A method for stabilizing the meniscus of a thin slab continuous casting peritectic steel

Abstract

This application provides a method for stabilizing the liquid level in a crystallizer for continuous casting of peritectic steel in thin slabs. The method includes: continuously casting molten steel in a continuous casting machine to obtain a continuously cast billet with a thickness of 60mm-90mm; wherein the continuous casting machine includes a crystallizer, which includes a pair of wide copper plates and a pair of narrow copper plates, the thickness of the wide copper plates being 19mm-24mm, and the thickness ratio of the wide copper plates to the narrow copper plates being (1.25-1.35):1. This is beneficial for stabilizing the liquid level in the crystallizer, improving the surface quality of the cast billet, reducing cracks and slag contamination defects, and increasing the production smoothness and the qualified rate of the cast billet.

Description

Technical Field

[0001] This application relates to the field of steel technology, and specifically to a method for stabilizing the liquid level in a crystallizer for continuous casting of peritectic steel in thin slabs. Background Technology

[0002] Peritectic steel undergoes a peritectic reaction during solidification, resulting in a large linear shrinkage rate. This leads to air gaps between the billet shell and the mold wall, causing uneven heat transfer and uneven shell growth. This uneven shell undergoes dynamic bulging deformation between the fan-shaped rolls, triggering periodic liquid level fluctuations in the mold. This problem is more pronounced in thin slab continuous casting due to the thin shell and rapid cooling rate, often leading to surface cracks and other defects, and in severe cases, even leaks. Current technologies for controlling liquid level fluctuations in peritectic steel typically target conventional slabs, neglecting the unique characteristics of thin slabs, making conventional control methods ineffective. Summary of the Invention

[0003] This application provides a method for stabilizing the liquid level in the crystallizer during continuous casting of peritectic steel from thin slabs, aiming to solve the problem of large fluctuations in the liquid level in the crystallizer during continuous casting of peritectic steel from thin slabs.

[0004] The method for stabilizing the liquid level in a crystallizer for continuous casting of peritectic steel in thin slabs provided in this application includes: continuously casting molten steel in a continuous casting machine to obtain a continuously cast billet with a thickness of 60mm-90mm; wherein the continuous casting machine includes a crystallizer, the crystallizer includes a pair of wide copper plates and a pair of narrow copper plates, the thickness of the wide copper plates is 19mm-24mm, and the thickness ratio of the wide copper plates to the narrow copper plates is (1.25-1.35):1.

[0005] According to the embodiments of this application, for thin slab continuous casting peritectic steel, the crystallizer uses a copper plate with the above-mentioned thickness range, which helps to slow down heat transfer, thereby providing a milder cooling environment for the nascent billet shell in the meniscus region of the crystallizer, improving heat transfer uniformity, thereby promoting uniform growth of the billet shell, reducing billet shell deformation, and improving the stability of the liquid surface in the crystallizer.

[0006] In some embodiments, the inlet temperature of the cooling water for the crystallizer is 38.5°C-39.5°C. This further slows down heat transfer, providing a milder cooling environment for the continuously cast billet shell and improving heat transfer uniformity.

[0007] In some embodiments, the flow rate ratio of the cooling water flow rate on the wide side of the crystallizer to the cooling water flow rate on the narrow side is (29-29.5):1.

[0008] In some embodiments, the crystallizer employs a non-sinusoidal vibration mode, wherein the negative slip time ratio (NSR) of the crystallizer vibration is 30%-50%.

[0009] In some embodiments, the negative slip rate NS of the crystallizer vibration is -25% to -10%.

[0010] According to the embodiments of this application, by using a non-sinusoidal vibration mode with high frequency and low amplitude for the crystallizer vibration, and controlling the negative slip time ratio and negative slip rate of the crystallizer vibration within the above range, the depth of the vibration mark can be significantly reduced, stress concentration can be reduced, and the crack sensitivity of the billet surface can be reduced.

[0011] In some embodiments, the basicity of the crystallizer protective slag is 0.95-1.

[0012] In some embodiments, the melting point of the crystallizer protective slag is 960℃-1000℃.

[0013] In some embodiments, the viscosity of the mold flux is 0.16 Pa·s-0.2 Pa·s.

[0014] By controlling the melting point and viscosity of the mold flux within the aforementioned range, a lower melting point ensures that a sufficiently thick liquid slag film can be formed at the meniscus, providing stable and continuous lubrication; while a higher viscosity can effectively control the flow rate of the liquid slag, avoiding excessive inflow, thereby ensuring that the slag film formed between the billet shell and the copper plate is uniform and stable, providing both sufficient lubrication and uniform heat transfer, preventing cracks caused by uneven frictional stress and excessive local heat flow.

[0015] In some embodiments, the total specific water volume for secondary cooling in the continuous casting process is 1.4 L / kg to 1.9 L / kg.

[0016] In some embodiments, when the liquid level fluctuation value of the crystallizer is less than or equal to 10 mm, the total specific water volume for secondary cooling is 1.4 L / kg to 1.6 L / kg; when the liquid level fluctuation value of the crystallizer is greater than 10 mm, the total specific water volume for secondary cooling is 1.6 L / kg to 1.9 L / kg.

[0017] In some embodiments, during the continuous casting process, the superheat of the continuous casting tundish is 10°C-20°C; and / or, the continuous casting speed is 3.7m / min-4.2m / min.

[0018] According to the embodiments of this application, the cooling intensity of the secondary cooling zone adopts a dynamic adjustment strategy based on the feedback of the liquid level fluctuation in the crystallizer: when the fluctuation value is ≤10mm, the total specific water volume of the secondary cooling is 1.4~1.6L / kg; when the fluctuation value is >10mm, the total specific water volume of the secondary cooling is increased to 1.6~1.9L / kg. Large liquid level fluctuations usually mean unstable casting flow and potentially uneven billet shell growth. In this case, appropriately enhancing cooling promotes rapid billet shell thickening, thereby improving its ability to resist bulging deformation caused by the static pressure of molten steel.

[0019] In some embodiments, during the continuous casting process, the fan-shaped section of the continuous casting machine adopts a fixed roll gap, and the difference between the roll gap at the exit of the fan-shaped section and the entrance of the fan-shaped section is 1.9mm-2.2mm.

[0020] According to the embodiments of this application, the continuous casting sector section adopts a fixed roll gap mode instead of hydraulic cylinder adjustment. The fixed roll gap eliminates the intermittent and uneven extrusion force exerted by the rollers on the high-temperature billet shell caused by frequent hydraulic system operation. This uneven extrusion force is a significant factor inducing surface strain and internal stress concentration in the billet shell, leading to crack initiation and propagation. The fixed roll gap provides a stable and consistent support environment, which is conducive to uniform billet shell growth and thus reduces fluctuations in the liquid level in the crystallizer.

[0021] In some embodiments, during the continuous casting process, the C content in the first batch of molten steel is less than or equal to 0.075 wt%.

[0022] According to the embodiments of this application, the cooling rate inside the crystallizer is extremely high because the working conditions during the initial casting stage have not yet reached thermal equilibrium and a stable state. The low carbon content design is because low carbon steel has a higher solidification point and better high-temperature ductility, and its initial billet shell can better resist thermal stress under rapid cooling conditions, thereby reducing the occurrence of cracks in the billet shell during the initial casting stage when the working conditions fluctuate drastically.

[0023] In some embodiments, the molten steel comprises the following components in weight percentage: C: 0.055%-0.12%, Si: ≤0.5%, Mn: 0.2%-1.9%, P: ≤0.02%, S: ≤0.01%, Al: 0.02%-0.06%, with the balance being Fe and unavoidable impurities.

[0024] Compared with the prior art, this application has at least the following beneficial effects: This application provides a method for stabilizing the liquid level in the crystallizer for continuous casting of peritectic steel in thin slabs. Addressing issues such as liquid level fluctuations, uneven shell growth, and surface quality problems easily caused by solidification characteristics during peritectic steel continuous casting, this method utilizes crystallizer copper plates with specific thickness ranges and aspect ratios, combined with controlled cooling water inlet temperature and flow rate ratio, to mitigate initial heat transfer and promote uniform shell growth. It reduces vibration mark depth by employing a high-frequency, low-amplitude non-sinusoidal vibration mode and limiting negative sliding parameters; optimizes lubrication and heat transfer by applying a low-melting-point, high-viscosity protective slag; uses a fixed roll gap in the continuous casting fan section to provide stable support; and employs pure water for secondary cooling, dynamically adjusting the specific water volume according to crystallizer liquid level fluctuations, enhancing cooling when liquid level fluctuations are large to improve shell strength and resistance to bulging deformation. This invention effectively stabilizes the crystallizer liquid level, improves billet surface quality, reduces cracks and slag entrapment defects, and increases production smoothness and billet qualification rate. Detailed Implementation

[0025] To make the purpose, technical solution, and beneficial technical effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the embodiments described in this specification are merely for explaining this application and are not intended to limit it.

[0026] For simplicity, this paper only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an undefined range; and any lower limit can be combined with other lower limits to form an undefined range, just as any upper limit can be combined with any other upper limit to form an undefined range. Furthermore, although not explicitly stated, every point or individual value between the endpoints of a range is included within that range. Therefore, each point or individual value can serve as its own lower or upper limit and be combined with any other point or individual value, or with other lower or upper limits, to form an undefined range.

[0027] In this description, it should be noted that, unless otherwise stated, "above" and "below" include the stated number, and "multiple" in "one or more" means two or more.

[0028] The foregoing description of this application is not intended to describe every disclosed implementation or method. Instead, the following description provides more specific examples of exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments that can be combined in various ways.

[0029] As described in the background art, during the continuous casting process of thin slabs, due to the thinner slab shell and faster cooling rate, it is easier for uneven growth of the slab shell in the crystallizer to cause periodic liquid level fluctuations in the crystallizer, which in turn leads to defects such as surface cracks in the continuously cast slab.

[0030] Therefore, the embodiments of this application provide a method for controlling the stability of the liquid level in the crystallizer for continuous casting of peritectic steel in thin slabs. By adjusting the continuous casting process parameters, the stability of the liquid level in the crystallizer during continuous casting of peritectic steel in thin slabs can be improved, thereby improving the surface quality of the continuously cast billet.

[0031] The method for stabilizing the liquid level in a crystallizer for continuous casting of peritectic steel in thin slabs provided in this application includes: continuously casting molten steel in a continuous casting machine to obtain a continuously cast billet with a thickness of 60mm-90mm; wherein the continuous casting machine includes a crystallizer, the crystallizer includes a pair of wide copper plates and a pair of narrow copper plates, the thickness of the wide copper plates is 19mm-24mm, and the thickness ratio of the wide copper plates to the narrow copper plates is (1.25-1.35):1.

[0032] According to the embodiments of this application, for thin slab continuous casting peritectic steel, the crystallizer uses a copper plate with the above-mentioned thickness range, which helps to slow down heat transfer, thereby providing a milder cooling environment for the nascent billet shell in the meniscus region of the crystallizer, improving heat transfer uniformity, thereby promoting uniform growth of the billet shell, reducing billet shell deformation, and improving the stability of the liquid surface in the crystallizer.

[0033] In this application, both the wide-face copper plate and the narrow-face copper plate can be made from recycled copper plates. New copper plates may contain residual stress, which can easily lead to surface cracks in the billet shell within the crystallizer. In contrast, the residual stress within recycled copper plates that have been used for a period of time will be released, which is more conducive to reducing billet shell deformation.

[0034] In some embodiments, the inlet temperature of the cooling water for the crystallizer can be 38.5℃-39.5℃. For example, it can be 38.5℃, 38.6℃, 38.7℃, 38.8℃, 38.9℃, 39.0℃, 39.1℃, 39.2℃, 39.3℃, 39.4℃, 39.5℃, or any range of the above values.

[0035] By controlling the inlet temperature of the cooling water in the crystallizer within the above range, it is beneficial to further slow down heat transfer, thereby providing a milder cooling environment for the nascent billet shell in the meniscus region of the crystallizer, improving heat transfer uniformity, which can promote uniform growth of the billet shell, thereby reducing billet shell deformation and improving the stability of the liquid surface in the crystallizer.

[0036] In some embodiments, the flow rate ratio of the cooling water flow rate on the wide side of the crystallizer to the cooling water flow rate on the narrow side is (29-29.5):1, and the cooling water flow rate on the wide side of the crystallizer is 5700-6200 L / min.

[0037] According to the embodiments of this application, the ratio of the wide-face cooling water flow rate to the narrow-face cooling water flow rate of the crystallizer is within the above-mentioned range, which is beneficial to further provide a mild and orderly cooling environment, improve heat transfer uniformity, thereby promoting uniform growth of the billet shell and improving the stability of the liquid surface in the crystallizer.

[0038] In some embodiments, the crystallizer employs a non-sinusoidal vibration mode.

[0039] In some embodiments, the negative slip time ratio (NSR) of the crystallizer vibration can be 30%-50%. For example, it can be 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, or any range of the above values.

[0040] In continuous casting molds, when the downward vibration velocity of the mold exceeds the casting speed, the casting billet experiences an upward relative motion (opposite to the casting direction) relative to the mold; this stage is known as the negative slip stage. This stage helps the solidified billet shell detach from the mold wall, preventing sticking accidents. Simultaneously, it applies compressive stress to the solidified billet shell, which is beneficial for improving the surface quality of the cast billet. The negative slip time ratio (NSR) is the percentage of negative slip time to half a vibration cycle, and can be calculated as follows: NSR = (2t n / T) × 100% = 2f × t n × 100%, In the formula, t n The negative sliding time, in seconds, refers to the time period during which the downward movement speed of the crystallizer is greater than the billet pulling speed; T is the crystallizer vibration period, in seconds; f is the crystallizer vibration frequency, in Hz; where T = 1 / f.

[0041] In some embodiments, the negative slip rate NS of the crystallizer vibration can be from -25% to -10%. For example, it can be -25%, -24%, -23%, -22%, -21%, -20%, -19%, -18%, -17%, -16%, -15%, -14%, -13%, -11%, -10%, or any range of the above values.

[0042] The negative slip ratio NS refers to the ratio of the downward movement speed of the mold relative to the billet to the billet pulling speed during the negative slip stage of the mold. It can be calculated using the following method: NS = (V m -V c ) / V c ×100%, In the formula, V m V is the instantaneous velocity of the crystallizer vibrating downwards, measured in m / s. c The constant billet pulling speed is expressed in m / s.

[0043] When the crystallizer adopts a non-sinusoidal vibration mode, the downward oscillation velocity of the crystallizer changes non-uniformly, and the average negative slip ratio can be calculated by integration.

[0044] In this application, since the downward vibration speed of the crystallizer is opposite to the direction of the billet pulling speed, the negative slip ratio of the crystallizer vibration is taken as a negative number.

[0045] According to the embodiments of this application, by using a non-sinusoidal vibration mode with high frequency and low amplitude for the crystallizer vibration, and controlling the negative slip time ratio and negative slip rate of the crystallizer vibration within the above range, the depth of the vibration mark can be significantly reduced, stress concentration can be reduced, and the crack sensitivity of the billet surface can be reduced.

[0046] In some embodiments, the basicity of the crystallizer protective slag can be 0.95-1.

[0047] Mold flux is a CaO-SiO2-based metallurgical auxiliary material used in continuous casting processes. It is typically added to the surface of the molten steel in the mold in powder, granular, or paste form. This creates a three-layer gradient structure at the molten steel-mold interface: a powder layer, a sintered layer, and a liquid slag layer. The synergistic effect of the physical and physicochemical properties of each layer ensures smooth continuous casting and controls the surface quality of the cast billet. The basicity of the mold flux refers to the ratio of the mass fraction of the basic component CaO to the acidic component SiO2 in the mold.

[0048] In some embodiments, the melting point of the crystallizer protective slag can be 960℃-1000℃. For example, it can be 960℃, 965℃, 970℃, 975℃, 980℃, 985℃, 990℃, 995℃, 1000℃, or any range of the above values.

[0049] In some embodiments, the viscosity of the mold flux can be 0.16 Pa·s to 0.2 Pa·s. For example, it can be 0.16 Pa·s, 0.17 Pa·s, 0.18 Pa·s, 0.19 Pa·s, 0.20 Pa·s, or any range of the above values.

[0050] By controlling the melting point and viscosity of the mold flux within the aforementioned range, a lower melting point ensures that a sufficiently thick liquid slag film can be formed at the meniscus, providing stable and continuous lubrication; while a higher viscosity can effectively control the flow rate of the liquid slag, avoiding excessive inflow, thereby ensuring that the slag film formed between the billet shell and the copper plate is uniform and stable, providing both sufficient lubrication and uniform heat transfer, preventing cracks caused by uneven frictional stress and excessive local heat flow.

[0051] In some embodiments, the total specific water volume for secondary cooling in the continuous casting process can be between 1.4 L / kg and 1.9 L / kg. For example, it can be 1.4 L / kg, 1.5 L / kg, 1.6 L / kg, 1.7 L / kg, 1.8 L / kg, 1.9 L / kg, or any range of the above values.

[0052] Secondary cooling is a forced and controllable cooling zone for the billet after it leaves the crystallizer, which is achieved through methods such as air-water atomization, water spraying, and air-mist cooling. This can promote rapid and uniform growth of the billet shell and reduce steel leakage.

[0053] The intensity of secondary cooling can be dynamically adjusted based on feedback from the liquid level fluctuations in the crystallizer.

[0054] In some embodiments, when the liquid level fluctuation value of the crystallizer is less than or equal to 10 mm, the total specific water volume for secondary cooling is 1.4 L / kg to 1.6 L / kg; when the liquid level fluctuation value of the crystallizer is greater than 10 mm, the total specific water volume for secondary cooling is 1.6 L / kg to 1.9 L / kg.

[0055] According to the embodiments of this application, the cooling intensity of the secondary cooling zone adopts a dynamic adjustment strategy based on the feedback of the liquid level fluctuation in the crystallizer: when the fluctuation value is ≤10mm, the total specific water volume of the secondary cooling is 1.4~1.6L / kg; when the fluctuation value is >10mm, the total specific water volume of the secondary cooling is increased to 1.6~1.9L / kg. Large liquid level fluctuations usually mean unstable casting flow and potentially uneven billet shell growth. In this case, appropriately enhancing cooling promotes rapid billet shell thickening, thereby improving its ability to resist bulging deformation caused by the static pressure of molten steel.

[0056] In some embodiments, the superheat of the tundish in the continuous casting process can be 10℃-20℃. For example, it can be 10℃, 11℃, 12℃, 13℃, 14℃, 15℃, 16℃, 17℃, 18℃, 19℃, 20℃, or any range of the above values.

[0057] In some embodiments, the continuous casting speed in the continuous casting process can be 3.7 m / min to 4.2 m / min. For example, it can be 3.7 m / min, 3.8 m / min, 3.9 m / min, 4.0 m / min, 4.1 m / min, 4.2 m / min, or any range of the above values.

[0058] In some embodiments, during the continuous casting process, the fan-shaped section of the continuous casting machine adopts a fixed roll gap, and the difference between the roll gap at the exit of the fan-shaped section and the entrance of the fan-shaped section is 1.9mm-2.2mm.

[0059] According to the embodiments of this application, the continuous casting sector section adopts a fixed roll gap mode instead of hydraulic cylinder adjustment. The fixed roll gap eliminates the intermittent and uneven extrusion force exerted by the rollers on the high-temperature billet shell caused by frequent hydraulic system operation. This uneven extrusion force is a significant factor inducing surface strain and internal stress concentration in the billet shell, leading to crack initiation and propagation. The fixed roll gap provides a stable and consistent support environment, which is conducive to uniform billet shell growth and thus reduces fluctuations in the liquid level in the crystallizer.

[0060] In some embodiments, during the continuous casting process, the C content in the first batch of molten steel is less than or equal to 0.075 wt%.

[0061] According to the embodiments of this application, the cooling rate inside the crystallizer is extremely high because the working conditions during the initial casting stage have not yet reached thermal equilibrium and a stable state. The low carbon content design is because low carbon steel has a higher solidification point and better high-temperature ductility, and its initial billet shell can better resist thermal stress under rapid cooling conditions, thereby reducing the occurrence of cracks in the billet shell during the initial casting stage when the working conditions fluctuate drastically.

[0062] In some embodiments, molten steel may include the following components in weight percentage: C: 0.055%-0.12%, Si: ≤0.5%, Mn: 0.2%-1.9%, P: ≤0.02%, S: ≤0.01%, Al: 0.02%-0.06%, with the balance being Fe and unavoidable impurities.

[0063] Example The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on weight, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0064] Example 1 Peritectic steel molten steel is smelted and refined in a converter to obtain peritectic steel molten steel with controlled temperature and composition. The chemical composition of peritectic steel molten steel, by mass percentage, is: C: 0.075%, Si: 0.35%, Mn: 0.98%, P: 0.01%, S: 0.004%, Al: 0.03%. Molten steel for peritectic steel is poured into a continuous casting machine, and the thickness of the billet is controlled to be 80 mm, the superheat of the tundish is 13℃, and the casting speed is 4.0 m / min. The thickness of the copper plate on the wide side of the crystallizer is 22mm, and the thickness ratio of the copper plate on the wide side to the copper plate on the narrow side is 1.28:1. The inlet temperature of the cooling water for the crystallizer is 39℃, the ratio of the cooling water flow rate of the wide face to the narrow face is 29.5:1, and the cooling water flow rate of the wide face is 5800L / min. The crystallizer vibration adopts a non-sinusoidal vibration mode, with the negative slip time ratio (NSR) controlled at 40% and the negative slip rate (NS) controlled at -20%. The basicity of the crystallizer protective slag is 0.98, the melting point is 960℃, and the viscosity is 0.18 Pa·s; The carbon content of the first batch of molten steel was controlled at 0.065%. The continuous casting sector section uses a fixed roll gap, with a roll gap difference of 2mm at the inlet and outlet. The secondary cooling zone uses pure water cooling, with the total water volume controlled at 1.5L / kg.

[0065] Examples 2 to 13 Except for the differences in parameters listed in Table 1, the rest of the process is the same as in Example 1.

[0066] Comparative Examples 1 to 4 Except for the differences in parameters listed in Table 1, the rest of the process is the same as in Example 1.

[0067] Table 1 Performance section The performance data of Examples 1 to 14 and Comparative Examples 1 to 4 are shown in Table 2.

[0068] Table 2 As can be seen from the data in Table 2, controlling the process parameters during continuous casting within a specific range is beneficial to further stabilize the liquid level in the crystallizer, thereby improving the surface quality of the cast billet.

[0069] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for stabilizing the liquid level in a crystallizer for continuous casting of peritectic steel in thin slabs, characterized in that, Includes the following steps: Molten steel is continuously cast in a continuous casting machine to obtain a continuously cast billet, the thickness of which is 60mm-90mm; The continuous casting machine includes a crystallizer, which includes a pair of wide copper plates and a pair of narrow copper plates. The thickness of the wide copper plates is 19mm-24mm, and the thickness ratio of the wide copper plates to the narrow copper plates is (1.25-1.35):

1.

2. The method according to claim 1, characterized in that, The inlet temperature of the crystallizer cooling water is 38.5℃-39.5℃; and / or, The flow rate ratio of the cooling water flow rate on the wide side of the crystallizer to that on the narrow side is (29-29.5):

1.

3. The method according to claim 1, characterized in that, The crystallizer employs a non-sinusoidal vibration mode, wherein the negative slip time ratio (NSR) of the crystallizer vibration is 30%-50%, and / or, The negative slip rate (NS) of the crystallizer vibration is -25% to -10%.

4. The method according to claim 1, characterized in that, The basicity of the crystallizer protective slag is 0.95-1, and / or, The melting point of the mold flux is 960℃-1000℃; and / or, The viscosity of the mold flux is 0.16 Pa·s-0.2 Pa·s.

5. The method according to claim 1, characterized in that, In the continuous casting process, the total specific water volume for secondary cooling is 1.4L / kg-1.9L / kg.

6. The method according to claim 5, characterized in that, When the liquid level fluctuation value of the crystallizer is less than or equal to 10 mm, the total specific water volume for secondary cooling is 1.4 L / kg - 1.6 L / kg; When the liquid level fluctuation value in the crystallizer is greater than 10 mm, the total specific water volume for secondary cooling is 1.6 L / kg - 1.9 L / kg.

7. The method according to claim 1, characterized in that, In the continuous casting process, the superheat of the continuous casting tundish is 10℃-20℃; and / or, the continuous casting speed is 3.7m / min-4.2m / min.

8. The method according to claim 1, characterized in that, In the continuous casting process, the fan-shaped section of the continuous casting machine adopts a fixed roll gap, and the difference between the roll gap at the exit of the fan-shaped section and the entrance of the fan-shaped section is 1.9mm-2.2mm.

9. The method according to claim 1, characterized in that, In the continuous casting process, the carbon content in the first batch of molten steel is less than or equal to 0.075 wt%.

10. The method according to claim 1, characterized in that, The molten steel comprises the following components in mass percentage: C: 0.055%-0.12%, Si: ≤0.5%, Mn: 0.2%-1.9%, P: ≤0.02%, S: ≤0.01%, Al: 0.02%-0.06%, with the balance being Fe and unavoidable impurities.

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