Method for solving hot charging crack on slab surface in hot charging and hot feeding process and related device

Abstract

This invention provides a solution and related apparatus for hot-charging cracks on the surface of slabs during hot charging and hot conveying, relating to the field of iron and steel metallurgy. By forming a highly plasticized martensitic structure through quenching treatment and strictly controlling the temperature, the structural stress caused by phase transformation in the two-phase region and precipitation of microalloying elements is avoided, thereby effectively preventing hot-charging cracks on the slab surface and improving product quality and production continuity.

Description

Technical Field

[0001] This application relates to the field of iron and steel metallurgy technology, and in particular to a solution for hot charging cracks on the surface of slabs during hot charging and hot delivery, and related devices. Background Technology

[0002] Hot charging and hot delivery technology for continuously cast slabs is a key process in steel production. By directly conveying high-temperature slabs to the rolling mill, it fully utilizes the sensible heat resources of the slabs, significantly reducing energy consumption, shortening the production process, and improving yield and product quality. This process achieves efficient integration of steelmaking and rolling stages, demonstrating significant energy-saving, consumption-reducing, and process-optimized advantages compared to the traditional method of cooling and reheating slabs after they leave the production line. However, in practical industrial applications, for alloy steel slabs containing microalloying elements such as niobium, aluminum, titanium, and boron, due to objective limitations in production line layout, the surface temperature of the slabs during the process of being conveyed to the heating furnace is often in the two-phase region of 700°C to 900°C. Within this temperature range, the slab surface undergoes a phase transformation from austenite to ferrite, generating significant structural stress. At the same time, the carbonitride precipitates formed by microalloying elements weaken the grain boundary bonding strength, leading to frequent surface hot charging cracks in the slabs during subsequent heating stages, severely damaging product surface quality and production continuity. To address this challenge, existing technologies mainly employ strategies such as alloy addition, high-temperature hot charging, delayed hot charging, and billet surface quenching. Alloy addition improves the high-temperature plasticity of the billet by introducing specific elements, but increases raw material costs and is unsuitable for steel grades with strict titanium content control. High-temperature hot charging effectively avoids the two-phase region problem, but places stringent requirements on the cooling capacity of continuous casting equipment and the compactness of the workshop layout, limiting its implementation. Delayed hot charging relies on facilities such as insulation pits to extend cooling time, resulting in a solidification structure close to that of cold charging, but it occupies a large amount of space, prolongs the production cycle, and reduces overall efficiency. Billet surface quenching forms a strengthening layer on the surface through rapid cooling to suppress cracks, offering convenient operation and significant economic benefits. However, in actual operation, insufficient precision in controlling quenching parameters such as casting speed, cooling water flow rate, and pressure often leads to uneven quenching, uneven surface banding, or excessive temperature, making it difficult to reliably control cracks, and requiring additional equipment investment.

[0003] To address the aforementioned issues, existing technologies urgently need improvement. Summary of the Invention

[0004] This application provides a solution and related apparatus for preventing surface cracking during hot charging and hot conveying of slabs. It effectively prevents surface cracking during hot charging, improving product quality and production continuity.

[0005] Firstly, this application provides a solution to the problem of hot-charging cracks on the surface of slabs during hot charging and hot delivery, which adopts the following technical solution: A solution to hot-charging cracks on the surface of slabs during hot charging and hot delivery includes: The original sector section of the continuous casting machine was modified into a pure water-cooled quenching sector section. The surface of the alloy steel continuous casting slab is subjected to quenching treatment to form a highly plasticized martensitic structure on the slab surface; Controlling key quenching parameters: Quenching is initiated when the slab is drawn at a speed ≥0.6m / min through the quenching fan-shaped section. The minimum flow rate of the intermediate cooling water inside the quenching fan-shaped section is ≥300L / min and the pressure is ≥0.08MPa. The minimum flow rate of the external intermediate cooling water is ≥1800L / min and the pressure is ≥0.08MPa. After quenching, the slab surface turns black without any bright bands, the quenching is uniform, and the slab surface temperature is ≤600℃. Then, the slab is hot-charged and hot-sent.

[0006] Optionally, the chemical composition and mass percentage of the alloy steel continuously cast slab are as follows: C: 0.06-0.28%, Si≤0.50%, Mn≤0.50%, P≤0.030%, S≤0.020%, N≤0.0085%, and also contain one or more alloying elements selected from Nb, Ti, Al, and B.

[0007] Optionally, the quenching sector is equipped with an inner arc spraying device, an outer arc spraying device, and matching inner arc spraying pipe supports and outer arc spraying pipe supports.

[0008] Optionally, the depth of the quenched layer on the surface of the slab after quenching is 4.5 mm to 7.0 mm.

[0009] Optionally, after the slab is cut, the core temperature and surface temperature are measured. Once the temperature meets the standard, it is sent into the conveyor roller table to complete the heat packing.

[0010] Optionally, the alloy steel is CCS-A ship plate steel, with a slab cross-section of 1882mm, a drawing speed of 1.3m / min, and a slab surface temperature of 542℃ after quenching.

[0011] Optionally, the alloy steel is DP780-LV steel, the slab cross-section is 970mm, the drawing speed is 1.2m / min, and the slab surface temperature after quenching is 509℃.

[0012] Secondly, this application provides a system for resolving surface cracks in slabs during hot charging and hot delivery, comprising: The shape adjustment module is used to transform the original fan-shaped section of the continuous casting machine into a pure water-cooled quenching fan-shaped section; The surface hardening module is used to perform surface hardening treatment on alloy steel continuous casting slabs, so that a highly plasticized martensitic structure is formed on the surface of the slab. The parameter control module is used to control the key parameters of quenching: quenching is started when the slab passes through the quenching fan section at a speed ≥0.6m / min, the minimum flow rate of the intermediate cooling water inside the quenching fan section is ≥300L / min and the pressure is ≥0.08MPa, and the minimum flow rate of the external intermediate cooling water is ≥1800L / min and the pressure is ≥0.08MPa. The output module is used to ensure that the surface of the quenched slab is black without any bright bands, the quenching is uniform, and the surface temperature of the slab is ≤600℃, and then the slab is hot-charged and hot-delivered.

[0013] Thirdly, this application provides a computer device, the device comprising: a memory and a processor, wherein the processor, when executing computer instructions stored in the memory, performs the method described above.

[0014] Fourthly, this application provides a computer-readable storage medium including instructions that, when executed on a computer, cause the computer to perform the method described above.

[0015] In summary, this application avoids structural stress caused by phase transformation in the two-phase region and precipitation of microalloying elements by forming a highly plasticized martensitic structure through quenching treatment and strictly controlling the temperature, thereby effectively preventing hot-fitting cracks on the slab surface and improving product quality and production continuity. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the computer device structure of the hardware operating environment involved in the embodiments of this application; Figure 2 This is a flowchart illustrating the first embodiment of the solution to the problem of hot-loading cracks on the slab surface during the hot-loading and hot-loading process of this application; Figure 3 This is a diagram showing the microstructure after quenching of the first embodiment of the solution to the hot charging cracks on the slab surface during the hot charging and hot delivery process of this application. Figure 4 This is a structural block diagram of the first embodiment of the system for solving surface cracks in slabs during hot charging and hot delivery in this application. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0018] Reference Figure 1 , Figure 1 This is a schematic diagram of the computer device structure of the hardware operating environment involved in the embodiments of this application.

[0019] like Figure 1As shown, the computer device may include: a processor 1001, such as a central processing unit (CPU), a communication bus 1002, a user interface 1003, a network interface 1004, and a memory 1005. The communication bus 1002 is used to enable communication between these components. The user interface 1003 may include a display screen or an input unit such as a keyboard; optionally, the user interface 1003 may also include a standard wired interface or a wireless interface. The network interface 1004 may optionally include a standard wired interface or a wireless interface (such as a Wireless-Fidelity (Wi-Fi) interface). The memory 1005 may be high-speed random access memory (RAM) or stable non-volatile memory (NVM), such as a disk drive. The memory 1005 may also optionally be a storage device independent of the aforementioned processor 1001.

[0020] Those skilled in the art will understand that Figure 1 The structure shown does not constitute a limitation on the computer device and may include more or fewer components than shown, or combine certain components, or have different component arrangements.

[0021] like Figure 1 As shown, the memory 1005, which serves as a storage medium, may include an operating system, a network communication module, a user interface module, and a program for resolving surface cracks on slabs during hot-loading and hot-delivery processes.

[0022] exist Figure 1 In the computer device shown, the network interface 1004 is mainly used for data communication with the network server; the user interface 1003 is mainly used for data interaction with the user; the processor 1001 and the memory 1005 in this application can be set in the computer device. The computer device calls the program for solving hot-fixing cracks on the surface of the slab during the hot-fixing and hot-delivery process stored in the memory 1005 through the processor 1001, and executes the solution for hot-fixing cracks on the surface of the slab during the hot-fixing and hot-delivery process provided in the embodiment of this application.

[0023] Traditional hot-charging and hot-delivery technologies for continuously cast billets, when processing alloy steel slabs containing elements such as Nb, Al, Ti, and B, often result in surface hot-charging cracks during heating due to production line layout limitations. Existing technologies such as alloy addition, high-temperature hot delivery, delayed hot delivery, and billet surface quenching all have their limitations, including increased costs, high equipment requirements, large space requirements, and investment needs.

[0024] To address this issue, this application provides a solution for hot-charging cracks on the slab surface during the hot-charging and hot-delivery process, referring to... Figure 2 , Figure 2 This is a flowchart illustrating the first embodiment of the solution to the problem of hot-loading cracks on the surface of the slab during the hot-loading and hot-loading process of this application.

[0025] In this embodiment, the solution to the hot-loading cracks on the slab surface during the hot-loading and hot-loading process includes the following steps: Step S10: Modify the original sector section of the continuous casting machine into a pure water-cooled quenching sector section; Step S20: Perform surface quenching treatment on the alloy steel continuous casting slab to form a highly plasticized martensitic structure on the slab surface; Step S30: Control key quenching parameters: Quenching is started when the slab passes through the quenching fan section at a drawing speed ≥ 0.6 m / min. The minimum flow rate of the intermediate cooling water inside the quenching fan section is ≥ 300 L / min and the pressure is ≥ 0.08 MPa. The minimum flow rate of the external intermediate cooling water is ≥ 1800 L / min and the pressure is ≥ 0.08 MPa. Step S40: After quenching, the surface of the slab is black without any bright bands, the quenching is uniform, and the surface temperature of the slab is ≤600℃. Then, the slab is hot-charged and hot-delivered.

[0026] For ease of understanding, the following explains some key terms in this embodiment: Pure water-cooled quenching fan-shaped section: This fan-shaped section refers to the equipment used in continuous casting machines to rapidly cool slabs. Its cooling medium is pure water, and the quenching of the slab surface is achieved through spraying or immersion to achieve a specific microstructure transformation.

[0027] Surface hardening: This process involves rapidly cooling the surface of a metal material to induce a phase transformation, resulting in a structure with high hardness and good plasticity, while the core retains its original structure or undergoes other phase transformations, thereby improving the surface properties of the material.

[0028] Highly plasticized martensite structure: This structure refers to martensite formed during the quenching process. It has high plasticity and can effectively alleviate the tendency to crack caused by quenching stress, while maintaining a certain strength and hardness.

[0029] Key parameters for quenching: These parameters refer to the process variables that need to be strictly controlled during the surface quenching process, including but not limited to slab drawing speed, cooling water flow rate, and cooling water pressure. These parameters directly affect the quenching effect and the surface structure of the slab.

[0030] Hot charging and hot delivery: This process refers to sending the high-temperature billet produced by continuous casting directly or after a short period of heat preservation into the steel rolling furnace for rolling without complete cooling, so as to utilize the sensible heat of the billet and achieve the purpose of energy saving and consumption reduction.

[0031] Specifically, this embodiment first transforms the original fan-shaped section of the continuous casting machine into a pure water-cooled quenching fan-shaped section. This transformation can be achieved in several ways. For example, the original cooling system of the fan-shaped section can be removed, and a new spray cooling system based on pure water circulation can be installed, along with corresponding water supply, drainage, and water treatment equipment. Alternatively, pure water spray pipes and nozzles can be added to the original fan-shaped section to enable pure water cooling of the slab. This transformation aims to provide the necessary cooling conditions for subsequent surface quenching treatment.

[0032] Secondly, the alloy steel continuously cast slab undergoes surface quenching treatment to form a highly plasticized martensitic structure on the slab surface. This surface quenching treatment can be achieved by controlling the cooling intensity and cooling time. For example, the slab surface can be rapidly cooled in a short time by adjusting the flow rate and pressure of the sprayed water, thereby inducing the transformation of austenite to martensite. This martensitic structure has high plasticity and can effectively alleviate stress concentration that may occur during subsequent heating and rolling processes.

[0033] Furthermore, key quenching parameters are controlled. Specifically, quenching is initiated when the slab's drawing speed through the quenching fan-shaped section reaches or exceeds 0.6 m / min. The minimum flow rate of the intermediate cooling water inside the quenching fan-shaped section is set to 300 L / min, and the pressure is set to 0.08 MPa. Simultaneously, the minimum flow rate of the external intermediate cooling water is set to 1800 L / min, and the pressure is set to 0.08 MPa. These parameter settings aim to ensure the stability of the quenching process and the uniformity of the cooling effect. For example, if the drawing speed is lower than the set value, it may lead to excessively long cooling time, affecting the quenching effect; if the cooling water flow rate or pressure is insufficient, it may lead to uneven cooling or insufficient cooling intensity.

[0034] Therefore, the quenched slab surface appears blackened without any bright bands, indicating uniform quenching and that the slab surface temperature was controlled below 600℃. Subsequently, the slab is hot-charged and hot-transported. The blackened slab surface without bright bands is a macroscopic indication of good quenching, meaning a uniform surface microstructure. Controlling the slab surface temperature below 600℃ helps avoid microstructure coarsening or secondary heating cracks caused by excessively high temperatures during hot charging and hot-transporting. For example, if the surface temperature is too high, it may cause the already formed martensite structure to temper, reducing its plasticity.

[0035] In summary, this embodiment modifies the continuous casting machine's sector section into a pure water-cooled quenching sector section to perform surface quenching treatment on alloy steel continuously cast slabs, forming a highly plasticized martensitic structure on the surface. By strictly controlling key parameters such as quenching speed, cooling water flow rate, and pressure, it ensures uniform quenching and that the slab surface temperature remains below 600℃. This effectively suppresses surface hot-charging cracks caused by the temperature difference in the two-phase region during the hot charging and conveying process of the alloy steel slab, thereby improving production efficiency and product quality. The effect of the microstructure after quenching is shown in the figure below. Figure 3 As shown.

[0036] In some of the embodiments described above, a method of surface quenching of alloy steel continuously cast slabs was proposed to solve the problem of hot-charging cracks on the slab surface during hot charging and hot delivery. However, in practical applications, if the chemical composition of the alloy steel continuously cast slab is not precisely controlled, its response to quenching treatment may vary significantly. This may lead to instability in the surface microstructure and properties of the slab after quenching, thereby affecting the formation of highly plasticized martensite and ultimately failing to effectively guarantee the complete elimination of hot-charging cracks.

[0037] To address this, this embodiment further specifies the chemical composition and mass percentage of the alloy steel continuously cast slab. Specifically, the chemical composition and mass percentage of the alloy steel continuously cast slab are limited as follows: the carbon (C) content is within the range of 0.06% to 0.28%, aiming to ensure the formation of an appropriate amount of martensitic structure with good plasticity during quenching, while avoiding increased quenching crack sensitivity or decreased plasticity due to excessive carbon content. The silicon (Si) and manganese (Mn) contents are both controlled below 0.50% to optimize the deoxidation effect, solid solution strengthening effect, and hardenability of the steel, and to inhibit the formation of harmful phases. Phosphorus (P) and sulfur (S), as harmful impurities, are strictly controlled below 0.030% and 0.020%, respectively, to minimize the cold brittleness and hot brittleness of the steel and improve the overall toughness and crack resistance of the slab. Nitrogen (N) content is limited to below 0.0085% to avoid the formation of coarse nitrides, thereby maintaining the steel's good plasticity and impact toughness. Furthermore, the addition of one or more microalloying elements from niobium (Nb), titanium (Ti), aluminum (Al), and boron (B) can further refine the austenite grains, improve the steel's hardenability, and enhance its strength and toughness through precipitation strengthening, providing favorable conditions for the formation of a uniform, highly plasticized martensitic structure.

[0038] By precisely controlling the chemical composition of the alloy steel continuously cast slab through the above technical solution, the slab can stably form the required high-plasticity martensite structure during subsequent surface quenching. This specific composition design, especially the addition of carbon content, microalloying elements, and strict control of harmful impurities, ensures that the steel has excellent hardenability and plasticity. This allows for uniform and effective surface quenching under the cooling effect of the quenching fan-shaped section, avoiding problems such as poor quenching effect or uneven structure caused by composition fluctuations. This not only significantly improves the slab surface's resistance to hot charging cracks but also ensures the stability and reliability of the hot charging and hot delivery process, ultimately effectively solving the problem of hot charging cracks on the slab surface during hot charging and hot delivery, and improving product quality and production efficiency.

[0039] In some of the embodiments described above, it was proposed to modify the original sector section of the continuous casting machine into a pure water-cooled quenching sector section, and to perform surface quenching treatment on the alloy steel continuous casting slab to form a highly plasticized martensitic structure. However, in actual operation, how to ensure that the quenching cooling water can act uniformly and efficiently on the slab surface to achieve the ideal quenching effect is a technical problem that needs to be further solved.

[0040] In this embodiment, the quenching fan-shaped segment is further provided with an inner arc spraying device, an outer arc spraying device, and matching inner arc spraying pipe supports and outer arc spraying pipe supports.

[0041] Specifically, an inner arc spraying device is a piece of equipment used to spray cooling water onto the inner arc side of a continuously cast slab. Its function is to uniformly spray cooling water onto the inner arc surface of the slab, achieving rapid and uniform cooling of the inner arc side. This can be achieved by a series of nozzles arranged at specific intervals and angles to ensure that the cooling water covers the entire width of the inner arc of the slab and forms a uniform water film or mist. The type, orifice diameter, spray pressure, and flow rate of the nozzles can all be optimized according to the slab size, casting speed, and required cooling intensity.

[0042] An external arc spraying device is a type of equipment used to spray cooling water onto the outer arc side of a continuously cast slab. Its function is to evenly spray cooling water onto the outer arc surface of the slab, achieving rapid and uniform cooling of the outer arc side. Similar to an internal arc spraying device, the external arc spraying device also includes a series of nozzles. Their arrangement and parameter settings are designed to ensure that the cooling water effectively covers the outer arc surface of the slab and works in conjunction with the internal arc side to achieve uniform quenching of the slab as a whole.

[0043] The inner arc spray pipe support is used to support and fix the spray pipe in the inner arc spray device. Its function is to ensure that the inner arc spray pipe maintains a precise position and angle within the quenching fan-shaped section, preventing displacement or deformation under high-speed water flow impact or equipment vibration, thereby ensuring the stability and uniformity of the cooling water spray. The design of the support needs to consider factors such as high temperature resistance, corrosion resistance, and ease of installation and maintenance.

[0044] The outer arc spray pipe support is used to support and fix the spray pipe in the outer arc spray device. Its function is to ensure that the outer arc spray pipe maintains a precise position and angle within the quenching sector, and works together with the inner arc spray pipe support to maintain the stability of the entire quenching system. Its design also needs to meet the requirement of long-term stable operation in harsh working environments.

[0045] Through the above technical solution, the inner arc spraying device and outer arc spraying device configured in the quenching fan-shaped section can accurately and independently spray cooling water onto the inner and outer arc surfaces of the continuously cast slab. The matching inner arc spray pipe supports and outer arc spray pipe supports ensure the stability of the spray pipe position and the accuracy of the spray angle, effectively avoiding uneven spraying caused by water flow impact or equipment vibration. This allows the quenching cooling water to act uniformly and efficiently on the entire surface of the slab, thereby ensuring the uniformity of quenching on the slab surface, avoiding localized overcooling or undercooling, and ultimately contributing to the formation of a uniform, highly plasticized martensite structure, significantly reducing the occurrence of hot-charging cracks on the slab surface during hot charging and hot conveying.

[0046] In some of the embodiments described above, a method was proposed to solve the problem of surface cracking during hot charging by surface quenching of alloy steel continuously cast slabs to form a highly plasticized martensitic structure on the slab surface. However, in actual operation, if the quenching layer depth is not properly controlled, the quenching effect may be poor, failing to effectively suppress crack formation; or the quenching layer may be too deep, increasing the internal stress of the slab and causing other quality problems, affecting the subsequent processing performance of the slab.

[0047] To address this, this embodiment further proposes a surface hardening layer depth of 4.5mm to 7.0mm after slab quenching. Specifically, the surface hardening layer depth refers to the distance the martensitic layer formed on the surface of the alloy steel continuously cast slab extends from the slab surface inward after surface quenching. This depth range is designed to ensure sufficient hardness and plasticity on the slab surface to effectively resist the thermal stress generated during hot charging and conveying, thereby inhibiting the formation of hot charging cracks. Simultaneously, controlling the hardening layer depth within this range avoids excessive residual stress inside the slab due to an excessively deep hardening layer, or insufficient hardening layer resulting in unsatisfactory effects. This specific hardening layer depth can be achieved by precisely controlling parameters such as the cooling intensity and cooling time of the quenching fan-shaped section, as well as the slab drawing speed. For example, the cooling rate of the slab surface can be finely adjusted by adjusting the flow rate and pressure of the intermediate cooling water inside and outside the quenching fan-shaped section, as well as the drawing speed of the slab through the quenching fan-shaped section, thereby controlling the depth of the martensitic phase transformation. In addition, the chemical composition of the slab also affects its hardenability. Therefore, under specific composition, it is necessary to determine the optimal combination of quenching parameters through experiments or simulations to achieve the target depth.

[0048] By precisely controlling the depth of the quenched layer on the slab surface within the range of 4.5mm to 7.0mm after quenching, this embodiment ensures the formation of a stable and highly ductile martensitic structure on the slab surface, effectively resisting cracks caused by temperature changes and thermal stress concentration during hot charging and hot conveying. This specific depth range avoids the problem of insufficient crack resistance due to an excessively shallow quenched layer, and also avoids the negative impacts of excessive residual stress and increased brittleness that may result from an excessively deep quenched layer. Thus, while effectively solving hot charging cracks, it ensures the overall mechanical properties of the slab and the stability of subsequent processing. This precise control achieves an optimal balance in the quenching treatment effect, significantly improving the surface quality and yield of alloy steel continuously cast slabs during hot charging and hot conveying.

[0049] In some of the embodiments described above, it is proposed to perform surface quenching treatment on alloy steel continuously cast slabs and control the surface temperature of the slabs after quenching to ≤600℃, followed by hot charging and hot delivery of the slabs. However, in actual operation, relying solely on surface temperature control may not be sufficient to fully assess the overall thermal state of the slabs, which may affect the efficiency and quality of subsequent hot charging and hot delivery, and even cause new defects.

[0050] To address this, this embodiment further proposes that after slab cutting, the core and surface temperatures need to be measured, and the slab should be fed into the conveyor rollers for heat treatment once the temperatures meet the specified standards. Specifically, after slab cutting, to fully understand the internal thermal state of the slab, the core temperature needs to be measured. Core temperature measurement can be achieved in various ways. For example, an insertion thermocouple can be used to directly measure the temperature at a specific depth inside the slab, or a non-contact infrared thermometer combined with a heat conduction model can be used to estimate the core temperature. Simultaneously, the surface temperature of the slab also needs to be measured in real-time or at fixed points using a non-contact infrared thermometer. These measurements should be performed rapidly after slab cutting to obtain the most accurate thermal state data.

[0051] "Temperature compliance" means that both the core and surface temperatures of the slab meet the preset requirements for hot charging and hot delivery processes. For example, for certain alloy steel grades, the core temperature may need to be maintained in a higher range of 800℃ to 1000℃ to ensure uniform internal structure and reduce subsequent heating energy consumption; while the surface temperature needs to be stabilized in the range of 400℃ to 600℃ after quenching to ensure good plasticity and avoid new surface defects. These compliance standards are precisely set based on factors such as the specific steel grade, slab size, subsequent rolling processes, and the distance and time of hot charging and hot delivery.

[0052] Once the core and surface temperatures of the slab reach the preset standards, the slab is fed into the conveyor roller table for hot charging. The conveyor roller table typically consists of a series of powered rollers that smoothly and efficiently transport the slab from the cutting area to the mill inlet. During the conveying process, insulation covers or auxiliary heating devices can be configured as needed to minimize heat loss from the slab and ensure that it remains in an ideal thermal state when entering the mill.

[0053] By employing the aforementioned technical solution, precise measurement of the core and surface temperatures after slab cutting allows for a comprehensive understanding of the slab's overall thermal state. This avoids the inaccuracies that can arise from relying solely on surface temperature, ensuring that both the internal and external temperatures of the slab meet the preset process standards before it is fed into the conveyor rollers for hot charging. This effectively prevents subsequent rolling defects caused by uneven or substandard internal temperatures of the slab, significantly reduces secondary heating energy consumption, and optimizes the overall efficiency and product quality stability of hot charging and hot conveying.

[0054] When performing surface quenching on alloy steel continuously cast slabs to address hot-charging cracks during hot charging and conveying, although the chemical composition range and basic quenching parameters of the alloy steel are well-defined, accurately matching the properties of a specific grade of alloy steel to optimize the quenching effect, ensure quenching uniformity, and achieve the ideal slab surface temperature remains a problem that requires further refinement. Inappropriate parameter selection may lead to poor quenching results or even introduce new surface defects.

[0055] In this embodiment, it is further proposed that the alloy steel is CCS-A ship plate steel, the slab cross section is 1882mm, the drawing speed is 1.3m / min, and the surface temperature of the slab after quenching is 542℃.

[0056] Specifically, CCS-A ship plate steel is a specific grade of alloy steel with the following chemical composition and mass percentage: C: 0.06~0.28%, Si≤0.50%, Mn≤0.50%, P≤0.030%, S≤0.020%, N≤0.0085%, and also contains one or more alloying elements selected from Nb, Ti, Al, and B. This steel is widely used in shipbuilding and possesses good strength, toughness, and weldability. During continuous casting, due to its specific chemical composition and microstructure, it is highly sensitive to the quenching process. Choosing CCS-A ship plate steel as the quenching target means that precise matching of process parameters is required based on its material properties to ensure the formation of a highly plasticized martensite structure on the slab surface after quenching, while avoiding the generation of new defects. The 1882mm slab cross-section is one of the key geometric parameters affecting the quenching effect. For such a wide slab cross-section, special attention needs to be paid to cooling uniformity during quenching to prevent areas of uneven temperature or incomplete quenching along the width of the slab. This typically requires the spray system in the quenching sector to cover the entire width of the slab and provide uniform cooling intensity. A casting speed of 1.3 m / min is a crucial process parameter in continuous casting, directly affecting the slab's residence time within the quenching sector, thus influencing the quenching cooling intensity and effect. A casting speed of 1.3 m / min is higher than the lower limit for quenching initiation speed (≥0.6 m / min), indicating that the slab passes through the quenching zone at a relatively fast speed. At higher casting speeds, it is necessary to ensure that the quenching sector provides sufficient cooling capacity to rapidly reduce the slab surface temperature and form the desired martensite structure within a limited residence time. A slab surface temperature of 542℃ after quenching is a key indicator for evaluating the quenching effect and the feasibility of subsequent hot charging and hot delivery. A surface temperature of 542℃ falls within the range of ≤600℃ and represents a relatively precise control target. The surface temperature is controlled at 542℃ to ensure that the slab surface can obtain the ideal microstructure after quenching, namely a highly plasticized martensite structure, while avoiding the increase of brittleness due to excessively low temperature or the insufficient quenching due to excessively high temperature.

[0057] The above technical solution applies the quenching method to a specific grade of CCS-A ship plate steel. Targeting its 1882mm wide cross-section and relatively high drawing speed of 1.3m / min, the quenching process is precisely controlled, ensuring that the surface temperature of the slab after quenching can stably reach 542℃. This precise parameter matching and control ensures that the surface of the CCS-A ship plate steel can form a uniform and appropriately deep highly plasticized martensite structure before hot charging and conveying. This effectively avoids problems such as uneven quenching and unsatisfactory microstructure caused by differences in material properties or mismatched process parameters, thus significantly reducing the probability of hot charging cracks on the slab surface during hot charging and conveying, and improving product quality and production efficiency.

[0058] In some of the embodiments described above, surface quenching of alloy steel continuously cast slabs was proposed to solve the problem of hot charging cracks on the slab surface during hot charging and conveying, and a range of chemical composition for alloy steel continuously cast slabs was given. However, different grades of alloy steel have significantly different metallurgical properties and sensitivities to quenching processes. If only a general range of chemical composition and quenching parameters are used, it may be difficult to achieve the best quenching effect for specific high-strength steel grades, especially in ensuring the formation of a highly plasticized martensitic structure on the slab surface while precisely controlling the surface temperature after quenching to meet the stringent requirements of subsequent hot charging and conveying, which may affect the performance of the final product and production efficiency.

[0059] In this embodiment, the alloy steel is further specified as DP780-LV steel, the slab cross-section is 970mm, the drawing speed is 1.2m / min, and the surface temperature of the slab after quenching is 509℃.

[0060] DP780-LV steel is a typical dual-phase steel, belonging to the category of Advanced High-Strength Steels (AHSS), characterized by its combination of high strength and good ductility. The microstructure of this steel typically consists of a soft ferrite matrix and hard martensite islands. During continuous casting and subsequent cooling, the phase transformation behavior and thermodynamic properties of DP780-LV steel differ significantly from those of ordinary carbon steel or low-alloy steel, making it more sensitive to quenching processes. The specific designation of the DP780-LV steel grade aims to optimize quenching treatment schemes to address its unique metallurgical characteristics, ensuring effective suppression of surface crack formation during hot charging and hot delivery, and meeting the stringent requirements for microstructure and residual stress control in its final mechanical properties.

[0061] The slab cross-section refers to the cross-sectional dimensions of a continuously cast slab, specifically a width of 970 mm. The slab's cross-sectional dimensions are a key parameter affecting the quenching cooling effect, as they directly determine the path length for heat conduction from the slab's interior to the surface and the heat dissipation area in contact with the cooling medium. For a 970 mm slab cross-section, its relatively small size affects the rate of heat loss and the internal temperature gradient during quenching. Under a given cooling intensity, a smaller cross-section slab generally achieves faster cooling, but may also face problems such as uneven cooling or localized overcooling. Therefore, for this cross-sectional dimension, quenching parameters need to be precisely adjusted to ensure that the surface quenched layer depth and microstructure uniformity meet expectations.

[0062] Casting speed refers to the speed at which the continuously cast slab is pulled from the crystallizer, and also the speed at which it passes through the quenching sector. The casting speed directly determines the residence time of the slab within the quenching sector, thus affecting the cumulative strength and effect of quenching cooling. A casting speed of 1.2 m / min is considered a relatively high production speed, meaning the slab's residence time in the quenching zone is short. Under these conditions, to achieve the desired quenching effect, the quenching system needs stronger cooling capacity and faster response speed. For DP780-LV steel, a higher casting speed helps improve production efficiency, but it also places higher demands on the cooling uniformity and stability of the quenching system to ensure that surface martensitic transformation is achieved within a limited time and that the surface temperature after quenching is precisely controlled.

[0063] The surface temperature of the slab after quenching is the actual measured temperature of the slab surface upon completion of the quenching process. This temperature is a key indicator for evaluating the quenching effect, directly related to the residual heat inside the slab, the subsequent hot charging and hot conveying process conditions, and the microstructure and properties of the final product. Precisely controlling the surface temperature of the quenched slab at 509℃ indicates that this temperature is the optimal temperature point after systematic optimization for DP780-LV steel under specific drawing speed and cross-sectional conditions. This temperature effectively ensures the formation of a highly plasticized martensitic structure on the slab surface, avoiding increased brittleness due to overcooling, while also providing a suitable starting temperature for subsequent hot charging and hot conveying processes, helping to reduce thermal stress and further suppressing crack initiation.

[0064] Through the aforementioned technical solution, for the specific grade of alloy steel DP780-LV, combined with its 970mm slab cross-section and a drawing speed of 1.2m / min, the surface temperature of the quenched slab was precisely controlled to reach 509℃. This refined parameter setting allows the quenching process to fully adapt to the unique phase transformation kinetics and thermophysical properties of DP780-LV steel, ensuring that a highly plasticized martensitic structure is formed on the slab surface while avoiding uneven microstructure or overcooling embrittlement caused by improper cooling. This precise surface temperature control not only effectively suppresses surface cracks that may occur during hot charging and hot conveying but also provides an ideal starting temperature for subsequent processes, significantly reducing thermal stress. This ensures the intrinsic quality of the DP780-LV steel slab and the mechanical properties of the final product, improving the production stability and product qualification of this specific high-strength steel grade.

[0065] Furthermore, this application also proposes a computer-readable storage medium storing a program for resolving hot-fitting cracks on the surface of a slab during the hot-fitting and hot-delivery process. When the program for resolving hot-fitting cracks on the surface of a slab during the hot-fitting and hot-delivery process is executed by a processor, it implements the steps of the method for resolving hot-fitting cracks on the surface of a slab during the hot-fitting and hot-delivery process described above.

[0066] Reference Figure 4 , Figure 4 This is a structural block diagram of the first embodiment of the system for solving surface cracks in slabs during hot charging and hot delivery in this application.

[0067] like Figure 4 As shown in the embodiments of this application, the system for resolving surface cracks in slabs during hot charging and hot delivery includes: Shape adjustment module 10 is used to transform the original fan-shaped section of the continuous casting machine into a pure water-cooled quenching fan-shaped section. The surface hardening module 20 is used to perform surface hardening treatment on the alloy steel continuous casting slab, so that a highly plasticized martensitic structure is formed on the surface of the slab. The parameter control module 30 is used to control the key parameters of quenching: quenching is started when the slab passes through the quenching fan section at a speed ≥ 0.6 m / min, the minimum flow rate of the intermediate cooling water inside the quenching fan section is ≥ 300 L / min and the pressure is ≥ 0.08 MPa, and the minimum flow rate of the external intermediate cooling water is ≥ 1800 L / min and the pressure is ≥ 0.08 MPa. Output module 40 is used to ensure that the surface of the quenched slab is black without bright bands, the quenching is uniform, and the surface temperature of the slab is ≤600℃, and then the slab is hot-loaded and hot-delivered.

[0068] It should be understood that the above are merely illustrative examples and do not constitute any limitation on the technical solution of this application. In specific applications, those skilled in the art can make settings as needed, and this application does not impose any restrictions on this.

[0069] This embodiment forms a highly plasticized martensitic structure through quenching treatment and strictly controls the temperature, avoiding structural stress caused by phase transformation in the two-phase region and precipitation of microalloying elements, thereby effectively preventing hot-fitting cracks on the slab surface and improving product quality and production continuity.

[0070] It should be noted that the workflow described above is merely illustrative and does not limit the scope of protection of this application. In practical applications, those skilled in the art can select some or all of it to achieve the purpose of this embodiment according to actual needs, and no restrictions are imposed here.

[0071] In addition, for technical details not described in detail in this embodiment, please refer to the method for solving the hot charging cracks on the surface of the slab during the hot charging and hot delivery process provided in any embodiment of this application, which will not be repeated here.

[0072] Furthermore, it should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or system. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or system that includes that element.

[0073] The sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0074] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as read-only memory (ROM) / RAM, magnetic disk, optical disk), and includes several instructions to cause a terminal device (which may be a mobile phone, computer, server, or network device, etc.) to execute the methods of the various embodiments of this application. The above are only preferred embodiments of this application and do not limit the patent scope of this application. All equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A solution to the problem of surface cracks in slabs during hot charging and hot delivery, characterized in that, include: The original sector section of the continuous casting machine was modified into a pure water-cooled quenching sector section. The surface of the alloy steel continuous casting slab is subjected to quenching treatment to form a highly plasticized martensitic structure on the slab surface; Controlling key quenching parameters: Quenching is initiated when the slab is drawn at a speed ≥0.6m / min through the quenching fan-shaped section. The minimum flow rate of the intermediate cooling water inside the quenching fan-shaped section is ≥300L / min and the pressure is ≥0.08MPa. The minimum flow rate of the external intermediate cooling water is ≥1800L / min and the pressure is ≥0.08MPa. After quenching, the slab surface turns black without any bright bands, the quenching is uniform, and the slab surface temperature is ≤600℃. Then, the slab is hot-charged and hot-sent.

2. The method according to claim 1, characterized in that, The chemical composition and mass percentage of the alloy steel continuously cast slab are as follows: C: 0.06-0.28%, Si≤0.50%, Mn≤0.50%, P≤0.030%, S≤0.020%, N≤0.0085%, and also contain one or more alloying elements selected from Nb, Ti, Al, and B.

3. The method according to claim 1, characterized in that, The quenching fan-shaped section is equipped with an inner arc spraying device, an outer arc spraying device, and matching inner arc spraying pipe supports and outer arc spraying pipe supports.

4. The method according to claim 1, characterized in that, The depth of the hardened layer on the surface of the slab after quenching is 4.5mm to 7.0mm.

5. The method according to claim 1, characterized in that, After the slab is cut, the core temperature and surface temperature are measured. Once the temperature meets the standard, it is sent into the conveyor roller table to complete the heat loading.

6. The method according to claim 2, characterized in that, The alloy steel is CCS-A ship plate steel, with a slab cross-section of 1882mm, a drawing speed of 1.3m / min, and a slab surface temperature of 542℃ after quenching.

7. The method according to claim 2, characterized in that, The alloy steel is DP780-LV steel, the slab cross section is 970mm, the drawing speed is 1.2m / min, and the surface temperature of the slab after quenching is 509℃.

8. A system for resolving surface cracks in slabs during hot charging and hot delivery, characterized in that, include: The shape adjustment module is used to transform the original fan-shaped section of the continuous casting machine into a pure water-cooled quenching fan-shaped section; The surface hardening module is used to perform surface hardening treatment on alloy steel continuous casting slabs, so that a highly plasticized martensitic structure is formed on the surface of the slab. The parameter control module is used to control the key parameters of quenching: quenching is started when the slab passes through the quenching fan section at a speed ≥0.6m / min; the minimum flow rate of the intermediate cooling water inside the quenching fan section is ≥300L / min and the pressure is ≥0.08MPa; the minimum flow rate of the external intermediate cooling water is ≥1800L / min and the pressure is ≥0.08MPa. The output module is used to ensure that the surface of the quenched slab is black without any bright bands, the quenching is uniform, and the surface temperature of the slab is ≤600℃, and then the slab is hot-charged and hot-delivered.

9. A computer device, characterized in that, The device includes a memory and a processor, wherein the processor, when executing computer instructions stored in the memory, performs the method as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, Includes instructions that, when executed on a computer, cause the computer to perform the method as described in any one of claims 1 to 7.

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