Low-carbon low-silicon aluminum-containing steel smelting method

Abstract

The invention discloses a smelting method of low-carbon low-silicon aluminum-containing steel. The smelting method comprises the following steps: a molten iron pretreatment stage; in the converter smelting stage, converter tapping components and temperature are controlled, in the tapping process, aluminum alloy, slagging materials and a deoxidizing agent are sequentially added into a steel ladle to conduct deoxidation slagging in the LF refining stage, an LF refining furnace enters a station, the early-stage bottom blowing flow is adjusted, a steel slag layer is blown to be broken, and a buggy ladle is driven to a soft blowing position to conduct calcium treatment; and in the continuous casting and casting stage, the steel ladle after soft blowing is hoisted to a continuous casting machine for casting. According to the method, deoxidation and slagging are carried out in advance to the converter process, a deoxidizing agent is added in advance to complete deoxidation operation, the LF refining furnace smelting time is shortened, the operation process is simple and easy to implement, the technical problems of large aluminum loss, many inclusions, continuous casting ladle nozzle nodulation and the like in the prior art are solved, and therefore the low-cost smelting process of the type of steel is achieved.

Description

Technical Field

[0001] This invention relates to the field of iron and steel smelting technology, and in particular to a method for smelting low-carbon, low-silicon aluminum-containing steel. Background Technology

[0002] A publicly disclosed method for smelting low-carbon, low-silicon, aluminum-containing steel employs a process flow of hot metal pretreatment, converter smelting, LF refining, and continuous casting. The final carbon content in the converter is controlled at 0.03-0.06%, resulting in high oxygen content and strong oxidizing properties in the molten steel. During tapping, aluminum alloy is added for deoxidation and alloying. However, improper timing of aluminum alloy addition leads to low aluminum recovery and excessive aluminum formation. Inclusions. The LF refining furnace initially uses large amounts of argon gas for slag formation and slag treatment, further increasing aluminum loss. Therefore, a large amount of aluminum particles are added in the early stages for deoxidation and aluminum enrichment, increasing the cost of aluminum alloys while generating more inclusions. Inclusions require prolonged refining and slag retention to promote flotation. An improper calcium treatment process at the end of refining can lead to nodule formation at the continuous casting ladle nozzle during pouring, thus affecting the quality of the cast billet. Therefore, achieving low-cost smelting of low-carbon, low-silicon, aluminum-containing steel has become a pressing technical challenge in the steelmaking industry.

[0003] The information disclosed in this background section is only intended to enhance the understanding of the background technology of this application, and therefore may include prior art that is not known to those skilled in the art. Summary of the Invention

[0004] To address the problems mentioned in the background art, this invention proposes a method for smelting low-carbon, low-silicon aluminum-containing steel. By optimizing the deoxidation and slag-forming process in the LF refining furnace, which is advanced to the converter stage, the steel tapping process utilizes kinetic conditions to employ a slag washing process incorporating refining synthetic slag and lime. The deoxidizer is added in advance to complete the deoxidation operation, shortening the LF refining furnace smelting time. The operation is simple and easy to implement, solving the problems of high aluminum loss in existing technologies. Technical challenges such as numerous inclusions and nodule formation at the sprue of the continuous casting ladle were overcome, thus enabling a low-cost smelting process for this type of steel.

[0005] To achieve the above-mentioned objectives, the present invention employs the following technical solution: In some embodiments of this application, a method for smelting low-carbon, low-silicon aluminum-containing steel is provided, comprising: Hot metal pretreatment stage; During the converter smelting stage, the composition and temperature of the steel tapped from the converter are controlled. During the tapping process, aluminum alloy, slag-forming material and deoxidizer are added to the ladle in sequence for deoxidation and slag formation. During the LF refining stage, the bottom blowing flow rate of the LF refining furnace is adjusted to break the steel slag layer, and the ladle car is driven to the soft blowing position for calcium treatment. During the continuous casting stage, the ladle after the soft blowing is completed is hoisted to the continuous casting machine for casting.

[0006] In some embodiments of this application, during the molten iron treatment stage, KR stirring desulfurization is used, and the final sulfur content after treatment is ≤0.015%.

[0007] In some embodiments of this application, during the converter smelting stage, aluminum alloy, slag-forming material, ferromanganese, and deoxidizer are sequentially added to the ladle during the tapping process to carry out deoxidation and slag formation.

[0008] In some embodiments of this application, the slag-forming material is refined synthetic slag and lime, and the steelmaking process adopts slag washing process.

[0009] In some embodiments of this application, the deoxidizer is calcium carbide or silicon carbide.

[0010] In some embodiments of this application, aluminum alloy is added when W1 tons of steel are tapped from the converter; slag-forming material is added when W2 tons of steel are tapped, followed by high-carbon ferromanganese alloy; deoxidizer is added when W3 tons of steel are tapped for deoxidation; W1 < W2 < W3.

[0011] In some embodiments of this application, during the converter smelting stage, the argon flow rate is controlled at 300-400 NL / min after the steel tapping is completed, and the stirring time is greater than 2 minutes.

[0012] In some embodiments of this application, during the LF refining stage, after the ladle is hoisted to the LF refining furnace, the initial bottom blowing flow rate is adjusted to 150-200 NL / min to break the slag layer for temperature measurement and sampling.

[0013] In some embodiments of this application, during the LF refining stage, the LF refining furnace is no longer supplemented with slag-forming material.

[0014] In some embodiments of this application, during the LF refining stage, the power supply time is controlled within 10 minutes based on the incoming temperature. Once the composition and temperature are qualified, the ladle car is driven to the soft blowing position for calcium treatment. After the soft blowing is completed, the ladle is hoisted to the continuous casting machine for casting.

[0015] Compared with the prior art, the advantages and positive effects of the present invention are: The low-carbon, low-silicon aluminum-containing steel smelting method of the present invention significantly solves the problems of high cost, numerous inclusions, and poor continuous casting stability in traditional smelting technologies through optimization and innovation of existing processes. The specific beneficial effects are as follows: Significantly reducing smelting costs: Traditional processes require the addition of large amounts of aluminum granules for deoxidation and aluminum enrichment during the LF refining stage, resulting in high aluminum alloy consumption and significant material waste due to low aluminum recovery rates. This invention advances the key deoxidation and slag-forming operations to the converter tapping process. Utilizing the kinetic conditions during tapping, it employs refined synthetic slag and lime for slag washing, and adds deoxidizers such as silicon carbide and calcium carbide to complete the main deoxidation task, effectively reducing aluminum alloy consumption. Simultaneously, early deoxidation avoids aluminum loss caused by the highly oxidizing molten steel during the LF refining stage, improving aluminum utilization and significantly reducing aluminum alloy costs, fundamentally solving the industry problem of high smelting costs for this type of steel.

[0016] Reduce steel Inclusions: In traditional processes, the high oxygen content at the converter endpoint and the improper timing of aluminum alloy addition lead to a large amount of inclusions. Inclusion formation is a significant issue; the large-scale argon slag-forming operation in the early stages of LF refining further exacerbates inclusion formation, requiring prolonged refining and slag maintenance to promote flotation, thus extending the smelting cycle. This invention optimizes the order and type of deoxidizer addition during converter tapping, achieving efficient deoxidation during the tapping process and reducing inclusion formation. The source of inclusion formation; at the same time, the bottom blowing flow rate in the early stage of LF refining was adjusted to avoid secondary formation of inclusions caused by strong agitation, shorten the refining time required for inclusions to float, and significantly improve the purity of molten steel.

[0017] Improving casting stability and billet quality in continuous casting: Traditional calcium treatment processes at the end of refining are flawed, leading to nodule formation at the ladle nozzle during continuous casting, affecting casting continuity and billet quality. This invention addresses this by moving the ladle car to the soft blowing position during the LF refining stage for calcium treatment, optimizing the kinetics of the treatment and allowing calcium to react more evenly with the molten steel. The inclusions react to form low-melting-point calcium aluminate, effectively preventing nozzle clogging. This improvement not only ensures the stability of continuous casting and reduces production interruptions and scrap rates caused by nozzle blockage, but also significantly improves the internal and surface quality of the cast billet.

[0018] Shortening the smelting cycle and improving production efficiency: In traditional processes, the LF refining stage requires lengthy deoxidation, slag formation, and inclusion flotation operations, resulting in an excessively long smelting cycle. This invention reduces the load on the LF refining process by transferring some of the deoxidation and slag formation tasks to the converter tapping process. Simultaneously, the optimized LF refining bottom blowing system and calcium treatment process further shorten the refining time, resulting in a more compact overall process flow, effectively improving production efficiency, and enhancing equipment utilization and capacity. Detailed Implementation

[0019] The following disclosure provides many different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this invention, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0020] In some embodiments of this application, a method for smelting low-carbon, low-silicon aluminum-containing steel is provided. The low-carbon, low-silicon aluminum-containing steel comprises the following components: C: 0.13%-0.18%, Si≤0.07%, Mn: 0.30%-0.60%, P≤0.020%, S≤0.020%, Al: 0.020-0.050%, Ni≤0.10%, Cr≤0.10%, Cu≤0.08%, with the remainder being Fe and unavoidable impurities.

[0021] The smelting method for low-carbon, low-silicon aluminum-containing steel includes a process flow of hot metal pretreatment, converter smelting, LF refining, and continuous casting.

[0022] In the converter smelting stage, the composition and temperature of the steel tapped from the converter are controlled. During the tapping process, aluminum alloy, slag-forming material, other alloys (such as ferromanganese), and deoxidizer are added to the ladle in sequence to carry out deoxidation and slag formation.

[0023] During the LF refining stage, the bottom blowing flow rate of the LF refining furnace is adjusted to break the steel slag layer, and the ladle car is driven to the soft blowing position for calcium treatment.

[0024] During the continuous casting stage, the ladle after the soft blowing is completed is hoisted to the continuous casting machine for casting.

[0025] The present invention provides a low-cost smelting method for low-carbon, low-silicon aluminum-containing steel. By optimizing the deoxidation and slag-making process of the LF refining furnace and advancing it to the converter process, the steel tapping process utilizes kinetic conditions to adopt a slag washing process with the addition of refining synthetic slag and lime, and the deoxidizer is added in advance to complete the deoxidation operation, thus shortening the smelting time of the LF refining furnace and effectively solving the problem of high production costs for this type of steel.

[0026] This invention targets the low-cost smelting of low-carbon, low-silicon, aluminum-containing steel. It employs an innovative converter tapping process utilizing refined synthetic slag to complete slag washing and slag-forming. During tapping, deoxidizers such as silicon carbide and calcium carbide are added to achieve deoxidation, thus solving the problems of high aluminum loss and poor molten steel quality in existing LF refining processes. It effectively solves the industry problem of high smelting costs for this type of steel, which is characterized by numerous inclusions and easy nodule formation at the ladle nozzle during continuous casting.

[0027] The low-carbon, low-silicon aluminum-containing steel smelting method of the present invention significantly solves the problems of high cost, numerous inclusions, and poor continuous casting stability in traditional smelting technologies through optimization and innovation of existing processes. The specific beneficial effects are as follows: Significantly reducing smelting costs: Traditional processes require the addition of large amounts of aluminum granules for deoxidation and aluminum enrichment during the LF refining stage, resulting in high aluminum alloy consumption and significant material waste due to low aluminum recovery rates. This invention advances the key deoxidation and slag-forming operations to the converter tapping process. Utilizing the kinetic conditions during tapping, it employs refined synthetic slag and lime for slag washing, and adds deoxidizers such as silicon carbide and calcium carbide to complete the main deoxidation task, effectively reducing aluminum alloy consumption. Simultaneously, early deoxidation avoids aluminum loss caused by the highly oxidizing molten steel during the LF refining stage, improving aluminum utilization and significantly reducing aluminum alloy costs, fundamentally solving the industry problem of high smelting costs for this type of steel.

[0028] Reduce steel Inclusions: In traditional processes, the high oxygen content at the converter endpoint and the improper timing of aluminum alloy addition lead to a large amount of inclusions. Inclusion formation is a significant issue; the large-scale argon slag-forming operation in the early stages of LF refining further exacerbates inclusion formation, requiring prolonged refining and slag maintenance to promote flotation, thus extending the smelting cycle. This invention optimizes the order and type of deoxidizer addition during converter tapping, achieving efficient deoxidation during the tapping process and reducing inclusion formation. The source of inclusion formation; at the same time, the bottom blowing flow rate in the early stage of LF refining was adjusted to avoid secondary formation of inclusions caused by strong agitation, shorten the refining time required for inclusions to float, and significantly improve the purity of molten steel.

[0029] Improving casting stability and billet quality in continuous casting: Traditional calcium treatment processes at the end of refining are flawed, leading to nodule formation at the ladle nozzle during continuous casting, affecting casting continuity and billet quality. This invention addresses this by moving the ladle car to the soft blowing position during the LF refining stage for calcium treatment, optimizing the kinetics of the treatment and allowing calcium to react more evenly with the molten steel. The inclusions react to form low-melting-point calcium aluminate, effectively preventing nozzle clogging. This improvement not only ensures the stability of continuous casting and reduces production interruptions and scrap rates caused by nozzle blockage, but also significantly improves the internal and surface quality of the cast billet.

[0030] Shortening the smelting cycle and improving production efficiency: In traditional processes, the LF refining stage requires lengthy deoxidation, slag formation, and inclusion flotation operations, resulting in an excessively long smelting cycle. This invention reduces the load on the LF refining process by transferring some of the deoxidation and slag formation tasks to the converter tapping process. Simultaneously, the optimized LF refining bottom blowing system and calcium treatment process further shorten the refining time, resulting in a more compact overall process flow, effectively improving production efficiency, and enhancing equipment utilization and capacity.

[0031] In summary, this invention, through innovative optimization of the converter tapping process and LF refining system, has achieved significant results in reducing smelting costs, minimizing inclusions, improving continuous casting stability, and increasing production efficiency. It provides a practical and feasible technical solution for low-cost, high-quality smelting of low-carbon, low-silicon, aluminum-containing steel, and has important industrial application value.

[0032] In some embodiments of this application, during the molten iron treatment stage, KR stirring desulfurization is used, and the final sulfur content after treatment is ≤0.015%.

[0033] KR stirred desulfurization utilizes a rotating agitator to intensely agitate molten iron, ensuring thorough contact and mixing of the desulfurizing agent (such as lime-based desulfurizer) with the molten iron, significantly improving the kinetics of the desulfurization reaction. This highly efficient agitation method breaks down the boundary layer on the surface of the molten iron, allowing the desulfurizing agent to be more evenly dispersed in the molten iron, ensuring the desulfurization reaction proceeds fully, thereby effectively reducing the sulfur content in the molten iron.

[0034] The use of KR stirring desulfurization can significantly improve desulfurization efficiency. Compared with traditional processes such as injection desulfurization, its desulfurization effect is more stable and can accurately control the sulfur content in molten iron within the range of ≤0.015%. This provides low-sulfur molten iron raw materials for subsequent converter smelting, LF refining and other processes, reducing the need for additional treatment due to excessive sulfur content in subsequent processes, and reducing the complexity and cost of the smelting process.

[0035] Controlling the final sulfur content to ≤0.015% can prevent sulfur from adversely affecting the quality of molten steel in subsequent smelting processes. Sulfur readily combines with iron in steel to form low-melting-point FeS. During solidification, FeS accumulates at grain boundaries, leading to deterioration of the steel's hot brittleness and severely impacting its processing performance and safety. Strict control of sulfur content is crucial, especially for low-carbon, low-silicon, aluminum-containing steels, which have high requirements for material properties.

[0036] Low-sulfur molten iron helps improve the quality of final steel products, avoiding hot brittleness caused by sulfur, and enhancing key performance indicators such as toughness, weldability, and corrosion resistance. This also expands the application areas of low-carbon, low-silicon, aluminum-containing steel. Furthermore, stable low-sulfur content control reduces production failures caused by sulfur fluctuations during steelmaking, ensuring the continuity and stability of the smelting process and further improving production efficiency.

[0037] In some embodiments of this application, during the converter smelting stage, the composition and temperature of the converter tapping steel are controlled, and aluminum alloy, slag-forming material, ferromanganese, and deoxidizer are sequentially added to the ladle during the tapping process to carry out deoxidation and slag formation.

[0038] In the converter smelting stage, by controlling the steel composition and temperature, and sequentially adding aluminum alloy, slag-forming material, ferromanganese, and deoxidizer to the ladle for deoxidation and slag formation, this technical solution plays an important role in the smelting of low-carbon, low-silicon, aluminum-containing steel and produces significant results. Its specific effects are as follows: The importance of controlling the steel composition and temperature: The steel composition directly determines the starting point of subsequent refining processes. Precisely controlling the content of elements such as carbon, silicon, and aluminum at the time of converter tapping can reduce the amount of adjustment required in the LF refining stage and avoid prolonged refining time and increased alloy consumption due to excessive composition deviation. A suitable tapping temperature provides appropriate thermodynamic conditions for deoxidation and slagging reactions in the ladle. Excessively high temperatures will exacerbate secondary oxidation of the molten steel and alloy loss, while excessively low temperatures will slow down the reaction rate, affecting deoxidation and slagging effects.

[0039] The purpose of adding materials in a specific order is as follows: Adding aluminum alloy first allows for the rapid reduction of oxygen content in molten steel by utilizing its strong deoxidizing ability, thus creating a low-oxygen environment for the subsequent addition of other alloys and reducing the oxidation loss of alloying elements. Then, slag-forming material is added to form slag with good fluidity and adsorption properties in a timely manner. It can adsorb oxide inclusions generated by deoxidation reaction in molten steel, while isolating air and preventing secondary oxidation of molten steel. The timing of adding ferromanganese is after the slag-forming material, at which point the oxygen content in the molten steel has been significantly reduced, which can effectively improve the recovery rate of manganese and ensure that the manganese content in the molten steel meets the target requirements. Finally, the addition of a deoxidizer can further deepen deoxidation, remove trace amounts of residual oxygen in the molten steel, ensure thorough deoxidation, and reduce the formation of inclusions in subsequent processes.

[0040] The specific effects are as follows: Improving deoxidation efficiency and reducing inclusion formation: By optimizing the material addition sequence, the aluminum alloy first exerts a strong deoxidizing effect, followed by further deoxidation by the deoxidizing agent, resulting in more thorough deoxidation of the molten steel. This significantly reduces the oxygen content in the molten steel, thereby reducing... The amount of oxide inclusions generated is reduced. Simultaneously, the timely formation of slag from the slag-forming material effectively adsorbs existing inclusions, improving the purity of the molten steel.

[0041] Improving alloy recovery rate and reducing smelting costs: Adding alloys such as ferromanganese in a low-oxygen environment reduces the oxidation loss of alloying elements, improves their recovery rate, and reduces the total consumption of alloys. Furthermore, precise control of the steel composition and temperature reduces the amount of alloy adjustments and refining time in the LF refining stage, indirectly lowering energy consumption and production costs in the refining process.

[0042] Shortening the refining cycle and improving production efficiency: Most of the deoxidation and composition adjustment work has been completed when the steel is tapped from the converter, which reduces the burden on LF refining and allows LF refining to complete subsequent processing more quickly, thereby shortening the entire smelting cycle and improving the utilization rate and production efficiency of steelmaking equipment.

[0043] Ensuring the stability of molten steel quality: Stable steel composition and temperature, as well as effective deoxidation and slag formation, provide molten steel with stable quality for subsequent continuous casting, reduce billet defects caused by fluctuations in molten steel quality, and improve the quality stability and pass rate of the final product.

[0044] In some embodiments of this application, the aluminum alloy is aluminum ingot or aluminum-iron. The slag-forming material is refined synthetic slag and lime, and the steelmaking process adopts a slag washing process, which can bring the following beneficial effects: Optimize deoxidation effect and improve inclusion morphology and distribution: Appropriate selection of aluminum ingots or aluminum-iron can ensure deoxidation efficiency and allow for control of the deoxidation process according to needs, reducing the amount of concentrated inclusions. Inclusion formation. Combined with the adsorption effect of refining slag and lime, as well as the enhanced mixing of the slag washing process, inclusions in molten steel can be captured by the slag more efficiently, and the inclusion particles are finer and more evenly distributed, significantly improving the purity of molten steel.

[0045] Improving material utilization and reducing smelting costs: The targeted selection of aluminum ingots and ferroaluminum can be flexibly adjusted according to actual smelting needs, avoiding waste caused by improper deoxidizer selection; the synergistic effect of refining slag and lime reduces the total amount of slag-forming material used, and the slag washing process improves the utilization rate of slag-forming material. At the same time, the efficient deoxidation and slag-forming effects reduce the processing time and material consumption of subsequent LF refining, indirectly reducing the overall smelting cost.

[0046] Stabilizing steel composition and properties: The stabilizing deoxidation effect of aluminum ingots or ferrosilicon, combined with the effective removal of inclusions by slag washing, makes it easier to control the aluminum content and other components in the molten steel within the target range, reducing compositional fluctuations. Optimization of slag properties also reduces the risk of secondary oxidation of the molten steel, ensuring the stability of steel properties and laying a solid foundation for subsequent continuous casting and final product quality.

[0047] Enhancing the continuity and stability of the smelting process: The slag washing process completes part of the refining task during the tapping stage, reducing the pressure on LF refining and enabling LF refining to carry out subsequent processing more quickly and stably, thus shortening the overall smelting cycle. At the same time, reasonable material selection and process control reduce production interruptions caused by problems such as excessive inclusions and unqualified steel composition, thereby improving the continuity and stability of the smelting process.

[0048] In some embodiments of this application, the deoxidizer is calcium carbide or silicon carbide, which can bring the following beneficial effects: Synergistic deoxidation: When calcium carbide and silicon carbide are used together, they form a complementary deoxidation mechanism. Calcium carbide primarily deoxidizes using carbon, and the generated CaO helps optimize slag basicity; silicon carbide, on the other hand, synergistically deoxidizes using silicon and carbon, generating... The slag composition can be adjusted, and the two work together to more comprehensively remove dissolved oxygen and oxide inclusions from molten steel, while avoiding the problems of incomplete deoxidation or poor inclusion control that may be caused by a single deoxidizer.

[0049] Enhancing deoxidation depth and reducing aluminum loss: The addition of calcium carbide and silicon carbide can further reduce the oxygen content of molten steel after the initial deoxidation of aluminum alloys, reducing secondary oxidation reactions between molten steel and slag and air during the subsequent LF refining stage, thereby reducing aluminum consumption. In traditional processes, due to the high oxidizing power of molten steel, a large amount of aluminum is required for deoxidation. However, this solution reduces the oxygen content in advance through a composite deoxidizer, which can improve the aluminum recovery rate, significantly reduce the amount of aluminum alloy used, and lower smelting costs.

[0050] Improving inclusion control and enhancing steel purity: The reaction products of two deoxidizers, CaO, Able to They combine to form low-melting-point composite inclusions (such as CaO- - (System), its melting point can drop to below 1200℃, far lower than The temperature of 2050℃ significantly improves the floating speed of inclusions and the efficiency of their adsorption by slag.

[0051] Reduced refining load and shortened production cycle: Since deep deoxidation is completed through calcium carbide and silicon carbide during the converter tapping stage, the LF refining furnace does not need to perform extensive deoxidation operations, thus shortening the refining time. At the same time, the reduction in inclusion content eliminates the need for prolonged slag holding to promote flotation during the refining process, further improving production efficiency and creating conditions for continuous and stable production.

[0052] In some embodiments of this application, aluminum alloy is added when W1 tons of steel are tapped from the converter; slag-forming material is added when W2 tons of steel are tapped, followed by high-carbon ferromanganese alloy; deoxidizer is added when W3 tons of steel are tapped for deoxidation; W1 < W2 < W3.

[0053] For example, aluminum ingots or ferroaluminum are added when the converter produces 20 tons of steel, and refining synthetic slag and lime are added for slag washing when it produces 30 tons. High-carbon ferromanganese alloy is then added. Deoxidizers silicon carbide and calcium carbide are added when the converter produces 50 tons of steel for deoxidation. The deoxidation is completed ahead of schedule when the converter produces 90 tons of steel.

[0054] The core role of phased material addition: During converter tapping, the steel flow rate and kinetic conditions within the ladle dynamically change with the tapping volume. At W1 (e.g., 20 tons), the ladle contains relatively little molten steel but at a high velocity. Adding aluminum alloy at this stage utilizes the impact energy of the steel flow to rapidly disperse the aluminum, allowing it to quickly react with dissolved oxygen in the molten steel, thus providing initial strong deoxidation and creating a low-oxygen environment for subsequent alloying and slag formation. When tapping reaches W2 (e.g., 30 tons), the ladle contains a moderate amount of molten steel, and a stable flow interface forms on the steel surface. Adding slag-forming materials (refining synthetic slag and lime) at this stage allows for efficient slag washing through turbulent mixing of the molten steel. Simultaneously, the subsequent addition of high-carbon ferromanganese reduces manganese oxidation loss in the low-oxygen environment. At W3 (e.g., 50 tons), the ladle contains sufficient molten steel, and the previous deoxidation has reduced oxygen activity. Adding deoxidizers (silicon carbide, calcium carbide) at this stage allows for deep deoxidation, and the reaction products are fully adsorbed by the already formed slag, avoiding secondary pollution.

[0055] Synergistic effect of timing logic: The timing design of W1 < W2 < W3 forms a progressive operation chain of "first deoxidation for initial preparation → then slag formation and protection + alloying → finally deep deoxidation". The priority addition of aluminum alloy can quickly reduce the oxygen content of molten steel and prevent the oxidation of subsequent materials (such as ferromanganese); the slag-forming material is added after aluminum alloy deoxidation, which can not only improve slag formation efficiency by utilizing the low oxygen environment, but also reduce secondary oxidation of molten steel by covering the slag layer; the deoxidizer is added last, which can further remove residual oxygen on the basis of the previous treatment to ensure thorough deoxidation. The three form a seamless synergistic effect.

[0056] Improve aluminum alloy utilization and reduce aluminum loss: When aluminum alloy is added at the initial stage of steel tapping (W1), the turbulence intensity of the molten steel is high, the aluminum powder is evenly dispersed, and the reaction with oxygen is more complete, avoiding the local over-addition and waste of unreacted aluminum caused by concentrated addition of aluminum in traditional processes.

[0057] Enhanced slag-forming effect and improved inclusion removal rate: When the slag-forming material is added in the W2 stage, the oxygen content of the molten steel has already been reduced through preliminary deoxidation. At this time, the interfacial tension between the slag and the molten steel is more suitable for inclusion adsorption, and the slag washing process is carried out simultaneously with the steel flow impact, thus improving the inclusion capture efficiency. Combined with the CaO generated by the subsequent deoxidizer reaction, The products can form a low-melting-point composite slag system, which accelerates the floating of inclusions and ultimately reduces the number of inclusions in the molten steel significantly compared to traditional processes.

[0058] Stable alloy composition control to meet low carbon and low silicon requirements: High-carbon ferromanganese is added promptly after the slag-forming materials, at which point the oxygen activity of the molten steel is low, reducing the oxidation loss rate of manganese and ensuring precise control of the manganese content within the target range. Simultaneously, when the deoxidizer is added in the W3 stage, the carbon content of the molten steel is already basically stable, allowing for precise control of the carbon element introduction amounts of silicon carbide and calcium carbide, avoiding carbon content fluctuations and meeting the converter's final carbon requirements.

[0059] Shorten refining time and improve production efficiency: Since most of the deoxidation and slag formation tasks have been completed in sequence during the converter tapping stage, the LF refining furnace does not need to undergo a large amount of pretreatment after entering the station, thus shortening the refining cycle.

[0060] Reduce sprue nodule formation in continuous casting and improve billet quality: Due to the reduction in the number and optimization of the morphology of inclusions (mostly low-melting-point composite inclusions), the incidence of sprue nodule formation in the ladle during continuous casting is significantly reduced, the number of casting interruptions is reduced, and the rate of defects such as subcutaneous bubbles and inclusions in the billet is significantly reduced.

[0061] In some embodiments of this application, during the converter smelting stage, the argon flow rate is controlled at 300-400 NL / min after the steel tapping is completed, and the stirring time is greater than 2 minutes.

[0062] An argon flow rate of 300-400 NL / min falls within the range of moderate-intensity stirring. This provides sufficient kinetic energy to drive thorough convection circulation of the molten steel within the ladle, while avoiding excessive turbulence caused by an excessive flow rate. Excessive turbulence increases the contact area between the molten steel and air, leading to secondary oxidation and potentially entraining slag into the molten steel, causing secondary contamination. This flow rate range ensures uniform mixing of the molten steel in a stable flow field, creating conditions conducive to subsequent reactions.

[0063] Stirring for more than 2 minutes ensures that the molten steel completes sufficient mass transfer and reaction under argon gas stirring. Sufficient stirring time allows alloying elements (such as aluminum and manganese) in the molten steel to be evenly distributed, avoiding localized compositional deviations; simultaneously, it promotes the formation of inclusions (such as...) from the deoxidation reaction. CaO- The composite inclusions are fully in contact with the slag and are adsorbed, ensuring that the inclusions have enough time to float to the slag layer and reduce the amount of inclusions remaining in the molten steel.

[0064] The combination of a moderate argon flow rate and sufficient stirring time creates a continuous process of "efficient mixing - full reaction - inclusion flotation". As the argon-generated bubble cluster rises, it enhances the homogeneity of the molten steel composition through stirring, and the bubbles themselves act as "carriers" for inclusions, carrying small inclusions to the surface and improving impurity removal efficiency. A stirring time of more than 2 minutes provides sufficient time for this process, ensuring that all functions are fully realized.

[0065] In some embodiments of this application, during the LF refining stage, after the ladle is hoisted to the LF refining furnace, the initial bottom blowing flow rate is adjusted to 150-200 NL / min to break the slag layer for temperature measurement, sampling, and other operations.

[0066] A bottom blowing flow rate of 150-200 NL / min falls within the range of weak to moderate stirring intensity. Its core function is to break up the slag layer on the ladle surface through the impact force of the argon gas flow, creating locally exposed areas of molten steel, without drastically disturbing the molten steel. This flow rate range ensures effective slag layer removal (avoiding insufficient flow that prevents the slag layer from penetrating and directly contacting the molten steel) while preventing excessive flow that causes violent turbulence in the molten steel. Excessive turbulence can exacerbate secondary oxidation of the molten steel, potentially drawing slag into the molten steel, causing inclusion contamination, and increasing temperature loss.

[0067] During the process of hoisting the ladle from the converter to the LF refining furnace, the slag on the surface of the molten steel gradually solidifies or forms a dense layer, hindering direct detection of the molten steel and subsequent refining reactions. Breaking through the slag layer allows direct contact with the molten steel, ensuring accurate temperature measurement and sampling: temperature measurement directly obtains the true temperature of the molten steel (avoiding measurement deviations caused by slag insulation), and sampling allows for the collection of representative molten steel samples (avoiding the impact of slag contamination on the accuracy of compositional analysis). Simultaneously, the exposed molten steel area provides a reaction interface for subsequent operations such as electrode heating and slag-forming material addition, facilitating full contact between the refining agents and the molten steel.

[0068] The bottom blowing flow rate setting at this stage is coordinated with the argon gas stirring after the converter tapping. The medium-intensity stirring of 300-400 NL / min after the converter tapping has achieved the initial homogenization of the steel composition and temperature, while the weak stirring of 150-200 NL / min in the early stage of LF is precisely controlled while maintaining the stability of the molten steel, avoiding the secondary generation of inclusions caused by sudden changes in stirring intensity. This forms a gradient stirring system of "strong mixing in the converter - weak adjustment in LF", ensuring a smooth transition of the molten steel state.

[0069] In some embodiments of this application, during the LF refining stage, the LF refining furnace is no longer supplemented with slag-forming material.

[0070] During the converter tapping process, refined synthetic slag and lime have been added in proportion, and a slag washing process is used to form a slag with suitable basicity (CaO / ). The slag is fluid and its composition and properties already meet the core requirements of inclusion adsorption and prevention of secondary oxidation. No additional slag-forming material is added during the LF refining stage, avoiding fluctuations in slag composition due to the addition of new material. This ensures that the slag maintains stable physical and chemical properties during the refining process, continuously protecting and purifying the molten steel.

[0071] The addition of slag-forming material usually requires strong stirring to promote melting and mixing. This increases the disturbance of the molten steel, which may lead to slag being entrained into the molten steel, forming secondary inclusions, or exacerbate the contact between the molten steel and air, causing secondary oxidation. Stopping the addition of slag-forming material during the LF stage can reduce process intervention caused by material addition and stirring adjustments, reduce the intensity of molten steel flow, and create a stable kinetic environment for inclusions to float.

[0072] The slag-forming operation during the converter tapping stage has completed most of the inclusion removal work. The core tasks of LF refining have shifted to fine-tuning the composition, precise temperature control, and calcium treatment. Eliminating the need for additional slag-forming material simplifies the refining process, allowing the focus to be on temperature compensation, composition homogenization, and inclusion morphology control. This avoids the time and resources wasted on adding slag-forming material, thus improving refining efficiency.

[0073] In some embodiments of this application, during the LF refining stage, the power supply time is controlled within 10 minutes based on the incoming temperature. Once the composition and temperature are qualified, the ladle car is driven to the soft blowing position for calcium treatment. After the soft blowing is completed, the ladle is hoisted to the continuous casting machine for casting.

[0074] By controlling the power supply time to within 10 minutes based on the incoming temperature, the system can accurately compensate for temperature losses in molten steel during the process from converter tapping to LF refining, avoiding overheating. Overheating leads to increased oxidizability of the molten steel, increasing aluminum burn-off and... The formation of inclusions also exacerbates the corrosion of the ladle refractory material. Appropriate power supply timing can adjust the molten steel temperature to the target range required for continuous casting, while also reducing the negative impacts of high temperatures, thus providing molten steel at a suitable temperature for subsequent processes.

[0075] The ladle car is driven to the soft-blowing position for calcium treatment. The smooth agitation of the molten steel during soft blowing ensures the calcium wire is evenly inserted into the molten steel and reacts fully. Calcium, as a strong deoxidizing element, can react with the... Inclusions react to form low-melting-point calcium aluminate, improving the morphology and flowability of inclusions and avoiding... Inclusions accumulate and clog the nozzle during continuous casting. A stable stirring environment provided by soft blowing ensures sufficient contact between calcium and inclusions, improving the efficiency and uniformity of calcium treatment.

[0076] The soft blowing process further promotes the flotation of fine inclusions in the molten steel, making it easier for low-melting-point inclusions generated by calcium treatment to be adsorbed by the slag. After soft blowing, the ladle is directly hoisted to the continuous casting machine for casting, which reduces the temperature loss and secondary oxidation risk of the molten steel in the intermediate stages and ensures the stability of the continuous casting process. Example 1

[0077] Low-cost smelting of low-carbon, low-silicon, aluminum-containing steel includes the following steps: (1) Hot metal pretreatment: KR stirring desulfurization was adopted. The final sulfur content was 0.007% after the treatment. The hot metal was clean and there was no obvious floating slag on the surface. (2) Converter smelting: The final carbon content of the converter is 0.036%, and the final temperature is 1662℃. 220kg of aluminum ingots are added after 20 tons of steel are tapped. 300kg of refined D slag and 300kg of lime are added after 30 tons of steel are tapped. At the same time, 40kg of ferrosilicon and 580kg of high-carbon ferromanganese are added. 20kg of silicon carbide and 100kg of calcium carbide are added after 50 tons of steel are tapped. After tapping, the argon flow rate after the furnace is adjusted to 300-400NL / min. The stirring time is 2.5 minutes to ensure the deoxidation effect while promoting the floating of inclusions. The slag is yellow-white slag, and the deoxidation effect is good. (3) LF refining: After the ladle is hoisted to the LF refining furnace, the initial bottom blowing flow rate is adjusted to 150-200NL / min to break the slag layer. The temperature is measured at 1593℃. Then, samples are taken and dipped in slag. No slag-forming material is added. A small current is supplied for 5 minutes, and the temperature is 1600℃. The composition of the returned sample is qualified. The ladle car is driven to the soft blowing position and fed with 120 meters of calcium wire. Soft blowing is carried out for 14.2 minutes. The composition of the returned sample is C 0.158%, Si 0.039%, Mn 0.458%, P 0.0135%, S 0.0103%, Al 0.041%, Ca 0.0028%, and the rest are residual elements. After the soft blowing is completed, the ladle is hoisted to the continuous casting machine for casting. (4) Continuous casting: After the soft blowing of the LF refining furnace is completed, the continuous casting machine is hoisted for casting. The stopper rod is stable during the continuous casting process. Example 2

[0078] (1) Hot metal pretreatment: KR stirring desulfurization was adopted. The final sulfur content was 0.010% after the treatment. The hot metal was clean and there was no obvious floating slag on the surface. (2) Converter smelting: The converter end point C is 0.040%, the end point temperature is 1666℃. After tapping 20 tons of steel, add 230 kg of aluminum ingots. After tapping 30 tons of steel, add 300 kg of refined D slag and 300 kg of lime. At the same time, add 45 kg of ferrosilicon and 570 kg of high carbon ferromanganese. After tapping 50 tons of steel, add 20 kg of silicon carbide and 100 kg of calcium carbide. After tapping, adjust the argon flow rate after the furnace to 300-400 NL / min. Stir for 3 minutes to ensure the deoxidation effect while promoting the floating of inclusions. The slag is yellow-white slag, and the deoxidation effect is good. (3) LF refining: After the ladle is hoisted to the LF refining furnace, the initial bottom blowing flow rate is adjusted to 150-200NL / min to break the slag layer. The temperature is measured at 1596℃. Then, samples are taken and slag is dipped. No slag-forming material is added. The small current is supplied for 4.2 minutes, and the temperature is 1602℃. The composition of the returned sample is qualified. The ladle car is driven to the soft blowing position and fed with 120 meters of calcium wire. Soft blowing is carried out for 12.6 minutes. The composition of the returned sample is C 0.151%, Si 0.042%, Mn 0.436%, P 0.0155%, S 0.009%, Al 0.038%, Ca 0.0027%, and the rest are residual elements. After the soft blowing is completed, the ladle is hoisted to the continuous casting machine for casting. (4) Continuous casting: After the soft blowing of the LF refining furnace is completed, the continuous casting machine is hoisted for casting. The stopper rod is stable during the continuous casting process.

[0079] In the description of the above embodiments, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0080] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for smelting low-carbon, low-silicon aluminum-containing steel, characterized in that, Including: Hot metal pretreatment stage; During the converter smelting stage, the composition and temperature of the steel tapped from the converter are controlled. During the tapping process, aluminum alloy, slag-forming material and deoxidizer are added to the ladle in sequence for deoxidation and slag formation. During the LF refining stage, the bottom blowing flow rate of the LF refining furnace is adjusted to break the steel slag layer, and the ladle car is driven to the soft blowing position for calcium treatment. During the continuous casting stage, the ladle after the soft blowing is completed is hoisted to the continuous casting machine for casting.

2. The method for smelting low-carbon, low-silicon aluminum-containing steel according to claim 1, characterized in that, During the molten iron treatment stage, KR stirring desulfurization was used, and the final sulfur content was ≤0.015% after the treatment.

3. The method for smelting low-carbon, low-silicon aluminum-containing steel according to claim 1, characterized in that, During the converter smelting stage, aluminum alloy, slag-forming material, ferromanganese, and deoxidizer are sequentially added to the ladle during the tapping process to carry out deoxidation and slag formation.

4. The method for smelting low-carbon, low-silicon aluminum-containing steel according to claim 3, characterized in that, The slag-forming materials are refined synthetic slag and lime, and the slag washing process is adopted in the steel tapping process.

5. The method for smelting low-carbon, low-silicon aluminum-containing steel according to claim 3, characterized in that, The deoxidizer is calcium carbide or silicon carbide.

6. The method for smelting low-carbon, low-silicon aluminum-containing steel according to claim 3, characterized in that, Aluminum alloy is added when the converter taps 1 ton of steel; slag-forming material is added when tapping 2 tons of steel, followed by high-carbon ferromanganese alloy; deoxidizer is added when tapping 3 tons of steel. W1 < W2 < W3.

7. The method for smelting low-carbon, low-silicon aluminum-containing steel according to claim 1, characterized in that, During the converter smelting stage, the argon flow rate is controlled at 300-400 NL / min after the steel tapping is completed, and the stirring time is greater than 2 minutes.

8. The method for smelting low-carbon, low-silicon aluminum-containing steel according to claim 1, characterized in that, During the LF refining stage, after the ladle is hoisted to the LF refining furnace, the initial bottom blowing flow rate is adjusted to 150-200 NL / min to break the slag layer for temperature measurement and sampling.

9. The method for smelting low-carbon, low-silicon aluminum-containing steel according to claim 1, characterized in that, During the LF refining stage, no more slag-forming materials are added to the LF refining furnace.

10. The method for smelting low-carbon, low-silicon aluminum-containing steel according to claim 1, characterized in that, During the LF refining stage, the power supply time is controlled within 10 minutes according to the inlet temperature. Once the composition and temperature are qualified, the ladle car is driven to the soft blowing position for calcium treatment. After the soft blowing is completed, the ladle is hoisted to the continuous casting machine for casting.

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