High-vanadium wear-resistant steel plate and manufacturing method thereof

Abstract

The invention discloses a high-vanadium wear-resistant steel plate and a manufacturing method thereof, and belongs to the field of ferrous metallurgy. The thickness of the steel plate is less than or equal to 40mm, the steel plate comprises the following chemical components in percentage by weight: 0.20-0.30% of C, 0.20-0.60% of V and the like, and the carbon equivalent CEV is less than or equal to 0.70%; the microscopic structure is tempered martensite, and VC particles with the particle size of 50-200 nm are uniformly dispersed and distributed. According to the performance indexes, the yield strength is larger than or equal to 1200 MPa, the tensile strength is larger than or equal to 1350 MPa, the impact energy at the temperature of-40 DEG C is larger than or equal to 15 J, the surface hardness is 420-480 HBW, and the wear resistance is improved by 30% or above compared with existing wear-resistant steel with the same hardness. The manufacturing method comprises the steps of molten iron pretreatment, converter smelting, LF refining, RH vacuum degassing, Ca treatment, continuous casting, heating, temperature control rolling and double-stage heat treatment. The wear resistance is improved through VC particle dispersion strengthening, high strength, high toughness and welding performance are considered, the process is economical and environmentally friendly, and the high-strength wear-resistant aluminum alloy is suitable for easily-worn equipment parts in the fields of coal, mines and the like.

Description

Technical Field

[0001] This invention belongs to the field of iron and steel metallurgy technology, specifically relating to a high vanadium wear-resistant steel plate and its manufacturing method, which is particularly suitable for easily worn parts of equipment (such as buckets, scrapers, chutes, etc.) in coal mining, mine transportation and other fields with a thickness ≤40mm and requiring high wear resistance, high strength and high toughness. Background Technology

[0002] During coal mining and transportation, equipment components such as buckets, scrapers, and chutes are in constant contact with hard materials like gangue and gravel, resulting in severe abrasive wear and frequent component failures and replacements. This not only increases maintenance costs for companies but also reduces production efficiency, making it a critical issue that urgently needs to be addressed in the industry.

[0003] In existing technologies, the main way to improve the wear resistance of steel is to increase the material's hardness, usually by increasing the carbon content or adding a large amount of alloying elements. However, this method has obvious drawbacks: on the one hand, excessively high carbon content or excessive alloying elements will lead to increased brittleness of the steel and deterioration of its weldability, making it difficult to process and manufacture parts and install them on site; on the other hand, the wear resistance limit achieved by simply relying on increased hardness is limited and cannot meet the long-term use requirements under harsh working conditions.

[0004] Vanadium carbide (VC), a high-hardness ceramic phase with a hardness reaching 2800 HV, possesses characteristics of high wear resistance, resistance to deformation, and good chemical stability. If uniformly dispersed within a steel matrix, it can significantly improve the wear resistance of the steel. However, in current technologies, precisely controlling the precipitation amount, particle size, and distribution of VC particles while simultaneously considering the strength, toughness, and processing performance of the steel remains an unsolved technical challenge. Therefore, developing a high-vanadium wear-resistant steel plate with excellent comprehensive performance based on VC particle reinforcement and its manufacturing method has significant industrial application value. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a high vanadium wear-resistant steel plate with a thickness of ≤40mm and its manufacturing method, which improves wear resistance by VC particle dispersion strengthening, while ensuring that the steel has high strength, high toughness and good processing performance, thereby extending the service life of wear-resistant equipment.

[0006] The technical solution adopted by this invention to solve the above problems is as follows: a high-vanadium wear-resistant steel plate, wherein the chemical composition of the steel plate, by mass percentage, is: C: 0.20-0.30%, Si: 0.10-0.50%, Mn: 0.5-1.0%, Nb: <0.010%, V: 0.20-0.60%, Ti: 0.010-0.030%, Al: 0.02-0.07%, Ni: 0.01-1.0%, Cu: <0.50%, Cr: 0.6-1.2%, Mo: 0.1-0.7%, B: 0.0010-0.0030%, Ca: 0.010-0.030%, P: ≤0.010%, S: ≤0.001%, O: ≤0.0015%, N ≤0.0020%, H: ≤0.0001%, with the balance being Fe. And unavoidable impurity elements; Carbon equivalent (CEV): ≤0.70%.

[0007] The performance indicators of the high-vanadium wear-resistant steel plate are as follows: Thickness ≤ 40mm; Yield strength ≥ 1200MPa, tensile strength ≥ 1350MPa, elongation ≥ 8%; Low-temperature impact energy Akv ≥ 15J at -40℃; Surface Brinell hardness 420-480HBW, core hardness not less than 80% of surface hardness; Microstructure is tempered martensite; Wear resistance is more than 30% higher than existing wear-resistant steels of the same hardness (tested using ASTM G65 weight loss method, wear amount reduced by more than 30%).

[0008] The rationale for limiting the steel composition in this invention is explained as follows: C: Carbon is the core element for the formation of VC particles and also improves the hardness of the matrix through solid solution strengthening. However, if the content is too high, it will lead to increased brittleness of the steel. Therefore, it is limited to 0.20-0.30% to ensure that the VC particles are fully extracted and the matrix has good toughness.

[0009] V: Vanadium reacts with carbon to form VC strengthening phase, which is a key element for improving wear resistance. If the content is too low, the number of VC particles will be insufficient, and the improvement in wear resistance will be limited; if the content is too high, VC particles will agglomerate and grow, reducing strength and toughness. Therefore, it is limited to 0.20-0.60%.

[0010] Si plays a role in solid solution strengthening and deoxidation. If the content is too low, deoxidation will be insufficient, and if it is too high, it will lead to increased brittleness of steel. It is limited to 0.10-0.50% to ensure the surface quality and comprehensive performance of steel plates.

[0011] Mn: Improves the hardenability and strength of steel, but Mn is prone to segregation. Excessive Mn content can lead to severe core segregation, so it is limited to 0.5-1.0%.

[0012] Ti: A strong carbonitride forming element, it can preferentially combine with N to form TiN, reducing the formation of VN and avoiding interference of VN on VC precipitation, and is limited to 0.010-0.030%.

[0013] Al: a deoxidizer and grain refiner, which also plays a role in fixing N and preventing the formation of large amounts of TiN. Its content is limited to 0.02-0.07%.

[0014] Cr: Improves hardenability, inhibits the formation of polygonal ferrite and pearlite, and promotes martensite transformation; limited to 0.6-1.2%.

[0015] Mo: Improves hardenability and tempering resistance, enhances the strength and stability of steel, limited to 0.1-0.7%.

[0016] B: Trace amounts of B can significantly improve hardenability and reduce the critical cooling rate, limited to 0.0010–0.0030%.

[0017] Ca: Improves the morphology of inclusions, transforms long strip-shaped MnS into spherical CaS, transforms Al2O3 inclusions into spherical low-melting-point inclusions, promotes the flotation of inclusions, and improves the purity of molten steel, limited to 0.010~0.030%.

[0018] P and S: Harmful elements that are prone to segregation, leading to increased brittleness and delamination cracking in steel. Strict control of P≤0.010% and S≤0.001% is required.

[0019] O, N, H: Harmful gaseous elements that can form inclusions and reduce plasticity and toughness. The limits are O≤0.0015%, N≤0.0020%, and H≤0.0001%.

[0020] Carbon equivalent (CEV) ≤ 0.70%: This ensures that the steel has good weldability and avoids cold cracking during the welding process.

[0021] This invention provides a method for preparing a high-vanadium wear-resistant steel plate with a thickness ≤40mm, the specific process of which is as follows: Hot metal pretreatment: The hot metal is desulfurized to ensure that the sulfur content is ≤0.005% after desulfurization, thus ensuring the purity of the subsequent molten steel.

[0022] Smelting: A converter is used for smelting. The raw materials are precisely proportioned according to the above chemical composition, and the carbon content at the end of the smelting process is controlled at 0.18-0.28% and the temperature is 1620-1650℃.

[0023] Ladle refining: Molten steel from the converter is fed into the LF refining furnace. Through slag formation and alloy fine-tuning, the chemical composition is precisely controlled. The refining time is ≥40 minutes to ensure that alloying elements are fully dissolved and inclusions float to the surface.

[0024] Vacuum degassing: RH vacuum degassing treatment is adopted, with a vacuum degree ≤67Pa and a degassing time ≥20min, to reduce the content of harmful gases such as O, N, and H in molten steel.

[0025] Ca treatment: After vacuum degassing, the air is broken, and Ca-Si wire is fed into the molten steel at a rate of 0.2-0.5 kg / t steel to achieve inclusion modification treatment.

[0026] Continuous casting: A special protective slag (basicity CaO / SiO2=1.0~1.5, viscosity 0.05~0.15Pa·s at 1300℃) is used for casting with low superheat (superheat 5~28℃), and argon gas protection is used throughout the process to prevent secondary oxidation; the center segregation of the continuous casting billet is ≤C1.0 grade and the center porosity is ≤1.0 grade. The billet thickness is set to 120~200mm according to the finished product specifications.

[0027] Heating: The continuously cast billet is fed into a walking beam furnace and heated at 1150-1250℃ for 1.0-1.2 min / mm (calculated based on the billet thickness) to ensure that alloying elements such as V and C are fully dissolved, laying the foundation for the subsequent precipitation of VC particles.

[0028] Rolling: Dephosphorization: After the billet exits the furnace, it is dephosphorized by high-pressure water (pressure ≥15MPa) to remove the iron oxide scale on the surface; before the start of finishing rolling, it is dephosphorized again by high-pressure water, with a total of ≥3 dephosphorization passes.

[0029] Rough rolling: Rolling in the recrystallization zone at a rolling temperature ≥1000℃ and a cumulative reduction rate ≥60% to refine the austenite grains.

[0030] Finish rolling: initial rolling temperature 820~920℃, final rolling temperature 760~840℃, cumulative reduction rate ≥40%, to ensure sufficient grain deformation and refinement, and improve the strength, toughness and cold bending performance of steel plate.

[0031] Post-rolling cooling: After rolling, the steel plate is air-cooled to room temperature.

[0032] Heat treatment: Quenching: Heat the steel plate to 900-940℃ and hold for 1.5-2.5 min / mm (calculated based on the finished product thickness). Then, use water spray cooling at a rate of >20℃ / s to cool to room temperature to obtain a martensitic structure.

[0033] Tempering: The quenched steel plate is heated to 150-250℃ and held for 3.0-5.0 min / mm (calculated based on the finished product thickness), and then air-cooled to room temperature to obtain tempered martensite structure, eliminate internal stress, and improve toughness.

[0034] Compared with the prior art, the present invention has the following beneficial effects: (1) Significantly improved wear resistance: Through VC particle dispersion reinforcement, the wear resistance is increased by more than 30% compared with the existing wear-resistant steel of the same hardness without increasing the material hardness, extending the service life of easily worn parts of equipment by 30% to 50%.

[0035] (2) Excellent comprehensive performance: It combines high strength (yield strength ≥1200MPa), high toughness (impact energy ≥15J at -40℃) and good weldability (CEV≤0.70%), meeting the comprehensive performance requirements of components under harsh working conditions.

[0036] (3) The process is economical and environmentally friendly: it adopts continuous casting billet production, which does not require special equipment modification. The process is stable and controllable, and the production cost is low, making it suitable for large-scale industrial production.

[0037] (4) Good processing performance: the core hardness is not less than 80% of the surface hardness, the steel plate has uniform properties in the thickness direction, and it is not easy to crack during cold bending, cutting and other processing. Attached Figure Description

[0038] Figure 1 The image shows the microstructure (optical microscope, 200×) of the 15mm thick high vanadium wear-resistant steel plate in Example 1, showing the tempered martensite matrix and uniformly distributed VC particles. Figure 2 The image shows a microstructure (optical microscope, 500×) of the 40mm thick high-vanadium wear-resistant steel plate in Example 2, revealing a tempered martensitic matrix and finely dispersed VC particles.

[0039] Figure 3 The image shows a microstructure (optical microscope, 500×) of the 20mm thick high-vanadium wear-resistant steel plate in Example 3, revealing a tempered martensitic matrix and finely dispersed VC particles.

[0040] Figure 4 The image shows a microstructure (optical microscope, 500×) of the 30mm thick high-vanadium wear-resistant steel plate in Example 4, revealing a tempered martensitic matrix and finely dispersed VC particles. Detailed Implementation

[0041] The technical solution of the present invention will be described in more detail below with reference to preferred embodiments. However, these embodiments are merely descriptions of preferred implementations of the present invention and should not be construed as limiting the scope of the present invention.

[0042] Example 1: 15mm thick high vanadium wear-resistant steel plate Chemical composition (wt%): C=0.22, Si=0.25, Mn=0.7, Nb=0.008, V=0.38, Ti=0.012, Al=0.038, Ni=0.3, Cu=0.2, Cr=0.8, Mo=0.3, B=0.0015, Ca=0.015, P=0.006, S=0.001, O=0.0012, N=0.0018, H=0.00008, Fe and unavoidable impurities balance; CEV=0.65.

[0043] Manufacturing process: Hot metal pretreatment: S=0.004% after desulfurization.

[0044] Converter smelting: final C=0.20, temperature 1630℃.

[0045] LF Refining: Refining time 45 minutes, with the composition fine-tuned to the above range.

[0046] RH vacuum degassing: vacuum degree 50Pa, degassing time 25min.

[0047] Ca treatment: 0.3 kg / t of steel is fed into the Ca-Si wire.

[0048] Continuous casting: basicity of protective slag 1.2, superheat 15℃, billet thickness 120mm, center segregation C grade 0.8, center porosity grade 0.8.

[0049] Heating: Heating temperature 1200℃, holding time 18min (15mm×1.2min / mm).

[0050] Rolling: High-pressure water descaling pressure 18MPa, roughing temperature 1050℃, finishing rolling start temperature 960℃, finishing rolling temperature 840℃, followed by air cooling.

[0051] Heat treatment: Quenching at 920℃ for 37.5 min (15 mm × 2.5 min / mm), water cooling rate 25℃ / s; tempering at 200℃ for 70.5 min (15 mm × 4.7 min / mm), air cooling.

[0052] Performance test results: Yield strength: 1367 MPa, tensile strength: 1492 MPa, elongation: 10%; -40℃ low temperature impact energy: 37J, 35J, 40J (average value 37.3J); Surface Brinell hardness: 450HBW, core hardness: 385HBW (≥450×80%=360); Abrasion resistance: According to ASTM G65 testing, the wear rate is 62% of that of existing abrasion-resistant steels of the same hardness (abrasion resistance is improved by 38%). Microstructure: tempered martensite, VC particles with a diameter of 50-150 nm, uniformly dispersed, accounting for about 5-8% of the volume.

[0053] Example 2: 40mm thick high-vanadium wear-resistant steel plate Chemical composition (wt%): C=0.23, Si=0.25, Mn=0.7, Nb=0.007, V=0.39, Ti=0.012, Al=0.039, Ni=0.4, Cu=0.25, Cr=0.85, Mo=0.35, B=0.0015, Ca=0.016, P=0.005, S=0.001, O=0.0011, N=0.0017, H=0.00007, Fe and unavoidable impurities balance; CEV=0.66.

[0054] Manufacturing process: Hot metal pretreatment: S=0.003% after desulfurization.

[0055] Converter smelting: final C=0.21, temperature 1640℃.

[0056] LF Refining: Refining time 50 minutes, with the composition fine-tuned to the above range.

[0057] RH vacuum degassing: vacuum degree 45Pa, degassing time 30min.

[0058] Ca treatment: 0.4 kg / t of steel is fed into the Ca-Si wire.

[0059] Continuous casting: basicity of protective slag 1.3, superheat 20℃, billet thickness 200mm, center segregation C grade 0.9, center porosity grade 0.9.

[0060] Heating: Heating temperature 1220℃, holding time 48min (40mm×1.2min / mm).

[0061] Rolling: High-pressure water descaling pressure 20MPa, roughing temperature 1025℃, finishing rolling start temperature 900℃, finishing rolling temperature 830℃, followed by air cooling.

[0062] Heat treatment: Quenching at 920℃ for 100 min (40 mm × 2.5 min / mm), water cooling rate 22℃ / s; tempering at 200℃ for 160 min (40 mm × 4.0 min / mm), air cooling.

[0063] Performance test results: Yield strength: 1358 MPa, tensile strength: 1485 MPa, elongation: 11%; -40℃ low temperature impact energy: 35J, 38J, 36J (average value 36.3J); Surface Brinell hardness: 445HBW, core hardness: 378HBW (≥445×80%=356); Abrasion resistance: Tested according to ASTM G65, the wear rate is 65% of that of existing abrasion-resistant steels of the same hardness (abrasion resistance is improved by 35%). Microstructure: tempered martensite, VC particles with a diameter of 80-200 nm, uniformly dispersed, accounting for about 5-8% of the volume.

[0064] Example 3: 20mm thick high-vanadium wear-resistant steel plate Chemical composition (wt%): C=0.25, Si=0.30, Mn=0.8, Nb=0.009, V=0.45, Ti=0.018, Al=0.045, Ni=0.5, Cu=0.3, Cr=1.0, Mo=0.4, B=0.0020, Ca=0.020, P=0.007, S=0.001, O=0.0013, N=0.0019, H=0.00009, Fe and unavoidable impurities balance; CEV=0.68.

[0065] Manufacturing process: Hot metal pretreatment: S=0.004% after desulfurization.

[0066] Converter smelting: final C=0.23, temperature 1635℃.

[0067] LF Refining: Refining time 48 minutes, with the composition fine-tuned to the above range.

[0068] RH vacuum degassing: vacuum degree 55Pa, degassing time 22min.

[0069] Ca treatment: 0.35 kg / t of steel is fed into the Ca-Si wire.

[0070] Continuous casting: basicity of protective slag 1.4, superheat 18℃, billet thickness 150mm, center segregation C grade 0.9, center porosity grade 0.9.

[0071] Heating: Heating temperature 1180℃, holding time 24min (20mm×1.2min / mm).

[0072] Rolling: High-pressure water descaling pressure 17MPa, roughing temperature 1030℃, finishing rolling start temperature 920℃, finishing rolling temperature 800℃, followed by air cooling.

[0073] Heat treatment: Quenching at 930℃ for 50 min (20 mm × 2.5 min / mm), water cooling rate 23℃ / s; tempering at 220℃ for 100 min (20 mm × 5.0 min / mm), air cooling.

[0074] Performance test results: Yield strength: 1370 MPa, tensile strength: 1490 MPa, elongation: 10.5%; -40℃ low temperature impact energy: 38J, 36J, 40J (average 38J). Surface Brinell hardness: 450HBW, core hardness: 380HBW (≥450×80%=360); Abrasion resistance: According to ASTM G65 testing, the wear rate is 60% of that of existing wear-resistant steels of the same hardness (abrasion resistance is improved by 40%). Microstructure: tempered martensite, VC particles with a diameter of 60-180 nm, uniformly dispersed, accounting for about 5-8% of the volume.

[0075] Example 4: 30mm thick high-vanadium wear-resistant steel plate Chemical composition (wt%): C=0.28, Si=0.40, Mn=0.9, Nb=0.008, V=0.55, Ti=0.025, Al=0.060, Ni=0.8, Cu=0.4, Cr=1.1, Mo=0.6, B=0.0025, Ca=0.025, P=0.008, S=0.001, O=0.0014, N=0.0019, H=0.00008, Fe and unavoidable impurities balance; CEV=0.69.

[0076] Manufacturing process: Hot metal pretreatment: S=0.003% after desulfurization.

[0077] Converter smelting: final C=0.26, temperature 1645℃.

[0078] LF Refining: Refining time 52 minutes, with the composition fine-tuned to the above range.

[0079] RH vacuum degassing: vacuum degree 48Pa, degassing time 28min.

[0080] Ca treatment: 0.45 kg / t of steel is fed into the Ca-Si wire.

[0081] Continuous casting: basicity of protective slag 1.3, superheat 22℃, billet thickness 180mm, center segregation C1.0 grade, center porosity 1.0 grade.

[0082] Heating: Heating temperature 1220℃, holding time 36min (30mm×1.2min / mm).

[0083] Rolling: High-pressure water descaling pressure 19MPa, roughing temperature 1040℃, finishing rolling start temperature 880℃, finishing rolling temperature 780℃, followed by air cooling.

[0084] Heat treatment: Quenching at 910℃ for 75 min (30 mm × 2.5 min / mm), water cooling rate 24℃ / s; tempering at 240℃ for 150 min (30 mm × 5.0 min / mm), air cooling.

[0085] Performance test results: Yield strength: 1385 MPa, tensile strength: 1510 MPa, elongation: 9%; -40℃ low temperature impact energy: 32J, 35J, 33J (average value 33.3J); Surface Brinell hardness: 470HBW, core hardness: 395HBW (≥470×80%=376); Abrasion resistance: According to ASTM G65 testing, the wear rate is 58% of that of existing abrasion-resistant steels of the same hardness (abrasion resistance is improved by 42%). Microstructure: tempered martensite, VC particles with a diameter of 70-190 nm, uniformly dispersed, accounting for about 5-8% of the volume.

[0086] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A high-vanadium wear-resistant steel plate, characterized in that, Thickness ≤40mm, microstructure is tempered martensite, chemical composition by weight percentage: C: 0.20~0.30%, Si: 0.10~0.50%, Mn: 0.5~1.0%, Nb: <0.010%, V: 0.20~0.60%, Ti: 0.010~0.030%, Al: 0.02~0.07%, Ni: 0.01~1.0%, Cu: <0.50%, Cr: 0.6~1.2%, Mo: 0.1~0.7%, B: 0.0010~0.0030%, Ca: 0.010~0.030%, P: ≤0.010%, S: ≤0.001%, O: ≤0.0015%, N: ≤0.0020%, H: ≤0.0001%, balance Fe. and unavoidable impurity elements; carbon equivalent (CEV) ≤ 0.70%; The performance indicators of the steel plate are as follows: yield strength ≥1200MPa, tensile strength ≥1350MPa, elongation ≥8%; low temperature impact energy Akv ≥15J at -40℃; surface Brinell hardness 420-480HBW, core hardness not less than 80% of surface hardness; wear resistance is improved by more than 30% compared with existing wear-resistant steels of the same hardness.

2. The high-vanadium wear-resistant steel plate according to claim 1, characterized in that, The chemical composition, by weight percentage, is as follows: C: 0.22–0.28%, V: 0.30–0.50%, Ti: 0.015–0.025%, Al: 0.03–0.05%, Cr: 0.8–1.0%, Mo: 0.3–0.5%, Ca: 0.015–0.025%.

3. The high-vanadium wear-resistant steel plate according to claim 1, characterized in that, The VC particles have a particle size of 50–200 nm and are uniformly dispersed in the tempered martensitic matrix.

4. The high-vanadium wear-resistant steel plate according to claim 1, characterized in that, The carbon equivalent (CEV) is 0.65–0.69%.

5. A method for manufacturing a high-vanadium wear-resistant steel plate as described in any one of claims 1 to 4, characterized in that, Includes the following steps: (1) Pretreatment of molten iron: Desulfurization treatment is carried out on the molten iron, and the sulfur content after desulfurization is ≤0.005%; (2) Smelting: A converter is used for smelting, and the carbon content at the end of the smelting process is controlled at 0.18-0.28% and the temperature is 1620-1650℃; (3) Ladle refining: The molten steel from the converter is sent into the LF refining furnace, and the refining time is ≥40min; (4) Vacuum degassing: RH vacuum degassing treatment is adopted, with a vacuum degree ≤67Pa and a degassing time ≥20min; (5) Ca treatment: After vacuum degassing, Ca-Si wire is fed in, with a Ca wire feeding amount of 0.2-0.5 kg / t steel; (6) Continuous casting: Special protective slag is used, and casting is carried out at low superheat, with a superheat of 5 to 28°C and argon protection throughout the process; the low-magnification center segregation of the continuous casting billet is ≤C1.0 grade, and the center porosity is ≤1.0 grade; (7) Heating: The continuously cast billet is fed into a walking beam furnace, heated at 1150-1250℃ for 1.0-1.2 min / mm; (8) Rolling: After the billet is taken out of the furnace, it is descaled by high pressure water. The rough rolling temperature is ≥1000℃; the finishing rolling temperature is 820~920℃ and the finishing rolling temperature is 760~840℃. The high pressure water descaling passes before finishing rolling are ≥3 times; after rolling, it is air-cooled to room temperature. (9) Heat treatment: First heat the steel plate to 900-940℃ and hold for 1.5-2.5 min / mm, then water cool to room temperature at a rate of >20℃ / s; then heat the steel plate to 150-250℃ and hold for 3.0-5.0 min / mm, then air cool to room temperature.

6. The manufacturing method according to claim 5, characterized in that, The special protective slag mentioned in step (6) has an alkalinity of CaO / SiO2 = 1.0 to 1.5 and a viscosity of 0.05 to 0.15 Pa·s at 1300℃.

7. The manufacturing method according to claim 5, characterized in that, The pressure of the high-pressure water dephosphorization in step (8) is ≥15MPa.

8. The manufacturing method according to claim 5, characterized in that, The quenching temperature in step (9) is 920-930℃, and the tempering temperature is 200-220℃.

9. The manufacturing method according to claim 5, characterized in that, In step (8), the cumulative reduction rate of rough rolling is ≥60%, and the cumulative reduction rate of finish rolling is ≥40%.

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