A pickling plate RH refining method considering sulfur control and casting stability

Abstract

The application relates to a pickling plate RH refining method considering sulfur control and casting stability, which comprises the following steps: converter smelting of molten iron, control of end-point tapping temperature, obtaining of molten steel meeting the heat demand of RH refining; vacuumizing of an environment containing the molten steel meeting the heat demand of RH refining to discharge air in the environment and obtaining of a vacuum environment; sampling detection of the molten steel meeting the heat demand of RH refining in the vacuum environment to obtain a composition report; addition of aluminum into the molten steel meeting the heat demand of RH refining for deoxidation treatment according to the composition report to obtain deoxidized molten steel; alloying treatment of the deoxidized molten steel to obtain alloyed molten steel; pure circulation treatment, calcium treatment and air breaking of the alloyed molten steel in sequence to end the RH refining and obtain molten steel after the vacuum refining; and soft blowing treatment of the molten steel after the vacuum refining to obtain pure molten steel. Key process parameters are optimized in cooperation to ensure the composition and surface quality of the pickling plate.

Description

Technical Field

[0001] This application relates to the field of iron and steel metallurgy technology, and in particular to a method for RH refining of pickled plates that takes into account both sulfur control and casting stability. Background Technology

[0002] Pickled steel sheet is a key steel widely used in industries such as automobile manufacturing, machining, and home appliances. Pickled steel sheet has excellent stamping formability, but also has extremely high requirements for surface quality (such as no inclusions and no streaks). Therefore, the extreme stability of the molten steel composition and the precise control of the production process are the core challenges.

[0003] Currently, the refining process of pickled steel plates faces two major technical bottlenecks. First, during the alloying stage of RH vacuum refining, adding alloys such as ferromanganese and ferrosilicon alone can easily cause abnormal fluctuations in the sulfur composition of the molten steel, leading to defects such as inclusions and streaks on the final plate surface. These defects severely affect the subsequent pickling quality and stamping performance of the plate. Second, in the continuous casting stage, fluctuations in the liquid level in the crystallizer and nozzle clogging often induce casting interruptions and the risk of steel leakage, while also causing uneven slab quality. This situation directly restricts the improvement of production continuity and yield.

[0004] To address these issues, existing methods involve adding a silicon-calcium alloy during the refining process to stabilize sulfur content and improve steel castability. However, improper timing and method of addition can easily trigger violent reactions in the molten steel, disrupting the balance of the RH vacuum system. This can lead to a dramatic rise in the molten steel level, damaging equipment and posing serious safety risks. Consequently, the effectiveness and stability of silicon-calcium alloy applications are significantly limited. Summary of the Invention

[0005] This application provides a pickling plate RH refining method that balances sulfur control and casting stability to solve the following technical problem: how to achieve a balance between deep desulfurization and casting stability during the RH refining process. This application provides a method for RH refining of pickled plates that balances sulfur control and casting stability. The method includes: The molten iron is smelted in a converter, and the final tapping temperature is controlled to obtain molten steel that meets the heat requirements of RH refining. The environment containing the molten steel that meets the RH refining heat requirements is evacuated to remove the air from the environment, thus obtaining a vacuum environment. The molten steel that meets the RH refining heat requirements and is placed in a vacuum environment is sampled and tested to obtain an on-site composition report. According to the arrival composition report, aluminum is added to the molten steel that meets the RH refining heat requirements and then deoxidized to obtain deoxidized molten steel. The deoxidized molten steel is alloyed. During the alloying process, a sandwich feeding method is used to sandwich the first silicon-calcium alloy in the middle of a portion of ferromanganese to form a mixture. The mixture is added to the RH vacuum chamber through a vacuum lock. After the mixture is added, the remaining ferromanganese and ferrosilicon are continuously added to the deoxidized molten steel through a vacuum hopper to obtain alloyed molten steel. The alloyed molten steel is subjected to pure circulation treatment, calcium treatment, and void breaking in sequence to complete RH refining. During the calcium treatment, a second silicon-calcium alloy is added to the alloyed molten steel, and void breaking is performed immediately after the addition to obtain molten steel that has undergone vacuum refining. The mass of the second silicon-calcium alloy added is 22% to 44% of the mass of the first silicon-calcium alloy added. The molten steel that has undergone vacuum refining is subjected to soft blowing treatment to obtain pure molten steel. The total processing time for RH refining is 30-35 minutes, and the temperature of the pure molten steel is 1540℃-1560℃.

[0006] Optionally, the mass ratio of the first silicon-calcium alloy to the partial manganese-iron alloy is 1:1.5 to 1:3; The mass of the first silicon-calcium alloy added is 100kg to 300kg; the mass of the second silicon-calcium alloy added is 40kg to 80kg.

[0007] Optionally, the final tapping temperature is 3°C to 8°C higher than the conventional tapping temperature of the corresponding pickled plate, and the resulting molten steel temperature that meets the RH refining heat requirement is ≥1580°C.

[0008] Optionally, the vacuuming time is 3 to 5 minutes.

[0009] Optionally, the amount of aluminum added is ≤1kg / t steel, and the cycle time of the deoxidation treatment is 2min~3min.

[0010] Optionally, the RH vacuum degree of the alloying treatment is 60mbar~90mbar, and the circulating gas flow rate of the alloying treatment is 2200L / min~3000L / min.

[0011] Optionally, the chemical composition of the first silicon-calcium alloy and the second silicon-calcium alloy both meet the following requirements: Si content ≥ 60 wt%, Ca content ≥ 25 wt%, S content ≤ 0.02 wt%, P content ≤ 0.03 wt%, C content ≤ 0.3 wt%, and Ti content ≤ 0.2 wt%.

[0012] Optionally, the alloying treatment involves adjusting the composition of the deoxidized steel to: C ≤ 0.12 wt%, Mn: 0.30 wt%~0.60 wt%, Si ≤ 0.30 wt%; or, C: 0.08wt%~0.15wt%, Mn: 0.80wt%~1.20wt%, Si: 0.40wt%~0.80wt%.

[0013] Optionally, the pure cyclic processing time is 4 min to 6 min.

[0014] Optionally, the soft blowing treatment time is 4 min to 6 min; the argon flow rate of the soft blowing treatment is ≤70 NL / min.

[0015] Optionally, when preparing ordinary carbonate pickled plates, the total processing time of RH refining is 30 min to 33 min; when preparing low alloy pickled plates, the total processing time of RH refining is 32 min to 35 min.

[0016] The technical solutions provided in this application have the following advantages compared with the prior art: This application provides a method for RH refining of pickled steel plates that balances sulfur control and casting stability. The method includes: smelting molten iron in a converter, controlling the final tapping temperature to obtain molten steel that meets the RH refining heat requirements; evacuating the environment containing the molten steel to remove air and create a vacuum environment; sampling and testing the molten steel in the vacuum environment to obtain an on-site composition report; adding aluminum to the molten steel according to the on-site composition report and then performing deoxidation treatment to obtain deoxidized steel; and alloying the deoxidized steel, wherein a sandwich feeding method is used to sandwich a first silicon-calcium alloy in the middle of a portion of ferromanganese to form a mixture. The mixture is added to the RH vacuum chamber via a vacuum lock. After the mixture is added, the remaining ferromanganese and ferrosilicon are continuously added to the deoxidized molten steel through a vacuum hopper to obtain alloyed molten steel. The alloyed molten steel is then subjected to pure circulation treatment, calcium treatment, and void breaking to complete the RH refining process. During the calcium treatment, a second silicon-calcium alloy is added to the alloyed molten steel, and void breaking is performed immediately after the addition to obtain molten steel that has undergone vacuum refining. The mass of the second silicon-calcium alloy added is 22% to 44% of the mass of the first silicon-calcium alloy added. The molten steel that has undergone vacuum refining is then subjected to soft blowing treatment to obtain pure molten steel. The total processing time for the RH refining process is 30 to 35 minutes, and the temperature of the pure molten steel is 1540°C to 1560°C. By precisely controlling the converter tapping temperature, sufficient and stable thermal compensation space can be provided for subsequent vacuum refining. This temperature control is the energy basis for ensuring the strict execution of the entire process sequence. Pre-deoxidation treatment based on the on-site composition report creates a stable chemical environment with extremely low oxidation for subsequent alloying, thus avoiding abnormal oxidation loss of alloying elements. During the alloying stage, a specific synergistic feeding mode is employed, utilizing the physical encapsulation and buffering effect of ferromanganese on the silicon-calcium alloy. This achieves efficient modification of sulfides by calcium, reaching the goal of deep desulfurization, while effectively suppressing the violent splashing that can easily occur when silicon-calcium alloy is added alone, maintaining the balance of the vacuum system and operational safety. A short period of pure circulation and calcium treatment is then performed to further promote the full flotation and removal of deoxidation products and modified inclusions. The final soft-blowing process uses an extremely low flow rate of inert gas to gently stir the molten steel, aiming to remove residual micro-inclusions while avoiding violent turbulence or excessive temperature drop, thereby precisely adjusting the molten steel temperature to the optimal casting range.

[0017] In summary, by constructing an interconnected and precisely controlled process framework, and by synergistically controlling heat input, chemical reaction, and physical purification processes, pure molten steel that simultaneously meets the requirements of ultra-low sulfur content and excellent castability can be obtained in the RH refining process, ultimately achieving a balance between deep desulfurization and casting stability. Attached Figure Description

[0018] 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.

[0019] 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.

[0020] Figure 1 A flowchart of an RH refining method for pickled plates that balances sulfur control and casting stability, provided for embodiments of this application. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. 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.

[0022] 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.

[0023] Figure 1 A flowchart of an RH refining method for pickled plates that balances sulfur control and casting stability, provided for embodiments of this application.

[0024] Please see Figure 1This application provides a method for RH refining of pickled steel plates that balances sulfur control and casting stability. The method includes: S1. The molten iron is smelted in a converter, and the final tapping temperature is controlled to obtain molten steel that meets the heat requirements of RH refining. S2. Evacuate the environment containing the molten steel that meets the RH refining heat requirements to remove the air in the environment and obtain a vacuum environment. S3. Take samples of the molten steel that meets the RH refining heat requirements in a vacuum environment and test them to obtain the on-site composition report. S4. According to the arrival composition report, aluminum is added to the molten steel that meets the RH refining heat requirements and then deoxidized to obtain deoxidized molten steel. S5. The deoxidized molten steel is alloyed. During the alloying process, a sandwich feeding method is adopted to sandwich the first silicon-calcium alloy in the middle of a portion of ferromanganese to form a mixture. The mixture is added to the RH vacuum chamber through a vacuum lock. After the mixture is added, the remaining ferromanganese and ferrosilicon are continuously added to the deoxidized molten steel through a vacuum hopper to obtain alloyed molten steel. S6. The alloyed molten steel is subjected to pure circulation treatment, calcium treatment, and void breaking in sequence to complete RH refining. During the calcium treatment, a second silicon-calcium alloy is added to the alloyed molten steel, and void breaking is performed immediately after the addition to obtain molten steel that has completed vacuum refining. The mass of the second silicon-calcium alloy added is 22% to 44% of the mass of the first silicon-calcium alloy added. S7. The molten steel that has undergone vacuum refining is subjected to soft blowing treatment to obtain pure molten steel; The total processing time for RH refining is 30-35 minutes, and the temperature of the pure molten steel is 1540℃-1560℃.

[0025] Steel meeting the heat requirements of RH refining: After being smelted in the converter, the tapping temperature of the molten iron is specially controlled to provide sufficient heat margin for subsequent RH refining processes such as deoxidation, alloying, calcium treatment, and steel circulation, which are characterized by strong heat absorption or heat loss. Vacuum environment: After the molten steel enters the RH vacuum chamber, the sealed chamber is evacuated by a vacuum pump unit to reduce the ambient pressure to a predetermined low-pressure state sufficient to initiate subsequent vacuum metallurgical treatments.

[0026] In the above technical solution, firstly, the initial thermodynamic conditions are established for subsequent processes by precisely controlling the converter's final temperature. Next, in a preparatory environment created by vacuuming, aluminum deoxidation is performed based on the composition report obtained from sampling and testing to create a stable low-oxygen environment. On this basis, alloying and calcium treatment using a specific method are employed to synergistically achieve composition adjustment and effective modification of sulfides. Finally, a combination of pure circulation and soft blowing treatment is used to remove inclusions and precisely match the casting temperature.

[0027] In some embodiments, the mass ratio of the first silicon-calcium alloy to the partial manganese-iron alloy is 1:1.5 to 1:3; The mass of the first silicon-calcium alloy added is 100kg to 300kg; the mass of the second silicon-calcium alloy added is 40kg to 80kg.

[0028] The mass ratio of the first silicon-calcium alloy to a portion of ferromanganese is controlled at 1:1.5 to 1:3, and the added mass of the first silicon-calcium alloy is set at 100 kg to 300 kg. This aims to precisely match the calcium treatment requirements of deoxidized steel with different sulfur contents, ensuring stable desulfurization effects and avoiding the impact of excessive addition on casting performance. After the mixed materials are added, the remaining ferromanganese and other alloys, such as ferrosilicon, are continuously added through devices such as vacuum silos to complete the final composition fine-tuning and homogenization. For example, the mass ratio of the first silicon-calcium alloy to a portion of ferromanganese can be 1:1.5, 1:2, 1:2.5, 1:3, etc.; the added mass of the first silicon-calcium alloy can be 100 kg, 200 kg, 300 kg, etc.

[0029] The addition of the second silicon-calcium alloy is controlled between 40 kg and 80 kg to ensure that the calcium element can fully react with the sulfur and oxides in the molten steel to form stable inclusions that are easy to float and remove, thereby achieving the core objective of deep desulfurization. For example, the addition mass of the second silicon-calcium alloy can be 40 kg, 50 kg, 60 kg, 70 kg, or 80 kg.

[0030] In some embodiments, the final tapping temperature is 3°C to 8°C higher than the conventional tapping temperature of the corresponding pickled plate, and the resulting molten steel temperature that meets the RH refining heat requirements is ≥1580°C.

[0031] The final tapping temperature is 3°C to 8°C higher than the conventional tapping temperature of the corresponding pickled plate, providing sufficient and stable heat reserves for subsequent RH processes. This temperature range firstly provides the necessary thermodynamic conditions for strongly endothermic metallurgical reactions such as deoxidation, alloying, and calcium treatment, thus ensuring deep desulfurization. Simultaneously, the steel temperature ≥1580°C meets the RH refining heat requirements, laying the foundation for completing all refining operations within the specified processing cycle and ultimately accurately controlling the casting temperature within the target range. These controls collaboratively ensure the thermal stability of the process and the smooth progress of the final casting from the source. For example, the final tapping temperature can be 3°C, 4°C, 5°C, 6°C, 7°C, or 8°C higher than the liquidus temperature in the steel; the steel temperature meeting the RH refining heat requirements can be 1580°C, 1600°C, or 1620°C.

[0032] In some embodiments, the vacuuming time is 3 to 5 minutes.

[0033] The vacuuming time is controlled between 3 and 5 minutes to quickly establish a stable low-pressure environment, creating conditions for subsequent efficient degassing and metallurgical reactions. This also avoids process delays caused by excessively long vacuuming times, thus ensuring the overall process cycle is compact. For example, the vacuuming time can be 3 minutes, 4 minutes, or 5 minutes.

[0034] In some embodiments, the amount of aluminum added is ≤1 kg / t steel, and the cycle time of the deoxidation treatment is 2 min to 3 min.

[0035] The addition of aluminum is ≤1 kg / t of steel, enabling precise control of the oxygen content in the molten steel to meet the heat requirements of RH refining. This establishes a necessary and stable low-oxidation chemical basis for subsequent alloying, avoiding the composition control difficulties and inclusion formation risks associated with excessive deoxidation. For example, the aluminum addition can be 0.2 kg / t of steel, 0.4 kg / t of steel, 0.6 kg / t of steel, 0.8 kg / t of steel, or 1 kg / t of steel. The deoxidation cycle time is controlled between 2 and 3 minutes to ensure the deoxidation reaction is fully completed and the composition of the deoxidized steel is initially homogenized. For example, the deoxidation cycle time can be 2 minutes, 3 minutes, etc.

[0036] In some embodiments, the RH vacuum degree of the alloying treatment is 60 mbar to 90 mbar, and the circulating gas flow rate of the alloying treatment is 2200 L / min to 3000 L / min.

[0037] The RH vacuum degree during alloying treatment is controlled between 60 mbar and 90 mbar, maintaining a moderately low-pressure environment. This low-pressure environment drives the circulation of deoxidized molten steel, promoting alloy melting and uniform distribution, while also inhibiting excessive boiling of the deoxidized molten steel, thus maintaining system stability and operational safety. Simultaneously, a circulating gas flow rate of 2200 L / min to 3000 L / min provides sufficient and stable stirring power, ensuring rapid homogenization of the alloy composition and facilitating the flotation of inclusions. For example, the RH vacuum degree during alloying treatment can be 60 mbar, 70 mbar, 80 mbar, or 90 mbar; the circulating gas flow rate can be 2200 L / min, 2400 L / min, 2600 L / min, 2800 L / min, or 3000 L / min.

[0038] In some embodiments, the chemical compositions of the first silicon-calcium alloy and the second silicon-calcium alloy both satisfy the following: Si content ≥ 60 wt%, Ca content ≥ 25 wt%, S content ≤ 0.02 wt%, P content ≤ 0.03 wt%, C content ≤ 0.3 wt%, and Ti content ≤ 0.2 wt%.

[0039] Controlling the Si content to ≥60wt% and the Ca content to ≥25wt% aims to ensure sufficient effective reactive elements during calcium treatment, providing the necessary chemical driving force for deep desulfurization and inclusion modification. Simultaneously, limiting the contents of impurity elements such as S, P, C, and Ti to extremely low levels is to minimize the introduction of new inclusions or interfering elements into the molten steel due to impurities in the alloy materials, thereby ensuring the final purity of the molten steel and making the behavior and effects of the calcium treatment process more predictable and controllable. For example, the Si content can be 60wt%, 70wt%, 80wt%, etc.; the Ca content can be 25wt%, 30wt%, 35wt%, etc.; the S content can be 0.01wt%, 0.02wt%, etc.; the P content can be 0.01wt%, 0.02wt%, 0.03wt%, etc.; the C content can be 0.1wt%, 0.2wt%, 0.3wt%, etc.; and the Ti content can be 0.01wt%, 0.02wt%, etc.

[0040] In some embodiments, the alloying treatment involves adjusting the composition of the deoxidized steel to: C ≤ 0.12 wt%, Mn: 0.30 wt%~0.60 wt%, Si ≤ 0.30 wt%; or, C: 0.08wt%~0.15wt%, Mn: 0.80wt%~1.20wt%, Si: 0.40wt%~0.80wt%.

[0041] When preparing ordinary carbonated steel sheets with extremely high formability requirements, alloying treatment is used to adjust the composition of the deoxidized steel to the range of C ≤ 0.12wt%, Mn: 0.30wt%~0.60wt%, and Si ≤ 0.30wt%. This aims to obtain a pure and soft steel base, minimizing the risk of high-hardness inclusions, which provides a fundamental guarantee for obtaining excellent surface quality and stamping performance. When preparing low-alloy pickled steel sheets requiring a certain strength, alloying treatment is used to adjust the composition of the deoxidized steel to the range of C: 0.08wt%~0.15wt%, Mn: 0.80wt%~1.20wt%, and Si: 0.40wt%~0.80wt%. While meeting the strength requirements of low-alloy pickled steel sheets, each element is strictly limited to a narrow range to suppress component segregation and control inclusion morphology, thereby improving strength while ensuring good casting stability and subsequent processing performance.

[0042] In some implementations, the pure cyclic processing time is 4 to 6 minutes.

[0043] The pure circulation treatment time is controlled between 4 and 6 minutes, providing a sufficient period for homogenization and stabilization of the alloyed steel. Pure circulation treatment promotes complete melting of alloying elements and further homogenization of composition, while also creating more stable steel conditions for subsequent calcium treatment. For example, the pure circulation treatment time can be 4 minutes, 5 minutes, or 6 minutes.

[0044] In some embodiments, the mass of the second silicon-calcium alloy added is 22% to 44% of the mass of the first silicon-calcium alloy added.

[0045] The addition of the second silicon-calcium alloy is controlled to be 22% to 44% of the addition of the first silicon-calcium alloy. This ratio aims to achieve precise staged control and functional synergy in the calcium treatment process. This ratio ensures that the first silicon-calcium alloy added during the alloying stage can play a major role in desulfurization and preliminary inclusion modification, while the second silicon-calcium alloy added in the subsequent calcium treatment stage is mainly used for final fine-tuning and stabilization of the sulfur content and inclusion morphology in the molten steel. For example, the addition of the second silicon-calcium alloy can be 22%, 33%, or 44% of the addition of the first silicon-calcium alloy, etc.

[0046] In some embodiments, the soft blowing treatment time is 4 min to 6 min; the argon flow rate of the soft blowing treatment is ≤70 NL / min.

[0047] The soft blowing treatment time is controlled between 4 and 6 minutes. This treatment allows tiny inclusions in the ladle to float and separate fully under gentle stirring, while ensuring that the temperature of the vacuum-refined molten steel drops uniformly and stably to the target casting temperature range. Soft blowing provides the continuous casting process with stable, high-cleanliness molten steel, directly guaranteeing smooth casting and the internal quality of the slab. For example, the soft blowing treatment time can be 4, 5, or 6 minutes. The argon flow rate for soft blowing is ≤70 NL / min. This low-flow stirring effectively promotes the removal of tiny inclusions without causing violent turbulence on the molten steel surface, thus avoiding secondary oxidation, slag entrapment, or uneven temperature caused by excessive gas flow in the vacuum-refined molten steel. For example, the argon flow rate for soft blowing can be 50 NL / min, 60 NL / min, or 70 NL / min.

[0048] In some embodiments, the sulfur content of the purified molten steel is ≤0.010wt%, and the sulfur fluctuation range of the purified molten steel is ≤15ppm.

[0049] The sulfur content of the molten steel is controlled to ≤0.010 wt%, while the sulfur fluctuation range is limited to ≤15 ppm. These control objectives aim to simultaneously achieve deep desulfurization and high compositional stability. These dual indicators not only ensure that the molten steel reaches an extremely low average sulfur level, but also mean that the sulfur content of each heat is highly uniform and predictable. For example, the sulfur content of the molten steel can be 0.002 wt%, 0.004 wt%, 0.006 wt%, 0.008 wt%, 0.010 wt%, etc.; the sulfur fluctuation range can be 10 ppm, 13 ppm, 15 ppm, etc.

[0050] In some embodiments, the temperature of the pure molten steel is 1540°C to 1560°C.

[0051] The temperature of the molten steel is controlled between 1540℃ and 1560℃. This temperature range closely matches the optimal process window for continuous casting, providing ideal thermodynamic conditions for the stable solidification of the molten steel in the crystallizer. This effectively avoids casting fluctuations, nozzle clogging, and even the risk of steel leakage caused by excessively high or low temperatures, thus ensuring the stability and continuity of the casting process from the perspective of the final physical state. For example, the temperature of the molten steel can be 1540℃, 1550℃, 1560℃, etc.

[0052] In some embodiments, when preparing ordinary carbonate pickled plates, the total processing time of RH refining is 30 min to 33 min; when preparing low alloy pickled plates, the total processing time of RH refining is 32 min to 35 min.

[0053] When preparing ordinary carbonated steel plates, the total RH refining time is between 30 and 33 minutes. This compact cycle allows for complete desulfurization and purification, minimizing heat loss and process fluctuations in the pure steel. This ensures deep desulfurization while maintaining the pure steel in a more stable thermal state before casting, guaranteeing the excellent surface quality of the ordinary carbonated steel plates. For example, the total RH refining time for preparing ordinary carbonated steel plates can be 30, 31, 32, or 33 minutes. When preparing low-alloy pickled steel plates, the total RH refining time is between 32 and 35 minutes. This cycle provides the necessary time window for more complex composition adjustments, alloy homogenization, and deep desulfurization reactions. While meeting strength requirements, this timing ensures uniform composition and sufficient modification and flotation of inclusions, thereby improving the performance of the low-alloy pickled steel plates while maintaining high stability in the casting process. For example, the total RH refining time for preparing low-alloy pickled steel plates can be 32, 33, 34, or 35 minutes.

[0054] 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.

[0055] Example 1 Ordinary carbonate washed slabs were prepared under the equipment conditions of a 220t converter and ladle, a single-station RH furnace and a 2160mm slab continuous casting machine.

[0056] The molten iron is smelted in a converter, and the final tapping temperature is controlled at 1660℃, which is 5℃ higher than the target tapping temperature of the steel grade, to obtain molten steel that meets the heat requirements of RH refining. The environment containing molten steel that meets the heat requirements for RH refining is evacuated for 4 minutes, and the pressure of the vacuum system is reduced to 295 mbar to remove the air in the environment and obtain a vacuum environment. The molten steel that meets the RH refining heat requirements in a vacuum environment is sampled and tested to obtain the on-site composition report. According to the composition report upon arrival, the amount of aluminum added was determined to be 85 kg. After adding aluminum to the molten steel that meets the heat requirements for RH refining, deoxidation and aluminum alloying treatment were carried out. The cycle time for deoxidation treatment was 3 minutes, resulting in deoxidized molten steel. The deoxidized molten steel was alloyed, and it was calculated that 540 kg of ferromanganese was required. Based on the preset mixing ratio of silicon-calcium alloy and ferromanganese of 1:1.5, the amount of the first silicon-calcium alloy added was determined to be 180 kg. A sandwich feeding method was used, and 270 kg of ferromanganese and 180 kg of the first silicon-calcium alloy were added to the vacuum chamber sequentially through a vacuum lock, followed by the addition of 270 kg of ferromanganese. During the feeding process, the RH vacuum degree was maintained at 70 mbar, and the circulating gas flow rate was controlled at 2300 L / min to ensure that the maximum fluctuation of the vacuum degree did not exceed 85 mbar, thus obtaining alloyed molten steel. The alloyed molten steel was subjected to pure circulation treatment for 5 minutes. Then, 60 kg of second silicon-calcium alloy was added to the alloyed molten steel for calcium treatment. After the calcium treatment was completed, the vacuum was immediately broken to end the RH refining and obtain molten steel that had been vacuum refined. The molten steel that has been vacuum refined is subjected to soft blowing treatment for 6 minutes, and the argon flow rate for soft blowing treatment is 50 NL / min, to obtain pure molten steel. Pure molten steel is continuously cast, hot rolled, and pickled in sequence to obtain ordinary carbonated steel plates.

[0057] Performance data: The chemical composition of the primary carbonate washed slab includes: C: 0.08wt%, Mn: 0.45wt%, Si: 0.22wt%, S: 0.0089wt%. The slab surface is free of inclusions and streaks, the liquid level in the crystallizer is stable, there are no nodules at the nozzle, the casting process is stable, and there are no cracks on the edges of the slab. After pickling treatment, the surface quality of the primary carbonate washed slab meets the standards, and its stamping formability is good.

[0058] Example 2 Ordinary carbonate washed slabs were prepared under the equipment conditions of a 220t converter and ladle, a single-station RH furnace and a 2160mm slab continuous casting machine.

[0059] The molten iron is smelted in a converter, and the final tapping temperature is controlled at 1657℃, which is 3℃ higher than the target tapping temperature of the steel grade, to obtain molten steel that meets the heat requirements of RH refining. The environment containing molten steel that meets the heat requirements for RH refining is evacuated for 3 minutes. The pressure of the vacuum system is reduced to 60 mbar to remove the air from the environment and obtain a vacuum environment. The molten steel that meets the RH refining heat requirements in a vacuum environment is sampled and tested to obtain the on-site composition report. According to the composition report upon arrival, the amount of aluminum added was determined to be 75 kg. After adding aluminum to the molten steel that meets the heat requirements for RH refining, deoxidation and aluminum alloying treatment were carried out. The cycle time for deoxidation treatment was 2 minutes, resulting in deoxidized molten steel. The deoxidized molten steel was alloyed, and calculations showed that 600 kg of ferromanganese was required. Based on the preset mixing ratio of silicon-calcium alloy and ferromanganese (1:2), the amount of the first silicon-calcium alloy added was determined to be 200 kg. A sandwich feeding method was used, and 400 kg of ferromanganese and 200 kg of the first silicon-calcium alloy were added sequentially to the vacuum chamber through a vacuum lock, followed by the addition of 200 kg of ferromanganese. During the feeding process, the RH vacuum degree was maintained at 65 mbar, and the circulating gas flow rate was controlled at 2500 L / min to ensure that the maximum fluctuation of the vacuum degree did not exceed 85 mbar, thus obtaining alloyed molten steel. The alloyed molten steel was subjected to pure circulation treatment for 4 minutes. Then, 58 kg of second silicon-calcium alloy was added to the alloyed molten steel for calcium treatment. After the calcium treatment was completed, the vacuum was immediately broken to end the RH refining and obtain molten steel that had been vacuum refined. The molten steel that has been vacuum refined is subjected to soft blowing treatment for 5 minutes, and the argon flow rate for soft blowing treatment is 60 NL / min, to obtain pure molten steel. Pure molten steel is continuously cast, hot rolled, and pickled in sequence to obtain ordinary carbonated steel plates.

[0060] Performance data: The chemical composition of the ordinary carbonate washed slab includes: C: 0.09wt%, Mn: 0.42wt%, Si: 0.25wt%, S: 0.0092wt%. The slab surface is free of inclusions and streaks; the liquid level in the crystallizer is stable and without fluctuations; there are nodules or blockages at the nozzle; the casting process is stable and smooth throughout; and there are no cracks or defects on the edges of the slab. After pickling treatment, the surface quality of the ordinary carbonate washed slab meets the standards and exhibits excellent stamping formability.

[0061] Example 3 Ordinary carbonate washed slabs were prepared under the equipment conditions of a 220t converter and ladle, a single-station RH furnace and a 2160mm slab continuous casting machine.

[0062] The molten iron is smelted in a converter, and the final tapping temperature is controlled at 1662℃, which is 7℃ higher than the target tapping temperature of the steel grade, to obtain molten steel that meets the heat requirements of RH refining. The environment containing molten steel that meets the heat requirements for RH refining is evacuated for 5 minutes. The pressure of the vacuum system is reduced to 58 mbar to remove the air from the environment and obtain a vacuum environment. The molten steel that meets the RH refining heat requirements in a vacuum environment is sampled and tested to obtain the on-site composition report. According to the composition report upon arrival, the amount of aluminum added was determined to be 92 kg. After adding aluminum to the molten steel that meets the heat requirements for RH refining, deoxidation and aluminum alloying treatment were carried out. The cycle time for deoxidation treatment was 3 minutes, resulting in deoxidized molten steel. The deoxidized molten steel was alloyed, and calculations showed that 750 kg of ferromanganese was required. Based on the preset mixing ratio of silicon-calcium alloy and ferromanganese (1:2.5), the amount of the first silicon-calcium alloy added was determined to be 300 kg. A sandwich feeding method was used, and 375 kg of ferromanganese and 300 kg of the first silicon-calcium alloy were added sequentially to the vacuum chamber through a vacuum lock, followed by the addition of 375 kg of ferromanganese. During the feeding process, the RH vacuum degree was maintained at 80 mbar, and the circulating gas flow rate was controlled at 2800 L / min to ensure that the maximum fluctuation of the vacuum degree did not exceed 85 mbar, thus obtaining alloyed molten steel. The alloyed molten steel was subjected to pure circulation treatment for 6 minutes. Then, 72 kg of second silicon-calcium alloy was added to the alloyed molten steel for calcium treatment. After the calcium treatment was completed, the vacuum was immediately broken to end the RH refining and obtain molten steel that had been vacuum refined. The molten steel that has been vacuum refined is subjected to soft blowing treatment for 4 minutes, and the argon flow rate for soft blowing treatment is 70 NL / min, to obtain pure molten steel. Pure molten steel is continuously cast, hot rolled, and pickled in sequence to obtain ordinary carbonated steel plates.

[0063] Performance data: The chemical composition of the ordinary carbonate washed slab includes: C: 0.07wt%, Mn: 0.52wt%, Si: 0.27wt%, S: 0.0085wt%. The slab surface is free of inclusions and streaks, the liquid level fluctuation in the crystallizer is minimal, there are nodules at the nozzle, the casting process is stable and continuous, and there are no cracks on the edges of the slab. After pickling treatment, the ordinary carbonate washed slab has excellent surface quality, and its stamping formability meets the requirements for use.

[0064] Example 4 Low-alloy pickled plates were prepared under the equipment conditions of a 220t converter and ladle, a single-station RH furnace and a 2160mm slab continuous casting machine.

[0065] The molten iron is smelted in a converter, and the final tapping temperature is controlled at 1665℃, which is 8℃ higher than the target tapping temperature of the steel grade, to obtain molten steel that meets the heat requirements of RH refining. The environment containing molten steel that meets the heat requirements for RH refining is evacuated for 4 minutes, and the pressure of the vacuum system is reduced to 62 mbar to remove the air in the environment and obtain a vacuum environment. The molten steel that meets the RH refining heat requirements in a vacuum environment is sampled and tested to obtain the on-site composition report. According to the composition report upon arrival, the amount of aluminum added was determined to be 80 kg. After adding aluminum to the molten steel that meets the heat requirements for RH refining, deoxidation and aluminum alloying treatment were carried out. The cycle time for deoxidation treatment was 2 min, resulting in deoxidized molten steel. The deoxidized molten steel was alloyed, and calculations showed that 600 kg of ferromanganese was required. Based on the preset mixing ratio of silicon-calcium alloy and ferromanganese (1:3), the amount of the first silicon-calcium alloy added was determined to be 200 kg. A sandwich feeding method was used, and 300 kg of ferromanganese and 200 kg of the first silicon-calcium alloy were added sequentially to the vacuum chamber through a vacuum lock, followed by the addition of 300 kg of ferromanganese. During the feeding process, the RH vacuum degree was maintained at 75 mbar, and the circulating gas flow rate was controlled at 3000 L / min to ensure that the maximum fluctuation of the vacuum degree did not exceed 85 mbar, thus obtaining alloyed molten steel. The alloyed molten steel was subjected to pure circulation treatment for 5 minutes. Then, 80 kg of second silicon-calcium alloy was added to the alloyed molten steel for calcium treatment. After the calcium treatment was completed, the vacuum was immediately broken to end the RH refining and obtain molten steel that had been vacuum refined. The molten steel that has been vacuum refined is subjected to soft blowing treatment for 6 minutes, and the argon flow rate for soft blowing treatment is 55 NL / min, to obtain pure molten steel. Pure molten steel is continuously cast, hot rolled, and pickled in sequence to obtain low-alloy pickled plates.

[0066] Performance data: The chemical composition of the low-alloy pickled sheet includes: C: 0.12wt%, Mn: 1.05wt%, Si: 0.62wt%, S: 0.0095wt%. The slab surface is free of subcutaneous inclusions and surface streaks; the liquid level in the crystallizer is stable and controllable; there are no adhesions or nodules at the nozzle; the casting process is uninterrupted and free of leakage risks; and there are no warping cracks at the edges of the slab. After pickling, the surface quality of the low-alloy pickled sheet meets the standards, and its stamping formability is excellent.

[0067] Example 5 Low-alloy pickled plates were prepared under the equipment conditions of a 220t converter and ladle, a single-station RH furnace and a 2160mm slab continuous casting machine.

[0068] The molten iron is smelted in a converter, and the final tapping temperature is controlled at 1659℃, which is 4℃ higher than the target tapping temperature of the steel grade, to obtain molten steel that meets the heat requirements of RH refining. The environment containing molten steel that meets the heat requirements for RH refining is evacuated for 3 minutes. The pressure of the vacuum system is reduced to 60 mbar to remove the air from the environment and obtain a vacuum environment. The molten steel that meets the RH refining heat requirements in a vacuum environment is sampled and tested to obtain the on-site composition report. According to the composition report upon arrival, the amount of aluminum added was determined to be 68 kg. After adding aluminum to the molten steel that meets the heat requirements for RH refining, deoxidation and aluminum alloying treatment were carried out. The cycle time for deoxidation treatment was 3 minutes, resulting in deoxidized molten steel. The deoxidized molten steel was alloyed, and calculations showed that 450 kg of ferromanganese was required. Based on the preset mixing ratio of silicon-calcium alloy and ferromanganese (1:1.5), the amount of the first silicon-calcium alloy added was determined to be 300 kg. A sandwich feeding method was used, and 225 kg of ferromanganese and 300 kg of the first silicon-calcium alloy were added sequentially to the vacuum chamber through a vacuum lock, followed by the addition of 225 kg of ferromanganese. During the feeding process, the RH vacuum degree was maintained at 60 mbar, and the circulating gas flow rate was controlled at 2200 L / min to ensure that the maximum fluctuation of the vacuum degree did not exceed 85 mbar, thus obtaining alloyed molten steel. The alloyed molten steel was subjected to pure circulation treatment for 6 minutes. Then, 66 kg of second silicon-calcium alloy was added to the alloyed molten steel for calcium treatment. After the calcium treatment was completed, the vacuum was immediately broken to end the RH refining and obtain molten steel that had been vacuum refined. The molten steel that has been vacuum refined is subjected to soft blowing treatment for 5 minutes, and the argon flow rate for soft blowing treatment is 48 NL / min, to obtain pure molten steel. Pure molten steel is continuously cast, hot rolled, and pickled in sequence to obtain low-alloy pickled plates.

[0069] Results data: The chemical composition of the low-alloy pickled steel sheet includes: C: 0.10wt%, Mn: 0.92wt%, Si: 0.51wt%, S: 0.0082wt%. The slab surface is clean and defect-free, the liquid level fluctuation in the crystallizer is minimal, the nozzle is unobstructed and free of nodules, the casting process is stable and smooth over a long period, and there are no fine cracks on the edges of the slab. After pickling treatment, the low-alloy pickled steel sheet has excellent surface quality, and its stamping formability meets the requirements for deep processing.

[0070] Comparative Example 1 Ordinary carbonate washed slabs were prepared under the equipment conditions of a 220t converter and ladle, a single-station RH furnace and a 2160mm slab continuous casting machine.

[0071] The molten iron is smelted in a converter, and the final tapping temperature is controlled at 1660℃, which is 5℃ higher than the target tapping temperature of the steel grade, to obtain molten steel that meets the heat requirements of RH refining. The environment containing molten steel that meets the heat requirements for RH refining is evacuated for 4 minutes. The pressure of the vacuum system is reduced to 60 mbar to remove the air from the environment and obtain a vacuum environment. The molten steel that meets the RH refining heat requirements in a vacuum environment is sampled and tested to obtain the on-site composition report. According to the composition report upon arrival, the amount of aluminum added was determined to be 85 kg. After adding aluminum to the molten steel that meets the heat requirements for RH refining, deoxidation and aluminum alloying treatment were carried out. The cycle time for deoxidation treatment was 3 minutes, resulting in deoxidized molten steel. The deoxidized molten steel was alloyed, and it was calculated that 540 kg of ferromanganese was required. In this comparative example, no silicon-calcium alloy was added throughout the process, and the sandwich feeding process was eliminated. All the ferromanganese, along with the matching ferrosilicon, was directly added to the deoxidized molten steel in batches through a vacuum silo. During the feeding process, the RH vacuum degree was maintained at 70 mbar, and the circulating gas flow rate was controlled at 2300 L / min to ensure that the maximum fluctuation of the vacuum degree did not exceed 85 mbar, thus obtaining alloyed molten steel. The alloyed molten steel is subjected to pure circulation treatment for 5 minutes; the calcium treatment process is cancelled, and no silicon-calcium alloy is added. After the pure circulation is completed, the RH refining is directly terminated by breaking the air, and molten steel that has been vacuum refined is obtained. The molten steel that has been vacuum refined is subjected to soft blowing treatment for 6 minutes, and the argon flow rate for soft blowing treatment is 50 NL / min, to obtain pure molten steel. Pure molten steel is continuously cast, hot rolled, and pickled in sequence to obtain ordinary carbonated steel plates.

[0072] Results data: The chemical composition of the ordinary carbonate washed slab includes: C: 0.08wt%, Mn: 0.45wt%, Si: 0.22wt%, S: 0.0152wt%. The slab surface exhibits numerous inclusions, frequent long pickling streaks, frequent and significant fluctuations in the crystallizer level, severe nozzle adhesion, and repeated forced reductions in casting speed during the casting process, posing a risk of nozzle blockage. Scattered micro-cracks are also present on the slab edges. After pickling treatment, the surface quality of the ordinary carbonate washed slab is unqualified, resulting in poor stamping formability and a high scrap rate due to stamping cracks.

[0073] Comparative Example 2 Low-alloy pickled plates were prepared under the equipment conditions of a 220t converter and ladle, a single-station RH furnace and a 2160mm slab continuous casting machine.

[0074] The molten iron is smelted in a converter, and the final tapping temperature is controlled at 1663℃, which is 6℃ higher than the target tapping temperature of the steel grade, to obtain molten steel that meets the heat requirements of RH refining. The environment containing molten steel that meets the heat requirements for RH refining is evacuated for 4 minutes, and the pressure of the vacuum system is reduced to 58 mbar to remove the air in the environment and obtain a vacuum environment. The molten steel that meets the RH refining heat requirements in a vacuum environment is sampled and tested to obtain the on-site composition report. According to the composition report upon arrival, the amount of aluminum added was determined to be 78 kg. After adding aluminum to the molten steel that meets the heat requirements for RH refining, deoxidation and aluminum alloying treatment were carried out. The cycle time for deoxidation treatment was 3 minutes, resulting in deoxidized molten steel. The deoxidized molten steel was alloyed, and it was calculated that 720 kg of ferromanganese was required. The silicon-calcium alloy was not sandwiched. The first batch of silicon-calcium alloy was directly added from the silo in one go. The first batch of silicon-calcium alloy and ferromanganese were not layered. The ferromanganese alloy was added in two batches. During the addition, the RH vacuum degree was maintained at 72 mbar and the circulating gas flow rate was controlled at 2600 L / min to ensure that the maximum fluctuation of the vacuum degree did not exceed 85 mbar, thus obtaining alloyed molten steel. The alloyed molten steel is subjected to pure circulation treatment for 5 minutes; after adding a second batch of silicon-calcium alloy at once, the air is broken to obtain molten steel that has been vacuum refined. The molten steel that has been vacuum refined is subjected to soft blowing treatment for 5 minutes, and the argon flow rate for soft blowing treatment is 55 NL / min, to obtain pure molten steel. Pure molten steel is continuously cast, hot rolled, and pickled in sequence to obtain low-alloy pickled plates.

[0075] Results data: The chemical composition of the low-alloy pickled sheet includes: C: 0.11wt%, Mn: 0.98wt%, Si: 0.58wt%, S: 0.0128wt%. The slab surface exhibits a small number of dotted inclusions, the crystallizer level fluctuates slightly and intermittently, the nozzle shows mild nodule formation, and there are occasional slight decreases in casting speed during the casting process. The slab edges show very few micro-cracks. After pickling, the surface quality of the low-alloy pickled sheet is partially substandard, and its stamping formability is generally poor.

[0076] Based on the above performance data, the following conclusions can be drawn: As shown in Examples 1-5 and Comparative Examples 1-2, Examples 1-5, employing the defined converter temperature control, segmented silicon-calcium sandwich feeding and staged silicon-calcium ratio, RH vacuum and circulating gas volume, process time, and soft blowing parameters, can stably achieve a steel sulfur content ≤0.010wt%, sulfur fluctuation ≤15ppm, steel composition precisely within the designed range, slabs free of inclusions and cracks, stable crystallizer liquid level, no nozzle formation, continuous and stable casting process, and excellent surface quality and stamping performance of the pickled plates. However, Comparative Examples 1-2, deviating from these process parameters, omitting sandwich feeding, exceeding the silicon-calcium ratio range of 22%-44%, or exceeding the limits of process parameters, exhibit problems such as excessive sulfur content, uncontrolled composition, nozzle formation, liquid level fluctuation, increased slab defects, unstable casting, substandard quality of the pickled plates, and increased stamping scrap rate. The above comparison verifies the crucial role of the synergistic combination of these process parameters in controlling sulfur and ensuring casting stability during RH refining of pickled plates.

[0077] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages: This invention provides a pickled steel plate RH refining method that balances sulfur control and casting stability. By constructing an interlocking RH refining process, it synergistically resolves the inherent contradiction between deep desulfurization and casting stability, successfully achieving the dual goals of maintaining sulfur content at an extremely low level and ensuring smooth casting process, while significantly improving the surface purity of molten steel. This method precisely controls the parameters of the alloying and calcium treatment processes, ensuring a stable and controllable reaction when silicon-calcium alloys are added, effectively guaranteeing on-site operational safety and ladle molten steel level stability. Furthermore, this method exhibits good process adaptability to both ordinary carbonated steel plates and low-alloy pickled steel plates with different performance requirements, and can be stably applied without large-scale equipment modifications, thus comprehensively ensuring smooth continuous casting and final product quality while achieving efficient desulfurization.

[0078] 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 RH refining of pickled steel plates that balances sulfur control and casting stability, characterized in that, The method includes: The molten iron is smelted in a converter, and the final tapping temperature is controlled to obtain molten steel that meets the heat requirements of RH refining. The environment containing the molten steel that meets the RH refining heat requirements is evacuated to remove the air from the environment, thus obtaining a vacuum environment. The molten steel that meets the RH refining heat requirements and is placed in a vacuum environment is sampled and tested to obtain an on-site composition report. According to the arrival composition report, aluminum is added to the molten steel that meets the RH refining heat requirements and then deoxidized to obtain deoxidized molten steel. The deoxidized molten steel is alloyed. During the alloying process, a sandwich feeding method is used to sandwich the first silicon-calcium alloy in the middle of a portion of ferromanganese to form a mixture. The mixture is added to the RH vacuum chamber through a vacuum lock. After the mixture is added, the remaining ferromanganese and ferrosilicon are continuously added to the deoxidized molten steel through a vacuum hopper to obtain alloyed molten steel. The alloyed molten steel is subjected to pure circulation treatment, calcium treatment, and void breaking in sequence to complete RH refining. During the calcium treatment, a second silicon-calcium alloy is added to the alloyed molten steel, and void breaking is performed immediately after the addition to obtain molten steel that has undergone vacuum refining. The mass of the second silicon-calcium alloy added is 22% to 44% of the mass of the first silicon-calcium alloy added. The molten steel that has undergone vacuum refining is subjected to soft blowing treatment to obtain pure molten steel. The total processing time for RH refining is 30-35 minutes, and the temperature of the pure molten steel is 1540℃-1560℃.

2. The method according to claim 1, characterized in that, The mass ratio of the first silicon-calcium alloy to the partial manganese-iron alloy is 1:1.5 to 1:3; The mass of the first silicon-calcium alloy added is 100kg to 300kg; the mass of the second silicon-calcium alloy added is 40kg to 80kg.

3. The method according to claim 1, characterized in that, The final tapping temperature is 3℃~8℃ higher than the corresponding pickled plate's conventional tapping temperature, and the resulting molten steel temperature that meets the RH refining heat requirements is ≥1580℃.

4. The method according to claim 1, characterized in that, The vacuuming time is 3 to 5 minutes; and / or, The amount of aluminum added is ≤1kg / t of steel, and the deoxidation treatment cycle time is 2min~3min.

5. The method according to claim 1, characterized in that, The RH vacuum degree of the alloying treatment is 60mbar~90mbar, and the circulating gas flow rate of the alloying treatment is 2200L / min~3000L / min.

6. The method according to claim 1, characterized in that, The chemical compositions of the first silicon-calcium alloy and the second silicon-calcium alloy both meet the following requirements: Si content ≥ 60 wt%, Ca content ≥ 25 wt%, S content ≤ 0.02 wt%, P content ≤ 0.03 wt%, C content ≤ 0.3 wt%, and Ti content ≤ 0.2 wt%.

7. The method according to claim 1, characterized in that, The alloying treatment involves adjusting the composition of the deoxidized steel to: C ≤ 0.12 wt%, Mn: 0.30 wt%~0.60 wt%, Si ≤ 0.30 wt%; or, C: 0.08wt%~0.15wt%, Mn: 0.80wt%~1.20wt%, Si: 0.40wt%~0.80wt%.

8. The method according to claim 1, characterized in that, The pure cyclic processing time is 4 min to 6 min.

9. The method according to claim 1, characterized in that, The soft blowing treatment time is 4 min to 6 min; the argon flow rate of the soft blowing treatment is ≤70 NL / min.

10. The method according to claim 1, characterized in that, When preparing ordinary carbonate pickled plates, the total processing time of RH refining is 30 min to 33 min; when preparing low alloy pickled plates, the total processing time of RH refining is 32 min to 35 min.

Images