A continuous casting mold powder and a preparation method thereof

Abstract

This application relates to a continuous casting mold flux and its preparation method, belonging to the field of metallurgical materials technology. The chemical composition of the mold flux, by mass fraction, is as follows: Ta₂O₅: 1%~5%, CaO: 38.90%~40.80%, B₂O₃: 20%~25%, CaF₂: 6.50%~8.30%, MgO: 8%~10%, SiO₂: 4.30%~5.80%, Al₂O₃: 4.80%~5.60%, MnO: 3.50%~4.60%, with the remainder being unavoidable impurities. By rationally proportioning the components Ta₂O₅, CaO, B₂O₃, and CaF₂, a low-reactivity slag system structure is formed, enabling the mold flux to effectively suppress interfacial reactions and maintain stable performance during continuous casting. Pilot-scale and industrial tests show that this mold flux has a stable consumption rate and excellent lubrication performance, with an average heat flux density of 1.45 MW / m³. 2 It can achieve uniform heat transfer control, significantly improve the surface quality of slabs, and ensure the smooth operation of continuous casting process.

Description

Technical Field

[0001] This application relates to the field of metallurgical materials technology, and in particular to a protective slag for continuous casting crystallizers and its preparation method. Background Technology

[0002] In continuous casting of steel, the mold flux is crucial for ensuring the quality of the cast billet and the smooth operation of the process. However, during the continuous casting of high-alumina steel, the aluminum element in the steel reacts violently with components such as silicon dioxide in the mold flux, causing the composition and properties of the mold flux to deteriorate rapidly during the casting process. This not only leads to defects such as surface cracks and inclusions on the cast billet, but also easily causes blockage of the casting nozzle, seriously restricting the high-quality production of high-alumina steel.

[0003] To address this challenge, existing technologies have explored various protective slag design approaches, such as reducing SiO2 content to suppress the reaction or shifting to non-reactive calcium-aluminum-based slag systems. However, these solutions struggle to balance performance stability with process requirements: low-silicon designs often require the introduction of other fluxing components, which can introduce new risks such as slag entrapment; while calcium-aluminum-based systems can improve compositional stability, their inherent high crystallinity can lead to poor lubrication, and reaction consumption can still cause alkalinity imbalance, ultimately affecting heat transfer control and smooth casting. Summary of the Invention

[0004] This application provides a continuous casting mold flux and its preparation method to solve the following technical problem: how to prepare a continuous casting mold flux that can effectively suppress the slag-gold interface reaction during the continuous casting process of high-alumina steel.

[0005] In the first aspect, embodiments of this application provide a continuous casting mold flux, the chemical composition of which, by mass fraction, is: Ta2O5: 1%~5%, CaO: 38.90%~40.80%, B2O3: 20%~25%, CaF2: 6.50%~8.30%, MgO: 8%~10%, SiO2: 4.30%~5.80%, Al2O3: 4.80%~5.60%, MnO: 3.50%~4.60%, with the remainder being unavoidable impurities.

[0006] Optionally, the ternary basicity of the protective slag, CaO / (SiO2+Al2O3), is 3.40~4.48.

[0007] Optionally, the properties of the protective slag include at least one of the following: softening temperature of 985℃~1012℃, melting point of 1030℃~1164℃, viscosity of 0.08Pa·s~0.25Pa·s at 1300℃, and crystallization rate of 49%~63%.

[0008] Secondly, embodiments of this application provide a method for preparing the protective slag described in the first aspect, the method comprising: A mixture with the following chemical composition was obtained: Ta2O5: 1%~5%, CaO: 38.90%~40.80%, B2O3: 20%~25%, CaF2: 6.50%~8.30%, MgO: 8%~10%, SiO2: 4.30%~5.80%, Al2O3: 4.80%~5.60%, MnO: 3.50%~4.60%, with the remainder being unavoidable impurities; The mixture is melted and cooled sequentially to obtain a glassy protective slag block. The glassy protective slag block is dried and crushed sequentially to obtain the protective slag.

[0009] Optionally, the melting is carried out in a medium-frequency induction furnace, and the melting temperature is 200°C to 300°C higher than the melting point of the protective slag.

[0010] Optionally, the holding time for melting is 1.0h to 1.5h.

[0011] Optionally, the cooling is carried out by water quenching and rapid cooling, and the temperature of the cooling water is 15℃~25℃.

[0012] Optionally, the drying temperature is 105℃~120℃, and the drying time is 2h~4h.

[0013] Optionally, the moisture content of the dried glassy protective slag block is ≤2%.

[0014] Optionally, the crushing is carried out using a jaw crusher and a disc crusher.

[0015] The technical solutions provided in this application have the following advantages compared with the prior art: This application provides a continuous casting mold flux, whose chemical composition, by mass fraction, is as follows: Ta₂O₅: 1%~5%, CaO: 38.90%~40.80%, B₂O₃: 20%~25%, CaF₂: 6.50%~8.30%, MgO: 8%~10%, SiO₂: 4.30%~5.80%, Al₂O₃: 4.80%~5.60%, MnO: 3.50%~4.60%, with the remainder being unavoidable impurities. Through a synergistic composition design strategy, a novel slag system with thermodynamic stability and optimized physical properties is constructed to fundamentally solve the problem of flux performance instability caused by intense slag-metal interface reactions during high-alumina steel continuous casting. By significantly reducing the SiO₂ content to a low level of 4.30%~5.80%, the primary reduction target of aluminum in the molten steel is significantly reduced, weakening the driving force of the interface reaction at its source. Building upon this foundation, 1%–5% Ta₂O₅ is innovatively introduced as an inert and stable network former. The resistance of Ta₂O₅ to aluminum reduction helps form a barrier at the slag-metal interface, further isolating the molten steel and stabilizing the slag structure. To achieve a performance balance, a basic slag system is constructed using 38.90 wt%–40.80 wt% CaO and 20 wt%–25 wt% B₂O₃. B₂O₃, as a low-reactivity network former, partially replaces the function of SiO₂. Simultaneously, the addition of 6.50 wt%–8.30 wt% CaF₂ and 3.50 wt%–4.60 wt% MnO as potent fluxes ensures the slag possesses good fluidity and spreadability to fulfill its lubrication function; while the addition of 8 wt%–10 wt% MgO is used to suppress excessive crystallization and improve the heat transfer and lubrication properties of the slag film. In addition, the Al2O3 content is pre-set at 4.80%~5.60% to enable the slag system to have the initial capacity to accommodate the additional Al2O3 that may be generated in the reaction, thus buffering the component impact brought by this additional Al2O3.

[0016] In summary, this technical solution, through multiple mechanisms such as reducing the content of reducible oxides, introducing highly stable components, constructing a low-reactivity basic slag system, and synergistically optimizing fluxing and crystallization behavior, jointly ensures the stability of the composition and performance of the protective slag throughout the continuous casting process, thereby effectively suppressing slag-metal interface reactions. Attached Figure Description

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

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

[0019] Figure 1 A flowchart illustrating a continuous casting mold flux and its preparation method, provided as an embodiment of this application. Detailed Implementation

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

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

[0022] In the first aspect, embodiments of this application provide a continuous casting mold flux, the chemical composition of which, by mass fraction, is: Ta2O5: 1%~5%, CaO: 38.90%~40.80%, B2O3: 20%~25%, CaF2: 6.50%~8.30%, MgO: 8%~10%, SiO2: 4.30%~5.80%, Al2O3: 4.80%~5.60%, MnO: 3.50%~4.60%, with the remainder being unavoidable impurities.

[0023] The positive effects of limiting the mass fraction of Ta2O5 to 1%~5% include: Ta2O5, with its excellent chemical and high-temperature stability, effectively inhibits the performance degradation of the protective slag, stabilizes the slag layer structure, and thus significantly slows down the interfacial reaction between the high-alumina steel melt and the protective slag, ensuring smooth casting. The addition of even a small amount of Ta2O5 can significantly alter the crystallization behavior of the protective slag. The precipitated phase formed by Ta2O5 can replace the traditional gunmetal phase mainly formed by CaF2, which is beneficial for optimizing the performance of the protective slag. Simultaneously, the introduction of Ta2O5 can reduce the amount of CaF2 used; for example, 1%~3% Ta2O5 can reduce the amount of CaF2 added by about half. This not only helps maintain the necessary slag system performance but also plays a positive environmental role in reducing fluorine pollution. In summary, the addition of Ta2O5, through multiple mechanisms such as stabilizing the slag structure, inhibiting crystallization, and reducing fluorine content, synergistically ensures the performance stability of the protective slag during use. For example, the mass fraction of Ta2O5 can be 1%, 2%, 3%, 4%, 5%, etc.

[0024] The positive effects of limiting the CaO mass fraction to 38.90%~40.80% are as follows: CaO, as a major component of the protective slag, maintains a relatively high content. This positioning allows CaO to play multiple key roles: effectively reducing the viscosity of the protective slag and improving its fluidity; it also has a strong ability to absorb oxide inclusions at the steel-slag interface. Most importantly, in the continuous casting environment of high-alumina steel, CaO does not react with aluminum in the molten steel. This characteristic fundamentally avoids fluctuations in the protective slag composition caused by slag-metal reactions, thus ensuring stable performance of the protective slag during operation. For example, the CaO mass fraction can be 38.9%, 39.1%, 39.3%, 39.5%, 39.7%, 39.9%, 40.1%, 40.3%, 40.5%, 40.7%, etc.

[0025] The positive effects of limiting the mass fraction of B2O3 to 20%~25% include: utilizing the properties of B2O3 to effectively lower the melting point and high-temperature viscosity of the protective slag, and suppressing its crystallization tendency, thereby optimizing the slag's fluidity and glassy stability. Simultaneously, B2O3 can partially replace the network-forming function of SiO2 and Al2O3, enhancing the heat transfer uniformity and controllability of the solidified billet shell while maintaining the protective slag. For example, the mass fraction of B2O3 can be 20%, 21%, 22%, 23%, 24%, 25%, etc.

[0026] The positive effects of limiting the mass fraction of CaF2 to 6.50%~8.30%: Due to its inherent low reactivity, CaF2 is selected as one of the main fluxing agents. The addition of CaF2 can effectively depolymerize the complex silicate network structure in the slag, thereby significantly reducing the high-temperature viscosity of the slag. Simultaneously, the introduction of CaF2 inhibits the premature precipitation of the high-melting-point phase CaO, resulting in a corresponding decrease in the inflection point temperature of the viscosity-temperature curve, further optimizing the melting and solidification behavior of the protective slag. For example, the mass fraction of CaF2 can be 6.50%, 6.80%, 7.10%, 7.40%, 7.70%, 8.00%, 8.30%, etc.

[0027] The positive effects of limiting the mass fraction of MgO to 8%~10%: As an alkaline earth metal oxide, MgO provides O₂. 2- It can effectively reduce the network polymerization degree of the protective slag melt structure, thereby reducing the migration resistance between particles during crystallization and promoting a decrease in crystallization temperature. Simultaneously, increasing the MgO content can prolong the crystallization incubation time, which is beneficial for forming a uniform and stable crystalline slag film in the crystallizer, promoting uniform heat transfer, and inhibiting excessive slag ring formation. Furthermore, an appropriate amount of MgO helps enhance the protective slag's ability to maintain a glassy state during cooling, i.e., improving the glassy stability of the protective slag, which has a positive effect on improving the lubrication performance between the billet and the crystallizer. For example, the mass fraction of MgO can be 8%, 9%, 10%, etc.

[0028] The positive effects of limiting the SiO2 mass fraction to 4.30%~5.80%: SiO2 is the main basic component of traditional protective slag, and the physicochemical properties of the protective slag are mainly determined by the silicate network structure. As the SiO2 content decreases and the CaF2 content increases accordingly, the crystallization temperature of the protective slag gradually decreases, while the crystallization ability of the protective slag increases, and the relative crystallinity increases accordingly. For example, the SiO2 mass fraction can be 4.40%, 4.60%, 4.80%, 5.00%, 5.20%, 5.40%, 5.60%, 5.80%, etc.

[0029] The positive effects of limiting the Al2O3 mass fraction to 4.80%~5.60%: Al2O3 acts as a network former in weakly alkaline protective slag containing an appropriate amount of metal oxides, inhibiting crystal precipitation through a "chain-forming" effect, thereby improving the glass properties of the protective slag. However, when the Al2O3 content is too high and the metal oxide content is relatively insufficient, some Al2O3 will transform into network exosomes, promoting the precipitation of feldspar, which exists in the form of solid particles, leading to a deterioration of the glass properties of the protective slag. Therefore, by reasonably controlling the Al2O3 mass fraction, Al2O3 can stably perform its network former function, ensuring the structural stability of the protective slag in different temperature ranges, thereby achieving good lubrication and controllable heat transfer. For example, the Al2O3 mass fraction can be 4.80%, 5.00%, 5.20%, 5.40%, 5.60%, etc.

[0030] The positive effects of limiting the mass fraction of MnO to 3.50%~4.60%: As an alkaline oxide in the protective slag, MnO can effectively depolymerize the network structure of the protective slag, thereby reducing its viscosity. The effect of MnO is similar to that of the commonly used alkaline oxide Na2O. However, in the continuous casting process of conventional steel grades, the addition of MnO will lower the solidification (turning point) temperature of the protective slag, resulting in a thinner solid slag film and weakening the slag film's control over heat transfer in the meniscus region. Especially under the continuous casting conditions of high-alumina steel, due to the strong reducing properties of MnO, MnO in the slag will preferentially react with aluminum in the steel than SiO2. This reduces the degree to which SiO2 participates in the slag-steel reaction, and the low-melting-point compounds such as MnO-SiO2 and 2MnO·SiO2 generated by the reaction help to slow down the further reduction reaction of [Al], thereby inhibiting the deterioration of the protective slag viscosity and other physical properties. For example, the mass fraction of MnO can be 3.50%, 3.70%, 3.90%, 4.10%, 4.30%, 4.50%, etc.

[0031] In some embodiments, the ternary basicity of the protective slag, CaO / (SiO2+Al2O3), is 3.40~4.48.

[0032] The protective slag employs an ultra-high basicity ternary system design. By controlling the SiO2 content at a relatively low level of 4.3%~5.8%, the degree of reaction between aluminum in the molten steel and SiO2 in the protective slag during the casting of high-alumina steel is effectively reduced. This composition design helps avoid a significant decrease in SiO2 content and a sharp increase in Al2O3 caused by the reaction, thereby preventing drastic fluctuations in key properties such as melting point and viscosity of the protective slag and maintaining its operational stability. For example, the ternary basicity CaO / (SiO2+Al2O3) of the protective slag can be 3.40, 3.60, 3.80, 4.00, 4.20, 4.40, etc.

[0033] In some embodiments, the protective slag has the following properties: softening temperature of 985℃~1012℃, melting point of 1030℃~1164℃, viscosity of 0.08Pa·s~0.25Pa·s at 1300℃, and crystallization rate of 49%~63%.

[0034] Softening temperature: This refers to the temperature at which the protective slag begins to lose its original shape and soften during the heating process. A softening temperature between 985℃ and 1012℃ ensures that the protective slag melts promptly at the meniscus of the molten steel in the crystallizer, forming a reasonable molten structure, thereby stably providing liquid slag to lubricate the billet shell. Examples of softening temperatures include 985℃, 995℃, and 1005℃. Melting point: The temperature at which the protective slag completely transforms into a homogeneous liquid. A melting point between 1030℃ and 1164℃ ensures that the protective slag can completely melt under the operating temperature environment of the crystallizer, forming a liquid slag layer with appropriate fluidity, thereby effectively flowing into the space between the billet shell and the copper tube to form a lubricating slag film. Examples of melting points include 1030℃, 1050℃, 1070℃, 1090℃, 1110℃, 1130℃, and 1150℃. Viscosity: An indicator measuring the magnitude of internal frictional resistance in a fluid, i.e., the viscosity of the fluid. A viscosity of 0.08 Pa·s to 0.25 Pa·s at 1300℃ is ideal for lubrication. Lower viscosity ensures smooth flow and uniform distribution of the molten slag, forming a continuous and stable slag film that provides good lubrication and prevents the billet shell from sticking to the crystallizer. Simultaneously, viscosity also affects the slag's ability to absorb and dissolve floating inclusions. For example, viscosities at 1300℃ can be 0.08 Pa·s, 0.11 Pa·s, 0.14 Pa·s, 0.17 Pa·s, 0.20 Pa·s, and 0.23 Pa·s. Crystallization rate: This refers to the proportion of crystalline phase precipitated during the cooling and solidification process of the protective slag. A crystallization rate between 49% and 63% indicates that the protective slag tends to crystallize during cooling. This effectively increases the thermal flow resistance of the solidified slag film, thereby controlling and homogenizing heat transfer from the high-temperature billet to the water-cooled crystallizer, which is crucial for preventing surface cracking of the billet. At the same time, it is also necessary to balance other components (such as B2O3) to ensure that the crystallization properties do not excessively degrade the plasticity required for lubrication. For example, the crystallization rate can be 51%, 54%, 57%, 60%, 63%, etc.

[0035] Figure 1 A flowchart illustrating a continuous casting mold flux and its preparation method, provided as an embodiment of this application.

[0036] Please see Figure 1 Secondly, this application provides a method for preparing the protective slag described in the first aspect, the method comprising: S1. A mixture having the following chemical composition is obtained: Ta2O5: 1%~5%, CaO: 38.90%~40.80%, B2O3: 20%~25%, CaF2: 6.50%~8.30%, MgO: 8%~10%, SiO2: 4.30%~5.80%, Al2O3: 4.80%~5.60%, MnO: 3.50%~4.60%, with the remainder being unavoidable impurities; S2. The mixture is melted and cooled sequentially to obtain a glassy protective slag block; S3. The glassy protective slag block is dried and crushed in sequence to obtain protective slag.

[0037] In some embodiments, the melting is carried out in a medium-frequency induction furnace, and the melting temperature is 200°C to 300°C higher than the melting point of the protective slag.

[0038] Melting is carried out in a medium-frequency induction furnace, which utilizes the electromagnetic induction principle of the furnace to achieve rapid and uniform heating of the material, avoiding localized overheating or component segregation, thereby ensuring sufficient chemical reactions between the components. The melting temperature is 200℃~300℃ higher than the melting point of the protective slag. This serves two purposes: first, it provides sufficient thermodynamic driving force to completely melt all components (especially refractory materials) and form a highly homogeneous liquid phase; second, it promotes the effective removal of gases and volatile components, obtaining a pure and dense melt, laying the structural foundation for the subsequent formation of a stable glassy protective slag. For example, the melting temperature can be 1230℃, 1277℃, 1324℃, 1371℃, 1418℃, 1464℃, etc.

[0039] In some embodiments, the holding time for melting is 1.0h to 1.5h.

[0040] The holding time for melting is between 1.0 h and 1.5 h to ensure sufficient diffusion and melting of all components, achieving complete homogenization and eliminating segregation. This process helps form a uniform glassy or microcrystalline structure, avoiding viscosity abrupt changes or lubrication failure caused by structural inhomogeneity during subsequent use. Simultaneously, sufficient holding time promotes the full reaction of fluxes (such as B2O3 and CaF2) with the main components, forming a stable silicate / borate composite structure. This ensures the stability of the melting point, viscosity, crystallization rate, melting rate, and heat transfer characteristics of the protective slag, ultimately meeting the comprehensive performance requirements for lubrication, heat preservation, and inclusion absorption during continuous casting. For example, the holding time for melting can be 1.0 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, etc.

[0041] In some embodiments, the cooling is performed by water quenching, and the temperature of the cooling water is 15°C to 25°C.

[0042] The cooling water temperature is between 15℃ and 25℃, which not only creates a sufficient temperature gradient with the high-temperature molten slag to achieve rapid cooling and suppress crystalline phase formation, promoting the formation of an amorphous glassy structure in the slag, but also avoids problems such as boiling and splashing due to excessively high water temperature or freezing and clogging of pipelines due to excessively low water temperature, thus ensuring the safety and stability of the water quenching process. Furthermore, this temperature range is close to room temperature, making it readily available and cost-effective, meeting the practical requirements of industrial production. For example, the cooling water temperature can be 15℃, 17℃, 19℃, 21℃, 23℃, 25℃, etc.

[0043] In some embodiments, the drying temperature is 105°C to 120°C, and the drying time is 2 hours to 4 hours.

[0044] The drying temperature is between 105℃ and 120℃, which effectively removes free moisture from the water-quenched slag while preventing the oxidation of low-valence oxides or the transformation of the glassy structure to a crystalline state caused by excessively high temperatures. This ensures the fluidity and stable performance of the protective slag during subsequent grinding. Simultaneously, this temperature range prevents the slag from softening and sticking due to overheating, effectively avoiding clumping after drying. For example, drying temperatures can be 105℃, 108℃, 111℃, 114℃, 117℃, 120℃, etc.

[0045] The drying time is between 2 and 4 hours, which ensures that the free moisture in the water-quenched slag is completely removed, while avoiding energy waste and equipment heat loss caused by excessive drying time. It also prevents the glassy structure of the protective slag from crystallizing or being oxidized by low-valence oxides. This duration also ensures that the dried material remains loose and free of lumps, thus meeting the feeding requirements of subsequent grinding processes. For example, the drying time can be 2 hours, 3 hours, or 4 hours.

[0046] In some embodiments, the moisture content of the dried glassy protective slag block is ≤2%.

[0047] The moisture content of the dried glassy protective slag lumps is ≤2%, ensuring the smooth progress of subsequent crushing processes and guaranteeing the physical and chemical stability of the final protective slag powder. For example, the moisture content of the dried glassy protective slag lumps can be 0.5%, 1.0%, 1.5%, 2.0%, etc.

[0048] In some embodiments, the crushing is carried out using a jaw crusher and a disc crusher.

[0049] Crushing is carried out using a jaw crusher and a disc mill, achieving efficient preparation of uniform powder from lumpy slag through two-stage crushing. The jaw crusher first coarsely crushes the dried glassy slag blocks, breaking them into small particles suitable for subsequent processing; the disc mill then finely grinds the coarsely crushed particles, ultimately obtaining a protective slag powder with uniform particle size and good flowability.

[0050] The product prepared by the preparation method of the protective slag is the above-mentioned protective slag. Since the preparation method of the protective slag adopts some or all of the technical solutions of the protective slag embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above-mentioned embodiments, which will not be repeated here.

[0051] 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.

[0052] The chemical composition (mass percentage / %) of the examples and comparative examples is shown in Table 1.

[0053] Table 1

[0054] Example 1 A mixture of the chemical components described in Example 1 in Table 1 was obtained; The mixture was melted in a medium-frequency induction furnace at a temperature of 1297℃ for 1.2 hours. The melted mixture was then cooled by water quenching at a temperature of 25℃ to obtain a glassy protective slag block. The glassy protective slag blocks were dried at 110℃ for 3 hours to obtain glassy protective slag blocks with a moisture content of 1.5%. Finally, the glassy protective slag blocks were crushed using a jaw crusher and a disc crusher to obtain protective slag.

[0055] Example 2 A mixture of the chemical components described in Example 2 of Table 1 was obtained; The mixture was melted in a medium-frequency induction furnace at a temperature of 1351℃ for 1 hour. The melted mixture was then cooled by water quenching at a temperature of 25℃ to obtain a glassy protective slag block. The glassy protective slag blocks were dried at 120℃ for 3 hours to obtain glassy protective slag blocks with a moisture content of 1.2%. Finally, the glassy protective slag blocks were crushed using a jaw crusher and a disc crusher to obtain protective slag.

[0056] Example 3 A mixture of the chemical components described in Example 3 of Table 1 was obtained; The mixture was melted in a medium-frequency induction furnace at a temperature of 1355℃ for 1.5 hours. The melted mixture was then cooled by water quenching at a temperature of 25℃ to obtain a glassy protective slag block. The glassy protective slag block was dried at 120℃ for 3.5 hours to obtain a glassy protective slag block with a moisture content of 1.0%. Finally, the glassy protective slag block was crushed using a jaw crusher and a disc crusher to obtain the protective slag.

[0057] Example 4 A mixture of the chemical components described in Example 4 of Table 1 was obtained; The mixture was melted in a medium-frequency induction furnace at a temperature of 1250℃ for 1 hour. The melted mixture was then cooled by water quenching at a temperature of 20℃ to obtain a glassy protective slag block. The glassy protective slag blocks were dried at 110℃ for 4 hours to obtain glassy protective slag blocks with a moisture content of 0.9%. Finally, the glassy protective slag blocks were crushed using a jaw crusher and a disc crusher to obtain protective slag.

[0058] Example 5 A mixture of the chemical components described in Example 5 of Table 1 was obtained; The mixture was melted in a medium-frequency induction furnace at a temperature of 1385℃ for 1.2 hours. The melted mixture was then cooled by water quenching at a temperature of 20℃ to obtain a glassy protective slag block. The glassy protective slag blocks were dried at 115℃ for 3 hours to obtain glassy protective slag blocks with a moisture content of 1.2%. Finally, the glassy protective slag blocks were crushed using a jaw crusher and a disc crusher to obtain protective slag.

[0059] Comparative Example 1 A mixture of the chemical components described in Comparative Example 1 in Table 1 was obtained; The mixture was melted in a medium-frequency induction furnace at a temperature of 1280℃ for 1.5 hours. The melted mixture was then cooled by water quenching at a temperature of 20℃ to obtain a glassy protective slag block. The glassy protective slag blocks were dried at 110℃ for 3.5 hours to obtain glassy protective slag blocks with a moisture content of 1%. Finally, the glassy protective slag blocks were crushed using a jaw crusher and a disc crusher to obtain protective slag.

[0060] Comparative Example 2 A mixture of the chemical components described in Comparative Example 2 in Table 1 was obtained; The mixture was melted in a medium-frequency induction furnace at a temperature of 1350℃ for 1.2 hours. The melted mixture was then cooled by water quenching at a temperature of 25℃ to obtain a glassy protective slag block. The glassy protective slag blocks were dried at 110℃ for 3 hours to obtain glassy protective slag blocks with a moisture content of 1.2%. Finally, the glassy protective slag blocks were crushed using a jaw crusher and a disc crusher to obtain protective slag.

[0061] The performance of the embodiments and comparative examples is shown in Table 2.

[0062] Table 2

[0063] The data tables above provide a clear comparison of the differences between various embodiments and comparative examples. The following conclusions can be drawn: As can be seen from the data in Table 2, the protective slag provided in the embodiments of this application has a softening temperature of 985℃~1011℃, a melting point of 1045℃~1153℃, a viscosity of 0.08Pa·s~0.25Pa·s at 1300℃, and a crystallization rate of 51%~63%.

[0064] As can be seen from Examples 1-5 and Comparative Examples 1-2, Examples 1-5 successfully stabilized the softening temperature, melting point, high-temperature viscosity, and crystallization rate of the protective slag within a suitable range for continuous casting by controlling the Ta2O5 content to 3.4wt%~5.0wt% and synergistically regulating the proportions of components such as CaO, B2O3, and CaF2. This achieved a balance between lubrication, heat transfer control, and inclusion absorption capabilities. However, Comparative Example 1, due to its excessively low Ta2O5 content (0.1wt%), essentially failed to inhibit crystallization. Furthermore, because the CaO, B2O3, and CaF2 contents were all above the upper limit of the protective range, the viscosity of the protective slag was too low, resulting in insufficient stability against interfacial reactions and a tendency to cause slag entrapment during casting. Comparative Example 2, with its excessively high Ta2O5 content (8.7wt%), showed a significantly reduced crystallization rate, and the low contents of B2O3 and CaO resulted in excessively high high-temperature viscosity, which easily deteriorated lubrication performance. Furthermore, the B2O3 content needs to be maintained between 22.8wt% and 24.9wt%. Too low a content can lead to excessively high viscosity of the protective slag, while too high a content may result in excessively low viscosity. Simultaneously, when the ternary basicity falls below the lower limit, it significantly weakens the protective slag's ability to absorb inclusions.

[0065] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages: The continuous casting mold flux provided in this invention significantly suppresses the slag-metal interface reaction during the continuous casting of high-alumina steel through optimized component design, thereby ensuring the high stability of the chemical composition and high-temperature physicochemical properties of the mold flux throughout the entire casting cycle. Simultaneously, this design effectively coordinates the melting characteristics, lubrication properties, and crystallization behavior of the mold flux, enabling it to form a uniform and stable slag film within the mold. This achieves excellent control over the solidification heat transfer of the cast billet, significantly improving the surface quality of the billet, reducing the risk of cracks and inclusions, and also helping to reduce fluoride volatilization, demonstrating better environmental characteristics. Ultimately, this provides a reliable guarantee for the efficient and smooth continuous casting of high-alumina steel.

[0066] 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 protective slag for a continuous casting crystallizer, characterized in that, The chemical composition of the protective slag, by mass fraction, is as follows: Ta2O5: 1%~5%, CaO: 38.90%~40.80%, B2O3: 20%~25%, CaF2: 6.50%~8.30%, MgO: 8%~10%, SiO2: 4.30%~5.80%, Al2O3: 4.80%~5.60%, MnO: 3.50%~4.60%, with the remainder being unavoidable impurities.

2. The protective slag according to claim 1, characterized in that, The ternary basicity of the protective slag, CaO / (SiO2+Al2O3), is 3.40~4.

48.

3. The protective slag according to claim 1, characterized in that, The properties of the protective slag include at least one of the following: softening temperature of 985℃~1012℃, melting point of 1030℃~1164℃, viscosity of 0.08Pa·s~0.25Pa·s at 1300℃, and crystallization rate of 49%~63%.

4. A method for preparing the protective slag according to any one of claims 1 to 3, characterized in that, The method includes: A mixture having the chemical composition described in any one of claims 1 to 3 is obtained; The mixture is melted and cooled sequentially to obtain a glassy protective slag block. The glassy protective slag block is dried and crushed sequentially to obtain the protective slag.

5. The method according to claim 4, characterized in that, The melting is carried out in a medium-frequency induction furnace, and the melting temperature is 200°C to 300°C higher than the melting point of the protective slag.

6. The method according to claim 4, characterized in that, The holding time for melting is 1.0h to 1.5h.

7. The method according to claim 4, characterized in that, The cooling is performed by water quenching and rapid cooling, and the temperature of the cooling water is 15℃~25℃.

8. The method according to claim 4, characterized in that, The drying temperature is 105℃~120℃, and the drying time is 2h~4h.

9. The method according to claim 4, characterized in that, The moisture content of the dried glassy protective slag block is ≤2%.

10. The method according to claim 4, characterized in that, The crushing process is carried out using a jaw crusher and a disc crusher.

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