A continuous casting method of high manganese alloy steel slab

Abstract

This application relates to a continuous casting production method for high-manganese alloy steel slabs, belonging to the field of steel preparation technology. The method includes: casting molten high-manganese alloy steel with a predetermined chemical composition, starting the casting machine, and increasing the casting speed from zero to a target speed with controlled acceleration to obtain a stable casting flow state; introducing the molten high-manganese alloy steel in the stable casting flow state into a crystallizer with a predetermined taper ratio for initial solidification to obtain a slab with a uniform initial shell; during the initial solidification process, continuously adding a low-basicity protective slag to the crystallizer, and controlling the addition method of the low-basicity protective slag; sending the slab that has completed the initial solidification into the secondary cooling zone of the continuous casting machine, and performing segmented cooling of the slab according to a predetermined non-uniform cooling intensity distribution, so that the surface temperature history of the slab avoids the high-temperature brittleness range of high-manganese alloy steel, thereby obtaining a high-manganese alloy steel slab.

Description

Technical Field

[0001] This application relates to the field of steel preparation technology, and in particular to a continuous casting production method for high manganese alloy steel slabs. Background Technology

[0002] High-manganese alloy steel, typically referring to austenitic alloy steel with a manganese content greater than 10%, is renowned for its excellent work hardening ability, good wear resistance, and toughness. Developing stable and efficient production technologies for high-manganese alloy steel billets is of great significance for upgrading downstream industrial chains.

[0003] For a long time, the production of high-manganese alloy steel billets has mainly relied on ingot casting. While ingot casting offers simple equipment and flexible processes, its inherent drawbacks are also significant: low production efficiency, poor billet quality consistency, low yield, high energy consumption, and inability to integrate with modern high-efficiency continuous rolling production lines. In contrast, continuous casting technology offers significant advantages such as high production efficiency, low energy consumption, uniform and stable billet quality, and ease of automation, making it a core component of modern steel production. However, applying continuous casting technology to high-manganese alloy steel faces considerable technical challenges. High-manganese alloy steel is characterized by low thermal conductivity, large solidification shrinkage, a low liquidus line, and a wide solid-liquid two-phase region. Due to its high crack sensitivity, it is prone to leaks during casting, and cracks easily appear on the surface of continuously cast billets, affecting user performance. Summary of the Invention

[0004] This application provides a continuous casting production method for high manganese alloy steel slabs to solve the following technical problem: how to solve the problem of cracks easily occurring in the continuous casting production of high manganese alloy steel slabs.

[0005] This application provides a continuous casting production method for high-manganese alloy steel slabs, the method comprising:

[0006] The high-manganese alloy steel liquid with a set chemical composition is cast and started, and the billet speed is increased from zero to the target speed with controlled acceleration, so that the high-manganese alloy steel liquid obtains a stable casting flow state.

[0007] The high-manganese alloy steel liquid in a stable casting flow state is introduced into a crystallizer with a set taper ratio, so that the high-manganese alloy steel liquid undergoes initial solidification in the crystallizer and forms a billet with a uniform initial shell; during the initial solidification process, a low-basicity protective slag is continuously added to the crystallizer, and the method of adding the low-basicity protective slag is controlled.

[0008] The billet that has completed the initial solidification is sent to the secondary cooling zone of the continuous casting machine, and the billet is cooled in stages according to the set non-uniform cooling intensity distribution, so that the surface temperature history of the billet avoids the high temperature brittle range of high manganese alloy steel, and a high manganese alloy steel slab is obtained.

[0009] Optionally, the controlled acceleration 'a' satisfies the following formula: a = -0.05t + 0.175, where t represents the time after the casting machine starts. If the unit of t is min, then the unit of a is m / min. 2 The unit steel throughput at the target drawing speed is 1.5 tons / minute to 3.3 tons / minute.

[0010] Optionally, the ratio B / A of the taper coefficient A of the wide copper plate and the taper coefficient B of the narrow copper plate in the crystallizer is 1.2; wherein the value of the taper coefficient A of the wide copper plate ranges from 1.25% to 1.45%.

[0011] Optionally, during the initial solidification process, a weak cooling mode is implemented for the crystallizer. The weak cooling mode is achieved by controlling the cooling water flow rate in the copper plate of the crystallizer to be 4 m / s to 6 m / s, and the temperature difference between the cooling water at the inlet and outlet of the copper plate of the crystallizer is ≤9℃.

[0012] Optionally, the binary basicity R of the low-alkalinity protective slag is 0.6 to 0.9;

[0013] The low-alkalinity protective slag contains MnO2 and Li2O.

[0014] The mass fraction of MnO2 is 4% to 9%, and the mass fraction of Li2O satisfies the following relationship: [Li2O] = 1.05·[MnO2] - 3.8%, where [Li2O] represents the mass fraction of Li2O in the low-alkalinity protective slag, and [MnO2] represents the mass fraction of MnO2 in the low-alkalinity protective slag.

[0015] Optionally, the low-alkalinity protective slag is added at a frequency of 5 to 10 times per minute, with each addition being 100g to 280g.

[0016] Optionally, the non-uniform cooling intensity distribution is configured as follows: a strong cooling section, a first medium-strong cooling section, a weak cooling section, and a second medium-strong cooling section are sequentially arranged along the casting direction; wherein, the strong cooling section corresponds to the foot roll section of the continuous casting machine, the first medium-strong cooling section corresponds to the vertical section of the continuous casting machine, the weak cooling section corresponds to the curved section, the arc section, and the straightening section of the continuous casting machine, and the second medium-strong cooling section corresponds to the horizontal section of the continuous casting machine.

[0017] Optionally, the cooling water flow rate of the narrow-face foot roller in the strong cooling section is 180 NL / min to 260 NL / min;

[0018] The specific water volume of both the first and second medium-intensity cooling sections is 0.7 L / kg to 0.9 L / kg;

[0019] The specific water volume of the weak cooling section is 0.3L / kg to 0.5L / kg.

[0020] Optionally, the composition of the high-manganese alloy molten steel, by mass fraction, includes: Mn: 10% to 35%, C: 0.1% to 1.2%.

[0021] Optionally, the specifications of the high manganese alloy steel slab are: thickness 200mm to 400mm, width 1800mm to 3000mm.

[0022] The technical solutions provided in this application have the following advantages compared with the prior art:

[0023] This application provides a continuous casting production method for high-manganese alloy steel slabs. The method includes: casting and starting a high-manganese alloy steel molten steel with a set chemical composition, and increasing the casting speed from zero to a target casting speed with controlled acceleration to achieve a stable casting flow state for the high-manganese alloy steel molten steel; introducing the high-manganese alloy steel molten steel in a stable casting flow state into a crystallizer with a set taper ratio, allowing the high-manganese alloy steel molten steel to undergo initial solidification in the crystallizer and form a slab with a uniform initial shell; continuously adding low-basicity protective slag to the crystallizer during the initial solidification process, and controlling the addition method of the low-basicity protective slag; sending the slab that has completed the initial solidification into the secondary cooling zone of the continuous casting machine, and performing segmented cooling on the slab according to a set non-uniform cooling intensity distribution, so that the surface temperature history of the slab avoids the high-temperature brittle range of high-manganese alloy steel, thereby obtaining a high-manganese alloy steel slab. To address the characteristics of high-manganese alloy steel, such as low thermal conductivity, large solidification shrinkage, and high crack sensitivity, the following measures are taken: First, a slow start-up and a specific acceleration model are used to control the casting speed during the initial casting stage. This ensures uniform shell formation and avoids undercutting caused by excessively thin initial shells and insufficient lubrication due to excessively fast casting speeds. Simultaneously, it prevents poor surface quality and low production efficiency caused by excessively slow casting speeds. Second, the taper design of the crystallizer copper plate is optimized, employing a large taper and a precise ratio of wide to narrow taper surfaces to accommodate the solidification shrinkage of high-manganese alloy steel, reducing uneven pressure between the shell and the copper plate, and preventing shell deformation and cracking. Third, a special protective slag with low basicity, low reactivity, and high lubricity is selected to effectively control the melting and crystallization temperatures, reducing the chemical reaction between Mn and the components of the low-basicity protective slag, ensuring good lubrication and heat transfer, and further reducing the risk of cracking. Finally, during the secondary cooling process of continuous casting, a segmented cooling strategy was implemented. The cooling intensity was adjusted according to the solidification characteristics of different locations on the billet. In particular, strong cooling was used in the foot roll section after exiting the crystallizer to rapidly increase the billet shell thickness. Subsequently, appropriate cooling intensities were used in key areas such as the vertical and curved sections to avoid the high-temperature brittleness range of high-manganese alloy steel. Finally, enhanced cooling was applied in the horizontal section to prevent the billet from bulging, ensuring uniform solidification and good surface quality of the billet. Through these comprehensive technical measures, the embodiments of this application successfully achieved effective crack control during the continuous casting of high-manganese alloy steel slabs, improving production efficiency and product quality. Attached Figure Description

[0024] 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.

[0025] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic flowchart of a continuous casting production method for high manganese alloy steel slabs provided in an embodiment of this application. Detailed Implementation

[0027] 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 embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0028] 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 to 6" cover all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms "including" and "contains" as 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.

[0029] Figure 1 This is a schematic flowchart of a continuous casting production method for high manganese alloy steel slabs provided in an embodiment of this application.

[0030] Please see Figure 1 This application provides a continuous casting production method for high manganese alloy steel slabs, the method comprising:

[0031] S1. Casting high-manganese alloy steel liquid with a set chemical composition and starting the machine, and increasing the billet speed from zero to the target speed with controlled acceleration, so that the high-manganese alloy steel liquid obtains a stable casting flow state.

[0032] S2. The high-manganese alloy steel liquid in a stable casting flow state is introduced into a crystallizer with a set taper ratio, so that the high-manganese alloy steel liquid undergoes initial solidification in the crystallizer and forms a billet with a uniform initial shell; during the initial solidification process, a low-basicity protective slag is continuously added to the crystallizer and the method of adding the low-basicity protective slag is controlled.

[0033] S3. The billet that has completed the initial solidification is sent to the secondary cooling zone of the continuous casting machine, and the billet is cooled in stages according to the set non-uniform cooling intensity distribution, so that the surface temperature history of the billet avoids the high temperature brittle range of high manganese alloy steel, and a high manganese alloy steel slab is obtained.

[0034] In this embodiment, "stable casting flow state" means that the fluctuation of the molten steel surface in the crystallizer is ≤±3mm, and there is no exposed or crusting phenomenon on the surface of the molten steel in the crystallizer. "Uniform initial billet shell" means that the surface temperature difference of the billet is ≤50℃, and the thickness deviation of the billet shell is ≤15%.

[0035] In some implementations, the controlled acceleration 'a' satisfies the following formula: a = -0.05t + 0.175, where t represents the time after the casting machine starts. If the unit of t is min, then the unit of a is m / min. 2 The unit steel throughput at the target drawing speed is 1.5 tons / minute to 3.3 tons / minute.

[0036] A fundamental contradiction exists during the initial casting of high-manganese alloy steel: slow heat conduction requires time for billet shell growth, while the slow melting of the low-basicity protective slag necessitates a limited casting speed to ensure lubrication. Traditional constant acceleration or experience-based speed increases cannot accurately balance this contradiction, easily leading to missed castings or excessively deep vibration marks. The acceleration relationship a = -0.05t + 0.175 given in this application is essentially a decreasing acceleration model that is initially fast and then slows down. A relatively high acceleration (0.175 m / min) is applied at the instant of initial casting (t≈0). 2 Taking advantage of the high static pressure and deep molten pool of the steel, the process quickly bypasses the extremely low-speed zone, which is prone to leakage, thus shortening the critical window period. At this stage, although the billet shell is thin, the high casting speed drives the flow of the molten steel, facilitating heat transfer and the rapid spreading and melting of the initial low-basicity protective slag, creating initial conditions for the formation of a liquid slag film. As time progresses, the acceleration gradually decreases, and the casting speed increase curve flattens out. This perfectly suits the objective requirements of the billet shell needing time to grow stably and the low-basicity protective slag needing time to establish a stable liquid slag layer. Once the billet shell gradually thickens and lubrication conditions are established, the casting speed steadily approaches the target value, avoiding excessive stress on the still-consolidating billet shell caused by excessive acceleration in the later stages.

[0037] Unit throughput refers to the amount of molten steel passing through the continuous casting machine per unit time. This application controls the unit throughput within the range of 1.5 tons / minute to 3.3 tons / minute to ensure sufficient cooling and solidification of the molten steel in the crystallizer, thereby obtaining a high-quality cast billet. If the unit throughput exceeds 3.3 tons / minute, the billet shell will be too thin, making it prone to cracking; if the unit throughput is less than 1.5 tons / minute, production efficiency will be reduced.

[0038] In some embodiments, the ratio B / A of the taper coefficient A of the wide copper plate to the taper coefficient B of the narrow copper plate of the crystallizer is 1.2; wherein the value of the taper coefficient A of the wide copper plate ranges from 1.25% to 1.45%.

[0039] High-manganese alloy steel undergoes significant shrinkage during solidification. To accommodate this shrinkage, both the wide and narrow faces of the crystallizer plate need to be designed with a certain taper to ensure uniform shrinkage of the billet shell during solidification, preventing cracks or leaks. During solidification, the physical conditions and thermodynamic states of the wide and narrow faces of high-manganese alloy steel differ fundamentally, leading to asymmetrical shrinkage behavior.

[0040] Wide surface: It is sandwiched between two large copper plates, and the cooling is relatively uniform. The shrinkage is mainly along the thickness direction (inward), which is manifested as the blank shell separating from the copper plate.

[0041] Narrow facets are cooled not only by the copper plates on both sides, but also by the extra intense cooling (two-dimensional heat transfer) at their corners from the copper plates on the wider facets. Therefore, they experience higher cooling intensity, faster solidification, and more dramatic shrinkage. The shrinkage of narrow facets is complex, shrinking both in thickness and width inwards.

[0042] The taper coefficient refers to the ratio of the difference between the upper and lower widths of the copper plate in the crystallizer to the lower width, i.e., taper coefficient = (upper width of copper plate - lower width of copper plate) / (lower width of copper plate). It reflects the degree of shrinkage within the copper plate cavity of the crystallizer. In this embodiment, the taper coefficient A of the wide copper plate in the crystallizer is designed to be 1.25% to 1.45%, which ensures uniform cooling and solidification of the billet in the wide direction of the crystallizer, forming a billet shell of uniform thickness and good quality. The taper coefficient B of the narrow copper plate satisfies the ratio B / A = 1.2 with the taper coefficient A of the wide face, making the gap at the lower end of the crystallizer relatively smaller. This effectively offsets the greater shrinkage caused by intense cooling in the narrow face, preventing premature separation of the billet shell. This allows both the wide and narrow billet shells to obtain continuous, uniform, and efficient cooling, which is the geometric basis for generating a billet with a uniform initial billet shell.

[0043] In some embodiments, during the initial solidification process, a weak cooling mode is applied to the crystallizer. This weak cooling mode is achieved by controlling the cooling water flow rate within the copper plate of the crystallizer to be 4 m / s to 6 m / s, and the temperature difference between the cooling water at the inlet and outlet of the copper plate of the crystallizer is ≤9°C.

[0044] High-manganese alloy steel has a significantly lower thermal conductivity than ordinary carbon steel, meaning that heat transfer from the molten steel to the copper plate of the crystallizer is slower. If high-manganese alloy steel is subjected to the same strong cooling as conventional steel grades, the extremely high initial cooling intensity will drive the surface layer of the billet to solidify instantly and shrink dramatically. However, due to the slow heat dissipation from the interior, the overall temperature gradient of the billet increases sharply, generating enormous thermal stress. More importantly, the rapid and excessive shrinkage of the surface billet shell will cause it to detach from the copper plate of the crystallizer prematurely and completely, forming a stable air gap. This air gap acts as an insulation layer; once formed, the heat transfer efficiency drops sharply, leading to slow and uneven subsequent billet shell growth, creating weak points and greatly increasing the risk of steel leakage. This application reduces the cooling water flow rate, essentially actively reducing the cooling intensity of the crystallizer. This allows the nascent billet shell to solidify and shrink at a relatively gentle rate. The core purpose is to delay the time it takes for the billet shell to detach from the copper plate, and even maintain a "soft contact" or "intermittent contact" state throughout the crystallizer, thereby maximizing the effective heat transfer time and promoting uniform and stable billet shell thickening. High-manganese alloy steel is extremely sensitive to thermal stress. Excessive local temperature differences mean localized overcooling of the copper plate, leading to an overcooled, overly thick, and abnormally shrinking billet shell in the corresponding location. Conversely, the high-temperature area results in a thinner billet shell. This uneven thickness creates a high concentration of internal stress, which is the root cause of longitudinal cracks. Controlling the cooling water temperature difference between the inlet and outlet of the crystallizer copper plate to ≤9℃ is a direct and quantifiable process guarantee for producing billets with a uniform initial shell.

[0045] In some embodiments, the binary basicity R of the low-alkalinity protective slag is 0.6 to 0.9;

[0046] The low-alkalinity protective slag contains MnO2 and Li2O.

[0047] The mass fraction of MnO2 is 4% to 9%, and the mass fraction of Li2O satisfies the following relationship: [Li2O] = 1.05·[MnO2] - 3.8%, where [Li2O] represents the mass fraction of Li2O in the low-alkalinity protective slag, and [MnO2] represents the mass fraction of MnO2 in the low-alkalinity protective slag.

[0048] Binary basicity R(CaO / SiO2) is defined as the mass ratio of calcium oxide (CaO) to silicon dioxide (SiO2). In the continuous casting production method of this application, the binary basicity of the low-basicity protective slag is controlled within the range of 0.6 to 0.9. This low-basicity design helps to reduce the melting temperature and the initiation crystallization temperature of the protective slag. The lower melting temperature means that the low-basicity protective slag is more likely to transform from a solid to a liquid state at high temperatures, thereby forming a liquid slag layer more quickly. The lower initiation crystallization temperature helps to maintain the stability of the liquid slag layer and prevent changes in slag layer properties caused by premature crystallization.

[0049] Under low alkalinity conditions, the mineral phase formed by the protective slag at high temperatures is mainly glassy. The disordered and fluid structure of the glassy phase facilitates the uniform spreading of the low-alkalinity protective slag within the crystallizer, forming a stable slag film. The glassy mineral phase also reduces the crystal content in the slag layer, thereby lowering its viscosity and improving its lubrication performance. This is crucial for reducing friction between the billet shell and the crystallizer copper plate, preventing billet shell adhesion and leakage. Furthermore, the glassy mineral phase in the low-alkalinity protective slag possesses excellent thermal conductivity, accelerating heat exchange between the billet shell and the crystallizer copper plate. This facilitates rapid heat transfer from the billet shell to the crystallizer copper plate in the early stages of shell formation, thus accelerating the solidification and thickening of the billet shell.

[0050] In the continuous casting process of high-manganese alloy steel, the manganese (Mn) element in the molten steel readily undergoes a redox reaction with the silicon dioxide (SiO2) in the low-basicity protective slag. This reaction alters the composition and properties of the low-basicity protective slag, thereby affecting the stability of the continuous casting process and the quality of the cast billet. The addition of MnO2 to the low-basicity protective slag can effectively limit this redox reaction, thus maintaining the stability of the slag's composition and properties.

[0051] Maintaining a MnO2 mass fraction between 4% and 9% ensures that the low-basicity protective slag maintains suitable viscosity and crystallization temperature at high temperatures. This facilitates the formation of a stable slag film within the crystallizer, providing excellent lubrication and heat transfer for the initial billet shell. When the MnO2 mass fraction is less than 4%, its effect on inhibiting the redox reaction between Mn and SiO2 is not significant, which may lead to changes in the composition and properties of the low-basicity protective slag, thereby affecting the stability of the continuous casting process and the quality of the billet. When the MnO2 mass fraction is greater than 9%, it significantly deteriorates the crystallization temperature and viscosity of the low-basicity protective slag, affecting its fluidity and film-forming properties within the crystallizer. This will greatly impact heat transfer and lubrication, potentially leading to serious problems such as decreased billet surface quality and steel leakage.

[0052] As the Mn content in molten high-manganese alloy steel increases, the MnO2 content in the low-basicity protective slag also increases accordingly. To balance the melting point and crystallization temperature of the low-basicity protective slag, the Li2O content needs to be precisely adjusted based on the MnO2 content. The mass fraction of Li2O in the low-basicity protective slag satisfies the relationship [Li2O] = 1.05·[MnO2] - 3.8%. This ratio ensures rapid melting of the low-basicity protective slag at high temperatures and the formation of a stable slag layer structure, playing a crucial role in heat transfer and lubrication performance.

[0053] In some embodiments, the low-alkalinity protective slag is added at a frequency of 5 to 10 times per minute, with each addition being 100g to 280g.

[0054] The core function of low-basicity protective slag in the crystallizer relies on a stable liquid slag film. The formation and consumption of this slag film is a dynamic process: it is generated by the melting of the added solid low-basicity protective slag and is continuously consumed by the downward-pulled billet shell (carried out with the billet). The method of adding small amounts of material multiple times (5 to 10 times / min, 100g / time to 280g / time) ensures that the addition of solid low-basicity protective slag is continuous and uniform, avoiding accumulation caused by concentrated large additions or supply interruptions caused by prolonged periods without addition.

[0055] In some embodiments, the set non-uniform cooling intensity distribution is arranged in sequence along the casting direction as a strong cooling section, a first medium-strong cooling section, a weak cooling section, and a second medium-strong cooling section; wherein, the strong cooling section corresponds to the foot roll section of the continuous casting machine, the first medium-strong cooling section corresponds to the vertical section of the continuous casting machine, the weak cooling section corresponds to the curved section, the arc section, and the straightening section of the continuous casting machine, and the second medium-strong cooling section corresponds to the horizontal section of the continuous casting machine.

[0056] The rapid cooling section (foot roll section) quickly cools the billet exiting the crystallizer, which has a uniform initial shell. At this stage, the billet has just left the crystallizer support, and the initial shell is relatively thin. At this point, the shell's strength and rigidity are relatively low, making it susceptible to deformation or cracking due to external factors. Therefore, it is necessary to increase the cooling intensity to rapidly increase the shell's thickness and strength, ensuring that the billet maintains a stable shape and size after leaving the crystallizer and preventing accidents such as leaks.

[0057] The first medium-intensity cooling section (vertical section) continues cooling of the billet following the strong cooling section at a moderate intensity. This is because high-manganese alloy steel has a relatively low thermal conductivity, making it difficult for heat inside the billet to dissipate quickly to the external environment. To accelerate the solidification rate of the billet, medium-intensity cooling is used, which increases the thickness of the billet shell while avoiding excessive thermal stress inside the billet caused by an excessively rapid cooling rate.

[0058] The weak cooling sections (bending section, arc section, and straightening section) significantly reduce the cooling intensity in the areas where the billet undergoes the three key mechanical processes of bending deformation, arc guiding, and straightening deformation in sequence. Through weak cooling, strategic warming of the billet is achieved. As internal heat is conducted outward, the surface temperature of the billet stops decreasing and begins to rise naturally. The direct result of this design is that when the billet is subjected to the greatest mechanical stress in the bending and straightening sections, the surface temperature has moved away from the brittle zone and risen to the high plasticity region, fundamentally eliminating the thermodynamic conditions for the formation of surface and corner transverse cracks.

[0059] The second medium-intensity cooling section (horizontal section) is used to intensify cooling after the billet has completed all deformation and left the weak cooling section. At this point, the mechanical risk of cracking has passed. The medium-intensity cooling aims to improve cooling efficiency, accelerate the solidification of the billet core, increase casting speed and production rhythm, and at the same time prevent bulging caused by residual static pressure of molten steel in the horizontal section.

[0060] In some embodiments, the cooling water flow rate of the narrow-face foot roller in the strong cooling section is 180 NL / min to 260 NL / min;

[0061] The specific water volume of both the first and second medium-intensity cooling sections is 0.7 L / kg to 0.9 L / kg;

[0062] The specific water volume of the weak cooling section is 0.3L / kg to 0.5L / kg.

[0063] The cooling water flow rate for the narrow-face foot rolls in the strong cooling section (foot roll section) is 180 NL / min to 260 NL / min. This flow rate is specifically designed for narrow-face foot rolls, as the narrow face experiences severe shrinkage and stress concentration due to its two-dimensional cooling, making it a prone area for longitudinal cracks. If the cooling water flow rate for the narrow-face foot rolls is lower than 180 NL / min, the billet shell will not grow sufficiently after detaching from the crystallizer support, failing to withstand the static pressure of the molten steel, and posing a risk of bulging or even steel leakage. On the other hand, high-manganese alloy steel has poor thermal conductivity, and excessive cooling will cause an excessive temperature difference between the inside and outside of the narrow-face billet shell, generating huge tensile thermal stress. This stress, combined with the shrinkage stress, can easily exceed the strength limit of the high-temperature billet shell, inducing longitudinal cracks. Therefore, the upper limit of the cooling water flow rate for the narrow-face foot rolls is set at 260 NL / min.

[0064] "Specific water volume" refers to the amount of water consumed to cool each kilogram of billet, and is a common indicator for measuring cooling intensity. The specific water volume of the first medium-intensity cooling section (vertical section) and the second medium-intensity cooling section (horizontal section) are both 0.7L / kg to 0.9L / kg, providing continuous and effective cooling for the billet.

[0065] In the weak cooling section (bending section, arc section and straightening section), the water content is controlled at 0.3-0.5L / kg. By reducing the amount of cooling water sprayed, the surface temperature of the billet is kept within a suitable range, ensuring that the billet can smoothly pass through these deformation stages without cracking.

[0066] In some embodiments, the high-manganese alloy molten steel comprises, by mass fraction: Mn: 10% to 35%, C: 0.1% to 1.2%.

[0067] The mass fraction of Mn in molten high-manganese alloy steel ranges from 10% to 35%, covering a broad range from traditional wear-resistant steels (such as Mn13) to advanced high-strength ductile steels (such as TWIP steel and Mn25), indicating that the proposed solution is a universal solution for continuous casting of high-manganese alloy steel, rather than a solution for a single grade.

[0068] In some embodiments, the high-manganese alloy steel slab has the following specifications: a thickness of 200 mm to 400 mm and a width of 1800 mm to 3000 mm.

[0069] This application provides high-quality high-manganese alloy steel continuously cast slabs with a thickness of 200-400mm and a width of 1800mm to 3000mm. This means that ultra-wide and extra-thick wear-resistant steel plates (such as those used in large mining equipment and special engineering machinery) can be directly rolled out. This completely breaks the historical reliance on inefficient die casting or limited dimensions for high-end high-manganese alloy steel products, and possesses enormous commercial application potential. It can be successfully implemented in different combinations of specifications, rather than being limited to a fixed size.

[0070] 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 / industry standards; if there is no corresponding national / industry standard, they are performed according to general international standards, conventional conditions, or conditions recommended by the manufacturer.

[0071] Example 1

[0072] Steel grade: High manganese alloy steel Mn13, key chemical composition (mass fraction) is: Mn: 13%, C: 0.95%.

[0073] Target slab specifications: thickness × width = 200mm × 2000mm.

[0074] Target pulling speed: 0.85m / min.

[0075] Start-up and casting speed control: A slow start-up rhythm was adopted during start-up, and the casting speed was increased according to the acceleration model a=-0.05t+0.175. After the casting speed stabilized, the unit steel throughput was 2.65 tons / minute.

[0076] Crystallizer parameter control: The cooling water flow rate inside the copper plates on both the wide and narrow sides of the crystallizer is 5.6 m / s, and the temperature difference between the cooling water at the copper plate inlet and the copper plate outlet is 6.8℃.

[0077] Crystallizer taper design: The taper coefficient A of the wide face is set to 1.25%, and the taper coefficient B of the narrow face is set to 1.50%, strictly ensuring the ratio of B / A=1.2 to match the large solidification shrinkage characteristics of high manganese alloy steel.

[0078] Low-alkalinity protective slag usage procedure: During the casting process, a small amount of low-alkalinity protective slag is uniformly pushed into the crystallizer, with a pushing frequency of 5-10 times / min and 100-280g / time.

[0079] The binary basicity R of the low-alkalinity protective slag is 0.83, and the key chemical components (mass fraction) are: CaO: 23.35%, SiO2: 28.27%, MnO2: 4.7%, Li2O: 1.13%, F: 11.17%, Na2O: 13.97%, Al2O3: 2.48%, MgO: 1.30%, TC (total carbon): 6.31%.

[0080] Secondary cooling system: Implements a segmented cooling mode, with the following specific parameters:

[0081] Foot roller section: The cooling water flow rate for the narrow-face foot roller is 235 NL / min.

[0082] Vertical section: water volume is 0.9L / kg.

[0083] The water concentration in the curved section, arc section, and straightening section is controlled at 0.5L / kg, 0.45L / kg, and 0.4L / kg, respectively.

[0084] Horizontal section: water volume is 0.85L / kg.

[0085] Implementation results:

[0086] The Mn13 slab cast using the above integrated process has a surface inspection showing a transverse crack rate of 0 and a longitudinal crack rate of ≤0.5%, indicating excellent surface quality.

[0087] Example 2

[0088] Steel grade: High manganese alloy steel Mn25, key chemical composition (mass fraction) is: Mn: 25%, C: 0.15%.

[0089] Target slab specifications: thickness × width = 300mm × 2400mm.

[0090] Target pulling speed: 0.58m / min.

[0091] Start-up and casting speed control: A slow start-up rhythm was adopted during start-up, and the casting speed was increased according to the acceleration model a=-0.05t+0.175. After the casting speed stabilized, the unit steel throughput was 3.26 tons / minute.

[0092] Crystallizer parameter control: The cooling water flow rate inside the copper plates on both the wide and narrow sides of the crystallizer is 5 m / s, and the temperature difference between the cooling water at the copper plate inlet and the copper plate outlet is 8.3℃.

[0093] Crystallizer taper design: The taper coefficient A of the wide face is set to 1.42%, and the taper coefficient B of the narrow face is set to 1.72%, strictly ensuring the ratio of B / A=1.2 to match the large solidification shrinkage characteristics of high manganese alloy steel.

[0094] Low-alkalinity protective slag usage procedure: During the casting process, a small amount of low-alkalinity protective slag is uniformly pushed into the crystallizer, with a pushing frequency of 5-10 times / min and 100-280g / time.

[0095] The binary basicity R of the low-alkalinity protective slag is 0.7, and the key chemical components (mass fraction) are: CaO: 20.86%, SiO2: 29.8%, MnO2: 6.8%, Li2O: 3.34%, F: 11.2%, Na2O: 12.6%, Al2O3: 1.88%, MgO: 1.35%, TC (total carbon): 5.45%.

[0096] Secondary cooling system: Implements a segmented cooling mode, with the following specific parameters:

[0097] Foot roller section: The cooling water flow rate for the narrow-face foot roller is 215 NL / min.

[0098] Vertical section: water volume is 0.8L / kg.

[0099] The water concentration in the curved section, arc section, and straightening section is controlled at 0.42 L / kg, 0.4 L / kg, and 0.38 L / kg, respectively.

[0100] Horizontal section: water volume is 0.8L / kg.

[0101] Implementation results:

[0102] The Mn25 slab cast using the above integrated process, after surface inspection, showed a transverse crack rate of 0 and a longitudinal crack rate of ≤1%, indicating excellent slab surface quality.

[0103] Example 3

[0104] Steel grade: High manganese alloy steel Mn35, key chemical composition (mass fraction) is: Mn: 35%, C: 0.16%.

[0105] Target slab specifications: thickness × width = 400mm × 1800mm.

[0106] Target pulling speed: 0.55m / min.

[0107] Start-up and casting speed control: A slow start-up rhythm was adopted during start-up, and the casting speed was increased according to the acceleration model a=-0.05t+0.175. After the casting speed stabilized, the unit steel throughput was 3.1 tons / minute.

[0108] Crystallizer parameter control: The cooling water flow rate inside the copper plates on both the wide and narrow sides of the crystallizer is 4.3 m / s, and the temperature difference between the cooling water at the copper plate inlet and the copper plate outlet is 7.3℃.

[0109] Crystallizer taper design: The taper coefficient A of the wide face is set to 1.3%, and the taper coefficient B of the narrow face is set to 1.56%, strictly ensuring the ratio of B / A=1.2 to match the large solidification shrinkage characteristics of high manganese alloy steel.

[0110] Low-alkalinity protective slag usage procedure: During the casting process, a small amount of low-alkalinity protective slag is uniformly pushed into the crystallizer, with a pushing frequency of 5-10 times / min and 100-280g / time.

[0111] The binary basicity R of the low-alkalinity protective slag is 0.65, and the key chemical components (mass fraction) are: CaO: 19.1%, SiO2: 29.3%, MnO2: 8.6%, Li2O: 5.23%, F: 11.6%, Na2O: 11.3%, Al2O3: 1.9%, MgO: 1.5%, TC (total carbon): 5.1%.

[0112] Secondary cooling system: Implements a segmented cooling mode, with the following specific parameters:

[0113] Foot roller section: The cooling water flow rate for the narrow-faced foot roller is 190 NL / min.

[0114] Vertical section: water volume is 0.7L / kg.

[0115] The water concentration in the curved section, arc section, and straightening section is controlled at 0.4 L / kg, 0.38 L / kg, and 0.3 L / kg, respectively.

[0116] Horizontal section: water volume is 0.7L / kg.

[0117] Implementation results:

[0118] The Mn25 slab cast using the above integrated process, after surface inspection, showed a transverse crack rate of 0 and a longitudinal crack rate of ≤1%, indicating excellent slab surface quality.

[0119] Furthermore, one or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0120] By implementing the technical solution of this invention, a high-manganese alloy steel continuous casting slab with a surface transverse crack rate of 0 and a longitudinal crack rate of ≤2% can be obtained, which significantly improves the quality of the casting slab and the user experience.

[0121] 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 continuous casting production method of a high manganese alloy steel slab, characterized by, The method includes: The high-manganese alloy steel with a set chemical composition is poured and the casting machine is started. The billet speed is increased from zero to the target speed with controlled acceleration to achieve a stable casting flow state for the high-manganese alloy steel. The controlled acceleration 'a' satisfies the relationship: a = -0.05t + 0.175, where t represents the time after the casting machine starts. If the unit of t is min, then the unit of a is m / min. 2 The unit steel throughput at the target drawing speed is 1.5 tons / minute to 3.3 tons / minute. The high-manganese alloy steel liquid in a stable casting flow state is introduced into a crystallizer with a set taper ratio, so that the high-manganese alloy steel liquid undergoes initial solidification in the crystallizer and forms a billet with a uniform initial shell; during the initial solidification process, a low-basicity protective slag is continuously added to the crystallizer, and the low-basicity protective slag is added at a frequency of 5 times / min to 10 times / min, with each addition being 100g to 280g of the low-basicity protective slag; The billet that has completed the initial solidification is sent to the secondary cooling zone of the continuous casting machine, and the billet is cooled in stages according to the set non-uniform cooling intensity distribution so that the surface temperature history of the billet avoids the high temperature brittle range of high manganese alloy steel, thus obtaining a high manganese alloy steel slab. The non-uniform cooling intensity distribution is configured as follows along the casting direction: a strong cooling section, a first medium-strong cooling section, a weak cooling section, and a second medium-strong cooling section. The strong cooling section corresponds to the foot roll section of the continuous casting machine; the first medium-strong cooling section corresponds to the vertical section of the continuous casting machine; the weak cooling section corresponds to the curved section, arc section, and straightening section of the continuous casting machine; and the second medium-strong cooling section corresponds to the horizontal section of the continuous casting machine. The cooling water flow rate of the narrow-face foot roll in the strong cooling section is 180 NL / min to 260 NL / min. The specific water volume of the first and second medium-strong cooling sections is 0.7 L / kg to 0.9 L / kg; and the specific water volume of the weak cooling section is 0.3 L / kg to 0.5 L / kg. The composition of the high manganese alloy molten steel includes: Mn: 10% to 35%, C: 0.1% to 1.2%.

2. The method of claim 1, wherein, The ratio B / A of the taper coefficient A of the wide copper plate and the taper coefficient B of the narrow copper plate in the crystallizer is 1.2; wherein the value of the taper coefficient A of the wide copper plate ranges from 1.25% to 1.45%.

3. The method of claim 1, wherein, During the initial solidification process, a weak cooling mode is implemented for the crystallizer. The weak cooling mode is achieved by controlling the cooling water flow rate in the copper plate of the crystallizer to be 4m / s to 6m / s, and the temperature difference between the cooling water at the inlet and outlet of the copper plate of the crystallizer is ≤9℃.

4. The method of claim 1, wherein, The binary basicity R of the low-alkalinity protective slag is 0.6 to 0.9; The low-alkalinity protective slag contains MnO2 and Li2O. The mass fraction of MnO2 is 4% to 9%, and the mass fraction of Li2O satisfies the following relationship: [Li2O] = 1.05·[MnO2] - 3.8%, where [Li2O] represents the mass fraction of Li2O in the low-alkalinity protective slag, and [MnO2] represents the mass fraction of MnO2 in the low-alkalinity protective slag.

5. The method of claim 1, wherein, The specifications of the high manganese alloy steel slab are: thickness of 200mm to 400mm and width of 1800mm to 3000mm.

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