Low-cost 800MPa-grade cold-rolled weather-resistant steel plate for railway vehicle and production method of cold-rolled weather-resistant steel plate

Abstract

The invention provides a low-cost 800MPa-grade cold-rolled weather-resistant steel plate for railway vehicles and a production method of the low-cost 800MPa-grade cold-rolled weather-resistant steel plate. The low-cost 800MPa-grade cold-rolled weather-resistant steel plate comprises the following components: 0.07-0.10% of C, 0.30-0.50% of Si, 0.40-0.60% of Mn, less than or equal to 0.018% of P, less than or equal to 0.006% of S, 0.30-0.50% of Cr, 0.20-0.40% of Cu, 0.03-0.05% of Al, 0.04-0.06% of Ti, less than or equal to 0.006% of N and the balance of Fe and inevitable impurities. Compared with the prior art, the Ti microalloying technology is combined with hot rolling, cold rolling and cover annealing processes, so that the yield strength of the cold-rolled steel plate is larger than or equal to 700 MPa, the tensile strength is larger than or equal to 800 MPa, the ductility is larger than or equal to 8%, and meanwhile the cold-rolled steel plate has good cold bending performance and weather resistance and is stable in performance.

Description

Technical Field

[0001] The present invention belongs to the field of alloy steel production, and in particular relates to a low-cost 800MPa grade cold-rolled weathering steel plate for railway vehicles and a production method thereof. Background Art

[0002] With the rapid development of railway vehicles, high strength and lightweight are the future development direction of weathering steel for railway carriages. At present, the steel plates mainly used for weathering steel for railway carriages are SPA-H and Q450NQR1 weathering steel with yield strength of 355MPa and 450MPa. They are heavy in weight, low in strength, and have high steel consumption and transportation costs. Increasing the strength of steel used in railway carriages and reducing the thickness of steel used in railway carriages are the most effective ways to achieve high strength and lightweight for railway carriages. Relevant research shows that if high-strength weathering steel with a strength greater than 800MPa is used as the material for railway carriages, the weight of the corner columns and bottom crossbeams of the carriages can be reduced by 30%, and other components such as top plates and gooseneck trough beams can be reduced by more than 13% to varying degrees.

[0003] Prior art search results:

[0004] The Chinese invention patent with publication number CN112176259A published on January 5, 2021 discloses "A 550MPa grade high-strength weathering steel and its production method". The composition of the invention is designed to be C: 0.06~0.09%, Si: 0.20~0.30%, Mn: 1.41~1.60%, P≤0.018%, S≤0.002%, Als: 0.015~0.050%, Nb: 0.020~0.040%, Cu: 0.30~0.40%, Cr: 0.30~0.50%, Ni: 0.21~0.25%, Ti: 0.05~0.07%, and the balance is Fe and unavoidable impurities. Although the invention has achieved a high yield strength of 550MPa, the alloy elements (Mn, Nb, Ni) of the invention are high in content and variety, and edge heaters are required to compensate the temperature of the edges of the intermediate billet before finishing rolling, resulting in high alloy and process costs.

[0005] The Chinese invention patent with publication number CN115976396A published on April 18, 2023 discloses "A high-strength, corrosion-resistant hot-rolled steel strip Q550NQR1 for containers and its production method". The composition of the invention is designed to be C: 0.05~0.07%, Si: 0.25~0.35%, Mn: 0.75~0.80%, P≤0.020%, S≤0.009%, Als: 0.20~0.32%, Cu: 0.35~0.50%, Cr: 0.50~0.55%, Ni: 0.20~0.35%, Ti: 0.55~0.70%, O≤0.004%, N≤0.0045%; the balance is Fe and unavoidable impurities. This invention uses carbon-manganese structural steel components and combines them with the CSP-specific short-process production process to obtain a thin-gauge weathering steel with a yield strength ≥550MPa. However, this invention has high Mn and Ti contents, low N content control, and is more difficult to smelt. In addition, the expensive Ni element is added, resulting in a high alloy cost.

[0006] The Chinese invention patent with publication number CN107267875A published on October 20, 2017 discloses "A weathering steel for railway containers with a yield strength ≥700MPa and a production method". The composition of the invention is designed to be C: 0.13-0.16%, Si: 0.50-0.60%, Mn: 1.10-1.20%, P≤0.015%, S≤0.010%, Cu: 0.20-0.30%, Cr: 0.30-0.50%, Nb: 0.025-0.04%, Ti: 0.072-0.108%, V: 0.010-0.020%, N≤0.007%; the balance is Fe and unavoidable impurities. This invention utilizes Nb and Ti composite microalloying and combines hot rolling + cold rolling + annealing processes to achieve a yield strength ≥ 700MPa, and the yield strength fluctuation of the entire coil is controlled within 20MPa; however, this invention has a high C content and is located in the peritectic reaction zone, resulting in large fluctuations in the liquid level during the solidification process of the molten steel; its Mn and Ti contents are also high, and the expensive Nb element is added, resulting in a high alloy cost and poor weldability.

[0007] The above existing technologies have problems such as low steel strength, high alloy and process costs, and thick steel specifications, and do not meet the requirements of low cost, high strength and lightweight. Summary of the Invention

[0008] The present invention provides a low-cost 800MPa-grade cold-rolled weathering steel plate for railway vehicles and a production method thereof. Through alloy element ratio and optimized design, controlled rolling and controlled cooling and a reasonable annealing process are adopted, which are suitable for traditional two-stage hot rolling production lines. In addition, Ti microalloying technology is used to prepare a high-strength and low-cost cold-rolled weathering steel with a yield strength of ≥700MPa, a tensile strength of ≥800MPa, and an elongation of ≥8%. The product thickness is 0.8mm to 2.0mm, and the performance is stable and the weathering resistance is excellent. It meets the requirements of the new generation of railway carriages for extremely thin and higher-strength weathering steel, does not require the addition of Nb and Ni, and has low cost.

[0009] The specific technical solutions of the present invention are as follows:

[0010] A low-cost 800 MPa grade cold-rolled weathering steel plate for railway vehicles, comprising the following components in percentage by mass:

[0011] C: 0.07~0.10%, Si: 0.30~0.50%, Mn: 0.40~0.60%, P: ≤0.018%, S: ≤0.006%, Cr: 0.30~0.50%, Cu: 0.20~0.40%, Al: 0.03~0.05%, Ti: 0.04~0.06%, N: ≤0.006%, and the rest are Fe and unavoidable impurities.

[0012] The microstructure of the low-cost 800MPa grade cold-rolled weathering steel plate for railway vehicles is ferrite, pearlite and free cementite.

[0013] The low-cost 800MPa grade cold-rolled weathering steel plate for railway vehicles has a yield strength of ≥700MPa, a tensile strength of ≥800MPa, and an elongation of ≥8%; and is qualified in cold bending d=2a, 180°.

[0014] The average corrosion rate of the low-cost 800MPa grade cold-rolled weathering steel plate for railway vehicles is ≤1.75g / m 2 ·h;

[0015] The low-cost 800MPa grade cold-rolled weathering steel plate for railway vehicles has a same-roll yield strength fluctuation range of ≤17MPa, a same-roll tensile strength fluctuation range of ≤18MPa, and an elongation fluctuation range of ≤1.8%.

[0016] The present invention provides a method for producing a low-cost 800 MPa grade cold-rolled weathering steel plate for railway vehicles, comprising the following steps:

[0017] 1) Molten steel smelting;

[0018] 2) Slab continuous casting;

[0019] 3) Hot rolling;

[0020] 4) Acid continuous rolling;

[0021] 5) bell annealing;

[0022] 6) Flat.

[0023] The molten steel smelting in step 1) includes: converter + refining; the steel tapping time in the converter process is ≥3 minutes, and a deoxidizer is added to produce white slag in the refining process, and the white slag is kept for ≥10 minutes.

[0024] During the slab continuous casting process in step 2), electromagnetic stirring and dynamic soft reduction are used, a chamfered crystallizer is used for production, and the slab casting speed is controlled at 1.1 to 1.35 m / min.

[0025] The hot rolling in step 3) includes: heating, roughing rolling, finishing rolling, laminar cooling and coiling; wherein, in the heating, the slab soaking temperature is 1200-1280°C, the slab furnace temperature is controlled at 1200-1240°C, and the furnace time is 150-190 min; in the roughing rolling, the roughing end temperature (RT2) is controlled at 1020-1060°C; in the finishing rolling, the finishing temperature is 860-920°C; in the laminar cooling, the laminar cooling water temperature is not higher than 35°C; and in the coiling, the coiling temperature is 580-620°C.

[0026] In step 3), the actual heating temperature of the slab is 1250-1280°C. On the one hand, it is necessary to ensure that the steel billet is fully austenitized, especially the composition of the steel billet is homogenized; on the other hand, it is necessary to ensure that the TiC precipitated during the continuous casting process of the steel billet is fully dissolved in the matrix, which is beneficial for the precipitation of TiC particles during the rough rolling and finishing rolling processes to inhibit austenite recrystallization and grain growth; the soaking time is 25-35min, and high-temperature fast burning is adopted to shorten the soaking period, mainly to prevent copper brittleness during the heating process of the steel billet. The end temperature of rough rolling (1020-1060°C): rolling in the austenite recrystallization zone, accumulating dislocations, and refining the austenite grains. The end temperature of finishing rolling (860-920°C) is rolling in the austenite non-recrystallization zone, refining the grains through strain-induced precipitation (such as TiC), and increasing the dislocation density.

[0027] In step 3), the coiling temperature of the steel coil is controlled at 580-620° C. In this temperature range, the matrix can precipitate fine and dispersed TiC or Ti(CN) second phase particles, which play a precipitation strengthening role and improve the strength of the steel coil.

[0028] In step 4), the pickling continuous rolling includes pickling and cold continuous rolling; wherein the cold continuous rolling reduction rate is 50% to 65%, and the thickness of the cold rolled plate is 0.8 to 2.0 mm.

[0029] In step 5), the bell annealing is performed at a temperature of 500-570°C for 8-12 hours. The purpose is to reduce the internal stress of the cold-rolled steel plate while maintaining the work-hardened state, thereby improving the corrosion resistance of the cold-rolled weathering steel and significantly improving its plasticity and toughness, thereby increasing the safety of the cold-rolled weathering steel plate. If the annealing temperature is too low, the stress relief effect will not be achieved, the plasticity and toughness of the material will remain low, and the material will be prone to cracking during processing. If the annealing temperature is too high, the grains will recrystallize, the material strength will be low, and it will not meet the safety requirements of the structural parts. Therefore, the optimal annealing temperature range of the present invention is 500-570°C. Keeping the temperature for 8-12 hours ensures the uniform distribution of the precipitated phase, stabilizes the structure, and reduces performance fluctuations.

[0030] In step 6), the leveling is performed with a leveling amount of ≤1.0%.

[0031] The design ideas of the present invention are as follows:

[0032] C: Carbon plays a major role in solid solution strengthening in steel and has a significant impact on steel strength. It is the most economical and effective element for improving steel strength. However, excessive carbon content can deteriorate the weldability of steel and reduce plasticity. Moreover, a carbon content exceeding 0.10% is prone to peritectic reaction during the steelmaking process, resulting in large fluctuations in the molten steel level. Therefore, the carbon content of the present invention is controlled within a range of 0.07 to 0.10%.

[0033] Si: Silicon plays a major role in solid solution strengthening in steel and is also a commonly used deoxidizing element. However, excessive silicon content makes phosphorus removal difficult during hot rolling and reduces the weldability of the steel. Therefore, the silicon content in the present invention is controlled at 0.30-0.50%.

[0034] Mn: Manganese is an important solid solution strengthening element in steel, which can significantly improve the strength and toughness of steel. However, too high a manganese content will not only increase the cost of the steel, but also deteriorate the welding performance of the steel. Therefore, the manganese content of the present invention is controlled at 0.40-0.60%.

[0035] P: Phosphorus can significantly improve the atmospheric corrosion resistance of steel, but too high a phosphorus content is likely to segregate at grain boundaries and reduce the toughness of the steel, especially the low-temperature impact toughness. Therefore, the phosphorus content of the present invention is ≤0.018%.

[0036] S: Sulfur is a harmful residual element in steel, which deteriorates the corrosion resistance and toughness of steel, and easily forms Ti4C2S2 with titanium, reducing the effective Ti content in steel, thereby affecting the Ti microalloying effect. Therefore, the sulfur content of the present invention is

[0037] ≤0.006%.

[0038] Al: Aluminum is a commonly used deoxidizer in steel. It can fix free nitrogen in steel and improve the steel strip matrix. The dispersed AlN can inhibit the growth of austenite grains during the heating process and refine the grains. However, too high an Al content can lead to a sharp increase in Class B inclusions in the steel, resulting in a decrease in the internal quality of the steel and reduced weldability and machinability of the steel strip. Therefore, the AlS content in the present invention is controlled at 0.03-0.05%.

[0039] Cu: Copper is the main weathering element in weathering steel and can significantly improve the weathering resistance of steel. Copper added to steel as an alloying element also plays a role in solid solution strengthening and precipitation strengthening. However, if the copper content is too high, it is easy to cause cracks in the steel billet during heating and hot rolling, and deteriorate the surface properties of the steel billet. Therefore, the copper content of the present invention is controlled at 0.20-0.40%.

[0040] Cr: Adding chromium in combination with copper and nickel can enrich the steel surface and promote the formation of a dense rust layer, significantly improving the steel's atmospheric corrosion resistance. Compared to copper and nickel, it is also more cost-effective. However, excessive chromium content can deteriorate the steel's weldability. Furthermore, Cr combines with Cu to form a composite precipitate phase, enhancing the precipitation strengthening effect. Therefore, the chromium content in this invention is controlled to 0.30-0.50%.

[0041] Ti: Titanium is the most economical microalloying element for improving the strength of steel and is also a strong nitride-forming element. The TiN formed in the steel prevents the austenite grains from growing during the heating process, and suppresses the growth of recrystallized austenite grains during the controlled rolling process, thereby refining the ferrite grains after the phase transformation. In the coiling process after rolling, fine second-phase TiC and Ti(CN) particles are precipitated, thereby improving the strength of the steel through grain refinement and precipitation strengthening. If the titanium content is too low, the strengthening effect on the steel grade is not obvious. If the titanium content is too high, the cost of the steel grade will be higher. In addition, Ti and Al jointly refine the grains and improve the strength and toughness. Therefore, the titanium content of the present invention is controlled at 0.04-0.06%.

[0042] N: Nitrogen is an element present in the smelting process. One of the characteristics of the present invention is the use of Ti microalloying technology. Ti will react with elements such as O, N, and S in the steel. If the N content is too high, coarse TiN will precipitate in the molten steel. This will neither prevent the growth of austenite grains nor achieve precipitation strengthening. On the contrary, it will reduce the fine grain strengthening and precipitation strengthening effects of titanium. Therefore, the nitrogen content of the present invention is ≤0.006%.

[0043] Compared with the prior art, the present invention has the following outstanding beneficial effects: the present invention optimizes the design of alloy elements, adopts a single Ti microalloying and low C and low S composition design, has few alloy types and low content, does not add precious metals such as Ni and Nb, and Ti is more abundant in resources and cheaper than other microalloying elements, and has low raw material costs. The present invention has low smelting difficulty, simple rolling and annealing processes, and low requirements for equipment. Most steel companies can produce without investing in new equipment. The present invention effectively solves the problem of large performance fluctuations of Ti microalloyed steel through controlled rolling and controlled cooling technology and a reasonable hood annealing process. The yield and tensile strength fluctuations of the entire coil of weathering steel do not exceed 18MPa, and the elongation fluctuation does not exceed 1.8%. The product obtained by the present invention has excellent comprehensive performance, and the yield strength of high-strength weathering steel is ≥700MPa, and the tensile strength is ≥1.8%.

[0044] ≥800MPa, elongation ≥8%, excellent cold bending performance and weather resistance, and stable performance, meeting the demand for high-strength weathering steel for the new generation of railway carriages. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is the microstructure obtained after hood annealing of the cold-rolled plate in Example 2. DETAILED DESCRIPTION

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0047] Example 1-Example 6

[0048] A low-cost 800 MPa grade cold-rolled weathering steel plate for railway vehicles comprises the composition shown in Table 1. The remainder not shown in Table 1 is Fe and unavoidable impurities.

[0049] Comparative Example 1-Comparative Example 6

[0050] A cold-rolled weathering steel plate comprises the components shown in Table 1, and the balance not shown in Table 1 is Fe and unavoidable impurities.

[0051] Table 1 Chemical composition values of various embodiments and comparative examples of the present invention (wt%)

[0052]

[0053]

[0054] The production method of the cold-rolled weathering steel sheets in the above embodiments and comparative examples comprises the following steps:

[0055] 1) Molten steel smelting: The tapping time of the converter process is ≥3min, and deoxidizer is added to produce white slag during the refining process, and the white slag retention time is ≥10min.

[0056] 2) Slab continuous casting: Electromagnetic stirring and dynamic soft reduction are used in the continuous casting process, and chamfered crystallizers are used for production. The slab casting speed is controlled at 1.1 to 1.35 m / min.

[0057] 3) Hot rolling: the slab soaking temperature is 1200-1280℃, the slab furnace temperature is controlled at 1200-1240℃, the furnace time is 150-190min, the rough rolling end temperature (RT2) is controlled at 1020-1060℃, the finishing temperature is 860-920℃, the laminar cooling water temperature is not higher than 35℃, and the coiling temperature is 580-620℃.

[0058] 4) Acid continuous rolling: The cold rolling reduction rate is 50% to 65%, and the thickness of the cold rolled plate is 0.8 to 2.0 mm.

[0059] 5) Hood annealing: The annealing temperature of cold-rolled weathering steel is 500-570℃, and the insulation time is 8-12h.

[0060] 6) Flatness: Cold rolled plate flatness ≤ 1.0%.

[0061] The production parameters of each embodiment and comparative example are shown in Table 2.

[0062] Table 2 List of main process parameters of various embodiments of the present invention

[0063]

[0064]

[0065] Weathering steel SPA-H and alloy steel Q355B are both commercially available products produced by Xinyu Iron and Steel Co., Ltd., and there is no need to describe their production methods.

[0066] It should be noted that, except for the annealing temperature which is not within the scope of the present invention, the chemical composition and rolling process of Comparative Examples 1 and 2 all meet the conditions of the present invention. The annealing temperature of Comparative Example 1 is 450°C, which is lower than the annealing temperature of the present invention. The annealing temperature is too low and cannot relieve stress. The plasticity and toughness of the material are still low. As shown in Table 3, its elongation is only 2.5%, and the material is prone to cracking during processing. The annealing temperature of Comparative Example 2 is 600°C, which is higher than the annealing temperature of the present invention. The annealing temperature is too high, and the grains undergo partial recrystallization, resulting in low material strength. As shown in Table 3, its tensile strength is only 565MPa, which cannot meet the safety requirements of structural parts. Therefore, the optimal annealing temperature range of the present invention is 500-570°C. Since the mechanical properties of Comparative Examples 1 and 2 do not meet the requirements, they are no longer involved in the corrosion resistance and performance fluctuation detection experiments of the present invention.

[0067] In addition, except for the Ti content of the microalloying element not being within the scope of the present invention, the rolling process and annealing temperature of Comparative Examples 3 and 4 all meet the conditions of the present invention. The Ti content of Comparative Example 3 is 0.023%, which is lower than the Ti content of the present invention. If the Ti content is too low, the TiC particles precipitated during the coiling process will greatly weaken the fine grain strengthening and precipitation strengthening effects on the steel. As shown in Table 3, its yield strength is 613 MPa and its tensile strength is 715 MPa, which does not meet the requirements of the present invention for yield strength ≥ 700 MPa and tensile strength ≥ 800 MPa. The Ti content of Comparative Example 4 is 0.082%, which is higher than the Ti content of the present invention. As can be seen from Table 3, despite the significant increase in Ti content, the mechanical properties of the steel are not significantly improved, and the cost of the steel is significantly increased. Therefore, the optimal range of Ti content of the present invention is 0.04-0.06%. Since the mechanical properties of Comparative Example 3 do not meet the requirements and Comparative Example 4 does not meet the low cost requirements, it is no longer included in the corrosion resistance and performance fluctuation detection experiments of the present invention.

[0068] In addition, except for the hot rolling furnace time which is not within the scope of the present invention, the chemical composition and annealing temperature of Comparative Examples 5 and 6 all meet the conditions of the present invention. The furnace time of Comparative Example 5 is 120 minutes, which is lower than the furnace time requirement of the present invention. If the furnace time is too short, the microalloying element Ti in the steel will not be completely dissolved in the matrix, and the subsequent coiling process cannot precipitate a large amount of fine dispersed TiC particles, making it difficult to fully exert the fine grain strengthening and precipitation strengthening effects of TiC, resulting in a decrease in the strength of the steel. The furnace time of Comparative Example 6 is 230 minutes, which exceeds the furnace time range of the present invention. If the furnace time is too long, the austenite grains are easily coarsened during the heating process, and the ferrite grains obtained by subsequent transformation are also relatively coarse, which significantly reduces the comprehensive mechanical properties of the steel. As can be seen from Table 3, the yield and tensile strength of Comparative Examples 5 and 6 do not meet the high strength requirements of the present invention. Therefore, the optimal range of the furnace time of the present invention is 150-190 minutes. Since the mechanical properties of Comparative Examples 5 and 6 do not meet the requirements of the present invention, they are no longer involved in the corrosion resistance and performance fluctuation detection experiments of the present invention.

[0069] The mechanical properties (tested in accordance with GB / T 228) and corrosion performance tests (referring to TB / T2375-1993 Test method for periodic immersion corrosion of weathering steel for railway use) of each embodiment and comparative example are shown in Tables 3 and 4, and the performance fluctuations are shown in Table 5.

[0070] Table 3 Mechanical properties test results of various embodiments of the present invention and comparative examples

[0071]

[0072] Table 4 Corrosion resistance test results of various embodiments of the present invention and comparative examples

[0073]

[0074] Table 5 List of mechanical property fluctuation detection results of the same roll in various embodiments of the present invention

[0075]

[0076] It can be seen from Tables 3 to 5 that the cold-rolled weathering steel produced by the present invention has a yield strength ≥700 MPa, a tensile strength ≥800 MPa, an elongation ≥8%, and the yield strength fluctuation range of the same coil does not exceed 17 MPa, the tensile strength fluctuation range does not exceed 18 MPa, and the elongation fluctuation range does not exceed 1.8%. It has good cold bending performance and corrosion resistance.

[0077] The underlined data above do not meet the requirements of the present invention.

[0078] The above embodiments are described to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A low-cost 800MPa grade cold-rolled weathering steel plate for railway vehicles, characterized in that: The low-cost 800MPa grade cold-rolled weathering steel plate for railway vehicles includes the following components in mass percentage: C: 0.07-0.10%, Si: 0.30-0.50%, Mn: 0.40-0.60%, P: ≤0.018%, S: ≤0.006%, Cr: 0.30-0.50%, Cu: 0.20-0.40%, Al: 0.03-0.05%, Ti: 0.04-0.06%, N: ≤0.006%, and the rest is Fe and unavoidable impurities.

2. The low-cost 800 MPa grade cold-rolled weathering steel plate for railway vehicles according to claim 1, characterized in that: The low-cost 800MPa grade cold-rolled weathering steel plate for railway vehicles has a yield strength of ≥700MPa, a tensile strength of ≥800MPa, and an elongation of ≥8%. It is qualified by cold bending d=2a, 180°, and has an average corrosion rate of ≤1.75g / m 2 ·h.

3. The low-cost 800 MPa grade cold-rolled weathering steel plate for railway vehicles according to claim 1, characterized in that: The low-cost 800MPa grade cold-rolled weathering steel plate for railway vehicles has a same-roll yield strength fluctuation range of ≤17MPa, a same-roll tensile strength fluctuation range of ≤18MPa, and an elongation fluctuation range of ≤1.8%.

4. A method for producing the low-cost 800 MPa grade cold-rolled weathering steel sheet for railway vehicles according to any one of claims 1 to 3, characterized in that: The production method comprises the following steps: 1) Molten steel smelting; 2) Slab continuous casting; 3) Hot rolling; 4) Acid continuous rolling; 5) bell annealing; 6) Flat.

5. The production method according to claim 4, characterized in that The molten steel smelting in step 1) includes: converter + refining; the steel tapping time in the converter process is ≥3 minutes, and a deoxidizer is added to produce white slag in the refining process, and the white slag is kept for ≥10 minutes.

6. The production method according to claim 4, characterized in that The hot rolling in step 3) includes: heating, rough rolling, finishing rolling, laminar cooling and coiling.

7. The production method according to claim 4 or 6, characterized in that In step 3), the slab soaking temperature is 1200-1280°C, the slab furnace exit temperature is controlled at 1200-1240°C, and the furnace time is 150-190 min; the rough rolling end temperature is controlled at 1020-1060°C, and the finishing rolling end temperature is 860-920°C; the laminar cooling water temperature is not higher than 35°C; and the coiling temperature is 580-620°C.

8. The production method according to claim 4, characterized in that In step 4), the pickling continuous rolling includes pickling and cold continuous rolling; wherein the cold continuous rolling reduction rate is 50% to 65%, and the thickness of the cold rolled plate is 0.8 to 2.0 mm.

9. The production method according to claim 4, characterized in that In step 5), the bell annealing is performed at a temperature of 500-570° C. for 8-12 hours.

10. The production method according to claim 4, characterized in that In step 6), the leveling is performed with a leveling amount of ≤1.0%.

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