (3) First stage cooling: The hot stamped part is rapidly cooled to Ms~Mf and held at that temperature for 5~200s; in some embodiments, the cooling rate can be controlled to 30-100℃ / s.

[0075] In some embodiments, a reheating step may be added between the first cooling step and the second cooling step: in some more specific embodiments, the hot stamped part may be reheated to Ms~500°C and held at that temperature for 10-300s.

[0076] (4) Second stage cooling: Cool the component to below 100°C; in some embodiments, the cooling rate can be controlled to be no higher than 30°C / s.

[0077] (5) Aging treatment: Reheat the component to 100-400℃, keep it at that temperature for 10-60 minutes, and then air cool it to room temperature.

[0078] In some embodiments, the aging process is followed by a step of plating a coating and / or applying a coating layer.

[0079] Tables 1-1 and 1-2 list the mass percentage of each chemical element in the hot-stamped parts of Examples 1-10.

[0080] Table 1-1. (wt.%, balance Fe and other unavoidable impurities besides P, S, N and B)

[0081] Table 1-2. (wt.%, balance Fe and other unavoidable impurities besides P, S, N and B)

[0082] Tables 2-1 and 2-2 list the specific process parameters for the hot-stamped parts of Examples 1-10 in the above process steps.

[0083] Table 2-1.

[0084] Table 2-2.

[0085] The hot-stamped parts obtained in Examples 1-10 were sampled and their microstructure was observed using SEM, EBSD, XRD, and TEM. Specifically, this invention prepared cross-sectional metallographic samples, selected the 1 / 4 position in the sample thickness direction to characterize the microstructure, and calculated the austenite and tempered martensite content in the samples by measuring the peak curves of the austenite γ phase and α phase using XRD. For K1, the austenite morphology was observed using TEM at a 20,000x field of view. Five fields of view were randomly selected for each sample group, and the major and minor axis dimensions of austenite were statistically analyzed. The content of γ1 with a major-to-minor axis ratio of not less than 4 was specified, and the total content was γ0. For K2, the Mn content in austenite and the surrounding tempered martensite was tested using TEM at a 20,000x field of view. Five fields of view were randomly selected for each sample group, and the average value of K2 was calculated as the final value. Test results: For K3, the austenite content was tested using the same method described above. The austenite content of the original sheet at room temperature, the austenite content at 2% stretching, and the austenite content at tensile fracture were obtained. Specifically, the austenite transformation variable V1 in the plastic stage = (austenite content at 2% stretching) - (austenite content at tensile fracture), and the austenite transformation variable V2 in the elastic stage = (austenite content of the original sheet) - (austenite content at 2% stretching). K3 was calculated from these values. The morphology of the particulate nanoprecipitates in the matrix was observed using TEM at a magnification of 50,000x. The precipitate sizes were statistically analyzed in five different magnifications, and their composition was determined. The microstructure observation results are listed in Table 3.

[0086] Table 3

[0087] As can be seen from Table 3 above, the hot-stamped components of Examples 1-10 of the present invention, through reasonable chemical element composition design and optimized process parameters, achieved ideal microstructure characteristics, with a microstructure containing at least 60% tempered martensite and 5-20% austenite. Simultaneously, the austenite shape factor of the hot-stamped components is K1≥0.7, the austenite composition factor is K2≥3, and the austenite stability factor is K3≥1.5. Furthermore, the microstructure of the hot-stamped components of Examples 1-10 of the present invention also contains particulate precipitates dispersed in the matrix, including TiC and Nb(C,N), and the diameter of the particulate precipitates is less than 30 nm.

[0088] Furthermore, the hot-stamped parts obtained in Examples 1-10 were sampled again and subjected to various performance tests. The test results are listed in Table 4. The relevant performance testing methods are described below:

[0089] Mechanical property testing: The hot-stamped parts of Examples 1-10 were tested in accordance with the national standard GB228.1 Metallic Materials Tensile Testing Part 1: Room Temperature Test Method.

[0090] VDA bending angle: The hot-stamped parts of Examples 1-10 were tested according to the plate bending test of metal materials in VDA238-100.

[0091] Table 4 lists the performance test results of the hot-stamped parts of Examples 1-10.

[0092] Table 4.

[0093] As can be seen from Table 4 above, the hot stamping parts of Embodiments 1-10 of the present invention, through reasonable chemical element composition design and optimized process parameters, obtained ultra-high strength cold-rolled strip steel with excellent performance. The tensile strength of the strip is greater than 1300MPa, the elongation A50 is greater than 10%, the uniform elongation is greater than 8%, and the VDA bending angle is greater than 60°.

[0094] It should be noted that the combination of the technical features in this case is not limited to the combination methods described in the claims of this case or the combination methods described in the specific embodiments. All technical features described in this case can be freely combined or combined in any way, unless they contradict each other.

[0095] It should also be noted that the embodiments listed above are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made thereto are those that can be directly derived or easily conceived by those skilled in the art from the content disclosed in the present invention, and should all fall within the protection scope of the present invention.

Claims

1. A hot-stamped part containing Fe and unavoidable impurities, characterized in that, It also contains the following chemical elements in the following percentages by mass: C: 0.24-0.34%, Si: 0.5-2.0%, Mn: 2.0-4.0%, Al: 0.05-1.0%, Nb: 0.03-0.1%; The microstructure of the hot-stamped component contains at least 60% tempered martensite and 5-20% austenite.

2. The hot-stamped component as described in claim 1, characterized in that, Its mass percentage content of each chemical element is as follows: C: 0.24-0.34%, Si: 0.5-2.0%, Mn: 2.0-4.0%, Al: 0.05-1.0%, Nb: 0.03-0.1%; balance Fe and unavoidable impurities.

3. The hot-stamped component as described in claim 1 or 2, characterized in that: The mass percentage content of Si is 1.0-2.0%; and / or, the mass percentage content of Mn is 3.0-4.0%; and / or, the mass percentage content of Al is 0.1-1.0% or 0.1-0.8%.

4. The hot-stamped component as described in any one of claims 1-3, characterized in that, It also contains at least one of the following chemical elements: 0 < Ti ≤ 0.15%; 0 < V ≤ 1.0%; 0 < Ni ≤ 1.0%; 0 < Cr ≤ 2.0%; 0 < Mo ≤ 1.0%; 0 < Cu ≤ 1.0%; 0 < Ca ≤ 0.01%; 0 < REM ≤ 0.1%.

5. The hot-stamped component as described in any one of claims 1-4, characterized in that, In unavoidable impurities, each impurity element satisfies at least one of the following conditions: P ≤ 0.05%, S ≤ 0.01%, N ≤ 0.01%, B ≤ 0.0005%.

6. The hot-stamped component as described in any one of claims 1-5, characterized in that: Its austenite shape factor K1 = γ1 / γ0, and K1 ≥ 0.7, where γ1 represents the austenite content with a major-to-minor-diameter ratio of not less than 4, and γ0 represents the total austenite content. Preferably, K1 is 0.7-1.0, such as 0.7-0.95; and / or, its austenite composition factor K2 = M1 / M2, and K2 ≥ 3, where M1 represents the mass percentage of Mn element in austenite, and M2 represents the mass percentage of Mn element in tempered martensite. Preferably, K2 is 3.0-7.0, such as 3.0-6.5; and / or, its austenite stability factor K3 = V1 / V2, and K3 ≥ 1.5, where V1 represents the austenite transformation amount in the plastic stage of the tensile test at room temperature, and V2 represents the austenite transformation amount in the elastic stage of the tensile test at room temperature. Preferably, K3 is 1.5-4.

0.

7. The hot-stamped component as described in any one of claims 1-6, characterized in that, The microstructure contains particulate precipitates dispersed in the matrix, the particulate precipitates including TiC and Nb(C,N), and the diameter of the particulate precipitates is less than or equal to 30 nm.

8. The hot-stamped component as described in claim 1 or 2, characterized in that, Its surface is also covered with a plating and / or coating.

9. The hot-stamped component as described in claim 1 or 2, characterized in that, Its tensile strength is ≥1300MPa, elongation A50 is ≥10%, uniform elongation is ≥8%, and VDA bending angle is ≥60°.

10. The hot-stamped component as described in claim 9, characterized in that: Its tensile strength is ≥1380MPa, or ≥1420MPa, ≥1500MPa, or ≥1600MPa, or between 1300 and 1900MPa, such as 1400 to 1900MPa; and / or, the elongation A50 is 10 to 16%; and / or, the uniform elongation is 8 to 12%; and / or, the VDA bending angle is ≥65°, or between 60° and 75° or between 65° and 75°.

11. The method for manufacturing a hot-stamped part according to any one of claims 1-10, characterized in that, It includes the following steps: Steel plates were produced; Hot stamping: Heat the steel plate to (Ac1+50)-(Ac3+150)℃ and hold for 2-15 minutes, then complete the hot stamping process. First stage of cooling: The hot-stamped parts are rapidly cooled to Ms-Mf and held at that temperature for 5-200 seconds; Second stage cooling: Cooling the component to below 100°C; Aging treatment: Reheat the component to 100-400℃, hold for 10-60 minutes, and then air cool to room temperature.

12. The manufacturing method as described in claim 11, characterized in that, Between the first and second cooling steps, there is a reheating step: the hot-stamped part is reheated to Ms-500℃ and held for 10-300s.

13. The manufacturing method as described in claim 11, characterized in that, In the first cooling step, the cooling rate is 30-100℃ / s.

14. The manufacturing method as described in claim 11, characterized in that, In the second cooling step, the cooling rate shall not exceed 30°C / s.

15. The manufacturing method as described in claim 11, characterized in that, The aging process is followed by steps of plating and / or coating.

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