Steel plate base body, pre-plated steel plate and preparation method thereof, hot stamping forming component and preparation method thereof, and automobile structural part

Abstract

The invention relates to a steel plate base body, a pre-plated steel plate and a preparation method thereof, a hot stamping forming component and a preparation method thereof and an automobile structural part. The steel plate substrate comprises 0.29 to 0.42 wt% of C, 0.15 to 0.50 wt% of Si, 0.30 to 0.90 wt% of Mn, 0.10 wt% or less of P, 0.10 wt% or less of S, 0.10 to 0.50 wt% of Al, 0.05 to 0.10 wt% of Nb, 0.001 to 0.02 wt% of B, 0.20 to 0.80 wt% of W, 0.10 wt% or less of impurities, and the balance of Fe. The hot-stamping formed steel plate disclosed by the invention can have high strength and high hydrogen embrittlement-resistant delayed cracking performance at the same time.

Description

Technical Field

[0001] The present invention relates to the field of automotive hot - formed components, and particularly to a steel plate substrate, a pre - plated steel plate and its preparation method, a hot stamping forming member and its preparation method, and an automotive structural member. Background Art

[0002] As an important way to achieve vehicle lightweighting and improve vehicle body collision safety, the hot stamping forming technology of ultra - high strength steel has been widely used in the automotive industry. However, generally, the increase in the strength of steel plates leads to a decrease in plasticity and toughness. Therefore, in the application in the vehicle field, the problems caused by insufficient toughness and delayed cracking of hot stamping forming members have increasingly attracted the attention of technicians. For example, in the actual production process, it is often found that some hot stamping forming members undergo brittle cracking during placement, processing, transportation, or welding after hot stamping, resulting in the scrapping of parts or even the entire vehicle body, thus increasing production costs. Even some hot stamping forming members undergo delayed cracking after the vehicle assembly is completed, thus increasing the safety hazards during vehicle driving.

[0003] Therefore, when using hot stamping forming members, especially when their strength reaches above 1800 MPa, it is crucial to ensure a low risk of hydrogen embrittlement cracking for hot stamping forming members. Summary of the Invention

[0004] The object of the present disclosure is to provide a steel plate substrate, a pre - plated steel plate and its preparation method, a hot stamping forming member and its preparation method, and an automotive structural member, which can have both high strength and excellent high - resistance to hydrogen embrittlement and delayed cracking performance.

[0005] To solve the above - mentioned technical problems, in the first aspect of the present disclosure, a steel plate substrate is provided. Based on the total weight of the steel plate substrate, the steel plate substrate includes 0.29 - 0.42 wt% of C, 0.15 - 0.50 wt% of Si, 0.30 - 0.90 wt% of Mn, P below 0.10 wt%, S below 0.10 wt%, 0.10 - 0.50 wt% of Al, 0.05 - 0.10 wt% of Nb, 0.001 - 0.02 wt% of B, 0.20 - 0.80 wt% of W, impurities below 0.10 wt%, and the balance of Fe.

[0006] Optionally, the steel plate substrate includes 0.32 - 0.38 wt% of C, 0.15 - 0.50 wt% of Si, 0.30 - 0.50 wt% of Mn, P below 0.10 wt%, S below 0.10 wt%, 0.25 - 0.40 wt% of Al, 0.05 - 0.10 wt% of Nb, 0.005 - 0.01 wt% of B, 0.40 - 0.70 wt% of W, impurities below 0.10 wt%, and the balance of Fe.

[0007] Optionally, based on the total weight of the steel plate substrate, the total content of B + W + Nb is 0.42 to 0.90 wt%, preferably 0.45 to 0.70 wt%.

[0008] The second aspect of the present disclosure provides a method for preparing a pre-coated steel plate, comprising the following steps: S1. Annealing the steel plate substrate described in the first aspect of the present disclosure to obtain a first product; S2. After cooling the first product, performing hot-dip plating treatment in a plating solution.

[0009] Optionally, in step S1, the conditions of the annealing treatment include: the annealing temperature is 780 to 830 °C, the dew point is -20 to -3 °C, and the soaking time is 25 to 35 s.

[0010] Optionally, in step S2, the plating solution includes 9 to 12 wt% of Si, 2 to 3 wt% of Fe, impurities below 0.10 wt%, and the balance of Al; The conditions of the hot-dip plating treatment include: the temperature of the first product after cooling is 600 to 680 °C, the temperature of the plating solution is 650 to 700 °C, and the hot-dip plating time is 2 to 15 s; The thickness of the coating obtained by the hot-dip plating treatment is 6 to 16 μm.

[0011] The third aspect of the present disclosure provides a pre-coated steel plate prepared by the method described in the second aspect of the present disclosure.

[0012] The fourth aspect of the present disclosure provides a method for preparing a hot stamping formed component, comprising the following steps: Performing hot stamping treatment on the pre-coated steel plate described in the third aspect of the present disclosure.

[0013] Optionally, the conditions of the hot stamping treatment include: the heating temperature is 880 to 920 °C, the heating time is 180 to 240 s, the hot forming temperature is 680 to 720 °C, the pressure holding time is 8 to 10 s, the cooling rate after hot stamping is 40 to 60 °C / s, and the die-out temperature is below 200 °C.

[0014] The fifth aspect of the present disclosure provides a hot stamping formed component prepared by the method described in the fourth aspect of the present disclosure.

[0015] Optionally, the yield strength of the hot stamping formed component is ≥1250 MPa, the tensile strength is ≥2000 MPa, and the elongation is ≥5%.

[0016] The sixth aspect of the present disclosure provides an automotive structural member comprising the hot stamping formed component described in the fifth aspect of the present disclosure.

[0017] Through the above technical solution, the present disclosure provides a steel plate substrate, a pre-coated steel plate and its preparation method, a hot stamping formed component and its preparation method, and an automotive structural component. By adding and controlling the C content and the contents of other alloying elements in the steel plate substrate, especially controlling the contents of Si, Mn, and Al and adding W and B, and then performing plating treatment and hot stamping treatment on the steel plate substrate, an ultra-high strength steel plate with high resistance to hydrogen embrittlement delayed cracking can be obtained, which has good application effects in automotive structural components.

[0018] Other features and advantages of the present disclosure will be described in detail in the following specific implementation section. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings are used to provide a further understanding of the present disclosure, and constitute a part of the specification. Together with the following specific implementation, they are used to explain the present disclosure, but do not constitute a limitation to the present disclosure. In the drawings: Figure 1 is the stress-strain curve of the hot stamping formed component obtained in Example 1 of the present disclosure; Figure 2 is a photo of the 300h delayed cracking result (no cracking) of the hot stamping formed component obtained in Example 1 of the present disclosure; Figure 3 is a photo of the 300h delayed cracking result (fracture occurred) of the hot stamping formed component obtained in Comparative Example 1 of the present disclosure; Figure 4 is a photo of the 300h delayed cracking result (fracture occurred) of the hot stamping formed component obtained in Comparative Example 9 of the present disclosure. SPECIFIC IMPLEMENTATION

[0020] The following will describe the specific implementation of the present disclosure in detail with reference to the drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the present disclosure, and is not used to limit the present disclosure.

[0021] In the first aspect of the present disclosure, a steel plate substrate is provided. Based on the total weight of the steel plate substrate, the steel plate substrate includes 0.29 - 0.42 wt% of C (carbon), 0.15 - 0.50 wt% of Si (silicon), 0.30 - 0.90 wt% of Mn (manganese), less than 0.10 wt% of P (phosphorus), less than 0.10 wt% of S (sulfur), 0.10 - 0.50 wt% of Al (aluminum), 0.05 - 0.10 wt% of Nb (niobium), 0.001 - 0.02 wt% of B (boron), 0.20 - 0.80 wt% of W (tungsten), less than 0.10 wt% of impurities, and the balance of Fe (iron).

[0022] The present disclosure provides a steel plate substrate. By adding and controlling the C content and the contents of other alloying elements in the steel plate substrate, especially controlling the contents of Si, Mn, and Al and adding W and B, and then performing plating treatment and hot stamping treatment on the steel plate substrate, an ultra-high strength steel plate with high resistance to hydrogen embrittlement and delayed cracking can be obtained, which has good application effects in automotive structural parts.

[0023] According to the present disclosure, C is the most cost-effective element for improving the strength of steel. However, simply increasing the C content will, in addition to increasing the strength, also promote the formation of twinned martensite and deteriorate the toughness of the final steel plate structure. The present disclosure controls the C content in the steel plate substrate to 0.29 - 0.42 wt%, which can balance strength and toughness.

[0024] According to the present disclosure, on the one hand, Si is dissolved in the matrix and has the effect of increasing the matrix strength, and on the other hand, it can also be used as a deoxidizer during the steelmaking process. However, more Si will cause different degrees of grain boundary oxidation and decarburization on the surface of the steel plate at different positions during the cooling process after hot rolling coiling of the steel coil, affecting the pickling effect of the steel coil and ultimately the surface quality of the finished product. The present disclosure controls the Si content to 0.15 - 0.50 wt%, and a steel plate substrate with better performance can be obtained.

[0025] According to the present disclosure, Mn has the effect of improving hardenability and significantly increasing the stability of austenite. When a certain content of Mn is added to the alloy composition, during the heating process, Mn can expand the temperature range of complete austenitization, and during the cooling process, it can delay the formation of ferrite and bainite to promote martensite transformation. The present disclosure controls the Mn content within the range of 0.30 - 0.90 wt%, which can not only give full play to the role of Mn but also avoid the disadvantages of segregation caused by excessive addition of Mn and reducing the toughness of the material.

[0026] According to the present disclosure, Al is an element that can increase the Mf temperature of the steel plate. The present disclosure controls the Al content within the range of 0.10 - 0.50 wt%, which can make the steel plate substrate have a better self-tempering effect.

[0027] According to the present disclosure, Nb(CN) precipitates can pin dislocations, thereby increasing the yield strength. At the same time, undissolved NbC can be retained during the hot forming heating stage to delay the coarsening of austenite grains. The present disclosure controls the Nb content within the range of 0.05 - 0.10 wt%, which can give better play to the effect of Nb.

[0028] According to the present disclosure, controlling the B content within the range of 0.001 - 0.02 wt% can not only significantly improve the hardenability of the steel plate substrate but also avoid the negative effect of boron embrittlement caused by too high B content and being unfavorable to performance.

[0029] According to the present disclosure, adding W metal to the steel plate matrix, there is a chemical affinity between the precipitated WC phase formed and hydrogen atoms, which can combine with hydrogen atoms to form a stable compound W2C·H. The formation of the W2C·H hydride fixes hydrogen atoms, preventing them from freely migrating and aggregating in the material, thereby significantly improving the hydrogen embrittlement resistance of the material. W can dissolve in the iron matrix to form a solid solution, changing the lattice structure of the material, thereby slowing down the diffusion rate of hydrogen atoms. At the same time, it can also reduce the migration path of hydrogen atoms in the material, further improving the hydrogen embrittlement resistance of the material. The present disclosure controls the W content to be 0.20 - 0.80 wt%, which can improve the stability of martensite and greatly improve the hardenability.

[0030] In a preferred embodiment, the steel plate matrix comprises 0.32 - 0.38 wt% of C, 0.15 - 0.50 wt% of Si, 0.30 - 0.50 wt% of Mn, P below 0.10 wt%, S below 0.10 wt%, 0.25 - 0.40 wt% of Al, 0.05 - 0.10 wt% of Nb, 0.005 - 0.01 wt% of B, 0.40 - 0.70 wt% of W, impurities below 0.10 wt% and the balance of Fe. The steel plate matrix with the preferred component contents provided by this embodiment can further improve the hardenability and toughness of the steel plate matrix, and is more conducive to obtaining a hot stamping forming component with a martensite matrix having high strength and high hydrogen embrittlement resistance to delayed cracking.

[0031] In one embodiment, based on the total weight of the steel plate matrix, the total content of B + W + Nb is 0.42 - 0.90 wt%, preferably 0.45 - 0.70 wt%. The inventors of the present disclosure have found that controlling the total content of B, W, and Nb in the steel plate matrix within the range of this embodiment, especially within the preferred range, can further improve the hardenability and toughness of the steel plate matrix to improve the mechanical properties and hydrogen embrittlement resistance to delayed cracking of the hot stamping steel plate.

[0032] In a specific embodiment, the steel plate matrix can be prepared by conventional processes in the art.

[0033] The second aspect of the present disclosure provides a method for preparing a pre-coated steel plate, comprising the following steps: S1. Annealing the steel plate matrix described in the first aspect of the present disclosure to obtain a first product; S2. After cooling the first product, performing hot dip coating treatment in a plating solution.

[0034] The present disclosure provides a method for preparing a pre-coated steel plate. First, through annealing treatment, a first product with an initial low-carbon region can be obtained, which is beneficial to subsequent coating and other processes; then, through hot dip coating treatment, a coating is introduced onto the surface of the steel plate matrix, having an antioxidant and anti-corrosion effect.

[0035] In one embodiment, before the annealing treatment in step S1, the following steps are further included: After the steel plate substrate is pre-degreased, electrolytically degreased, brushed, rinsed, and dried in the cleaning section, more than 90% of the oil and iron powder on the surface of the steel plate substrate can be removed; then the annealed treatment is performed on the cleaned steel plate substrate; the annealing treatment can be carried out in a vertical continuous annealing furnace.

[0036] In one embodiment, the conditions of the annealing treatment in step S1 include: the annealing temperature is 780-830°C, the dew point is -20 to -3°C, and the soaking time is 25-35 s; preferably, the annealing temperature is 790-820°C, the dew point is -22 to -5°C, and the soaking time is 28-32 s. According to the process conditions in this embodiment, especially according to the preferred process conditions, annealing treatment is beneficial to obtain hot stamping steel plates with higher strength and toughness.

[0037] In one embodiment, in step S2, the plating solution includes 9-12% by weight of Si, 2-3% by weight of Fe, impurities below 0.10% by weight, and the balance is Al; preferably, the plating solution includes 10-11% by weight of Si, 2.5-3.0% by weight of Fe, impurities below 0.10% by weight, and the balance is A; using the plating solution provided by this embodiment has a better corrosion resistance effect.

[0038] In one embodiment, the conditions of the hot dip plating treatment include: the temperature of the first product after cooling is 600-680°C, the temperature of the plating solution is 650-700°C, and the hot dip plating time is 2-15 s; preferably, the temperature of the first product after cooling is 620-670°C, the temperature of the plating solution is 660-690°C, and the hot dip plating time is 5-10 s; the first product can be cooled by conventional rapid cooling and / or slow cooling methods. Through the process conditions in this embodiment, especially according to the preferred process conditions, hot dip plating treatment is beneficial to improve the coating quality.

[0039] In a specific embodiment, after step S3, the following steps are further included: S3. After the steel plate substrate leaves the plating solution and before the plating solution on at least one surface of the steel plate substrate solidifies, the excess plating solution on at least one surface is removed by air knife blowing to control the coating thickness on at least one surface; the air knife can adopt conventional processes in the art; S4. After coming out of the loop, the strip steel (steel plate substrate) is subjected to skin pass rolling and tension leveling, and then a passivation solution is coated by a roll coater. The strip steel coated with the passivation solution needs to be dried by hot air; then the strip steel enters the horizontal inspection table and the vertical inspection table for surface quality inspection, and then enters an oiling machine for oiling. After slitting and sampling by a flying shear, it enters a coiler; after packaging, it is warehoused.

[0040] In a specific embodiment, the thickness of the coating obtained by the hot-dip plating treatment is 6 - 16 μm, and it can have good oxidation resistance and anti-corrosion effects.

[0041] The third aspect of the present disclosure provides a pre-coated steel plate prepared by the method according to the second aspect of the present disclosure.

[0042] The fourth aspect of the present disclosure provides a method for preparing a hot stamping forming member, including the following steps: Performing hot stamping treatment on the pre-coated steel plate according to the third aspect of the present disclosure.

[0043] In a preferred embodiment, the conditions of the hot stamping treatment include: the heating temperature is 880 - 920 °C, preferably 900 - 910 °C, the heating time is 180 - 240 s, the hot forming temperature is 680 - 720 °C, the pressure holding time is 8 - 10 s, the cooling rate after hot stamping is 40 - 60 °C / s, and the die exit temperature is below 200 °C. Performing hot stamping treatment according to the process conditions provided in this embodiment is beneficial to improving the performance of the hot stamping steel plate.

[0044] The fifth aspect of the present disclosure provides a hot stamping forming member prepared by the method according to the fourth aspect of the present disclosure.

[0045] In a specific embodiment, the yield strength of the hot stamping forming member is ≥1250 MPa, the tensile strength is ≥2000 MPa, and the elongation is ≥5%; preferably, the yield strength is ≥1350 MPa, the tensile strength is ≥2100 MPa, and the elongation is ≥6%.

[0046] In a specific embodiment, the thickness of the coating of the hot stamping forming member is 10 - 25 μm, and it can have good oxidation resistance and anti-corrosion effects.

[0047] The sixth aspect of the present disclosure provides an automotive structural member, including the hot stamping forming member according to the fifth aspect of the present disclosure.

[0048] In a specific embodiment, the automotive structural member includes, but is not limited to, safety structural members such as the front and rear door left and right anti-collision bars (beams), front and rear bumpers, A-pillar reinforcement plates, B-pillar reinforcement plates, C-pillar reinforcement plates, center tunnels, roof reinforcement beams, etc.; it can also be applied to the production of battery packs for new energy vehicles.

[0049] The present disclosure will be further described in detail below through examples. The raw materials used in the examples can all be obtained through commercial channels.

[0050] Example 1 (1) After the steel plate substrate (the composition of the steel plate substrate is listed in Table 1) is pre-degreased, electro-degreased, brushed, rinsed, and dried in the cleaning section, more than 90% of the oil and iron powder on the surface of the steel plate substrate can be removed; then the cleaned steel plate substrate enters a vertical continuous annealing furnace, is preheated, heated to the required strip annealing temperature of 800 °C, the dew point is -10 °C, and soaked for 30 s, so that the pre-coated steel plate has an initial low-carbon area, and a first product is obtained; (2) The first product is slowly cooled or quickly cooled to 650 °C and then enters the plating solution. The temperature of the plating solution is 660 °C, and the hot-dip plating time is 8 s; the plating solution includes 10% by weight of Si, 3% by weight of Fe, impurities below 0.10% by weight, and the balance is Al; (3) Cooling: After the steel plate substrate leaves the plating solution and before the plating solution on at least one surface of the steel plate substrate solidifies, the excess plating solution on at least one surface is removed by air knife blowing to control the thickness of the plating layer on at least one surface; the thickness of the plating layer is controlled within the range of 6 - 16 μm; (4) Oil coating: After coming out of the loop, the strip is skin-passed and stretch-leveled, and then a passivation solution is coated by a roll coater. The strip coated with the passivation solution needs to be dried by hot air. Then the strip enters a horizontal inspection table and a vertical inspection table for surface quality inspection, and then enters an oiling machine for oil coating. After slitting and sampling by a flying shear, it enters a coiler. Then it is packaged and stored in the warehouse (pre-coated steel plate); (5) Hot stamping treatment: The pre-coated steel plate is subjected to hot stamping treatment. The hot stamping treatment conditions include: the heating temperature is 910 °C, the heating time is 210 s, the hot forming temperature is 690 °C, the holding pressure time is 9 s, the cooling rate after hot stamping is 45 °C / s, and the die exit temperature is 180 °C. A hot-stamped forming component is obtained. The thickness of the plating layer is within the range of 10 - 25 μm.

[0051] Examples 2 - 9 Referring to the preparation method in Example 1, the difference from Example 1 is that the component content of the steel plate substrate used is as shown in Table 1; the remaining processes are the same as those in Example 1.

[0052] Comparative Examples 1 - 8 Referring to the preparation method in Example 1, the difference from Example 1 is that the component content of the steel plate substrate used is as shown in Table 1; the remaining processes are the same as those in Example 1.

[0053] Comparative Example 9 Referring to the preparation method in Example 1, the difference from Example 1 is that the components of the steel plate substrate used include (referring to the component content in WO2024104279A1): 0.33 wt% of C, 0.15 wt% of Si, 1.27 wt% of Mn, 0.013 wt% of P, 0.009 wt% of S, 0.29 wt% of Al, 0.008 wt% of Nb+Ti (by weight), 0.0025 wt% of B, 0.21 wt% of W (B+W+Nb<0.22 wt%), 0.28 wt% of Cr, 0.15 wt% of V, and the balance Fe; the remaining processes are the same as in Example 1.

[0054] Table 1

[0055] In Table 1, the unit of the data of each metal component is "wt%"; the balance of the steel plate substrate in each example and comparative example is Fe; the component content "-" means that the component is not added or the data is not available.

[0056] Test Example 1 Tensile strength test and elongation test were carried out on the hot stamping flat die parts obtained from the above examples and comparative examples in accordance with the "GBT228.1 - Room Temperature Tensile Standard"; the final test results were the average of 3 groups of test results to reduce errors. The test results are listed in Table 2 below.

[0057] Table 2

[0058] The stress-strain curve of the sample obtained in Example 1 is as Figure 1 shown.

[0059] It can be seen from the data in Table 2 that: Comparing Examples 1 - 9 with Comparative Examples 1 - 4, 6 - 7, in Comparative Examples 1 - 4, metal W was not added to the steel plate substrate used, and metal V was used to replace Nb. The hot stamping formed steel plates made from the steel plate substrates in Comparative Examples 1 - 4 could not obtain excellent yield strength, tensile strength, and elongation simultaneously; in Comparative Examples 6 - 7, the W content in the steel plate substrate used was outside the range of "0.20 - 0.80 wt%". The hot stamping formed steel plates obtained in Comparative Examples 6 - 7 had low yield strength and tensile strength, and low elongation, with poor comprehensive performance; the hot stamping formed steel plates prepared from the steel plate substrates provided by the present disclosure in Examples 1 - 9 could simultaneously have high yield strength, tensile strength, and good elongation, with better comprehensive performance; Examples 1 to 9 were compared with Comparative Example 5 and Comparative Example 8. In Comparative Example 5, W was not added to the steel plate substrate used, and in Comparative Example 8, B was not added to the steel plate substrate used. The yield strength and tensile strength of the hot stamping formed steel plates obtained in Comparative Example 5 and Comparative Example 8 were both low, and excellent comprehensive properties could not be obtained. However, W and B were added to the steel plate substrates used in Examples 1 to 9, and the synergistic application effect could be exerted. The hot stamping formed steel plates obtained in Examples 1 to 9 could simultaneously have high yield strength, tensile strength, and good elongation, and had better comprehensive properties. Examples 1 to 9 were compared with Comparative Example 9. The composition of the steel plate substrate in Comparative Example 9 was not within the scope provided by the present disclosure. The hot stamping formed steel plates prepared using the steel plate substrates provided by the present disclosure in Examples 1 to 9 could simultaneously have high yield strength, tensile strength, and good elongation, and had better comprehensive properties. Example 1 was compared with Examples 2 to 9. The composition of the steel plate substrate used in Example 1 was within the preferred scope provided by the present disclosure. The yield strength and tensile strength of the hot stamping formed steel plate obtained in Example 1 were higher, and the elongation was better, and it had better comprehensive properties. Example 7 was compared with Example 8. The total content of B + W + Nb in the steel plate substrate used in Example 7 was within the optimized scope provided by the present disclosure (0.42 to 0.90% by weight). The yield strength and tensile strength of the hot stamping formed steel plate obtained in Example 7 were higher, and it had good elongation, and it had better comprehensive properties. Example 1 was compared with Examples 6 and 9. The total content of B + W + Nb in the steel plate substrate used in Example 1 was within the further preferred scope provided by the present disclosure (0.45 to 0.70% by weight). The yield strength and tensile strength of the hot stamping formed steel plate obtained in Example 1 were higher, and the elongation was better, and it had better comprehensive properties.

[0060] Test Example 2 This test example was used to illustrate the test results of the delayed cracking performance of four-point bending specimens of the hot stamping flat die parts (hot stamping formed steel plates) obtained in Example 1, Comparative Example 1, and Comparative Example 9 above.

[0061] The delayed cracking performance of the hot stamping flat die parts obtained in the above examples and comparative examples was evaluated according to "GB / T 40403 - Method for Determining the Stress Corrosion Cracking Resistance of Metals by Four-Point Bending Method"; the final test results were the average values of 3 groups of test results to reduce errors. The standard for the delayed cracking performance of the hot stamping parts included: no cracking in the 300h hydrogen embrittlement test. This test included the following steps: (1)Obtain rectangular specimens with a cross-sectional size of 15 mm × 115 mm on the hot stamping formed steel plates obtained in the above examples and comparative examples by laser cutting. The length direction of the specimens is perpendicular to the steel plate rolling direction; (2)Select typical specimens and perform pre-tension on a tensile testing machine to obtain the yield strength of the material in the hot stamping state; (3)Perform prestress loading on the specimens through a four-point bending fixture. In this test example, the prestress σ of 100% of the yield strength obtained in step (2) is selected for the hot stamping state steel plate specimens; (5)After loading the specimens, place them in an air medium at a temperature of 15 - 30 °C to observe whether fracture occurs. There are 3 parallel specimens for each stress level. If 1 cracked specimen appears within 300 hours, it is determined that cracking has occurred.

[0062] List the test results in Table 3 below.

[0063] Table 3

[0064] It can be seen from the data in Table 3 that: In the delayed cracking performance test, after 300 h of testing, there is no fracture phenomenon in the hot stamping formed steel plate of Example 1. The photo of the 300 h delayed cracking test result of the steel plate specimen in Example 1 is as Figure 2 shown. It can be seen that there is no cracking phenomenon in the specimen of Example 1; During the testing process of the hot stamping formed steel plate of Comparative Example 1, fracture occurred, and the fracture time was all below 300 h. The photo of the 300 h delayed cracking test result of the specimen in Comparative Example 1 is as Figure 3 shown. It can be seen that obvious fracture occurred in the specimen of Comparative Example 1; During the testing process of the hot stamping steel plate of Comparative Example 9, there is a phenomenon that the sample fractures, and the fracture time is below 300 h. The photo of the 300 h delayed cracking test result of the specimen in Comparative Example 9 is as Figure 4 shown. It can be seen that fracture occurred in some of the hot stamping steel plates of Comparative Example 9.

[0065] The above test results show that the hot stamping formed components made of the steel matrix provided by the present disclosure have more excellent delayed cracking performance.

[0066] The preferred embodiments of the present disclosure have been described in detail above in conjunction with the accompanying drawings. However, the present disclosure is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0067] In addition, it should be noted that, in the above specific embodiments, the various specific technical features described can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present disclosure will not separately describe various possible combination manners.

[0068] Furthermore, any combination can be made among various different embodiments of the present disclosure, as long as it does not violate the idea of the present disclosure, and it should equally be regarded as the content disclosed by the present disclosure.

Claims

1. A steel plate substrate, characterized in that, Based on the total weight of the steel plate substrate, the steel plate substrate comprises 0.29 - 0.42 wt% of C, 0.15 - 0.50 wt% of Si, 0.30 - 0.90 wt% of Mn, P below 0.10 wt%, S below 0.10 wt%, 0.10 - 0.50 wt% of Al, 0.05 - 0.10 wt% of Nb, 0.001 - 0.02 wt% of B, 0.20 - 0.80 wt% of W, impurities below 0.10 wt% and the balance of Fe.

2. The steel plate substrate according to claim 1, wherein, The steel plate substrate comprises 0.32 - 0.38 wt% of C, 0.15 - 0.50 wt% of Si, 0.30 - 0.50 wt% of Mn, P below 0.10 wt%, S below 0.10 wt%, 0.25 - 0.40 wt% of Al, 0.05 - 0.10 wt% of Nb, 0.005 - 0.01 wt% of B, 0.40 - 0.70 wt% of W, impurities below 0.10 wt% and the balance of Fe.

3. The steel plate substrate according to claim 1, characterized in that, Based on the total weight of the steel plate substrate, the total content of B + W + Nb is 0.42 - 0.90 wt%, preferably 0.45 - 0.70 wt%.

4. A method for preparing a pre-coated steel sheet, characterized in that, Comprising the following steps: S1. Annealing the steel plate substrate as described in any one of claims 1 - 3 to obtain a first product; S2. After cooling the first product, subjecting it to hot dip plating treatment in a plating solution.

5. The method according to claim 4, wherein In step S1, the conditions of the annealing treatment include: the annealing temperature is 780 - 830 °C, the dew point is -20 to -3 °C, and the soaking time is 25 - 35 s.

6. The method according to claim 4, characterized in that, In step S2, the plating solution comprises 9 - 12 wt% of Si, 2 - 3 wt% of Fe, impurities below 0.10 wt% and the balance of Al; The conditions of the hot dip plating treatment include: the temperature of the first product after cooling is 600 - 680 °C, the temperature of the plating solution is 650 - 700 °C, and the hot dip plating time is 2 - 15 s; The thickness of the coating obtained by the hot dip plating treatment is 6 - 16 μm.

7. A pre-coated steel plate prepared by the method according to any one of claims 4 - 6.

8. A method for manufacturing a hot stamping formed component, characterized in that, Comprising the following steps: Subjecting the pre-coated steel plate as described in claim 7 to hot stamping treatment.

9. The method according to claim 8, wherein The conditions of the hot stamping treatment include: the heating temperature is 880 - 920 °C, the heating time is 180 - 240 s, the hot forming temperature is 680 - 720 °C, the pressure holding time is 8 - 10 s, the cooling rate after hot stamping is 40 - 60 °C / s, and the die exit temperature is below 200 °C.

10. A hot stamping formed component prepared by the method according to claim 8 or 9.

11. The hot stamping formed component according to claim 10, wherein The hot stamping formed component has a yield strength ≥ 1250 MPa, a tensile strength ≥ 2000 MPa, and an elongation ≥ 5%; preferably, the yield strength ≥ 1350 MPa, the tensile strength ≥ 2100 MPa, and the elongation ≥ 6%.

12. An automotive structural component, characterized in that, Comprising the hot stamping formed component as described in claim 10 or 11.

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