Low-cost high-corrosion-resistance steel and preparation method thereof

Abstract

The invention discloses low-cost high-corrosion-resisting steel and a preparation method thereof, belongs to the technical field of corrosion-resisting steel, and solves the problems that the corrosion-resisting steel in the prior art is high in high-cost element content, high in cost and complex in preparation process. The low-cost high-corrosion-resistance steel comprises the following components in percentage by mass: less than or equal to 0.08% of C, 0.25%-0.35% of Si, 0.60%-0.80% of Mn, 1.0%-1.5% of Ni, 0.4%-0.6% of Cr, 0.8%-1.3% of Cu and the balance of Fe and other inevitable impurities. The low-cost high-corrosion-resistance steel is low in cost and excellent in mechanical property and corrosion resistance.

Description

Technical Field

[0001] The invention relates to the technical field of corrosion-resistant steel, and in particular to low-cost high-corrosion-resistant steel and a preparation method thereof. Background Art

[0002] In recent years, China has conducted some research on corrosion-resistant steel for high-humidity and high-heat marine environments. At present, in the harsh marine atmospheric environment, only 3Ni steel has been widely recognized for its weather resistance, but since Ni is a rare metal, its mineral resources are not abundant, and its recovery rate in steel is extremely low, 3Ni steel has a high cost and limited application. Therefore, it is imperative to independently develop economical corrosion-resistant steel suitable for high-temperature, high-humidity and high-salt fog marine atmospheric environments.

[0003] 201911299435.X discloses a 420MPa grade low alloy corrosion-resistant steel, whose chemical composition wt% is C: 0.03-0.10, Si: 0.01-1.0, Mn: 1.0-2.1, S≤0.005, P≤0.01, Als≤0.02, Cu: 0.1-0.6, Ni: 0.2-4.0, Mg: 0.001-0.01, Ca: 0.001-0.01, O: 0.001-0.01, and the balance is Fe and unavoidable impurities. The corrosion resistance of low alloy steel is further guaranteed by using Ni as the main corrosion-resistant alloying element, assisted by a small amount of Cu, and combining Mg-Ca treatment to control the morphology and size of inclusions; 202111284679.8 discloses a 390MPa grade low alloy corrosion-resistant steel, whose chemical composition wt% is C: 0.03-0.08, Si: 0.25-0.35, S≤0.020, P≤0.02, Mn: 0.35-0.65, Mo: 0.20-0.40, Cr: 0.7-1.2, Ni: 0.8-1.2, V: 0.06-0.12, Ti: 0.006-0.012, N≤0.0020, and the rest is iron and unavoidable impurities. By utilizing the synergistic effect of various alloy elements in the iron-based structure to configure alloy elements with lower C content and Ni, Cr, and Mo contents that exceed their upper limits, the corrosion resistance is improved while ensuring welding performance and low-temperature toughness.

[0004] In summary, although some existing low-alloy steels can have corrosion resistance and matching mechanical properties suitable for high-humidity and hot marine environments by adding corrosion-resistant elements such as Ni and Cr and controlling inclusions, most of them contain high-cost elements such as Ni and Cr, and most corrosion-resistant steels must undergo hot rolling + "quenching-tempering" heat treatment process, and the preparation process is complicated. Summary of the invention

[0005] In view of the above situation, the present invention aims to provide low-cost high-corrosion-resistant steel and a preparation method thereof, so as to solve one of the following technical problems: the existing corrosion-resistant steel has a high content of high-cost elements and high cost; the existing corrosion-resistant steel preparation process is complicated.

[0006] The purpose of the present invention is mainly achieved through the following technical solutions:

[0007] On the one hand, the present invention provides a low-cost and high-corrosion-resistant steel, the components of which, by mass percentage, include: C≤0.08%, Si: 0.25%~0.35%, Mn: 0.60%~0.80%, Ni: 1.0%~1.5%, Cr: 0.4%~0.6%, Cu: 0.8%~1.3%, and the balance is Fe and other inevitable impurities.

[0008] Furthermore, the components of the low-cost and high-corrosion-resistant steel include, by mass percentage: C 0.04% to 0.08%, Si: 0.27% to 0.35%, Mn: 0.60% to 0.80%, Ni: 1.0% to 1.5%, Cr: 0.4% to 0.6%, Cu: 0.8% to 1.3%, and the remainder is Fe and other inevitable impurities.

[0009] Furthermore, the microstructure of the low-cost and high-corrosion-resistant steel is tempered martensite + nano-scale copper-rich phase.

[0010] Furthermore, the mass percentage of the copper-rich phase is 0.2% to 1.5%.

[0011] The present invention also provides a method for preparing the above-mentioned low-cost high-corrosion-resistant steel, comprising the following steps:

[0012] Step 1, smelting and casting into billet;

[0013] Step 2, subjecting the blank to controlled rolling to obtain a hot-rolled plate, wherein the controlled rolling includes two stages: recrystallization rolling and non-recrystallization rolling;

[0014] Step 3, directly quenching the hot-rolled plate;

[0015] Step 4: Perform tempering heat treatment to obtain low-cost and highly corrosion-resistant steel.

[0016] Furthermore, in step 2, the start rolling temperature of the recrystallization rolling is 1150-1100°C.

[0017] Furthermore, in step 2, the final rolling temperature of the recrystallization rolling is 900-990°C.

[0018] Furthermore, in step 2, the final rolling temperature of the non-recrystallization rolling is controlled to be 850-800°C.

[0019] Furthermore, in step 3, the cooling method of quenching is water cooling.

[0020] Furthermore, in step 4, the tempering heat treatment includes: heating the steel plate to 600-700° C. and keeping the temperature for 1-2 hours and then air-cooling to room temperature.

[0021] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0022] The low-cost and high-corrosion-resistant steel of the present invention can achieve low cost and good matching of mechanical properties and corrosion resistance by accurately controlling the contents of elements such as C, Si, Ni, Mn, Cr, and Cu.

[0023] The preparation method of the low-cost and high-corrosion-resistant steel of the present invention adopts two stages of recrystallization rolling and non-recrystallization rolling, combines direct quenching and tempering processes, and accurately controls the process parameters of each step to ensure that the low-cost and high-corrosion-resistant steel obtains a microstructure of tempered martensite + nano-scale copper-rich phase, and obtains a good match between mechanical properties and corrosion resistance.

[0024] The low-cost high-corrosion-resistant steel of the present invention has low content of toughening elements such as Cr and Ni, which reduces material cost. In the preparation method of the low-cost high-corrosion-resistant steel, direct quenching saves process cost compared with offline quenching, and the strength of the material is ensured by precipitation strengthening in combination with subsequent tempering heat treatment, and the corrosion resistance of the material in a high-humidity and hot environment is improved by precipitation of a Cu-rich phase. The preparation method is simple and suitable for large-scale application.

[0025] The low-cost high-corrosion-resistant steel of the present invention has low cost, excellent mechanical properties, and good corrosion resistance in a high-humidity and hot marine environment. For example, the yield strength reaches 590MPa or more, for example, the yield strength is 599-630MPa; the tensile strength reaches 670MPa or more, for example, the tensile strength is 673-720MPa; the elongation after fracture is more than 20%, for example, 21%-25%; the impact absorption energy at -84°C is more than 160J, for example, 160-190J; the corrosion resistance of the above low-cost high-corrosion-resistant steel is excellent, for example, the corrosion rate after 4 days of immersion corrosion in a simulated high-humidity and hot marine environment is 2g / m 2 h or less, for example, 1.6191 to 1.9041 g / m 2 ·h.

[0026] Other features and advantages of the present invention will be described in the following description, and part of them will become obvious from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the contents particularly pointed out in the written description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings are only for the purpose of illustrating specific embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0028] Figure 1 This is a metallographic microstructure photograph of the low-cost and highly corrosion-resistant steel of Example 1 of the present invention;

[0029] Figure 2 This is a SEM photo of the low-cost and high-corrosion-resistant steel of Example 2 of the present invention;

[0030] Figure 3 This is a TEM photo of the low-cost and high-corrosion-resistant steel of Example 3 of the present invention;

[0031] Figure 4 The Cu-rich phase diffraction spots of the low-cost and highly corrosion-resistant steel of Example 3 of the present invention;

[0032] Figure 5 This is the microscopic morphology of the rust layer of the low-cost and highly corrosion-resistant steel of Example 4 of the present invention after 4 days of corrosion. DETAILED DESCRIPTION

[0033] Preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used to explain the principles of the present invention together with the embodiments of the present invention.

[0034] The present invention provides a low-cost high-corrosion-resistant steel. The components of the low-cost high-corrosion-resistant steel include, by mass percentage: C≤0.08%, Si: 0.25%-0.35%, Mn: 0.60%-0.80%, Ni: 1.0%-1.5%, Cr: 0.4%-0.6%, Cu: 0.8%-1.3%, and the balance is Fe and other inevitable impurities.

[0035] The functions and dosages of the components in the present invention are described in detail below.

[0036] C is a basic element in steel, which has a solid solution strengthening effect and can improve the hardenability of steel, but too high a C content is very unfavorable to the low-temperature toughness and weldability of steel. Therefore, the present invention controls C≤0.08%.

[0037] Si is a basic element in steel and has a certain strengthening effect. It mainly plays a deoxidation role in the steelmaking process. A high content is unfavorable to the low-temperature toughness and weldability of steel. Taking comprehensive considerations, the present invention controls the Si content to 0.25% to 0.35%.

[0038] Mn is a major solid solution strengthening element and an austenite stabilizing element. Too much Mn is prone to segregation and is also detrimental to weldability. Taking all factors into consideration, the present invention controls the Mn content to be 0.60% to 0.80%.

[0039] Ni is the main corrosion-resistant element of the steel of the present invention. Ni and Cr work together to form spinel oxide NiFe with negative electric effect in the rust layer. 2 O 4 With Cr 2 O 3 , with a dense physical structure, strong corrosion resistance and high stability, making the rust layer resistant to Cl - Penetration can significantly improve the corrosion resistance of steel, improve the strength and low temperature toughness of steel, and also improve the hardenability, but the alloy cost is relatively high. Taking all factors into consideration, the present invention controls the Ni content to be 1.0% to 1.5%.

[0040] Cr is a solid solution strengthening element and a key hardenability element. It can also increase the corrosion potential of the material and work together with the Ni element to generate protective corrosion products in the rust layer, thereby improving the corrosion resistance of the material. Taking all factors into consideration, the Cr content is controlled to be 0.4% to 0.6% in the present invention.

[0041] Cu can generate protective product CuFeO in the rust layer after corrosion. 2 At the same time, nanometer-level C-rich phase is uniformly precipitated during the tempering process, and the strength of the material is improved by precipitation strengthening. Taking comprehensive considerations, the present invention controls the Cu content to be 0.8% to 1.3%.

[0042] Specifically, in order to further improve the comprehensive performance of the above-mentioned low-cost and high-corrosion-resistant steel, the components of the above-mentioned low-cost and high-corrosion-resistant steel include, by mass percentage: C 0.04%~0.08%, Si: 0.27%~0.35%, Mn: 0.60%~0.80%, Ni: 1.0%~1.5%, Cr: 0.4%~0.6%, Cu: 0.8%~1.3%, and the balance is Fe and other inevitable impurities.

[0043] Specifically, the low-cost high corrosion-resistant steel has excellent performance, with a yield strength of 590MPa or more, for example, a yield strength of 599-630MPa; a tensile strength of 670MPa or more, for example, a tensile strength of 673-720MPa; an elongation of 20% or more, for example, 21%-25%; an impact absorption energy of 160J or more at -84°C, for example, 160-190J; the low-cost high corrosion-resistant steel has excellent corrosion resistance, for example, the corrosion rate after 4 days of immersion corrosion in a simulated high-humidity and hot marine environment is 2g / m 2 h or less, for example, 1.6191 to 1.9041 g / m 2 ·h.

[0044] On the other hand, the present invention also provides a method for preparing the above-mentioned low-cost high-corrosion-resistant steel, comprising the following steps:

[0045] Step 1, smelting and casting into billet;

[0046] Step 2, subjecting the blank to controlled rolling to obtain a hot-rolled plate, wherein the controlled rolling includes two stages: recrystallization rolling and non-recrystallization rolling;

[0047] Step 3, directly quenching the hot-rolled plate;

[0048] Step 4: Perform tempering heat treatment to obtain low-cost and highly corrosion-resistant steel.

[0049] Specifically, in the above step 2, considering that too high a starting rolling temperature of the recrystallization rolling may easily cause grain coarsening, the starting rolling temperature is controlled to be 1150-1100°C.

[0050] Specifically, in the above step 2, considering that the final rolling temperature of the recrystallization rolling is too low, that is, lower than the recrystallization temperature, resulting in failure to obtain a fine austenite rolled structure, the final rolling temperature is controlled to be 900-990°C.

[0051] Specifically, in the above step 2, the reduction amount of the recrystallization rolling is controlled to be 70% to 75%.

[0052] Specifically, in the above step 2, if the final rolling temperature of the non-recrystallization rolling is too low, the material structure will be deformed too much in the non-recrystallization zone, and will be excessively flattened and elongated, which will affect the performance. Therefore, the final rolling temperature of the non-recrystallization rolling is controlled to be 850-800°C, which is lower than the recrystallization temperature of the steel plate.

[0053] Specifically, in the above step 2, the non-recrystallization rolling reduction is controlled to be 50% to 60%.

[0054] Specifically, in the above step 3, the quenching cooling method is water cooling. Considering that if the cooling rate is too low, the structural characteristics such as the high-density dislocation of the narrow strip generated by rolling cannot be retained in the quenched structure, and the martensite structure cannot be generated. Therefore, the cooling rate is controlled to be 20-40℃ / s.

[0055] Specifically, in the above step 3, the final cooling temperature of the steel plate surface is controlled to be ≤150°C.

[0056] Specifically, in the above step 4, if the holding temperature of the tempering heat treatment is too high or the holding time is too long, over-aging will occur, and the generated Cu-rich phase and other precipitates will be too coarse and harmful to the material properties; if the holding temperature is too low or the holding time is too short, the Cu-rich phase cannot be obtained. Therefore, the controlled tempering heat treatment includes: heating the steel plate to 600-700°C for holding, holding for 1-2 hours, and then air cooling to room temperature.

[0057] In the preparation method of the present invention, the dislocation density and the phase interface content inside the material are increased by non-recrystallization rolling, and the dislocation density and the number of phase interfaces accumulated during the rolling process are retained in the structure by direct quenching. During the tempering process, these dislocation densities and phase interfaces provide nucleation points for the precipitation of the Cu-rich phase, thereby promoting the precipitation behavior of the Cu-rich phase. The high dislocation density retained by direct quenching and the Cu-rich phase precipitated by tempering provide dislocation strengthening and precipitation strengthening for the material, ensuring the strength of the material. At the same time, the Cu-rich phase is more likely to generate CuO in the rust layer than Cu dissolved in the matrix, and the CuO in the rust layer and the NiFe 2 O 4 It can inhibit the anodic reaction process, promote uniform corrosion by hindering local corrosion dissolution, and is conducive to the formation of more protective α-FeOOH in the rust layer, thereby effectively improving the corrosion resistance of the material in a high humidity and heat environment.

[0058] Specifically, the microstructure of the low-cost high-corrosion-resistant steel is tempered martensite + nano-scale copper-rich phase, the mass percentage of the copper-rich phase is about 0.2% to 1.5%, the average size of the copper-rich phase is about 5 to 50 nm, and the copper-rich phase is granular or spherical and evenly distributed at crystal defects such as lath boundaries and dislocations. The average lath spacing of the tempered martensite is about 40 to 80 nm, for example, 50 to 70 nm.

[0059] The low-cost and high-corrosion-resistant steel of the present invention can achieve low cost and good matching of mechanical properties and corrosion resistance by accurately controlling the contents of elements such as C, Si, Ni, Mn, Cr, and Cu.

[0060] The preparation method of the low-cost and high-corrosion-resistant steel of the present invention adopts two stages of recrystallization rolling and non-recrystallization rolling, combines direct quenching and tempering processes, and accurately controls the process parameters of each step to ensure that the low-cost and high-corrosion-resistant steel obtains a microstructure of tempered martensite + nano-scale copper-rich phase, and obtains a good match between mechanical properties and corrosion resistance.

[0061] In the low-cost high-corrosion-resistant steel of the present invention, the content of toughening elements such as C and Ni is low, which reduces the material cost. In the preparation method of the low-cost high-corrosion-resistant steel, direct quenching saves process cost compared with offline quenching, and the strength of the material is guaranteed by precipitation strengthening combined with subsequent tempering heat treatment, and the corrosion resistance of the material in a high-humidity and hot environment is improved by precipitation of a Cu-rich phase. The preparation method is simple and suitable for large-scale application.

[0062] The low-cost high-corrosion-resistant steel of the present invention has low cost, excellent mechanical properties, and good corrosion resistance in a high-humidity and hot marine environment. For example, the corrosion rate after 4 days of immersion corrosion in a simulated high-humidity and hot marine environment is 2 g / m 2 ·h or less.

[0063] The advantages of precise control of the composition and process parameters of the steel of the present invention are demonstrated below with specific examples and comparative examples.

[0064] Examples 1-4 of the present invention provide a low-cost, highly corrosion-resistant steel and a preparation method thereof. The chemical compositions of the steels of Examples 1-4 are shown in Table 1.

[0065] The method for preparing the steel of Examples 1-4 comprises:

[0066] Step 1, smelting and casting into billet;

[0067] Step 2, subjecting the blank to controlled rolling to obtain a hot-rolled plate, wherein the controlled rolling includes two stages: recrystallization rolling and non-recrystallization rolling;

[0068] Step 3, directly quenching the hot-rolled plate;

[0069] Step 4: Perform tempering heat treatment to obtain low-cost and highly corrosion-resistant steel.

[0070] The specific process parameters of rolling of Examples 1-4 are shown in Table 2; the specific process parameters of quenching and tempering are shown in Table 3; the microstructure of the low-cost high corrosion-resistant steel is shown in Table 4, and the mechanical properties test results of the low-cost high corrosion-resistant steel are shown in Table 5.

[0071] The steel of the embodiment was subjected to a cyclic immersion corrosion test simulating a high-humidity and hot marine environment. The experimental solution was 3.5wt% NaCl, the solution temperature was 40±2°C, the relative humidity was 70±10% RH, the cycle period was 60min, the dry-wet ratio was 4:1, the sampling period was 1d, 2d, and 4d, the maximum surface temperature during drying was 70±5°C, the illumination time was all day, and the corrosion rate (g / m 2 h) The results are shown in Table 6.

[0072] Figure 1 This is a metallographic microstructure photograph of the low-cost and highly corrosion-resistant steel of Example 1 of the present invention; Figure 2 This is a SEM photo of the low-cost and high-corrosion-resistant steel of Example 2 of the present invention; Figure 3 This is a TEM photo of the low-cost and high-corrosion-resistant steel of Example 3 of the present invention; Figure 4 The Cu-rich phase diffraction spots of the low-cost and highly corrosion-resistant steel of Example 3 of the present invention; Figure 5 This is the microscopic morphology of the rust layer of the low-cost and highly corrosion-resistant steel of Example 4 of the present invention after 4 days of corrosion.

[0073] The inventor has conducted a large number of experimental studies during the research process, and now uses some solutions with poor performance as comparative examples.

[0074] Comparative Example 1

[0075] This comparative example provides a corrosion-resistant steel and a preparation method thereof. The components thereof are shown in Table 1, and the specific process parameters of the preparation method are shown in Tables 2-3.

[0076] Comparative Example 2

[0077] This comparative example provides a corrosion-resistant steel and a preparation method thereof. The components of the steel are shown in Table 1. The preparation method adopts a traditional off-line quenching + tempering heat treatment process.

[0078] Comparative Example 3

[0079] This comparative example provides a corrosion-resistant steel and a preparation method thereof. The components thereof are shown in Table 1 and are not described in detail herein. In the preparation method, the tempering temperature is 500° C. and no Cu-rich phase is precipitated during the tempering process.

[0080] The microstructure and main performance test results of the comparative steel are shown in Tables 4 to 6.

[0081] It can be seen from the results of Tables 3 to 6 that the embodiments of the present invention improve the dislocation density by controlling rolling and direct quenching, promote the precipitation of Cu-rich phase during tempering, and ensure the mechanical properties of the steel plate. The low-cost high corrosion-resistant steel of the present invention has low corrosion rates in the three cycles of 1d, 2d, and 4d in the corrosion test simulating a high-humidity and hot marine environment.

[0082] Table 1 Chemical composition, wt%

[0083] C Si Mn Ni Cr Cu Example 1 0.08 0.28 0.6 1.0 0.4 0.8 Example 2 0.06 0.35 0.8 1.5 0.6 1.3 Example 3 0.05 0.30 0.6 1.4 0.6 1.2 Example 4 0.04 0.27 0.7 1.5 0.5 1.2 Comparative Example 1 0.07 0.29 0.7 1.3 0.5 - Comparative Example 2 0.06 0.25 0.6 1.3 0.4 1.0 Comparative Example 3 0.07 0.28 0.7 1.5 0.6 1.2

[0084] Table 2 Specific process parameters of rolling

[0085]

[0086] Table 3 Specific process parameters of quenching and tempering

[0087]

[0088]

[0089] Table 4 Microstructure of steel

[0090] Serial number organize Average slat spacing Average size of copper-rich phase Example 1 Tempered martensite + about 0.5% copper-rich phase About 50nm 20nm Example 2 Tempered martensite + about 0.2% copper-rich phase About 70nm 30nm Example 3 Tempered martensite + about 0.7% copper-rich phase About 60nm 5nm Example 4 Tempered martensite + about 1.0% copper-rich phase About 50nm 50nm Comparative Example 1 Tempered martensite About 70nm - Comparative Example 2 Tempered martensite + about 0.1% copper-rich phase About 150nm 30nm Comparative Example 3 Tempered martensite About 80nm -

[0091] Table 5 Mechanical properties of steel

[0092]

[0093] Table 6 Corrosion resistance of steel

[0094] 1d 2d 4d Example 1 2.4133 2.6864 1.8945 Example 2 2.2224 2.4978 1.6191 Example 3 2.3245 2.5050 1.7923 Example 4 2.4331 2.7012 1.9041 Comparative Example 1 3.2127 3.3344 2.9549 Comparative Example 2 2.8832 2.9067 2.2181 Comparative Example 3 3.1198 3.2986 2.7801

[0095] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A low-cost, high-corrosion-resistant steel, characterized in that: The components of the low-cost and high-corrosion-resistant steel include, by mass percentage: C≤0.08%, Si: 0.25%-0.35%, Mn: 0.60%-0.80%, Ni: 1.0%-1.5%, Cr: 0.4%-0.6%, Cu: 0.8%-1.3%, and the remainder is Fe and other inevitable impurities.

2. The low-cost and highly corrosion-resistant steel according to claim 1, characterized in that: The components of the low-cost and high-corrosion-resistant steel include, by mass percentage, C 0.04%-0.08%, Si: 0.27%-0.35%, Mn: 0.60%-0.80%, Ni: 1.0%-1.5%, Cr: 0.4%-0.6%, Cu: 0.8%-1.3%, and the remainder is Fe and other inevitable impurities.

3. The low-cost, high-corrosion-resistant steel according to claim 1 or 2, characterized in that: The microstructure of the low-cost and high-corrosion-resistant steel is tempered martensite + nano-scale copper-rich phase.

4. The low-cost and highly corrosion-resistant steel according to claim 3, characterized in that: The mass percentage of the copper-rich phase is 0.2% to 1.5%.

5. A method for preparing low-cost high-corrosion-resistant steel, characterized in that: The preparation method is used to prepare the low-cost and high-corrosion-resistant steel according to any one of claims 1 to 4, and the preparation method comprises the following steps: Step 1, smelting and casting into billet; Step 2, subjecting the blank to controlled rolling to obtain a hot-rolled plate, wherein the controlled rolling includes two stages: recrystallization rolling and non-recrystallization rolling; Step 3, directly quenching the hot-rolled plate; Step 4: Perform tempering heat treatment to obtain low-cost and highly corrosion-resistant steel.

6. The preparation method according to claim 5, characterized in that: In the step 2, the start rolling temperature of the recrystallization rolling is 1150-1100°C.

7. The preparation method according to claim 5, characterized in that: In the step 2, the final rolling temperature of the recrystallization rolling is 900-990°C.

8. The preparation method according to claim 5, characterized in that: In the step 2, the final rolling temperature of the non-recrystallization rolling is controlled to be 850-800°C.

9. The preparation method according to claim 5, characterized in that: In step 3, the quenching cooling method is water cooling.

10. The preparation method according to any one of claims 5 to 9, characterized in that: In step 4, the tempering heat treatment includes: heating the steel plate to 600-700° C. and keeping the temperature for 1-2 hours, and then air-cooling to room temperature.

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