Method for accurately regulating and controlling ultralow carbon content of IF steel

Abstract

The invention relates to a method for accurately regulating and controlling ultralow carbon content of IF steel, which comprises the following steps: carrying out primary slag modification on original molten steel to obtain low-carbon oxygen-containing molten steel; the low-carbon oxygen-containing molten steel is subjected to vacuum decarburization, and decarburized molten steel is obtained; a deoxidizing agent and a carbon-containing alloy are added into the decarburized molten steel, and ultra-low carbon molten steel is obtained; the ultra-low carbon steel liquid is sequentially subjected to secondary slag modification and blank casting, and an IF steel blank is obtained; the termination signal of the vacuum decarburization comprises at least one of the following signals: a, when the decarburization time of the vacuum decarburization is greater than or equal to 8 minutes, the oxygen content of the molten steel is continuously measured twice every 2-3 minutes in the vacuum decarburization process, and the oxygen content deviation absolute value of the two measured values of the vacuum decarburization is less than or equal to 10 ppm; and b, the decarburization time of the vacuum decarburization is more than or equal to 12 minutes. Differentiation regulation and control are implemented based on steel grade requirements after vacuum decarburization, residual carbon is reduced while the carbon content of the IF steel is stably controlled, conditions are created for adopting low-cost alloy, and the problem of carbon content fluctuation in a traditional process is solved.

Description

Technical Field

[0001] This application relates to the field of steelmaking technology, and in particular to a method for precisely controlling the ultra-low carbon content of IF steel. Background Technology

[0002] IF steel, with its extremely low interstitial atom content, possesses excellent deep-drawing performance and aging-free properties. The performance requirements for IF steel vary significantly across different applications: parts with stringent deep-drawing requirements need to have their carbon content minimized to improve the ductility of the IF steel, while some IF steels with less stringent forming requirements need to retain a suitable amount of carbon to maintain basic strength, thus establishing a clear lower limit control target for carbon content.

[0003] Traditional production employs a decarburization-deoxidation process, relying on sampling and testing results to adjust carbon content. This process suffers from steam loss, temperature loss, and aluminum loss during the waiting period for sample results. Furthermore, the melting of cold steel within the vacuum furnace wall during this waiting period can lead to abnormal carbon increase, resulting in escalating production costs and quality control risks. Therefore, there is an urgent need to develop a real-time dynamic control strategy that eliminates the need for sampling and waiting, simultaneously achieving precise control of the carbon content of IF steel while mitigating the risk of carbon increase. Summary of the Invention

[0004] This application provides a method for precise control of ultra-low carbon content in IF steel to solve the following technical problem: how to achieve real-time closed-loop control of carbon content in IF steel. This application provides a method for precisely controlling the ultra-low carbon content of IF steel, including: The original molten steel is modified by slag to obtain low-carbon oxygen-containing molten steel. The low-carbon oxygen-containing molten steel is subjected to vacuum decarburization to obtain decarburized molten steel. Adding a deoxidizer and a carbon-containing alloy to the decarburized steel liquid yields an ultra-low carbon steel liquid; The ultra-low carbon steel liquid is subjected to secondary slag modification and casting ingot sequentially to obtain IF steel ingot; The termination signal for vacuum decarburization includes at least one of the following: a. When the decarburization time of the vacuum decarburization is ≥8min, the oxygen content of the molten steel is measured twice consecutively at intervals of 2min to 3min during the vacuum decarburization process, and the absolute value of the deviation of the oxygen content between the two measurements of the vacuum decarburization is ≤10ppm; b. The decarburization time of the vacuum decarburization is ≥12 min.

[0005] Optionally, the vacuum decarburization is carried out in a vacuum furnace, which includes at least one of RH, VD, VOD, VAD, DH and ASEA-SKF.

[0006] Optionally, the carbon content of the molten steel from the previous smelting furnace in the vacuum refining equipment is ≤0.2% by mass fraction before the vacuum decarburization is performed.

[0007] Optionally, the ultimate pressure of the vacuum chamber for vacuum decarburization is ≤100Pa.

[0008] Optionally, the modifiers used in the primary slag modification and the secondary slag modification both include at least one of aluminum particles, aluminum slag, aluminum slag balls, and silicon powder.

[0009] Optionally, the carbon content of the modifier is ≤1.0% by mass fraction.

[0010] Optionally, the carbon-containing alloy includes at least one of low-carbon ferromanganese, medium-carbon ferromanganese, high-carbon ferromanganese, and pig iron.

[0011] Optionally, the amount of carbon alloy added satisfies: (target value of C element - limit C content) × amount of molten steel / (yield of the carbon alloy × C element content in the carbon alloy).

[0012] Optionally, by mass fraction, the carbon content of all additives other than the carbon alloy is ≤0.10%.

[0013] Optionally, the primary slag modification and the secondary slag modification are carried out in a steel ladle, and the carbon content of the working lining of the steel ladle is ≤1.0% by mass fraction.

[0014] Optionally, the billet casting includes injecting the second decarburized steel liquid into a tundish, wherein the carbon content of the working lining of the tundish is ≤1.0% by mass fraction.

[0015] The technical solutions provided in this application have the following advantages compared with the prior art: This application provides a method for precisely controlling the ultra-low carbon content of IF steel. By reconstructing the determination logic of the vacuum decarburization endpoint and the thermodynamic environment of the alloying process, the core problem of carbon content instability in IF steel during dynamic smelting is overcome. Traditional processes rely on fixed decarburization time or delayed sampling analysis, which is essentially a passive response to the carbon-oxygen reaction state inside the molten steel, causing the carbon content to oscillate repeatedly between under-decarburization residue and over-decarburization oxygen pollution. This application pioneers a dual-track endpoint decision mechanism: firstly, by monitoring the dynamic convergence behavior of oxygen content at high frequency, the critical point of carbon-oxygen reaction kinetic exhaustion is captured in real time. When the oxygen activity fluctuation in adjacent detection windows enters a stagnant plateau period, it indicates that the decarburization reaction is nearing its end, realizing a leap from "inferential control" to "sensory control"; secondly, a safe threshold for decarburization time is set to construct a rigid meltdown defense line for equipment abnormalities or extreme operating conditions. The two form a closed-loop control paradigm of "dynamic balance precise stop + process limit forced braking", completely eliminating the blind spot of endpoint decision. More importantly, this application creatively adjusts the process sequence, performing alloying in a deeply deoxidized environment created by secondary slag modification. The highly reducing slag layer acts like an "anti-oxidation armor" for the molten steel, completely isolating oxygen interference from the carbon-containing alloy's carbonization process, allowing carbon atoms to dissolve into the molten steel with zero burn-off. Thus, the real-time closed-loop termination of vacuum decarburization and the pure fine-tuning of alloying are seamlessly connected, and the carbon element's transfer path from the set value to the final cast billet is locked on a controlled track throughout the entire process.

[0016] In summary, by using dual-modal intelligent determination of the decarburization endpoint and recreating the thermodynamic environment of the alloying process, a dual guarantee system for real-time closed-loop control of carbon content is built at the forefront of metallurgical reaction. This fundamentally cuts off the transmission chain of carbon trajectory distortion in traditional processes, realizing a paradigm revolution in ultra-low carbon steel grades from "experience-driven, open-loop intervention" to "data-driven, dynamic closed-loop control". Attached Figure Description

[0017] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0019] Figure 1 A flowchart illustrating a method for precisely controlling the ultra-low carbon content of IF steel, provided as an embodiment of this application. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0021] The range descriptions used herein, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within that range. For example, the range descriptions of "1 to 6" or "1~6" cover all sub-ranges between 1 and 6 (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6). Unless otherwise specified, the terms "including" and "contains" used herein mean "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or operations and do not imply an actual order or relationship. "And / or" indicates that multiple situations can exist individually or simultaneously. Expressions such as "at least one," "multiple," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships mentioned herein, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used herein can all be obtained through commercial purchase or prepared using existing methods.

[0022] Figure 1 A flowchart illustrating a method for precisely controlling the ultra-low carbon content of IF steel, provided as an embodiment of this application.

[0023] Please see Figure 1 This application provides a method for precisely controlling the ultra-low carbon content of IF steel, including: S1. The original molten steel is modified by slag to obtain low-carbon oxygen-containing molten steel. S2. Vacuum decarburize the low-carbon oxygen-containing steel liquid to obtain decarburized steel liquid; S3. Add a deoxidizer and a carbon-containing alloy to the decarburized steel liquid to obtain ultra-low carbon steel liquid; S4. The ultra-low carbon steel liquid is subjected to secondary slag modification and casting ingot sequentially to obtain IF steel billet; Primary slag modification: A process in which modifiers are added to molten steel in the ladle to adjust the slag composition, thereby reducing oxidizability and increasing basicity. Secondary slag modification: A process in which the slag composition is adjusted a second time after vacuum decarburization to form a liquid protective layer.

[0024] In the above technical solution, a reducing slag environment is first constructed in the ladle to lock the initial carbon-oxygen balance, providing a reaction driving force for deep decarburization; then, the carbon-oxygen reaction is stimulated by the vacuum kinetic effect to achieve deep decarburization, and the endpoint is dynamically controlled by real-time monitoring; then, under the protection of the liquid slag layer, the carbon content is accurately compensated and deoxidation products are adsorbed; finally, the zero-pollution transfer and controllable solidification of the molten steel are completed through a multi-stage protective casting system, simultaneously ensuring the cleanliness of the billet, the integrity of the microstructure and the accuracy of the carbon content, completely eliminating the sample delay and carbon increase risk of traditional processes.

[0025] The termination signal for vacuum decarburization includes at least one of the following: a. When the decarburization time of the vacuum decarburization is ≥8min, the oxygen content of the molten steel is measured twice consecutively at intervals of 2min to 3min during the vacuum decarburization process, and the absolute value of the deviation of the oxygen content between the two measurements of the vacuum decarburization is ≤10ppm; By establishing dual criteria based on a time baseline and dynamic oxygen content balance, an intelligent decision-making system is constructed that can accurately determine in real time when the decarburization reaction is nearing its end. This replaces the traditional lagging control that relies on manual experience and offline sampling, achieving a leap from "experience-based estimation" to "data-driven" decarburization endpoint, ultimately ensuring that the carbon content is stably controlled at an extremely low level. Simultaneously, an independent timing threshold is introduced as a system-level redundancy guarantee, providing a rigid safety gate for equipment malfunctions or extreme operating conditions. For example, the decarburization time for vacuum decarburization can be 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, etc.; during vacuum decarburization, the oxygen content of the molten steel can be measured twice consecutively at intervals of 2 min and 3 min; the absolute value of the oxygen content deviation between the two measurements during vacuum decarburization can be 5 ppm, 6 ppm, 7 ppm, 8 ppm, 9 ppm, 10 ppm, etc.

[0026] b. The decarburization time of the vacuum decarburization is ≥12 min.

[0027] Vacuum decarburization requires a decarburization time of ≥12 min to ensure deep circulation and full reaction of the molten steel, achieving ultimate removal of carbon and final composition homogenization. Sufficient decarburization time drives a deep reduction in carbon content and maintains a stable state. For example, the decarburization time in vacuum decarburization can be 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min, 20 min, etc.

[0028] In some embodiments, the vacuum decarburization is carried out in a vacuum furnace, which includes at least one of RH, VD, VOD, VAD, DH, and ASEA-SKF.

[0029] Vacuum decarburization is carried out in a vacuum furnace, utilizing the carbon-oxygen reaction under vacuum to reduce the carbon content in molten steel to the level of IF steel. RH: Vacuum Circulating Degassing Furnace. It uses argon to drive the circulation of molten steel, removing gases and adjusting the composition within a vacuum chamber. VD: Vacuum Degassing Furnace. The ladle is directly vacuumed, with bottom argon blowing for stirring and degassing; suitable for refining small to medium to medium tonnage molten steel. VOD: Vacuum Oxygen Blowing Decarburizing Furnace. Oxygen blowing in a vacuum environment enhances decarburization; mainly used for deep decarburization of high-chromium stainless steel and other high-alloy steels. VAD: Vacuum Arc Degassing Furnace. Equipped with arc-heated vacuum equipment, it combines degassing and temperature compensation functions. DH: Lifting Vacuum Degassing Furnace. It uses a lifting vacuum tank to repeatedly draw gas from the molten steel; the equipment has a compact structure. ASEA-SKF: Ladle Refining Furnace. Combining electromagnetic stirring and vacuum degassing technology, it improves the purity of molten steel and is suitable for high-end alloy steels.

[0030] In some embodiments, the carbon content of the molten steel from the previous smelting furnace in the vacuum refining equipment is ≤0.2% by mass fraction prior to the vacuum decarburization.

[0031] Before vacuum decarburization, the carbon content of the molten steel from the previous smelting furnace in the vacuum refining equipment is ≤0.2%. This aims to prevent abnormal carbon increase contamination caused by residual high-carbon cold steel melting within the vacuum refining equipment, thus providing a pure initial reaction environment for precise control of the ultra-low carbon content of IF steel. For example, the carbon content of the molten steel from the previous smelting furnace in the vacuum refining equipment can be 0.1%, 0.2%, etc., before vacuum decarburization.

[0032] In some embodiments, the ultimate pressure of the vacuum chamber for vacuum decarburization is ≤100 Pa.

[0033] The ultimate pressure of the vacuum chamber in vacuum decarburization is ≤100 Pa. By establishing an extremely low-pressure environment, the carbon-oxygen reaction equilibrium is strongly disrupted, driving the decarburization reaction to continue towards deep decarburization, achieving a breakthrough removal of carbon content from the molten steel. When the vacuum level is insufficient, the carbon content of the molten steel at the decarburization endpoint is too high and fluctuates significantly, disrupting the stability of carbon content control. For example, the ultimate pressure of the vacuum chamber in vacuum decarburization can be 60 Pa, 70 Pa, 80 Pa, 90 Pa, 100 Pa, etc.

[0034] In some embodiments, the modifiers used in the primary slag modification and the secondary slag modification both include at least one of aluminum particles, aluminum slag, aluminum slag balls, and silicon powder.

[0035] Through the synergistic effect of aluminum-based and silicon-based materials, a continuously strong reducing slag-steel interface environment is constructed and maintained in two slag modification processes to achieve deep deoxidation, precise control of oxygen potential, and efficient adsorption of harmful inclusions. This lays a crucial thermodynamic and kinetic foundation for subsequent deep vacuum decarburization and the final acquisition of high-purity molten steel.

[0036] In some embodiments, the carbon content of the modifier is ≤1% by mass fraction.

[0037] By limiting the carbon content of the modifier to ≤1.0%, the high-temperature carbon-oxygen mass transfer pathway is effectively blocked, eliminating the risk of abnormal carbon increase in molten steel, while maintaining the continuous strong reducing properties of the slag system, thereby ensuring the accuracy of carbon content control in molten steel. Conversely, high-carbon modifiers will cause uncontrolled carbon increase in molten steel. For example, the carbon content of the modifier can be 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, etc.

[0038] In some embodiments, the carbon-containing alloy includes at least one of low-carbon ferromanganese, medium-carbon ferromanganese, high-carbon ferromanganese, and pig iron.

[0039] Mn and Fe are the basic elements of steel. Using carbon-containing alloys facilitates precise control of the carbon content in IF steel and avoids the introduction of other residual elements. Simultaneous addition of the carbon-containing alloy with other alloys in one step accelerates the production process by shortening the vacuum treatment time, ensuring the efficient preparation of IF steel.

[0040] In some embodiments, the amount of carbon alloy added satisfies: (target value of C element - limit C content) × amount of molten steel / (yield of the carbon alloy × C element content in the carbon alloy).

[0041] C element target value: Target value for carbon content in steel grade. Limiting C content: Minimum carbon content in molten steel under these process conditions. Molten steel quantity: Mass of molten steel in the ladle. Yield of carbon-containing alloys: Actual carbon gain in molten steel / Theoretical carbon gain. C element content in carbon-containing alloys: Carbon content in the alloy.

[0042] In some embodiments, the carbon content of the additives other than the carbon alloy is ≤0.10% by mass fraction.

[0043] The carbon content of the added materials is ≤0.10%, completely blocking the secondary carbonization path of the molten steel and ensuring absolute precision in carbon content control after vacuum decarburization. For example, the carbon content of the added materials can be 0.02%, 0.04%, 0.06%, 0.08%, 0.10%, etc.

[0044] In some embodiments, the primary slag modification and the secondary slag modification are carried out in a ladle, and the carbon content of the working lining of the ladle is ≤1.0% by mass fraction.

[0045] The carbon content of the working lining of the ladle is ≤1.0%. Its function is to fundamentally block the carbon diffusion path from the refractory material to the molten steel during the high-temperature slag-steel reaction stage. This ensures that the primary and secondary slag modification processes are completed in a near-zero-carbon pollution environment, laying a pure steel foundation for subsequent precise fine-tuning of the carbon content. For example, the carbon content of the working lining of the ladle can be 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, etc.

[0046] In some embodiments, the billet casting includes injecting the second decarburized steel liquid into a tundish, wherein the carbon content of the working lining of the tundish is ≤1.0% by mass fraction.

[0047] The carbon content of the working lining in the tundish is ≤1.0%. Its function is to create an inert "transport channel" in the final stage before casting the billet, eliminating the risk of carbon gain in the molten steel during its journey from the tundish to the crystallizer. This ensures that the results of all the aforementioned precision metallurgical control are completely locked in and transferred to the final billet. For example, the carbon content of the working lining in the tundish can be 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, etc.

[0048] The present application is further illustrated below with reference to specific embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards / industry standards / the disclosure herein; if there are no corresponding national standards / industry standards / the disclosure herein, they are performed according to generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer.

[0049] This embodiment provides a method for precisely controlling the ultra-low carbon content of IF steel, including the following steps: The original molten steel is modified by slag to obtain low-carbon oxygen-containing molten steel. The low-carbon oxygen-containing molten steel is subjected to vacuum decarburization to obtain decarburized molten steel. Adding a deoxidizer and a carbon-containing alloy to the decarburized steel liquid yields an ultra-low carbon steel liquid; The ultra-low carbon steel molten steel was subjected to secondary slag modification and casting ingot sequentially to obtain IF steel billet. The process parameters for preparation are shown in Table 1.

[0050] The preparation process parameters for the examples and comparative examples are shown in Table 1.

[0051] Table 1

[0052] The above effect data table provides a clear comparison of the differences between various embodiments and comparative examples. The following conclusions can be drawn: As can be seen from Examples 1-3, differentiated regulation is implemented based on the performance requirements of different IF steel grades to achieve precise control of carbon content; the residual carbon content is reduced simultaneously, achieving breakthrough compatibility with the large-scale application of high-carbon ferromanganese alloys and significantly reducing production costs; and finally, the carbon content fluctuation defect of traditional processes is overcome, and the fluctuation is stably controlled within ±2ppm.

[0053] As shown in Comparative Example 1, the minimum vacuum degree during the decarburization process was only 800 Pa, which resulted in insufficient decarburization reaction. The carbon content of the final molten steel was high and fluctuated significantly, which disrupted the stability of carbon content control. Finally, the actual carbon content of the molten steel in the tundish deviated from the target value by 2.8 ppm.

[0054] As shown in Comparative Example 2, the decarburization time was only 8 minutes, and the insufficient reaction resulted in high carbon residue and significant fluctuations, which damaged the stability of carbon control. Finally, the actual carbon content of the molten steel in the tundish deviated from the target value by 3.9 ppm.

[0055] As shown in Comparative Example 3, after 10 minutes of vacuum decarburization, the carbon content deviation between the two detection values ​​was 39 ppm, which prematurely ended the decarburization process, resulting in incomplete carbon removal and inaccurate control. The carbon hit rate of IF steel deteriorated, and the actual carbon content of the molten steel in the tundish ultimately deviated from the target value by 3.4 ppm.

[0056] As shown in Comparative Example 4, the first batch of steel produced in the vacuum smelting furnace contained 0.8% high-carbon steel. The residual high-carbon cold steel in the vacuum tank melted and seeped in, causing abnormal carbon increase in the molten steel. The stability of carbon control was disrupted, and the actual carbon content of the molten steel in the tundish deviated from the target value by 3.7 ppm.

[0057] As shown in Comparative Example 5, the carbon content of the added material reached 1.0%, and the high-carbon alloy continuously released carbon elements, leading to loss of compensation control; the accuracy of the carbon content of IF steel was lost, and the actual carbon content of the molten steel in the tundish deviated from the target value by 4.1 ppm.

[0058] As shown in Comparative Example 6, the carbon content of the modifier is 3.0%, and carbon is transferred to the molten steel through the slag-steel reaction at high temperature; the carbon increase effect destroys carbon control, and the actual carbon content of the molten steel in the tundish deviates from the target value by 3.9 ppm.

[0059] As shown in Comparative Example 7, the carbon content of the working lining in the tundish was 5.0%, and carbon from the refractory material migrated into the molten steel during the steel-passing process. Abnormal carbon increase was blocked and precisely controlled, and the actual carbon content of the molten steel in the tundish ultimately deviated from the target value by 2.8 ppm.

[0060] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed in this application.

Claims

1. A method for precisely controlling the ultra-low carbon content of IF steel, characterized in that, The method includes: The original molten steel is modified by slag to obtain low-carbon oxygen-containing molten steel. The low-carbon oxygen-containing molten steel is subjected to vacuum decarburization to obtain decarburized molten steel. Adding a deoxidizer and a carbon-containing alloy to the decarburized steel liquid yields an ultra-low carbon steel liquid; The ultra-low carbon steel liquid is subjected to secondary slag modification and casting ingot sequentially to obtain IF steel ingot; The termination signal for vacuum decarburization includes at least one of the following: a. When the decarburization time of the vacuum decarburization is ≥8min, the oxygen content of the molten steel is measured twice consecutively at intervals of 2min to 3min during the vacuum decarburization process, and the absolute value of the deviation of the oxygen content between the two measurements of the vacuum decarburization is ≤10ppm; b. The decarburization time of the vacuum decarburization is ≥12 min.

2. The method according to claim 1, characterized in that, The vacuum decarburization is carried out in a vacuum furnace, which includes at least one of RH, VD, VOD, VAD, DH and ASEA-SKF.

3. The method according to claim 1, characterized in that, By mass fraction, the carbon content of the molten steel from the previous smelting furnace in the vacuum refining equipment before the aforementioned vacuum decarburization is ≤0.2%.

4. The method according to claim 1, characterized in that, The ultimate pressure of the vacuum chamber for vacuum decarburization is ≤100Pa.

5. The method according to claim 1, characterized in that, The modifiers used in both the primary and secondary slag modification include at least one of aluminum particles, aluminum slag, aluminum slag balls, and silicon powder.

6. The method according to claim 5, characterized in that, The carbon content of the modifier is ≤1.0% by mass fraction.

7. The method according to claim 1, characterized in that, The carbon-containing alloy includes at least one of low-carbon ferromanganese, medium-carbon ferromanganese, high-carbon ferromanganese, and pig iron.

8. The method according to claim 1, characterized in that, The amount of carbon-containing alloy added satisfies: (target value of C element - limit C content) × amount of molten steel / (the yield of the carbon-containing alloy × the C element content in the carbon-containing alloy).

9. The method according to claim 1, characterized in that, By mass fraction, the carbon content of all additives other than the carbon alloy is ≤0.10%.

10. The method according to claim 1, characterized in that, The primary slag modification and the secondary slag modification are carried out in a steel ladle, and the carbon content of the working lining of the steel ladle is ≤1.0% by mass fraction; and / or, The casting process involves injecting the second decarburized steel liquid into a tundish, wherein the carbon content of the working lining of the tundish is ≤1.0% by mass fraction.

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