High-strength high-fatigue-performance steel plate and method for manufacturing the same

Abstract

This invention specifically relates to a high-strength, high-fatigue-performance steel plate and its preparation method, belonging to the field of steel preparation technology. It employs a relatively simple composition design, using conventional alloying elements such as C, Si, Mn, Cr, Nb, and Ti. The addition of elements such as Cr and Mo ensures the hardenability of the material, resulting in more hard phases and guaranteeing strength. The low-carbon composition design, with the addition of elements such as Nb and V, ensures refined grains, which is beneficial for guaranteeing the yield strength and fatigue strength of the material. The addition of elements such as Cu and Ni ensures the corrosion resistance of the steel plate, resulting in a finished steel plate with a yield strength of 900-950 MPa, a tensile strength of 950 MPa-1050 MPa, an elongation after fracture of 3%-6%, a yield strength ratio ≥0.9, and a fatigue strength ≥850 MPa (number of cycles N = 1 × 10⁻⁶). 7 (Times), no cracks were found on the edge after 180° folding, and the weld point in the resistance spot welding shear tensile test showed a weld nugget pull-out fracture mode.

Description

Technical Field

[0001] This invention belongs to the field of steel preparation technology, and specifically relates to a high-strength, high-fatigue-performance steel plate and its preparation method. Background Technology

[0002] Steel for flexible header spring transition plates is widely used in agricultural machinery, especially in harvesting machinery. As a crucial component of combine harvesters, the spring transition plate is cantilevered between the auger and the cutter. Relying on its elasticity, the spring transition plate adheres tightly to the underside of the blade guard beam. As the cutter moves up and down with the terrain, relative sliding occurs between the spring plate and the blade guard beam. The shape of the spring transition plate should ensure sufficient pressure between it and the blade guard beam for good sealing. The material requires high strength and a high yield strength ratio (typically, the yield strength ratio Rp0.2 / Rm ≥ 0.9 for the spring transition plate), with a thickness of 0.6-1.2 mm. Currently, my country still relies entirely on imports for this component in agricultural machinery, and research on steel for flexible header spring transition plates remains lacking. Summary of the Invention

[0003] The purpose of this application is to provide a high-strength, high-fatigue-performance steel plate and its preparation method, so as to fill the gap in steel for flexible cutting table spring transition plates.

[0004] This invention provides a high-strength, high-fatigue-performance steel plate, the chemical composition of which, by mass fraction, comprises:

[0005] C: 0.02%-0.15%, Si: 0.1%-0.5%, Mn: 0.4%-1.5%, Alt: 0.01%-0.10%, Cr: 0.3%-1.5%, P: ≤0.015%, S: ≤0.015%, Mo: 0.10-0.50%, Ti: 0.01%-0.05%, Nb: 0.01%-0.10%, V: 0.01%-0.10%, Cu: 0.20%-0.50%, Ni: 0.20%-0.50%, with the remainder being Fe and unavoidable impurity elements.

[0006] Optionally, the chemical composition of the steel, in mass fraction, includes:

[0007] C: 0.06%-0.11%, Si: 0.2%-0.4%, Mn: 0.7%-1.2%, Alt: 0.03%-0.07%, Cr: 0.7%-1.1%, P: ≤0.015%, S: ≤0.015%, Mo: 0.20%-0.40%, Ti: 0.02%-0.04%, Nb: 0.04%-0.07%, V: 0.04%-0.07%, Cu: 0.30%-0.40%, Ni: 0.30%-0.40%, with the remainder being Fe and unavoidable impurity elements.

[0008] Optionally, the microstructure of the steel includes ferrite and pearlite, and the microstructure retains the cold-rolled fibrous microstructure characteristics.

[0009] Based on the same inventive concept, embodiments of the present invention also provide a method for preparing the high-strength, high-fatigue-performance steel plate as described above, the method comprising:

[0010] The cast billet is heated to obtain a heated billet;

[0011] The heated billet is subjected to rough descaling to obtain a rough descaled billet;

[0012] The rough descaling billet is rough rolled, and then fine descaling is performed to obtain a fine descaling billet;

[0013] The descaling billet is then precision rolled, cooled, and coiled to obtain a hot-rolled sheet.

[0014] The hot-rolled sheet is flattened and then pickled to obtain a pickled sheet;

[0015] The pickled sheet is cold rolled and then continuously annealed to obtain a steel sheet.

[0016] Optionally, the final heating temperature is 1240-1300℃, the heat soaking time is 1.0-4.0h, and the air-fuel ratio in the heat soaking section is 0.8-1.5.

[0017] Optionally, the descaling pressure of the rough descaling is 15-25 MPa; the initial rolling temperature of the rough rolling is 1220-1280℃, and the total reduction rate of the rough rolling is 80%-90%; the descaling pressure of the finish descaling is 30-35 MPa, the inlet temperature of the finish rolling is 1000-1100℃, the final rolling temperature of the finish rolling is 850-910℃, and the total reduction rate of the finish rolling is 85%-95%.

[0018] Optionally, the winding temperature is 480-540℃.

[0019] Optionally, the leveling force is 2000-4000KN.

[0020] Optionally, the pickling temperature is 70-100℃, and the pickling speed is 70-100m / min.

[0021] Optionally, the cold rolling reduction rate is 60%-80%, the continuous annealing temperature is 650-700℃, and the continuous annealing belt speed is 70-110m / min.

[0022] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0023] The high-strength, high-fatigue-performance steel plate provided in this invention employs a relatively simple composition design, using conventional alloying elements such as C, Si, Mn, Cr, Nb, and Ti. The addition of elements like Cr and Mo ensures the material's hardenability, resulting in more hard phases and guaranteeing strength. The low-carbon composition design, along with the addition of Nb and V, ensures refined grain structure, which is beneficial for maintaining yield strength and fatigue strength. The addition of Cu and Ni ensures the steel plate's corrosion resistance, resulting in a finished steel plate with a yield strength of 900-950 MPa, tensile strength of 950 MPa to 1050 MPa, elongation after fracture of 3% to 6%, yield strength ratio ≥0.9, and fatigue strength ≥850 MPa (number of cycles N = 1 × 10⁻⁶). 7 (Times), no cracks were found on the edge after 180° folding, and the weld point in the resistance spot welding shear tensile test showed a weld nugget pull-out fracture mode.

[0024] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a SEM image of the steel plate provided in Embodiment 1 of the present invention;

[0027] Figure 2 This is a topographic image of the edge of the steel plate after it has been folded 180°, as provided in Embodiment 1 of the present invention.

[0028] Figure 3 This is a flowchart of the method provided in an embodiment of the present invention. Detailed Implementation

[0029] The present invention will be described in detail below with reference to specific embodiments and examples, thereby making the advantages and various effects of the present invention more clearly apparent. Those skilled in the art should understand that these specific embodiments and examples are for illustrative purposes only and are not intended to limit the present invention.

[0030] Throughout this specification, unless otherwise specified, the terminology used herein should be understood as having the meaning commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In the event of any conflict, this specification shall prevail.

[0031] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0032] The technical solution of this application embodiment is to solve the above-mentioned technical problems, and the general idea is as follows:

[0033] According to a typical embodiment of the present invention, a high-strength, high-fatigue-performance steel plate is provided, wherein the chemical composition of the steel plate comprises, by mass fraction:

[0034] C: 0.02%-0.15%, Si: 0.1%-0.5%, Mn: 0.4%-1.5%, Alt: 0.01%-0.10%, Cr: 0.3%-1.5%, P: ≤0.015%, S: ≤0.015%, Mo: 0.10-0.50%, Ti: 0.01%-0.05%, Nb: 0.01%-0.10%, V: 0.01%-0.10%, Cu: 0.20%-0.50%, Ni: 0.20%-0.50%, with the remainder being Fe and unavoidable impurity elements.

[0035] The role of carbon (C) is to improve hardenability and ensure strength and hardness. Controlling the C mass fraction to 0.02%-0.15% ensures a yield strength greater than 900 MPa and a tensile strength greater than 950 MPa. It also guarantees high fatigue strength and high cold bending performance. High carbon content reduces fatigue strength and cold bending performance, making it impossible to guarantee a fatigue strength ≥850 MPa (number of cycles N = 1 × 10⁻⁶). 7 (Second) and there are no cracks at the 180° folded edge; if it is too low, sufficient yield strength and tensile strength cannot be guaranteed.

[0036] Si is introduced by deoxidizers and reducing agents. The reason for controlling the mass fraction of Si to be 0.1%-0.5% is to ensure the effect of deoxidation and reduction. If the mass fraction is too high, the adverse effect is to reduce the welding performance, especially for spring transition plates, which have high requirements for welding performance (the weld nugget is pulled out and fractured in the resistance spot welding shear tensile test). If the mass fraction is too low, the adverse effect is that the effect of deoxidation and reduction cannot be guaranteed.

[0037] Mn is an element that improves hardenability and ensures strength. Controlling the mass fraction of Mn to 0.4%-1.5% can ensure the strength and toughness of the spring transition plate. If the mass fraction is too high, the fatigue strength and cold bending performance will not meet the requirements. If it is too low, high strength cannot be guaranteed.

[0038] Al plays a role in deoxidation. Controlling the mass fraction of Al to 0.01%-0.10% can ensure the deoxidation effect. If the mass fraction is too large, it will damage the toughness; if it is too small, it will not have the deoxidation effect.

[0039] The role of Cr is to ensure the hardenability of the material, obtain more hard phase, and ensure strength. The mass fraction of Cr is controlled at 0.3%-1.5% to ensure strength and avoid damage to toughness. If the mass fraction is too high, the adverse effects are increased cost and damage to toughness; if it is too low, the adverse effect is that sufficient hardenability cannot be guaranteed.

[0040] Both P and S are harmful elements. The mass fraction of P should be controlled to be P≤0.015% and the mass fraction of S should be controlled to be ≤0.015% to ensure sufficient toughness and fatigue performance of the material. Excessive mass fraction values ​​will damage toughness and fatigue performance.

[0041] The role of Mo is to ensure the hardenability of the material, obtain more hard phase, and ensure strength. The reason for controlling the mass fraction of Mo to be 0.10-0.50% is to ensure both strength and hardenability. If the mass fraction is too high, it will significantly increase the cost, while if it is too low, hardenability and strength cannot be guaranteed.

[0042] The role of Ti is to fix nitrogen and carbon, deoxidize, refine grains and improve strength. The reason for controlling the mass fraction of Ti to 0.01%-0.05% is to ensure the effect of deoxidation and nitrogen fixation. If the mass fraction is too large, the cost will increase, and if it is too small, it will not achieve sufficient deoxidation and nitrogen fixation effect.

[0043] The role of Nb is to ensure that the material has refined grains, which is beneficial to ensuring the yield strength and fatigue strength of the material. The reason for controlling the mass fraction of Nb to be 0.01%-0.10% is to ensure the effect of grain refinement. If the mass fraction is too large, the cost will increase, and if it is too small, the effect of grain refinement cannot be guaranteed.

[0044] The role of V is to ensure that the material has refined grains, which is beneficial to ensuring the yield strength and fatigue strength of the material. Controlling the mass fraction of V to 0.01%-0.10% is to ensure the effect of grain refinement. If the mass fraction is too large, the cost will increase, and if it is too small, the effect of grain refinement cannot be guaranteed.

[0045] The role of Cu is to ensure the corrosion resistance of steel plates. The reason for controlling the mass fraction of Cu to be 0.20%-0.50% is to ensure sufficient corrosion resistance. If the mass fraction is too high, it will affect the welding performance, and if it is too low, it will not provide sufficient corrosion resistance.

[0046] The role of Ni is to work with Cu to ensure the corrosion resistance of the steel plate. The reason for controlling the mass fraction of Ni to be 0.20%-0.50% is to ensure corrosion resistance, avoid copper embrittlement, and improve toughness. If the mass fraction is too high, the disadvantage is that the cost will be too high; if it is too low, the disadvantage is that copper embrittlement cannot be avoided.

[0047] In some embodiments, the chemical composition of the steel, expressed as a mass fraction, includes:

[0048] C: 0.06%-0.11%, Si: 0.2%-0.4%, Mn: 0.7%-1.2%, Alt: 0.03%-0.07%, Cr: 0.7%-1.1%, P: ≤0.015%, S: ≤0.015%, Mo: 0.20%-0.40%, Ti: 0.02%-0.04%, Nb: 0.04%-0.07%, V: 0.04%-0.07%, Cu: 0.30%-0.40%, Ni: 0.30%-0.40%, with the remainder being Fe and unavoidable impurity elements.

[0049] In some embodiments, the chemical composition of the steel, expressed as a mass fraction, includes:

[0050] C: 0.06%-0.11%, Si: 0.2%-0.4%, Mn: 0.7%-1.2%, Alt: 0.03%-0.07%, Cr: 0.30%-1.20%, P: ≤0.015%, S: ≤0.015%, Mo: 0.10%-0.50%, Ti: 0.02%-0.04%, Nb: 0.02%-0.08%, V: 0.02%-0.08%, Cu: 0.30%-0.40%, Ni: 0.30%-0.40%, with the remainder being Fe and unavoidable impurity elements.

[0051] In some embodiments, the microstructure of the steel comprises ferrite and pearlite, wherein the volume fraction of ferrite is 10%-30% and the volume fraction of pearlite is 70%-90%, and the microstructure retains the cold-rolled fibrous microstructure characteristics.

[0052] According to another typical embodiment of the present invention, a method for preparing a high-strength, high-fatigue-performance steel plate as described above is provided, the method comprising:

[0053] S1. Heating the cast billet to obtain a heated billet;

[0054] In some embodiments, the final heating temperature is 1240-1300℃, the heat soaking time is 1.0-4.0h, and the air-fuel ratio of the heat soaking section is 0.8-1.5.

[0055] Controlling the final heating temperature to 1240-1300℃ ensures that alloying elements are uniformly present in the billet.

[0056] S2. Perform rough descaling on the heated billet to obtain a rough descaled billet;

[0057] In some embodiments, the descaling pressure for coarse descaling is 15-25 MPa.

[0058] S3. The rough descaling billet is rough rolled, and then fine descaling is performed to obtain a fine descaling billet;

[0059] In some embodiments, the initial rolling temperature of the roughing mill is 1220-1280°C, and the total reduction rate of the roughing mill is 80%-90%; a large roughing mill reduction is beneficial to reducing the pressure of the finishing mill.

[0060] In some embodiments, the descaling pressure is 30-35 MPa.

[0061] S4. The descaling billet is then precision rolled, cooled, and coiled to obtain a hot-rolled sheet.

[0062] Multi-pass descaling is beneficial for obtaining high-quality steel strip surface quality, and for removing oxide scale from the roughing and finishing rolling processes.

[0063] In some embodiments, the entry temperature of the finishing mill is 1000-1100°C, the finishing mill finishing temperature is 850-910°C, and the total reduction rate of the finishing mill is 85%-95%.

[0064] In some embodiments, the winding temperature is 480-540°C.

[0065] S5. The hot-rolled sheet is flattened and then pickled to obtain a pickled sheet. After pickling, the surface of the steel strip is free of acid residue, dry, free of contaminants, free of mechanical damage, free of oxide scale and yellow spots.

[0066] In some embodiments, the leveling force is 2000-4000KN.

[0067] In some embodiments, the pickling temperature is 70-100°C, and the pickling speed is 70-100 m / min.

[0068] S6. The pickled sheet is cold rolled and then continuously annealed to obtain a steel sheet.

[0069] In some embodiments, the reduction rate of cold rolling is 60%-80%.

[0070] In some embodiments, the continuous annealing temperature is 650-700°C, and the continuous annealing belt speed is 70-110 m / min.

[0071] The high-strength, high-fatigue-performance steel plate and its preparation method of this application will be described in detail below with reference to embodiments, comparative examples and experimental data.

[0072] Example 1

[0073] A high-strength, high-fatigue-resistance steel plate, the chemical composition of which is shown in the table below:

[0074]

[0075] Its preparation process is as follows:

[0076] Smelting, refining, and casting of billets; heating the billets to 1260℃ and holding for 2.0h; descaling at a pressure of 20MPa, followed by rough rolling at an initial rolling temperature of 1240℃ and a total reduction of 85%; descaling at a pressure of 32MPa, followed by finish rolling at an entry temperature of 1070℃ and a final rolling temperature of 870℃; laminar water cooling at a coiling temperature of 520℃; obtaining a hot-rolled sheet with a thickness of 3.0mm; leveling the hot-rolled sheet with a leveling force of 2500KN; pickling solution temperature of 85℃ and pickling speed of 80m / min; continuous annealing at a temperature of 680℃ and a belt speed of 90m / min.

[0077] Example 2

[0078] A high-strength, high-fatigue-resistance steel plate, the chemical composition of which is shown in the table below:

[0079]

[0080] Its preparation process is as follows:

[0081] Smelting, refining, and casting of billets; heating the billets to 1250℃ and holding for 2.5h; descaling at a pressure of 22MPa, followed by rough rolling at an initial rolling temperature of 1235℃ and a total reduction of 85%; descaling at a pressure of 30MPa, followed by finish rolling at an entry temperature of 1073℃ and a final rolling temperature of 885℃; laminar water cooling at a coiling temperature of 510℃; obtaining a hot-rolled sheet with a thickness of 3.0mm; leveling the hot-rolled sheet with a leveling force of 2600KN; pickling solution temperature of 80℃ and pickling speed of 85m / min; continuous annealing at a temperature of 670℃ and a belt speed of 80m / min.

[0082] Example 3

[0083] A high-strength, high-fatigue-resistance steel plate, the chemical composition of which is shown in the table below:

[0084]

[0085] Its preparation process is as follows:

[0086] Smelting, refining, and casting of billets; heating the billets to 1255℃ and holding for 2.0h; descaling at a pressure of 21MPa, followed by rough rolling at an initial rolling temperature of 1230℃ and a total reduction of 85%; descaling at a pressure of 33MPa, followed by finish rolling at an entry temperature of 1065℃ and a final rolling temperature of 880℃; laminar water cooling at a coiling temperature of 515℃; obtaining a hot-rolled sheet with a thickness of 3.0mm; leveling the hot-rolled sheet with a leveling force of 3000KN; pickling solution temperature of 90℃ and pickling speed of 83m / min; continuous annealing at a temperature of 660℃ and a belt speed of 75m / min.

[0087] Comparative Example 1

[0088] A high-strength, high-fatigue-resistance steel plate, the chemical composition of which is shown in the table below:

[0089] C Si Mn Al Cr P S V Mo Ti Nb Cu Ni 0.12 0.13 0.70 0.08 —— 0.01 0.01 —— —— 0.04 —— —— ——

[0090] Its preparation process is as follows:

[0091] Smelting, refining, and casting of billets; heating the billets to 1260℃ and holding for 2.0h; descaling at a pressure of 19MPa, followed by rough rolling at an initial rolling temperature of 1235℃ and a total reduction of 85%; descaling at a pressure of 33MPa, followed by finish rolling at an entry temperature of 1071℃ and a final rolling temperature of 880℃; laminar water cooling at a coiling temperature of 520℃; obtaining a hot-rolled sheet with a thickness of 3.0mm; leveling the hot-rolled sheet with a leveling force of 2500KN; pickling solution temperature of 85℃ and pickling speed of 80m / min; continuous annealing at a temperature of 860℃ and a belt speed of 100m / min.

[0092] Comparative Example 2

[0093] A high-strength, high-fatigue-resistance steel plate, the chemical composition of which is shown in the table below:

[0094] C Si Mn Al Cr P S V Mo Ti Nb Cu Ni 0.11 0.15 0.80 0.09 —— 0.01 0.01 —— —— 0.05 —— —— ——

[0095] Its preparation process is as follows:

[0096] Smelting, refining, and casting of billets; heating the billets to 1260℃ and holding for 2.0h; descaling at a pressure of 20MPa, followed by rough rolling at an initial rolling temperature of 1236℃ and a total reduction of 85%; descaling at a pressure of 33MPa, followed by finish rolling at an entry temperature of 1072℃ and a final rolling temperature of 870℃; laminar water cooling at a coiling temperature of 520℃; obtaining a hot-rolled sheet with a thickness of 3.0mm; leveling the hot-rolled sheet with a leveling force of 2500KN; pickling solution temperature of 85℃ and pickling speed of 85m / min; continuous annealing at a temperature of 865℃ and a belt speed of 95m / min.

[0097] Example

[0098] The steels obtained in Examples 1-3 and Comparative Examples 1-2 were subjected to performance testing, and the test results are shown in the table below.

[0099]

[0100] From the table above, we can see that the steel plate thickness is 0.6-1.2mm, the yield strength of the finished steel plate is 900-950MPa, the tensile strength is 950MPa~1050MPa, the elongation after fracture is 3%~6%, and the fatigue strength is ≥850MPa (number of cycles N=1×10). 7 (times), no cracks were found at the 180° folded edge, and the weld point in the resistance spot welding shear tensile test showed a weld nugget pull-out fracture mode, which meets the current requirements of the agricultural machinery industry for spring transition plates for headers; the fatigue strength of the embodiment of the present invention is significantly higher than that of the comparative example, the material has higher fatigue performance, and compared with the comparative example, the experimental steel exhibits higher corrosion resistance.

[0101] Salt spray tests revealed that, compared to Comparative Examples 1 and 2, the relative corrosion rates of Examples 1, 2, and 3 were reduced by 50%, exhibiting better corrosion resistance. This is attributed to the addition of Cu, Ni, and Cr.

[0102] Figure 1 and Figure 2 Detailed explanation:

[0103] like Figure 1The image shown is an SEM image of the steel plate provided in Embodiment 1 of the present invention. As can be seen from the image, the microstructure is ferrite + pearlite, and the microstructure maintains the cold-rolled fibrous microstructure characteristics. This microstructure characteristics can ensure a high yield strength ratio.

[0104] like Figure 2 The figure shows the edge morphology of the steel plate provided in Embodiment 1 of the present invention after being folded at 180°. As can be seen from the figure, no cracks appeared on the edge after being folded at 180°, indicating that there were no cracks on the edge after being folded at 180°, and the plate exhibited good cold bending performance.

[0105] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0106] (1) In the composition design of the steel plate provided in this embodiment of the invention, elements such as Cr and Mo are added to ensure the hardenability of the material, obtain more hard phase, and ensure strength; in the low carbon composition design, elements such as Nb and V are added to ensure that the material has fine grains, which is beneficial to ensure the yield strength and fatigue strength of the material; elements such as Cu and Ni are added to ensure the corrosion resistance of the spring transition plate.

[0107] (2) The steel plate provided in the embodiments of the present invention has a yield strength of 900-950 MPa, a tensile strength of 950 MPa to 1050 MPa, an elongation after fracture of 3% to 6%, a yield strength ratio ≥0.9, and a fatigue strength ≥850 MPa (number of cycles N = 1 × 10⁻⁶). 7 (Times), no cracks were found on the edge after 180° folding, and the weld point in the resistance spot welding shear tensile test showed a weld nugget pull-out fracture mode.

[0108] Finally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0109] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0110] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A high-strength, high-fatigue-resistance steel plate, characterized in that, The chemical composition of the steel plate, expressed as a mass fraction, is as follows: C: 0.02%-0.0.06%, Si: 0.2%-0.4%, Mn: 0.4%-1.5%, Alt: 0.01%-0.10%, Cr: 0.3%-1.5% , P: ≤0.015%, S: ≤0.015%, Mo: 0.10-0.50%, Ti: 0.01%-0.05%, Nb: 0.01%-0.10%, V: 0.0 1%-0.10%, Cu: 0.20%-0.50%, Ni: 0.20%-0.50%, with the remainder being Fe and unavoidable impurity elements. The microstructure of the steel retains the cold-rolled fibrous structure characteristics. The yield strength of the steel plate is 900-950 MPa, the tensile strength is 950 MPa-1050 MPa, the elongation after fracture is 3%-6%, the yield ratio is ≥0.9, and the cyclic strength is 10. 7 The fatigue strength of the first fold is ≥850MPa, and there are no cracks at the edge when folded at 180°. The method for preparing the high-strength, high-fatigue-performance steel plate includes: The cast billet is heated to obtain a heated billet; The heated billet is subjected to rough descaling to obtain a rough descaled billet; The rough descaling billet is rough rolled, and then fine descaling is performed to obtain a fine descaling billet; The descaling billet is then precision rolled, cooled, and coiled to obtain a hot-rolled sheet. The hot-rolled sheet is flattened and then pickled to obtain a pickled sheet; The pickled sheet is cold-rolled and then continuously annealed to obtain a steel sheet; The initial rolling temperature of the roughing mill is 1220-1280℃; the final rolling temperature of the finishing mill is 850-910℃; the coiling temperature is 480-540℃; the reduction rate of the cold rolling is 60%-80%; the continuous annealing temperature is 650-700℃; the continuous annealing belt speed is 70-110m / min; the total reduction rate of the finishing mill is 85%-95%; the leveling force of the leveling is 2000-4000KN; and the pickling temperature is 70-100℃.

2. A method for preparing a high-strength, high-fatigue-performance steel plate as described in claim 1, characterized in that, The method includes: The cast billet is heated to obtain a heated billet; The heated billet is subjected to rough descaling to obtain a rough descaled billet; The rough descaling billet is rough rolled, and then fine descaling is performed to obtain a fine descaling billet; The descaling billet is then precision rolled, cooled, and coiled to obtain a hot-rolled sheet. The hot-rolled sheet is flattened and then pickled to obtain a pickled sheet; The pickled sheet is cold-rolled and then continuously annealed to obtain a steel sheet; The initial rolling temperature of the roughing mill is 1220-1280℃; the final rolling temperature of the finishing mill is 850-910℃; the coiling temperature is 480-540℃; the reduction rate of the cold rolling is 60%-80%; the continuous annealing temperature is 650-700℃; the continuous annealing belt speed is 70-110m / min; the total reduction rate of the finishing mill is 85%-95%; the leveling force of the leveling is 2000-4000KN; and the pickling temperature is 70-100℃.

3. The method for preparing high-strength, high-fatigue-performance steel plates according to claim 2, characterized in that, The final heating temperature is 1240-1300℃, the heat soaking time is 1.0-4.0h, and the air-fuel ratio in the heat soaking section is 0.8-1.

5.

4. The method for preparing high-strength, high-fatigue-performance steel plates according to claim 2, characterized in that, The descaling pressure of the rough descaling is 15-25 MPa; the total reduction rate of the rough rolling is 80%-90%; the descaling pressure of the fine descaling is 30-35 MPa; and the inlet temperature of the fine rolling is 1000-1100℃.

5. The method for preparing high-strength, high-fatigue-performance steel plates according to claim 2, characterized in that, The pickling rate is 70-100 m / min.

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