Method for producing high-strength hot-stamped parts with high cold-bending performance, hot-stamped part

Abstract

The application discloses a method for producing high-strength hot-stamping parts with high cold-bending performance, which comprises the following steps: (1) manufacturing a steel plate for hot stamping; (2) part pre-processing; (3) part heat treatment, transfer and stamping: putting a part semi-finished product into a heat treatment furnace, controlling the heat treatment temperature to be 750-960 DEG C, controlling the total heat treatment time to be 1.5-10 min, and the time when the heat treatment temperature is higher than 880 DEG C being not less than 1.2 min; transferring the semi-finished product after the heat treatment to a die for die stamping, the temperature of the semi-finished product being not less than 900 DEG C when leaving the heat treatment furnace; when the thickness of the steel plate of the part is not more than 1.5 mm, the transfer time is controlled to be 11-20 s, and when the thickness of the steel plate of the part is more than 1.5 mm, the transfer time is controlled to be 13-25 s; (4) post-stamping treatment: carrying out isothermal homogenization on the part, and then carrying out mechanical processing to obtain a finished product. Accordingly, the above method can be used to produce a part with a product of strength and plasticity being not less than 10 GPa%, a cold-bending angle being not less than 60 degrees and a maximum load in three-point bending being not less than 13 MPa.

Description

TECHNICAL FIELD

[0001] The present application relates to a manufacturing method of a high-strength component, in particular to a manufacturing method of a high-strength hot-stamped component. BACKGROUND

[0002] In recent years, with the rapid development of the automobile industry, the market and users have increasingly high requirements for vehicles, and lightweight has gradually become a development trend of the future automobile industry.

[0003] In order to meet the requirements of vehicle lightweight, hot-stamped steel is currently often used to prepare automobile structural parts and safety parts, which can not only achieve the lightweight of vehicles but also improve the safety performance of vehicles. Among them, 1500MPA level hot-stamped steel has been widely used in the automobile industry, and 1800MPa and 2000MPa hot-stamped steel has also been used.

[0004] However, research has found that the higher the strength of hot-stamped steel with full martensite structure, the lower the toughness of the steel, and the risk of brittle fracture during the collision process and delayed cracking during the service process will also increase. This problem directly leads to the difficulty of current hot-stamped steel to have both high strength and good toughness.

[0005] In order to solve this problem, in recent years, a large number of scientific and technological workers have made a lot of beneficial attempts:

[0006] The Chinese patent document with publication number CN110799659A and publication date February 14, 2020, entitled "Method for producing high-strength steel components with improved ductility and components obtained by the method" discloses a method for producing high-strength steel components with improved ductility and its method, which mainly controls the Ni content and its distribution, and controls the Ni content in the matrix to be higher than 0.25%, to obtain high-strength steel components with good ductility.

[0007] The Chinese patent document with publication number CN106399837A and publication date February 15, 2017, entitled "Hot-stamping forming steel material, hot-stamping forming process, and hot-stamping forming component" discloses a fine-grained hot-stamped steel. The technical solution mainly adds V element to the matrix to obtain a hot-stamping forming steel material with fine grains, and simultaneously discloses a hot-stamping process. In the hot-stamping process of the technical solution, the mold surface temperature needs to be controlled below 200℃, and the cooling rate of the steel in the mold needs to be controlled to be not less than 10℃ / s.

[0008] A Chinese patent document with publication number CN111876676A, publication date of November 3, 2020, and title of "A production method of 1800MPa grade cold rolled steel for hot stamping forming" discloses a production method of 1800MPa grade cold rolled steel for hot stamping forming. This technical solution obtains a 1800MPa grade hot stamping forming steel under the premise of lower cost control and without adding any trace elements, but the toughness of the hot stamping forming steel, especially the cold bending performance, is insufficient.

[0009] A Chinese patent document with publication number CN101583486A, publication date of November 18, 2009, and title of "Coated steel strip, method of making same, method of using same, stamping blank made therefrom, stamped product made therefrom, and article containing such stamped product" reports a hot stamping method of coated steel material, which limits the residence time of the blank from leaving the heat treatment furnace to the start of stamping to no more than 10s, and controls the cooling rate of the blank from leaving the furnace to 400℃ to be greater than 50℃ / s, but this technical solution does not study the toughness of the material.

[0010] A Chinese patent document with publication number CN108588612A, publication date of September 28, 2018, and title of "Hot stamping forming member, hot stamping forming pre-coated steel sheet, and hot stamping forming process" discloses a pre-coated hot stamping steel and its hot stamping method. In this technical solution, it is mentioned that the temperature of the steel sheet is above 550℃ when it is transferred to the mold, and the patent CN101583486B has the problem of low cold bending performance. This patent improves the cold bending problem by reducing the thickness of the coating.

[0011] As can be seen, in the current prior art, there are few studies by those skilled in the art on high-strength hot stamping forming steel with good cold bending performance. In the above technical solutions, only the patent document with publication number CN110799659A studies the cold bending performance of the hot stamping forming steel while ensuring that the hot stamping forming steel has high strength.

[0012] Studies have found that the greater the cold bending angle of hot stamping forming steel, the more energy it can absorb under the same conditions, and the longer the time to failure can be delayed. Therefore, the inventors believe that it is particularly important to study the cold bending performance of high-strength hot stamping steel and its feasible production method. Based on this, the present application aims to obtain a method for producing high-strength hot stamping parts with high cold bending performance. SUMMARY

[0013] One of the purposes of the present application is to provide a method for producing high-strength hot stamping parts with high cold bending performance. The method is simple and feasible, and can effectively produce high-strength hot stamping parts with high cold bending performance, has good popularization prospect and application effect.

[0014] To achieve the above object, the present application proposes a method for producing high-strength hot-stamped parts with high cold-bending performance, which comprises the steps of:

[0015] (1) manufacturing a hot-stamping steel plate;

[0016] (2) part pre-processing;

[0017] (3) part heat treatment, transfer and stamping: placing the part semi-finished product processed into a specified shape into a heat treatment furnace, controlling the heat treatment temperature to be 750-960℃, controlling the total heat treatment time to be 1.5-10min, wherein the time at a heat treatment temperature above 880℃ is not less than 1.2min; transferring the semi-finished product after heat treatment to a die for die stamping, the temperature of the semi-finished product leaving the heat treatment furnace is not less than 900℃; wherein when the thickness of the steel plate of the produced part is ≤1.5mm, the transfer time is controlled to be 11-20s, and when the thickness of the steel plate of the produced part is >1.5mm, the transfer time is controlled to be 13-25s;

[0018] (4) post-stamping treatment: homogenizing the part by heat preservation, and then machining to obtain a finished product.

[0019] In the above technical solution of the present application, the inventors have optimized the design of the part heat treatment, transfer and stamping process in step (3), which is particularly important for the performance of the parts described in the present application, and the three are complementary to each other. The heat treatment process is very critical for the forming of the part, the transfer is very critical for the cold bending and strength of the part, and the stamping is very important for the forming and strength of the part.

[0020] The temperature and time of the heat treatment process can be flexibly adjusted according to the thickness specification and size of the part, and the main purpose is to ensure complete austenitization and surface characteristics. The optimized transfer process is the core of the technical solution of the present application. In the past, in order to ensure high strength, the transfer process is required to be as fast as possible, basically completed within 10s, but the present application has found that, combined with the phase transition temperature turning point of the substrate of the hot-stamping steel plate, the transfer time can be controlled within a suitable range, thereby ensuring high strength and improving cold-bending performance.

[0021] In the present application, in specific implementation, the heat treatment temperature in the above-mentioned temperature range of 750-960℃ can be different in different temperature stages, or can be only one stage temperature range, the heat treatment temperature can be freely increased or decreased, the total heat treatment time is controlled to be 1.5-10min, and the time at a heat treatment temperature above 880℃ is not less than 1.2min, the temperature of the semi-finished product leaving the heat treatment furnace is not less than 900℃, otherwise it may lead to incomplete austenitization and affect the strength and plasticity product. The heat treatment time represents the total time at all heat treatment temperatures.

[0022] Accordingly, in the step (4) of the present application, the post-stamping treatment process can further eliminate the residual stress of the forming process, solve the problem of uneven structure and hydrogen diffusion, and further improve the cold bending performance of the part.

[0023] It should be noted that in the step (2) of the present application, in some embodiments, the part pre-processing process can be completed by one or more steps of laser or shearing according to the shape of the required part, or two or more steel plates of different shapes and thicknesses can be combined to complete the part pre-processing process in the form of tailor-welding or patch-welding. Of course, the part pre-processing process of the present application is not limited to the operations described, and in some other embodiments, it can also include similar or equivalent operations.

[0024] In addition, it should be noted that if the tailor-welded part or the patch-welded part is obtained in step (2), and if one thickness is less than or equal to 1.5 mm and the other thickness is greater than 1.5 mm, the transfer time of the part should take both into account, for example, it can be selected to be 13-20 s.

[0025] Further, in the method for producing a high-strength hot-stamped part with high cold bending performance according to the present application, the hot-stamping steel sheet includes at least one of a non-coated steel sheet, an aluminum-silicon coated steel sheet, an aluminum-silicon-zinc-magnesium coated steel sheet, an aluminum-silicon-magnesium coated steel sheet, a hot-dipped galvanized coated steel sheet, and a zinc-iron alloy coated steel sheet.

[0026] Further, in the method for producing a high-strength hot-stamped part with high cold bending performance according to the present application, the chemical composition of the substrate of the hot-stamping steel sheet is as follows: C: 0.2-0.4%, Mn: 1.0-2.0%, Si: 0.1-0.5%, Al: 0.01-0.1%, Ti: 0.01-0.1%, B: 0.0005-0.01%, Cr: 0.1-0.5%, and Nb+Mo+Ni: 0.3-0.6%, wherein the mass percentage of any one of Nb, Mo, and Ni is not more than 0.3%.

[0027] In the substrate of the hot-stamping steel sheet according to the present application, the design principles of each chemical element are as follows:

[0028] C: In the substrate described in the present application, the appropriate amount of C element added in the substrate can ensure the strength of the steel material to ensure the strength of the hot stamping part. Therefore, the content of C element in the steel should not be too low, when the content of C element in the steel is lower than 0.2%, the strength cannot be guaranteed; at the same time, the content of C element in the steel should not be too high, when the content of C element in the steel is higher than 0.4%, the strength will be too high, which will make the welding performance of the steel material worse. Based on this, considering the performance of the substrate, in the substrate described in the present application, the mass percentage content of C element is controlled between 0.2-0.4%.

[0029] Mn: In the substrate described in the present application, Mn element, like C element, is also added to ensure the strength of the hot stamping part, and Mn element can further compensate the toughness of the substrate steel material. When the content of Mn element in the steel is lower than 1.0%, the strength of the steel material cannot be guaranteed; when the content of Mn element in the steel is higher than 2.0%, the element segregation and production cost will increase. Based on this, in order to exert the beneficial effect of Mn element, in the substrate described in the present application, the mass percentage content of Mn element is controlled between 1.0%-2.0%.

[0030] Si: In the substrate described in the present application, the appropriate amount of Si element added not only can improve the strength of the hot stamping part, but also is an important deoxidizer in the steelmaking process. When the content of Si element in the steel is too high, it will cause serious oxidation in the production process, which is difficult to ensure the good surface quality of the product. Therefore, in the substrate described in the present application, the mass percentage content of Si element is controlled between 0.1-0.5%.

[0031] Al: In the substrate described in the present application, Al element is also a deoxidizer, and the appropriate amount of Al element added can also improve the impact toughness of the steel material. Therefore, considering the influence of Al element on the performance of the steel material, in the substrate described in the present application, the mass percentage content of Al element is controlled between 0.01-0.1%.

[0032] B: In the substrate described in the present application, the appropriate amount of B element added can improve the hardenability of the steel material to ensure the full hardening of the hot stamping part at different positions. Therefore, in the substrate described in the present application, the mass percentage content of B element is controlled between 0.0005-0.01%.

[0033] Ti: In the substrate described in the present application, Ti is a C, N strengthening element, and the appropriate amount of Ti element added in the steel can improve the strength and toughness of the substrate, and further improve the strength and toughness of the hot stamping part. At the same time, Ti element can also interact with B element, so as to better exert the hardenability of B. Based on this, in order to exert the beneficial effect of Ti element, in the substrate described in the present application, the mass percentage content of Ti element is controlled between 0.01-0.1%.

[0034] Cr: In the substrate described in this invention, adding an appropriate amount of Cr element can also improve the hardenability of the steel and ensure that all parts of the hot-stamped component are fully hardened. Therefore, in the substrate described in this invention, the mass percentage content of Cr element is controlled between 0.1% and 0.5%.

[0035] It should be noted that the substrate described in this invention further contains appropriate amounts of Nb, Mo, and Ni elements. Nb and Mo elements can both refine the grain size and improve the toughness of the hot-stamped component; while Ni element can also improve the toughness of the hot-stamped component, and Ni also improves hydrogen diffusion. Therefore, in the substrate described in this invention, the mass percentage content of Nb, Mo, and Ni elements is controlled to satisfy: Nb + Mo + Ni: 0.3–0.6%. The mass percentage content of any one of Nb, Mo, and Ni does not exceed 0.3%.

[0036] Furthermore, in the method for producing high-strength hot-stamped parts with high cold bending performance according to the present invention, in step (3), the total heat treatment time is controlled to be 1.5 to 8 minutes.

[0037] Furthermore, in the method for producing high-strength hot-stamped parts with high cold bending performance according to the present invention, in step (3), the stamping speed is controlled to be 40-80 mm / s and held for 2-30 s.

[0038] Furthermore, in the method for producing high-strength hot stamped parts with high cold bending performance according to the present invention, in step (3), the die temperature is always below 200°C during the stamping process.

[0039] Furthermore, in the method for producing high-strength hot-stamped parts with high cold bending performance according to the present invention, in step (4), the temperature for heat preservation and homogenization is 150-250°C and the time is 10-30 min.

[0040] Furthermore, in the method for producing high-strength hot-stamped parts with high cold bending performance according to the present invention, in step (4), the machining includes at least one of cutting, trimming, punching, and welding.

[0041] Furthermore, in the method for producing high-strength hot-stamped parts with high cold bending performance according to the present invention, the parts form a martensitic structure with a volume ratio of 95% or more in step (3).

[0042] Accordingly, another objective of the present invention is to provide a high-strength hot-stamped component that, while possessing high strength, also exhibits high cold-bending performance. It has wide applicability and can be effectively applied in the automotive industry, demonstrating good resistance to frontal and side impacts during vehicle collisions.

[0043] To achieve the above objectives, the present invention proposes a high-strength hot-stamped component, which is manufactured by the method described above, and has a strength-ductility volume ≥10GPa·%, a cold bending angle ≥60 degrees, and a maximum load of ≥13MPa at three points.

[0044] Compared with the prior art, the method and hot-stamped parts for producing high-strength hot-stamped parts with high cold bending performance described in this invention have the following advantages and beneficial effects:

[0045] In this invention, the inventors have made reasonable optimization designs for the manufacturing method of high-strength hot stamping parts. By optimizing and controlling the three processes of heat treatment, transfer and stamping, it can ensure that the parts have high strength, good toughness and cold bending performance.

[0046] In the method for producing high-strength hot-stamped parts with high cold bending performance described in this invention, the parts can form a martensitic structure of more than 95% during heat treatment and stamping, thereby achieving high strength. Simultaneously, through precise transfer control, this invention fully utilizes the cooling difference between the surface and core layers, creating a gradient microstructure transformation control on the surface of the parts, which greatly contributes to improving the toughness and cold bending performance of the parts.

[0047] The high-strength hot-stamped parts prepared by the above method of the present invention have excellent performance, with a strength-ductility volume ≥10GPa·%, a cold bending angle ≥60 degrees, and a maximum three-point bending load ≥13MPa. The high-strength hot-stamped parts have a wide range of applications and can be effectively used in the automotive industry, exhibiting good resistance to frontal and side impacts during automotive collisions. Attached Figure Description

[0048] Figure 1 This is a microscopic photograph of the coating cross-section of the high-strength hot-stamped component in Example 2. Detailed Implementation

[0049] The method for producing high-strength hot-stamped parts with high cold bending performance and the hot-stamped parts described in this invention will be further explained and described below with reference to specific embodiments. However, this explanation and description do not constitute an improper limitation on the technical solution of this invention.

[0050] Examples 1-9

[0051] Table 1 lists the mass percentage of each chemical element in the substrate of the hot stamping steel plates of Examples 1-9 and the relationship between the various chemical elements.

[0052] Table 1. (wt%, balance is Fe and other unavoidable impurities)

[0053]

[0054] In the present application, the high-strength hot-stamped parts of Examples 1-9 are all prepared by the following steps:

[0055] (1) A base plate strip is prepared by steelmaking, hot rolling, cold rolling, annealing and other processes according to the mass percentage of each chemical element shown in Table 1 above. The prepared base plate strip can be directly used as a hot-stamping steel plate, or the base plate strip can be further plated with a plating layer to be used as a hot-stamping steel plate.

[0056] (2) Part pre-processing: according to the required part shape, blanking can be completed in one or more steps by laser or shearing, or two or more steel plates of different shapes and thicknesses can be combined to complete the blanking in the form of tailor-welding or patch-welding.

[0057] (3) Part heat treatment, transfer and stamping: the part semi-finished product processed into a specified shape is placed into a heat treatment furnace, the heat treatment temperature is controlled to be 750-960℃, the total heat treatment time is controlled to be 1.5-10min, and preferably 1.5-8min, and the time when the heat treatment temperature is above 880℃ is not less than 1.2min; the semi-finished product after completing the heat treatment is transferred to a die for die stamping, the temperature of the semi-finished product leaving the heat treatment furnace is not less than 900℃; the upper and lower dies are closed by a press, the stamping speed is controlled to be 40-80mm / s and maintained for 2-30s, and the die temperature is always below 200℃ during the stamping process; when the thickness of the steel plate of the prepared part is ≤1.5mm, the transfer time is controlled to be 11-20s, and when the thickness of the steel plate of the prepared part is >1.5mm, the transfer time is controlled to be 13-25s.

[0058] (4) Post-stamping treatment: the part is subjected to heat treatment homogenization, the heat treatment homogenization temperature is controlled to be 150-250℃ and the time is 10-30min, and then mechanical processing is performed to obtain a finished product; wherein the mechanical processing includes cutting, trimming, punching and welding.

[0059] It should be noted that in step (1) of the above manufacturing method, the hot-stamping steel plate can be a non-plated steel plate or a plated steel plate. When the hot-stamping steel plate is a plated steel plate, it can be specifically: an aluminum-silicon plated steel plate, an aluminum-silicon-zinc-magnesium plated steel plate, an aluminum-silicon-magnesium plated steel plate, a hot-dipped zinc plated steel plate, a zinc-iron alloy plated steel plate.

[0060] In the present application, the specific process steps of Examples 1-9 in steps (1) and (2) above are as follows:

[0061] Example 1: A 1.2 mm base plate strip was obtained by steel making, hot rolling, cold rolling, annealing, according to the mass percentage composition of each chemical element shown in Table 1 above. The 1.2 mm base plate strip was hot dip plated with aluminum silicon at 650°C to obtain an aluminum silicon plated steel plate, wherein the plating bath composition was 9% Si, 2.3% Fe, and the remainder Al and unavoidable impurities. In the pre-processing of the part, the aluminum silicon plated steel plate was continuously blanked into a part of a certain shape.

[0062] Example 2: A 1.5 mm and 1.8 mm base plate strip was obtained by steel making, hot rolling, cold rolling, annealing, according to the mass percentage composition of each chemical element shown in Table 1 above. The 1.5 mm and 1.8 mm base plate strip was hot dip plated with aluminum silicon at 650°C to obtain an aluminum silicon plated steel plate, wherein the plating bath composition was 9% Si, 2.3% Fe, and the remainder Al and unavoidable impurities. In the pre-processing of the part, the aluminum silicon plated steel plate was laser blanked into a part of a certain shape, and the two parts were connected by tailor welding to obtain a part of a certain shape.

[0063] Example 3: A 1.8 mm base plate strip was obtained by steel making, hot rolling, cold rolling, annealing, according to the mass percentage composition of each chemical element shown in Table 1 above. The 1.8 mm base plate strip was hot dip plated with aluminum silicon at 660°C to obtain an aluminum silicon plated steel plate, wherein the plating bath composition was 8.5% Si, 2.5% Fe, and the remainder Al and unavoidable impurities. In the pre-processing of the part, the aluminum silicon plated steel plate was continuously blanked into a blank of a certain shape, and a patch was made by spot welding at a local position of the blank (patch welding was made by two base plates with a thickness of 1.8 mm), to obtain a part of a certain shape.

[0064] Example 4: A 2.0 mm base plate strip was obtained by steel making, hot rolling, cold rolling, annealing, according to the mass percentage composition of each chemical element shown in Table 1 above, and was used as a hot stamping steel plate. In the pre-processing of the part, the strip was continuously blanked into a blank of a certain shape.

[0065] Example 5: A 2.3 mm base plate strip was obtained by steel making, hot rolling, cold rolling, annealing, according to the mass percentage composition of each chemical element shown in Table 1 above, and was used as a hot stamping steel plate. In the pre-processing of the part, the strip was continuously blanked into a blank of a certain shape.

[0066] Example 6: A 1.4 mm base plate strip was obtained by steel making, hot rolling, cold rolling, annealing, according to the mass percentage composition of each chemical element shown in Table 1 above. The 1.4 mm base plate strip was hot dip plated with zinc iron alloy at 680°C to obtain a zinc iron alloy plated steel plate, wherein the plating bath composition was 9% Si, 2.3% Fe, and the remainder Al and unavoidable impurities. In the pre-processing of the part, the zinc iron alloy plated steel plate was laser blanked into a blank of a certain shape.

[0067] Example 7: According to the mass percentage of each chemical element shown in Table 1 above, the steel plate with a thickness of 2.5 mm is obtained by steelmaking, hot rolling, cold rolling and annealing. The steel plate with a thickness of 2.5 mm is hot-dip plated with aluminum-silicon-magnesium coating at 680°C to obtain an aluminum-silicon-magnesium coated steel plate, wherein the composition of the plating solution is 8.5% Si, 1% Mg, and the rest is Al and inevitable impurities. In the pre-processing of the parts, the aluminum-silicon-magnesium coated steel plate is laser blanked into a blank with a certain shape.

[0068] Example 8: According to the mass percentage of each chemical element shown in Table 1 above, the steel plate with a thickness of 0.9 mm is obtained by steelmaking, hot rolling, cold rolling and annealing. The steel plate with a thickness of 0.9 mm is hot-dip plated at 680°C to obtain a hot-dip galvanized coated steel plate, wherein the composition of the plating solution is 0.13% Al, and the rest is Zn and inevitable impurities. In the pre-processing of the parts, the hot-dip galvanized coated steel plate is laser blanked into a blank with a certain shape.

[0069] Example 9: According to the mass percentage of each chemical element shown in Table 1 above, the steel plate with a thickness of 3.0 mm is obtained by steelmaking, hot rolling, cold rolling and annealing. The steel plate with a thickness of 3.0 mm is hot-dip plated at 680°C to obtain an aluminum-silicon-zinc-magnesium coated steel plate, wherein the composition of the plating solution is 8.5% Si, 1% Mg, 10% Zn, and the rest is Al and inevitable impurities. In the pre-processing of the parts, the aluminum-silicon-zinc-magnesium coated steel plate is laser blanked into a blank with a certain shape, and the blank is heat treated.

[0070] It should be noted that in the present application, the chemical composition design and related processes of the hot stamping steel plate of the high-strength hot stamping parts of Examples 1-9 meet the design specification requirements of the present application.

[0071] Table 2-1 and Table 2-2 list the related process parameters of the manufacturing method of the high-strength hot stamping parts of Examples 1-9.

[0072] Table 2-1.

[0073]

[0074] Table 2-2.

[0075]

[0076] It should be noted that in the above Table 2-1 of the present application, the heat treatment temperature in the heat treatment process of step (3) of Examples 1-9 is a range value rather than a single point value, because the heat treatment furnace is usually divided into segments, each segment can be controlled independently, and the temperatures of each segment can be different. The temperature range of the heat treatment temperature described in the present application is the distribution range of all temperatures of each segment.

[0077] In addition, it should be noted that, in the process of carrying out the manufacturing process described above, in step (3), after the component heat treatment, transfer and stamping of the embodiments 1-9 according to the design requirements, samples of the components of the embodiments 1-9 can be taken and the microstructure of the components of each embodiment can be detected to obtain the proportion of the martensite structure in the components of the embodiments 1-9, and the related test results are listed in Table 3 below.

[0078] Table 3.

[0079]

[0080] The high-strength hot-stamped components of the finished products of the embodiments 1-9 obtained through the above process steps are sampled respectively, and each performance test of each embodiment sample is carried out, and the performance test results are listed in Table 4 below.

[0081] In the present application, the performance detection means used are as follows:

[0082] (1) Strength-plasticity product: The strength-plasticity product is a comprehensive performance index representing the strength and toughness level of the metal material, and the product of the tensile strength and the elongation at break of the component is used to obtain the strength-plasticity product of each embodiment sample.

[0083] (2) Cold bending test: The cold bending test is carried out according to the VDA-238 standard to obtain the cold bending angle of the samples of the embodiments 1-9. The greater the cold bending angle, the better the material toughness; the smaller the cold bending angle, the lower the material toughness.

[0084] (3) Three-point bending test and drop hammer test: The three-point bending test and drop hammer test are to place the hot-stamped components of the embodiments on the bending device, adjust the span, load on the component to carry out the bending test, until the component breaks, and record the maximum load at which the component breaks. In the drop hammer test, a 30kg drop hammer is dropped freely from a height of 50cm, and the cracking of each embodiment sample component is observed.

[0085] (4) Diffusion hydrogen content test: The sample is obtained from the component by wire cutting, punching or sawing with water cooling, ultrasonic cleaned with acetone, and the diffusion hydrogen content of each embodiment sample is measured at 300-400°C by hydrogen analyzer.

[0086] Table 4 lists the related performance test results of the high-strength hot-stamped component samples of the embodiments 1-9.

[0087] Table 4.

[0088]

[0089] Note: * indicates that the high-strength hot-stamped components of the embodiments 1-9 used as the anti-collision beam components are subjected to the drop hammer test.

[0090] It should be noted that, since the example 2 is a tailor-welded part, the example 3 is a patch-welded part, both of which involve welds, the drop weight test is not well evaluated by the welds; at the same time, the maximum load test is also not well evaluated by the welds. Therefore, the example 2 and the example 3 do not perform the three-point bending test and the drop weight test.

[0091] As can be seen from Table 4, the high-strength hot stamping parts of examples 1-9 have higher strength, better toughness and better cold bending performance. In the present application, the high-strength hot stamping parts of examples 1-9 have a strength-toughness product of 10-12 GPa·%, a cold bending angle of 60-75 degrees, and a three-point bending maximum load of 13-20 KN.

[0092] Correspondingly, further referring to Table 4, when the high-strength hot stamping parts of examples 1-9 used as crash beam parts are subjected to drop weight test, the high-strength hot stamping parts of examples 1-9 do not crack, and have better strength-toughness product and toughness; at the same time, the diffusion hydrogen content of the high-strength hot stamping parts of examples 1-9 is between 0.01-0.06 ppm, and has better hydrogen embrittlement resistance.

[0093] Figure 1 The plated layer cross-section microstructure photograph of the high-strength hot stamping part of example 2.

[0094] As shown in Figure 1 , in the high-strength hot stamping part of example 2, example 2 has an aluminum-silicon plated layer, which comprises a substrate A and a plated layer B. There is an obvious interface layer C between the plated layer A and the substrate B.

[0095] It should be noted that the combination of the technical features in the present case is not limited to the combination mode described in the claims of the present case or the combination mode described in the specific embodiments. All the technical features described in the present case can be freely combined or combined in any way, unless contradictory to each other.

[0096] It should also be noted that the above examples are only specific embodiments of the present application. Obviously, the present application is not limited to the above examples, and similar changes or modifications made directly from the disclosure of the present application or easily thought of by those skilled in the art should all fall within the scope of protection of the present application.

Claims

1. A method for producing a high-strength hot-stamped part with high cold-bending performance, characterized in that, The method comprises the steps of: (1) manufacturing a hot stamping steel plate; (2) part pre-processing; (3) part heat treatment, transfer and stamping: placing the part semi-finished product processed into a specified shape into a heat treatment furnace, controlling the heat treatment temperature to be 750-960 DEG C, controlling the total heat treatment time to be 1.5-10 min, wherein the time of the heat treatment temperature being above 880 DEG C is not less than 1.2 min; transferring the semi-finished product completing the heat treatment to a die for die stamping, the temperature of the semi-finished product leaving the heat treatment furnace being not less than 900 DEG C; wherein when the thickness of the steel plate of the part is ≤1.5 mm, the transfer time is controlled to be 11-20 s, and when the thickness of the steel plate of the part is >1.5 mm, the transfer time is controlled to be 13-25 s; (4) post-stamping treatment: subjecting the part to temperature homogenization at 150-250 DEG C for 10-30 min, and then performing mechanical processing to obtain a finished product.

2. The method for producing high strength hot-stamped parts with high draw performance of claim 1, wherein, The hot stamping steel plate comprises at least one of a non-coated steel plate, an aluminum-silicon coated steel plate, an aluminum-silicon-zinc-magnesium coated steel plate, an aluminum-silicon-magnesium coated steel plate, a hot-dip galvanized coated steel plate, and a zinc-iron alloy coated steel plate.

3. The method for producing high strength hot-stamped parts with high draw performance of claim 1, wherein, The chemical composition of the substrate of the hot stamping steel plate comprises, by weight percentage: C: 0.2-0.4%, Mn: 1.0-2.0%, Si: 0.1-0.5%, Al: 0.01-0.1%, Ti: 0.01-0.1%, B: 0.0005-0.01%, Cr: 0.1-0.5%, and Nb+Mo+Ni: 0.3-0.6%, wherein the mass percentage content of any one of Nb, Mo and Ni is not more than 0.3%.

4. The method for producing high strength hot-stamped parts with high draw performance of claim 1, wherein, In step (3), the total heat treatment time is controlled to be 1.5-8 min.

5. The method for producing high strength hot-stamped parts with high draw performance of claim 1, wherein, In step (3), the stamping speed is controlled to be 40-80 mm / s and maintained for 2-30 s.

6. The method for producing high strength hot-stamped parts with high draw performance of claim 1 or 5, wherein, In step (3), the die temperature is always lower than 200 DEG C during stamping.

7. The method for producing high strength hot-stamped parts with high draw performance of claim 1, wherein, In step (4), the mechanical processing comprises at least one of cutting, trimming, punching and welding.

8. The method for producing high strength hot-stamped parts with high draw performance of claim 1, wherein, The part forms a martensite structure with a volume ratio of more than 95% in step (3).

9. High-strength hot-stamped part produced using the method according to any one of claims 1 to 8, characterized in that, The product has a strength and ductility product of ≥10 GPa%, a cold bending angle of ≥60 degrees, and a maximum three-point bending load of ≥13 MPa.

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