With the increasing improvement of the performance requirements for steel in high-end equipment, high titanium steel has drawn wide attention due to its high strength, toughness, wear resistance and corrosion resistance. However, new challenge has encountered in smelting and casting of high Ti steel, due to the fact that Ti shows high activity and strong affinity to react with oxygen and nitrogen to form high melting point inclusions. The general characteristic of the submerged nozzle clogging in continuous casting of high Ti steel was reviewed, and the multilayer structure and chemical composition of the clog were revealed. The submerged nozzle clogging process and mechanism during continuous casting by Ti addition was summarized, and the chemical reaction type, sequence and clog component at the interface of the continuous casting nozzle were compared between Ti containing steel (w(Ti)≤0.01%) and high Ti steel (w(Ti)>0.1%). The inner wall erosion, temperature drop and physical adhesion were regarded as the key influencing mechanisms. Finally, the effective control strategy to solve the nozzle clogging problem in high Ti steel continuous casting has been proposed, and the new achievements on Ca treatment, nozzle material design and external field implementation has been outlined particularly.

Continuous casting process occupies a “central” position and plays a connecting role in steel production process. The development of continuous casting technology has significantly promoted high quality, high efficiency and green production in steel industry. By reviewing the award-winning projects in the field of continuous casting in the “Metallurgical Science and Technology Award” from 2020 to 2024, The new progress made in continuous casting theory, production efficiency, billet homogenization, products development, key process equipment and intelligent control technology in China were summarized. Billet homogeneity, stable production, and high efficiency are the main indicators of high-quality continuous casting process. The collaborative optimization of mold metallurgical functions, secondary cooling control, electromagnetic stirring, and end pressing are the main technical measures to improve the quality of continuous casting billets. From the award-winning projects in recent years, it can be seen that the intelligent control technologies, such as digital twin factory, mold liquid level fluctuation control, billet defect detection and prediction, automatic steel casting, etc. have made remarkable progress. Continuous casting equipment is developing towards the direction of high efficiency, stabilization, flexibility, long service life, and more intelligence, and at the same time meeting the production requirements of stable, high quality and energy saving. Reference for readers to understand the whole development of continuous casting technology in China will be provided.

A transient three-dimensional numerical model coupling multiple physical fields in the slab mold was developed to investigate the effects of electromagnetic stirring on molten steel flow, initial solidification, and the non-steady-state fluctuation behavior of the steel/slag interface in a 1 500 mm×230 mm slab mold. The accuracy of the electromagnetic stirring model was validated by measuring the magnetic field intensity and electromagnetic forces within the mold during actual production. The results show that, compared to conditions without electromagnetic stirring, the traveling wave magnetic field generated by increased stirring transforms the flow pattern in the mold from an upward circulating flow to a horizontal circulating flow. This enhances the horizontal flow of molten steel, reducing the velocity of the solidification front along the casting direction and thinning the solidified shell. For instance, when the current is 500 A, the solidified shell thickness at the mold outlet decreases by approximately 3 mm. Additionally, the weakening of the upward circulation leads to a more uniform velocity distribution at the steel/slag interface. With the increase in current intensity, the horizontal flow of molten steel is further promoted, reducing the downward circulation velocity and effectively decreasing the impact depth. To quantitatively characterize the overall level fluctuation and flow of the steel/slag interface in the mold, evaluation criteria for the average level fluctuation and velocity uniformity were proposed. The results indicate that the level fluctuation and molten steel flow at the steel/slag interface are optimal under the electromagnetic stirring parameters of 500 A and 3.2 Hz.

To investigate the synergistic effects of electromagnetic stirring in the secondary cooling zone and at the solidification end during the slab continuous casting process, a slab arc continuous casting machine from a specific plant was used as a prototype. A three-dimensional transient electromagnetic field model was developed using the finite element method to analyze the electromagnetic stirring characteristics of the traveling wave magnetic field. Additionally, a three-dimensional transient model for flow, heat transfer, and solidification was created using the finite volume method, incorporating the time-averaged Lorentz force into the momentum equation through one-way coupling. Numerical simulations reveal the influence of different electromagnetic stirring configurations on the solidified shell growth behavior during continuous casting. In the reverse mode of electromagnetic stirring of the secondary cooling zone, the magnetic induction generated by the two stirring rollers is in opposite directions, with a maximum intensity of 0.15 T. Correspondingly, the Lorentz force acting on the molten steel also has opposite directions, reaching a peak value of 15 324 N/m³. The molten steel exhibits a flow pattern resembling the shape of an “8” with a maximum flow speed of 0.42 m/s, and the temperature distribution is symmetric. The solidified shells formed on the left narrow face at point A and the right narrow face at point B are thinner. In the co-directional mode of electromagnetic stirring, the magnetic induction generated by the two stirring rollers is aligned in the same direction, with a maximum intensity of 0.22 T. The Lorentz force on the molten steel also aligns in the same direction, with a peak value of 42 000 N/m³. The molten steel flow forms a double circulation pattern with a maximum speed of 0.78 m/s. At the mold exit, the temperature is higher on the left side, resulting in thinner solidified shells at points A and B on the left narrow faces. The metallurgical length is approximately 33.04 m, which is about 12% longer than in the reverse mode.

The size and distribution of bubbles play a crucial role in determining the efficiency of metallurgical processes and the quality of the resulting products. A common challenge in current practices is the formation of excessively large and poorly dispersed bubbles, which significantly restrict heat and mass transfer, reaction kinetics, and the removal of inclusions between molten metal and bubbles. This paper systematically reviews recent progress in the refinement and uniform dispersion of bubbles in metallurgical systems. Key techniques such as gas injection parameter control, forced bubble detachment, argon blowing via submerged entry nozzles, dissolved gas flotation, mechanical stirring, and high-shear methods are examined in terms of their underlying mechanisms and practical performance. The fundamental principle of bubble refinement involves enhancing turbulent flow in the liquid phase to facilitate bubble breakup and suppress coalescence. Owing to the limitations of contact-based approaches in high-temperature molten media, non-contact electromagnetic flow control has emerged as a promising alternative. By generating intense liquid turbulence through electromagnetic forces, this method enables effective bubble refinement and homogeneous dispersion, offering considerable potential for improving metal purity and process efficiency in metallurgical operations.

To address the issue of poor temperature compliance in IF steel production at a domestic steel factory, a statistical study was performed to examine the temperature evolution trend throughout the smelting process. The results show that the converter tapping and continuous casting temperature compliance rates were only 55.56% and 44.57%, respectively, with the converter continually producing excessive tapping temperatures. The RH arrival temperatures for both initial casting and continuous casting exceeded goal values by 15 ℃ and 10 ℃, respectively, necessitating scrap additions during secondary refining for temperature correction. Controlling the RH arrival temperature between 1 600 and 1 625 ℃ helps minimize scrap consumption during refining, limiting the influence on nitrogen pickup during RH treatment. Process optimization should focus on rational adjustment of converter tapping temperature, improvement of ladle heating systems and thermal management, and implementation of precise narrow-window temperature control throughout the entire production route to achieve more stable thermal conditions.

The clogging behaviors of sub-merged nozzle (SEN) in three types of Ti-baring Al-killed steels including ultra-pure ferritic stainless steel, austenitic stainless steel and interstitial-free steel were studied by cross section observation and acid dissolution method. The results show that Al₂O₃ inclusion is the main inclusion comprising the transition layer, and MgO·Al₂O₃ caused by poor calcium treatment is the main factor for the growth of nozzle clogs. TiO₂ formed by the reaction between liquid steel with refractory material is the main inclusion in the transition layer, and subsequently the TiN precipitation caused by poor control of titanium-nitrogen product and steel cleanliness combined with rapid heat transfer of transition layer deteriorates castability. Metallic iron comprises a major amount of the transient layer of interstitial-free steel and Al₂O₃inclusion plays a dominant role in the clogging layer. TiN inclusions have less influence on clogging behaviors during continuous of ultra-pure ferrite and interstitial-free steels. The good wettability of titanium-containing liquid steel and titanium oxide will accelerate the clogging process in interstitial-free steels. The personalized strategy should be adopted for the mitigation of SEN clogging according to the steel characteristics and refining equipment.

The finite difference model for 320 mm×410 mm continuously cast bloom of 1.4418 martensite stainless steel was established based on the equipment condition in a domestic factory, and it was verified by the shell thickness and surface temperature in the plant. The solidification characteristic and mechanical reduction reasonability in continuous casting of 1.4418 martensite stainless steel were discussed numerically, and the most suitable casting speed was found as 0.45 m/min. Two sets of mechanical reduction parameters were designed with total reduction amount of 12 mm and 15 mm, respectively. The industrial test was carried out according to the optimized schemes by numerical modelling, and the successful operation was achieved within the rated power range of withdraw units. The best center quality of the bloom for 1.4418 martensite stainless steel was obtained when the casting speed was 0.45 m/min with the designed reduction amount for No.2—5 withdraw units about 4 mm, 4 mm, 4 mm and 3 mm respectively, and the pass rate for the level A flaw detection was measured to be around 97%, satisfying the requirement of batch production and delivery.

To investigate the effect of electromagnetic swirling flow in the nozzle (EMSFN) technology on the molten steel flow behavior in a slab continuous casting mold, a water model system with a geometric scaling ratio of 3∶1 was established based on similarity criteria, using a slab mold (1 450 mm×200 mm) as the prototype. A mechanical swirling rotor was installed inside the submerged entry nozzle to simulate the external field intervention effect of EMSFN. The influence of the nozzle swirling flow on the fluid flow pattern, liquid level fluctuation, and velocity distribution within the mold under different outlet flow rates of water model system was systematically studied. The results show that under conventional casting conditions, the flow field in the mold is asymmetrically distributed, with interfering upward flow occurring in the lower recirculation zone. The liquid level fluctuation intensified with increasing outlet flow rate, exceeding ±2 mm near the nozzle. After applying the nozzle swirling flow, the flow field symmetry was significantly improved. The impingement point of the nozzle outflow on the narrow face shifted upward, effectively dissipating the kinetic energy of the lower flow and suppressing the lower vortex, thereby stabilizing the liquid level fluctuation within ±1 mm. This study confirms that applying nozzle swirling flow enables effective control of the mold flow field, which provides a theoretical basis for the industrial application of EMSFN technology in slab continuous casting.

Center porosity is one of the main defects of continuous casting round billet. In order to reduce the center defect of the continuous casting round billet, the mechanical reduction is performed at the solidification end of the continuous casting round billet. According to the actual production situation of a factory, a three-dimensional finite heat transfer model of the continuous casting round billet was first established to simulate solidification, and according to the results of the heat transfer model, different reduction positions were determined. Then, the mechanical reduction processes of the continuous casting round billet with a diameter of 350 mm were simulated using a thermodynamic coupling model. At the same time, the relative change of the shrinkage cavity volume was used as the standard to evaluate the influence of the reduction position on the shrinkage cavity healing. Finally, the experiment of continuous casting round billet pressing was carried out. The results show that during the reduction process of continuous casting of round billet, the central shrinkage cavity became closed under the combined effects of metal filling and compression deformation. The reduction position corresponds to the solid fraction in the center of the continuous casting billet, and the metal flow condition is different at various reduction positions. Under the same reduction amount, when the central solid fraction of the continuous casting round billet increases, the flow range of the central metal of the continuous casting round billet will gradually decrease, and the relative flow distance of the metal will first increase, then remain unchanged, and finally decrease, and the central shrinkage cavity of the casting round billet will gradually decrease and finally become close. When the reduction is 15 mm, the optimal reduction interval of the continuous casting round billet is f_s=0.6-1.0. The experimental results show that the inner porosity of continuous casting round billet decreases after reduction.

Nozzle clogging is widely present in low-carbon steel, stainless steel, rare earth steel and other steel. Numerical simulation of nozzle clogging during continuous casting can reveal the formation process of deposits and quantitatively analyze the influence of various factors on clogging. The results provide theoretical guidance for controlling and mitigating nozzle clogging. However, current simulations are performed off-line. Furthermore, numerical simulation can predict the location where clog deposits break off, the size of the broken fragments, as well as their distribution and inheritance within the cast strand. To date, researchers have developed corresponding mathematical models based on the four main formation mechanisms of nozzle clogging, and the findings have been validated through both laboratory and industrial experiments. Nevertheless, nozzle clogging incidents still occur occasionally in practice. There is currently a lack of real-time prediction methods for the evolution of clogging. Future studies on numerical simulation of nozzle clogging may focus on real-time forecasting of clogging development and prediction of the distribution of broken clog materials in the cast product.

Continuous casting is a key process in steel production, serving as an intermediate step between steelmaking and rolling. In order to reduce the computational power requirements of the slab identification model in practical deployment, the research on lightweighting the slab identification model while ensuring its accuracy was conducted. Initially, a detection algorithm based on the AD-PAN feature fusion structure incorporates the lightweight MobileNetV3 backbone network to extract features of the slab numbers, with the goal of enhancing image classification performance while maintaining the model's lightweight characteristic. Subsequently, the model underwent Collaborative Mutual Learning (CML) distillation to ensure the precision of slab number detection. Ultimately, experimental comparisons were conducted to assess the performance of the lightweight model. The outcomes demonstrate that although there was a modest trade-off in model accuracy due to the lightweight research, there was a significant reduction in the model's parameter volume and a marked improvement in the model's detection speed.

The flow and heat transfer state of molten steel within the slab continuous casting mold is a critical factor determining the quality of the final slab. Utilizing artificial intelligence technology to achieve real-time, precise prediction and intelligent control of this complex multiphysics field is of great significance for improving the quality of high-end steel and promoting the intelligent transformation of the steel industry. To this end, this study first established a mechanistic model of molten steel flow, heat transfer, and solidification under electromagnetic stirring (EMS) in a slab continuous casting mold. Furthermore, a set of flow field evaluation criteria for the mold was proposed—namely, a steel-slag interface slag entrapment-freezing index, a shell uniformity index, and an inclusion removal index—with the aim of optimizing the EMS process. Secondly, based on the dataset of 3D flow and temperature fields generated by the aforementioned model, a large-scale multiphysics prediction model for the mold was developed using a deep neural network (DNN) architecture, enabling rapid prediction of the multiphysics field within the mold. The results show that, compared to traditional numerical simulation results, the prediction errors of the large model for the multiphysics fields, including the flow and temperature fields within the mold, are all within 10%. Meanwhile, the model′s computational speed was significantly increased, with the average computation time to obtain the multiphysics field within the mold being drastically reduced from the original 24 hours to 2 seconds. This research provides key technical support for achieving online optimization and closed-loop control of the EMS process and for the construction of a "Digital Twin" system.

Both the pre and prost processing modules for the calculation of heat transfer and solidification in continuous casting were compiled to integrate with ProCAST simulation software by the treatment of bow geometry of the caster machine and the non-uniform water spray flux in the secondary cooling zone. The temperature distribution and solid fraction in both the longitudinal and transverse sections of the extra-thick slab were obtained by the numerical simulation of the practical continuous casting process. The results show that the liquid pool in the shape of “W” would form in the central broad section of the slab with the less water flux in the edge compared to that in the central broad face. The solidification homogeneity in the slab cross section could be improved by adjusting the spray flux in the secondary cooling zone.

In the continuous casting process, numerous factors influence product quality, among which the temperature control of steel billets is particularly critical. Excessively high temperatures can cause surface oxidation of billets, leading to resource waste, while excessively low temperatures can reduce billet plasticity. The secondary cooling zone regulates strand temperature in continuous casting via water spray systems, with spray intensity being the dominant control parameter for surface temperature. Malfunctions in the cooling water system, improper operation by on-site personnel, or delayed maintenance can sometimes affect the spray volume of the secondary cooling nozzles, leading to water leakage. Such leakage leads to excessive water accumulation in localized regions of the strand, inducing severe localized cooling that generates thermal stresses sufficient to cause cracking defects. This paper employs infrared imaging, utilizing machine vision and a water leakage detection algorithm to separate foreground objects from the background in video streams, enabling precise identification of water leakage in spray equipment. Experimental results demonstrate that this method effectively detects leakage areas in secondary cooling nozzles, achieving a 100% alarm accuracy rate during testing, thereby providing technical support for subsequent maintenance.

The systematic traceability analysis was conducted on the issue of linear defects (“sliver”) affecting the product qualification rate during the production of IF steel automotive panels using BOF-RH rimming steelmaking/vacuum decarburization/aluminum deoxidation process on a domestic production line. Through sampling, testing, and process data analysis of the entire smelting casting rolling process, the influencing factors and laws of the upstream process conditions of steelmaking and continuous casting on the “sliver” defects on the surface of the strip steel were systematically evaluated, and the process parameters were further improved. The research has shown that the “sliver” defects on the surface of IF cold-rolled strip steel are mainly caused by large-sized Al and O deoxidation products in the molten steel, and slag containing elements such as Si, Ca, Na, Mg, which are captured by the solidification of the casting slab and extended and exposed on the surface during the rolling process of the strip steel. The tapping temperature of the IF steel converter was controlled between 1 600 ℃ and 1 630 ℃, which was shown to reduce the necessity of oxygen blowing and aluminum heating operations due to low RH arrival temperatures, thereby effectively decreasing both total aluminum consumption and the quantity of Al-O inclusions in the steel liquid. The tapping temperature of the IF steel converter was controlled between 1 600 ℃ and 1 630 ℃, which was shown to reduce the necessity of oxygen blowing and aluminum heating operations due to low RH arrival temperatures, thereby effectively decreasing both total aluminum consumption and the quantity of Al-O inclusions in the steel liquid. Measures such as controlling the superheat of the ladle in the continuous casting process to 20-30 ℃ were implemented to alleviate the pressure on the heating value requirements of the upstream process. Additionally, the protection of the casting process was further strengthened, and the water nozzle insertion depth was optimized, which effectively promoted the upward floating of oxides in the steel to the powder slag. “sliver” defect coils are mostly located in the later stage of casting, mainly distributed from the inner arc to the center of the billet. Immersion nozzles are used to ensure active steel tapping, with a frequency of nozzle replacement less than 6 ladles and small steps adjustments to the cast speed. These measures can achieve stable control of the crystallizer flow field and slag/steel interface, effectively reducing the probability of slag rolling in the crystallizer.

In the steel continuous casting process, center porosity and shrinkage cavity are two common quality defects that can significantly affect product performance. Accurately predicting these defects is essential, as it not only avoids destructive testing but also supports technicians in adjusting process parameters, thereby ensuring the smooth progression of subsequent rolling operations. However, due to the nonlinear dynamics, strong coupling characteristics, and multiple external disturbances inherent in the continuous casting process, predicting center porosity and shrinkage cavity levels remains highly challenging. Existing approaches typically rely on single-task learning, which limits their ability to predict multiple defects simultaneously. This constraint not only reduces prediction efficiency but also often results in suboptimal accuracy that fails to meet production requirements. To overcome these limitations, this study proposes a novel defect prediction method based on a multi-task learning framework, which integrates multi-task learning with the TabNet deep learning model designed for tabular data. This approach enables simultaneous prediction of both center porosity and shrinkage cavity levels by leveraging the intrinsic relationship between the two defects, thereby improving both efficiency and predictive accuracy. Extensive experiments using real-world production data from a steel plant demonstrate that the proposed method achieves outstanding performance in industrial defect prediction, with prediction accuracies of 100% for center porosity and 99.9% for shrinkage cavity, and a 53.47% reduction in inference time, fully validating the effectiveness and practical value of the proposed multi-task learning strategy.

Linear slag defects, classified into parallel double-line, strip-type, and blister-type morphologies based on their characteristic features, have been identified as the predominant quality issue in cold-rolled automotive sheet production. Through systematic analysis, the formation mechanisms of these defect morphologies were determined to be correlated with the entrapment depth of liquid slag in the slab and its subsequent exposure characteristics during rolling. The defect distribution characteristics were quantitatively established, with parallel double-line and strip-type defects being predominantly observed at an average depth of 5 mm beneath the slab surface, with 95% of occurrences confined within an 8 mm subsurface layer. A proprietary defect tracing system was employed, revealing that 80% of cold-rolled slag defects were inherited from hot-rolled products, with slag entrapment primarily occurring within 200 mm of the mold meniscus. The mold flow field dynamics were investigated through combined thin steel plate and deflection rod measurement techniques, enabling both qualitative and quantitative characterization. Based on these findings, an optimized argon injection strategy was developed, incorporating low flow rates, increased nozzle immersion depth, and enhanced downward angle. This technological innovation resulted in the proportion of meniscus fluctuations within ±3 mm being elevated from 55% to over 90%, leading to a significant reduction in linear slag defect occurrence rates.

High-speed slab continuous casting can significantly improve production efficiency; however, severe fluctuations in liquid surface flow velocity under high casting speeds are prone to causing slag entrainment defects, and most conventional slab continuous casters are not equipped with electromagnetic braking systems. To explore a low-cost and high-efficiency flow field control method under high casting speeds, this study proposes a new approach: suppressing rapid liquid surface flow by inserting baffle rods. Using a combination of numerical simulation and physical water modeling, a 920 mm×180 mm mold model was established. With the diameter (30, 50, 70 mm) and insertion depth (10, 15 cm) of cylindrical refractory rods as variables, the regulation laws of cylindrical baffle rods on the liquid surface flow velocity and fluctuation in the mold were investigated.The results show that the diameter of the baffle rod plays a dominant role in regulating the mold flow field. Compared with the condition without a baffle rod, the 70 mm baffle rod reduces the overall flow velocity by 19.5%, which is 3.2 times the reduction rate of the 30 mm baffle rod (6.1%). The reduction in liquid surface fluctuation increases from 11% to 39%, a 3.5-fold improvement. The effect of insertion depth on the flow field exhibits a threshold effect: only when the diameter is no less than 50 mm, increasing the insertion depth to 15 cm can additionally reduce the flow velocity by 3.2%-5.4% and the fluctuation by 12.8%. For small-diameter rods (30 mm), increasing the depth has a weak regulatory effect.The optimal parameter combination in this study is a baffle rod with a diameter of 70 mm and an insertion depth of 15 cm. Under this condition, the maximum liquid surface velocity (at point P2) decreases to 0.2 m/s (a cumulative reduction of 17.7%), and the velocity in the central area (at point P4) decreases to 0.115 m/s (a reduction of 22.8%). The fluctuation value in the jet core area (at point P2) decreases to 0.21 cm (a reduction of 40.0%), and the fluctuation in the slag entrainment risk area (P2/P5) stabilizes at 0.21-0.23 cm.

To explore the causes of sliver defects on the surface of SPHC hot rolled plates produced by the third generation thin slab continuous casting and rolling technology in a factory, a comprehensive analysis was conducted. Samples of the SPHC hot rolled plates were collected, and both the morphology and composition of the defect surfaces and cross sections were examined using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and large sample electrolysis. The study revealed that the primary components of the inclusions at the defect sites were CaO-SiO₂-Al₂O₃-MgO-Na₂O composite inclusions and Al₂O₃ particles. The presence of CaO-SiO₂-Al₂O₃-MgO-Na₂O composite inclusions is attributed to mold slag entrainment, while the Al₂O₃ particles are likely a result of secondary oxidation of molten steel and nozzle clogging. Additionally, an analysis of the slab quality produced under identical process conditions was performed. Following slime electrolysis of the slab, it was determined that the major composition of large inclusions in the slab was Ca-Al-O. Out of 131 large inclusions extracted, 13% were primarily composed of Ca, Al, Si, Mg, K, and Na, supporting the hypothesis that these inclusions also arise from mold slag entrainment. Furthermore, 31.8% of the large inclusions contained more than 10% of elements such as Nb, Mo, Ni, and W. These elements are believed to originate mainly from scrap or alloy additions during the steelmaking or refining process prior to continuous casting, with the high content potentially due to ladle slag involvement during pouring. In conclusion, the research identified mold slag entrainment and secondary oxidation as significant contributors to the sliver defects on SPHC hot rolled plates.

The distribution law of heat flow inside the mold is crucial for calculating the temperature field of the casting billet, which will affect the process design of high casting speed. The average heat flux empirical formula, the maximum heat flux and the heat flux distribution formula related to the high drawing speed range in the literature were studied and analyzed. Based on the measured data of high speed for billet, the average heat flux formula was proposed. In response to the problems in the heat transfer distribution law of mold in the calculation and simulation of high speed temperature fields, the method for determining heat flux distribution was improved. The results show that the average heat flux fitting formula suitable for high pulling speed is 1.34·v_c^0.502 (v_c unit: m/min), and the simulated average heat flux is consistent with the measured value. According to this method, the average heat flux obtained by simulating the heat flux distribution of the mold is strictly equal to the given (according to regression or on-site measurement) average heat flux, ensuring that the calculated heat flux of the model is the same as the measured one. Combining with the actual example of high speed of billet, the decisive influence of heat flow distribution in the mold on the calculation results is demonstrated, and the selection of model coefficients is discussed. The most important thing is that the distribution index n is around -0.5, which is related to the variation of shell thickness in mechanism analysis.

Abnormal large austenite grains are considered a significant cause of transverse cracks in continuous cast billets. Thermal simulation methods combined with in-situ liquid quenching experiments are employed to investigate the growth process of surface austenite grains in nine types of microalloyed steel during the bending-type continuous casting process. Results show that at the straightening starting point, where corner transverse crack defects are likely to occur, the size of abnormally coarse austenite grains increases with rising austenite start growth temperature T_γ, exhibiting an extremum near the peritectic point. As the absolute difference |ΔT| between T_γ and the precipitation temperature of TiN increases monotonically, it indicates that the austenite start growth temperature and the TiN precipitation temperature are key factors influencing abnormal austenite growth. High-temperature tensile tests demonstrate that steels with higher austenite start growth temperatures and larger |ΔT| show greater crack sensitivity, which is consistent with the pattern of abnormal austenite growth.

For the continuous casting of high-speed small square billets, a solidification heat transfer model was constructed. A dual-mode water spray control algorithm based on the target surface temperature and effective casting speed was proposed, and front-end and back-end applications with a B/S architecture were developed using JAVA and VUE. This model was applied to the production of HRB400 steel grade on a 170 mm × 170 mm square billet continuous caster for practical verification. After application, the low magnification quality of the billets was significantly improved. The proportion of central segregation better than grade 1.5 increased by 3.5%, and the proportion of central porosity better than grade 1.0 increased by 1.2%.

Ti-bearing steel in continuous casting process exists serious problems such as nozzle clogging and steel slag reaction. The interface behavior of mold flux with different basicity on TiC substrates were investigated by the sessile drop method, which can provide a theoretical basis for optimizing the composition of the mold flux for Ti-bearing steel. Firstly, the evolution law of wetting behavior with temperature in the contact process between mold flux and TiC was analyzed. As the increase of the basicity of mold flux, the wettability between mold flux and TiC substrate gradually decreased, and the contact angle was CS slag(CaO-SiO₂, 19.8°)>CSA slag(CaO-SiO₂-Al₂O₃, 20.9°)>CA slag(CaO-Al₂O₃, 31.5°). The results show that there is no interfacial reaction behavior between the mold flux and the TiC, but there is a mass transfer process between the two interfacial phases. The basicity of mold flux is an important factor affecting the mass transfer process between mold flux and TiC interface, and the increase of basicity can inhibit the mass transfer process. The SEM-EDS analysis results show that the interaction layer between CS slag and TiC inclusion is the thickest, about 30-80 μm, and the absorption capacity of CS slag to TiC inclusion is the strongest. On the contrary, the interaction layer between CA slag and TiC inclusion is the thinnest, about 30-50 μm, and the absorption capacity of CA slag to TiC inclusion is the worst.

Continuous casting is one of the most critical processes in steelmaking. The occurrence of breakouts during continuous casting is influenced by multiple factors, with sticker-type breakouts being the most prevalent, accounting for approximately 70% of all breakout incidents. Breakout accidents in continuous casting can lead to molten steel leakage, posing severe safety hazards such as scalding, fires, and even explosions. These incidents may result in casualties and significant property damage. In view of the above difficulties, the factors influencing the bonded steel leakage of continuous casting from the process parameters of continuous casting production are systematically sorted out and the influence of slab size, casting speed, cooling water and heat flow on the bonded steel leakage of slabs are analyzed. The analysis of bonding in slabs with different widths (1 350, 1 500 and 1 550 mm) shows that the average heat flow fluctuates most significantly in the 1 550 mm thickness slab, and as the slab width increases, the fluctuation in average heat flow becomes more pronounced, leading to a higher likelihood of slab bonding. And for slabs with large wide surface sizes, a reasonable drawing speed should be selected during production to avoid the occurrence of bonding accidents. Finally, preventive measures are proposed to avoid bonded steel leakage, addressing process parameters, personnel operations, and management systems. These recommendations provide theoretical and technical support for the safe production of continuous casting.

The flow behavior of molten steel in the Ruhrstahl-Heraeus (RH) furnace critically influences the efficiency of refining processes, including decarburization and impurity removal. While the widely employed gas-stirring technique effectively enhances molten steel circulation, the associated bubble flow is difficult to control precisely, potentially leading to flow instabilities and uneven energy distribution that limit further gains in refining efficiency. Therefore, in order to optimize the flow behavior within the RH furnace, this paper conducts an optimization simulation of the electromagnetic stirrer in the RH riser. The results show that the inner diameter of the iron core should be minimized to 750 mm to maximize the magnetic field strength; The outer diameter and thickness are optimized to 1 500 mm and 100 mm respectively, at which point the magnetic field performance and material cost are balanced; The stirrer is positioned 125 mm from the top to generate the maximum force. When the coil is 75 mm away from the molten steel, the magnetic field distribution of the iron core is the most uniform, without local magnetic concentration areas, and the magnetic field strength of the molten steel reaches a relatively high level; The simulation determines that 110 turns of coil, a frequency of 5 Hz, and an current below 250 A are the optimal combination, which can generate an average magnetic induction intensity of over 0.04 T and achieve the best matching of electromagnetic force and penetration depth. After coupling the optimized electromagnetic field into the flow field, the circulation flow increases by 6.3%, which proves the optimization effect of the electromagnetic stirrer. This study clearly defines a set of optimal three-phase six-level electromagnetic stirrer parameters for the RH riser when the inner diameter is 650 mm, providing theoretical basis and parameter guidance for its industrial design.

The effect of stand electromagnetic stirring on the fluid flow and heat transfer behavior of molten steel during continuous casting of ø800 mm round billet was investigated. The results indicate that the stirring position has an important influence on the flow state, flow direction, stirred volume, and cooling rate in the molten steel. Within the strand zone, lowering the stirring position reduces the angle between the radio flow direction of the solidification front from 30° to 0°, while the helical angel of the longitudinal flow trajectory increases from 30° to 55°. The flow tendency toward the core weakened, and the stirring velocity at the solidification front decreased from 0.008 m/s to 0.003 6 m/s. Among them, when the stirrer is located in the upper-middle section of the CET zone, the flow stability of the molten steel is significantly improved. The stirring speed at the solidification front is 0.005 6 m/s, and the effective stirring volume of molten steel is the largest, which is 0.045 3 m³, with a tendency to flow to the core. In terms of heat transfer, the heat loss of molten steel in the stirring zone is faster. When the stirring is in the upper-middle section of the CET zone, it is beneficial to improve the equiaxed crystal rate and accelerate the solidification rate of the billet. Therefore, the stand electromagnetic stirring position in the upper-middle section of the CET zone is the best, which provides an important guiding significance for the optimization of the electromagnetic stirring process.

Focusing on slab defects such as longitudinal cracks and depressions in 2Cr13 martensitic stainless steel produced at a steel plant, the high-temperature characteristics of the steel and the physicochemical properties of the used mold fluxes were systematically investigated. Results indicate that 2Cr13 martensitic stainless steel undergoes a peritectic reaction during solidification, with the initial solid fraction reaching 88.77% at the onset of this reaction. The DSC curves exhibit significant fluctuations at high-temperature stage, indicating a poor thermal stability of the steel. Additionally, the steel has also the characteristics of high tensile strength but low thermal plasticity. These characteristics will easy to cause the non-uniform growth of the initial solidification shell, leading to the formation of the slab defects. Comparative analysis of two commercial mold fluxes (S1 and S2) reveals similar effective chemical compositions, viscosity, and melting temperature. However, S2 flux contains a significant lower proportion of pre-melted material compared to S1 flux. During actual application, low-melting-point Na₂CO₃ in the S2 flux tends to melt preferentially, inducing segregation phenomena. Consequently, the Na₂CO₃ content in the liquid slag exceeds designed values, reducing both the viscosity and break temperature of the slag. This results in an uneven distribution of flux films and weakens the heat transfer regulation capacity, thereby increasing the propensity for longitudinal cracks and depressions in the cast slab. These findings provide crucial insights for optimizing mold flux design and casting parameters in the continuous casting of martensitic stainless steels.

In the context of the global "dual carbon" strategy, ultra-high speed thin slab continuous casting has become a key technology for the green transformation of the iron and steel industry, owing to its significant advantages in energy saving, emission reduction, and product quality. However, high casting speeds (6-8 m/min) lead to issues such as unstable molten steel flow and inadequate lubrication by mold flux, which hinder further development. Although electromagnetic braking (EMBr) technology can suppress molten steel turbulence through applied magnetic fields, its specific effects on mold flux properties remain unclear. This study systematically investigates the evolution of physicochemical properties of ultra-high speed thin slab mold flux under magnetic fields. The results indicate that a mold flux with a basicity (R) of 1.67, viscosity of 0.22 Pa·s, melting point of 1 042 ℃, and a Na₂O-Li₂O-F flux system exhibits excellent process adaptability, meeting the requirements of rapid melting and uniform lubrication at high casting speeds. Under a magnetic field intensity ranging from 0 to 90 mT, the crystallization behavior of the mold flux is significantly influenced: increasing magnetic field strength advances nucleation time, prolongs the crystallization interval, inhibits crystal growth, and increases solidification volume expansion by 23%. Microstructural analysis reveals that the magnetic field promotes preferential growth of the Ca_0.87Mn_0.19Mg_0.94Si₂O₆ phase, increasing its proportion by 5.2%, and induces a transition in the silicate network from a disordered to an ordered structure. Water quenching experiments combined with XRD and Raman spectroscopy confirm that the magnetic field alters solute transport by suppressing melt flow, thereby regulating the solidification shrinkage behavior and microstructure of the mold flux. This study reveals, for the first time, the performance evolution mechanism of ultra-high speed casting mold flux under an electromagnetic field, providing a theoretical basis for developing mold fluxes compatible with EMBr technology and contributing to the industrial application of ultra-high speed continuous casting.

This study utilizes a low-Reynolds number k-ε turbulence model to construct a three-dimensional magnetohydrodynamic coupling numerical model, investigating the impact of electromagnetic stirring (EMS) current intensity and stirrer positioning on the flow, heat transfer, and solidification behavior of molten steel within the continuous casting mold for 140 mm×140 mm billets of 82B steel at a particular steel plant. The results demonstrate that the current intensity is a critical determinant of stirring efficacy; increasing the current intensity leads to a reduction in the depth of the primary steel jet impact, an increase in tangential velocity, and accelerated dissipation of superheat within the mold, resulting in a thinner solidified shell and a scouring effect on the shell due to backflow near the mold, which appears a slow growth zone in shell thickness. Variations in stirrer positioning also alter the flow field characteristics; the lower the position, the more the main flow core descends, and the position and shape of the vortex change accordingly, reducing liquid surface fluctuations, although an excessively high exit tangential velocity may lead to uneven shell growth. For the continuous casting production of high-carbon steel billets at this plant, it is beneficial to appropriately elevate the EMS installation to 515 mm and enhance the stirring current intensity to the rated 600 A. This configuration keeps the liquid surface fluctuations within a controllable range and further promotes rapid dissipation of superheated molten steel, while also ensuring a certain degree of undercooling at the center of the foot rolling area, facilitating early nucleation of molten steel and enhancing the ratio of equiaxed grains, which is advantageous for improving the center segregation of the billet.

To address center segregation and shrinkage cavities in GCr15 bearing steel continuous casting billets, a steel plant established a solidification heat transfer model for large billets by integrating principles of heat transfer, steel grade characteristics, and the spatial structure of the withdrawal and straightening equipment, employing the finite difference method. Leveraging the accuracy of this model, a final-stage reduction technology was developed and implemented on a seven-stand withdrawal and straightening system with 1 200 mm equal roller spacing, achieving safe and stable production with a total reduction of 22 mm. With this technology, the center carbon segregation index of high-carbon steel billets has been consistently maintained within 0.95-1.05, the proportion of billets with a carbon extreme deviation not exceeding 0.08% has increased to 98.4%, and 99.95% of billets now exhibit center shrinkage cavities of grade 0.5 or lower. This breakthrough enhancement in internal billet quality has enabled the plant to adopt a low compression ratio rolling process for producing large-size bars, which achieve an ultrasonic testing pass rate exceeding 99.95% in accordance with the AA grade of GB/T 4162.

As an important operation procedure in continuous casting process, tundish casting can be divided into two stages: steady casting and unsteady casting. Although the unsteady casting process is short, the pollution caused by the process is often the most serious. In order to reduce the pollution of molten steel during the unsteady and steady casting process and improve the quality of liquid steel, the parameters in tundish were optimized better, and a second-flow tundish water model with geometric similarity ratio of 1∶4 was established. The tracer experiment, residence time distribution (RTD) experiment and three-phase cold water model experiment were carried out respectively. The effects of insertion depth and filling flow rate on the flow pattern, mixing characteristics and the evolution of slag-steel interface were analyzed. Experimental results from steady casting tests demonstrate that both the average residence time and dead zone volume fraction decrease with increasing flow rate at the long nozzle. Additionally, increasing the insertion depth of the long nozzle extends the average residence time of liquid steel from 226 to 246 s. In the unsteady casting test, it is found that the slag layer will appear in the filling process, that is, the slag eye will appear around the long water outlet, and the slag eye will not disappear immediately after the filling of the stable stage. The increase of the filling flow rate and the insertion depth of the long water outlet will lead to the increase of the area of the slag eye and the increase of the appearance time of the slag eye in the re-stability stage. When the insertion depth of the long water outlet is 90 mm, the charging flow rate increased from 2.18 to 3.30 m³/h, the maximum slag hole area increased from 1 871 to 19 001 mm², and the existence time of the re-stable slag hole also increased from 41 to 232 s. Considering the overall performance during the pouring stage, a long nozzle insertion depth of 90 mm demonstrates optimal performance.

Crack breakout often occurs during the continuous casting process of peritectic steel, which seriously restricts the high-efficiency and high-quality production of peritectic steel continuous casting. Crack breakout mainly originates from solidification defects of the initial solidified shell in the mold. The phase transformation shrinkage of peritectic reaction forms air gaps, leading to uneven heat transfer and uneven thickness of the solidified shell, and crack breakout is prone to occur at the weak parts of the shell. This paper reviews the formation mechanism and conditions of depressions in peritectic steel continuous casting slabs, summarizes the typical characteristics and main influencing factors of slab corner crack breakout, wide-face off-corner breakout and wide-face center crack breakout, and also summarizes the influence laws of steel composition and process factors on crack formation. Aiming at the frequent crack breakout of peritectic steel, this paper puts forward requirements for improving crack breakout from aspects of process factors, mold flux properties and mold design, and points out that establishing a crack breakout risk prediction model for the continuous casting process based on the key influencing factors of crack breakout, and conducting early warning and timely intervention on accident precursor characteristics, is the development direction of future breakout prediction models.

This study investigates the effects of the upward traveling wave magnetic field (TMF) operating at different frequencies on the solidification process, microstructure refinement, and mechanical properties of an Al-7wt.% Si binary alloy. The alloy solidification samples were prepared using an electromagnetic casting device. A magnetic-flow-thermal multi-field coupling model was employed for numerical simulation of the melt solidification process, calculating the forced convection and liquid phase distribution within the Al-7 wt.% Si alloy melt subjected to TMF treatment. The results indicate that under 75 A 12 Hz-TMF, the peak velocity of the flow field within the Al-7 wt.% Si alloy melt reached 0.023 m/s. Under the combined effects of forced convection and Joule heating, the dendrite arm spacing (DAS) of the samples treated at 8 Hz-TMF was refined to 127.8 μm. Meanwhile, the ultimate tensile strength and elongation after fracture increased from 100.8 MPa and 6.9% (natural solidification, NMF) to 113.7 MPa and 8.3%. When the TMF frequency was increased to 12 Hz, the Joule heating generated within the melt gradually increased, leading to a reduction in the temperature gradient during the solidification process, thereby slowing down the solidification rate of the castings, and the refinement effect on the solidification structure decreased, with the average DAS increasing to 140.3 μm, and the mechanical properties consequently degraded. The results demonstrate that the convection induced by TMF and Joule heating are the primary reasons for the refinement of the solidification microstructure and the enhancement of mechanical properties. These findings provide a theoretical basis for the research on improving the quality and mechanical properties of castings through applied electromagnetic field casting technology.

Tundish plasma heating technology could reduce the tapping temperature and superheat fluctuation range, as well as improve the quality of casting billets, whose equipment has the advantages of easy installation, high heating efficiency, and low energy consumption. Focusing on the hot issues related to tundish plasma heating technology, the equipment characteristics were systematically described, the application progress of plasma heating technology in slab production was introduced, and the metallurgical effects of plasma heating technology in practical applications were analyzed. The effect of the device on the temperature, chemical composition, and inclusion removal in molten steel was revealed. It is demonstrated that the first domestically developed new hollow graphite electrode heating device has achieved a breakthrough in tundish heating technology. It effectively meets the production requirements of low-, medium-, and high-carbon steels, offering an effective solution to the problem of temperature heat loss in the tundish, and achieving the goal of energy-saving and consumption reduction.

Based on a finite element model, the magnetic induction intensity and Joule heat obtained from Maxwell were imported into Fluent as source terms to investigate the flow field and temperature field of molten steel in a five-strand four-channel induction heating tundish under the influence of ladle heat dissipation. The results show that, during the casting process, the temperatures at the three outlets of the tundish without ladle heat dissipation decrease slowly and exhibit a similar trend, with a temperature drop of less than 1 K among the outlets. In contrast, under the influence of ladle heat dissipation, the temperatures at the three outlets differ significantly, with a temperature difference of nearly 20 K between the early and late stages of casting. Although induction heating compensates for the temperature loss of molten steel in the ladle, it does not significantly reduce the temperature variation across different casting periods. The maximum outlet temperature is 11 K lower than the initial casting temperature. When the induction heating power is adjusted during casting, the maximum temperature difference between different time points remains within 2 K, and the temperatures remain relatively consistent across different periods and outlets.

To address the issues of flow field turbulence and unstable steel-slag interface in the thin slab continuous casting mold under high casting speed conditions, this study takes the FTSC thin slab mold and full-width single-segment electromagnetic braking (Ruler-EMBr) system of a steel plant as the research objects. A coupled model of Large Eddy Simulation (LES) and Volume of Fluid (VOF) is adopted for numerical simulation, with a focus on analyzing the influence law of different magnetic flux densities on the flow characteristics in the mold when the casting speed is 6.0 m/min. The results show that electromagnetic braking can effectively regulate the flow field in the mold, improve the stability of the steel-slag interface, and prevent the abnormal rise of the steel-slag interface. When the Ruler-EMBr system is applied with a magnetic flux density of 0.23 T, the maximum velocity of the steel-slag interface is controlled within 0.30 m/s, the maximum wave height is limited to 10 mm, the fluctuation range of the interface position is maintained within ±2 mm, and the turbulent kinetic energy of the steel-slag interface is suppressed below 0.045 J/kg. These findings fully verify the flow field regulation effect of the Ruler-EMBr system.

To address the significant erosion observed in the tundish dam with jet hole, a 65 t billet tundish from a domestic steel plant is researched. It employs numerical simulation to examine the distribution of impact stress on the upstream surface of the dam. The findings clarify the factors affecting the impact stress on tundish dam. Results indicate that the impact stress along the upper edge of the upstream surface is negative. Additionally, a specific impact stress exists at the lower section of the central axis, with peak stress recorded around the jet hole. The peak impact stress on the dam’s upstream surface exhibits a positive correlation with increasing casting speed. Variations in the distance between the weir and long nozzle show minimal effects on the peak impact stress, yet significantly alter the stress distribution around the jet hole. The impact stress distribution shows non-uniform characteristics at 1 400 mm, but demonstrates significantly improved uniformity at 1 800 mm.

As the primary feedstock for X65 pipeline steel, the continuous casting slab is prone to macrosegregation, which is one of the key defects limiting the performance of steel materials. To control solute segregation during the continuous casting process, a multiphase solidification model was established by coupling melt flow, macroscopic heat transfer, microstructural solidification evolution, and solute transport, with full consideration of the soft reduction process at the solidification end. The model was applied to systematically investigate the influence mechanisms of superheat and casting speed on slab macrosegregation. The computational accuracy was validated through carbon-sulfur analysis of industrial slabs. The results show that as the superheat increases from 14 ℃ to 30 ℃, columnar dendrite growth is enhanced and the equiaxed grain zone narrows. For every 8 ℃ increase in superheat, the equiaxed zone at the slab center decreases by 0.6-0.8 mm, and the segregation index increases by approximately 1.39%. The effect of casting speed on segregation control depends on the matching between the solidification end and the soft reduction zone: at 0.8 m/min, the solidification end (18.46 m) occurs before the reduction zone, resulting in ineffective reduction and a segregation index of 1.151; at 1.1 m/min, the solidification end (23.55 m) falls entirely within the reduction zone, where the reduction effect is most effective, yielding the lowest segregation index of 1.071; at 1.2 m/min, the solidification end (27.95 m) extends beyond the reduction zone, where insufficient coverage causes the segregation index to rise slightly to 1.082. This study clarifies the quantitative relationship among superheat, casting speed, and central segregation under fixed soft reduction conditions, providing a theoretical basis and process optimization guidance for the precise control of macrosegregation in slab continuous casting.

The size of bubbles directly influences the heat, mass, and momentum transfer processes between the bubbles and molten steel. The complexity of metallurgical processes and the high-temperature environment limit the application of conventional bubble refinement methods, resulting in generally large bubble sizes in molten steel, which severely restricts the production efficiency of metallurgical processes. This study proposes the periodically bidirectional rotating electromagnetic field to induce high-intensity turbulent flow in molten steel periodically, thereby achieving bubble refinement. Using numerical simulation methods, the turbulence intensity of molten steel under electromagnetic fields with different magnetic flux densities was investigated to determine the magnetic flux density suitable for bubble refinement. When the magnetic flux density increased to 240 mT, the turbulent flow of molten steel met the requirements for bubble breakup. The effect of the periodically bidirectional rotating electromagnetic field on the turbulent flow of molten steel was analyzed, and the bubble refinement effectiveness was examined. The proportion of large bubbles larger than 10 mm in the molten steel decreased to 3.09%, a reduction of 27.47% compared to conditions without the electromagnetic field. The number density proportion of bubbles in the 0.5-1 mm diameter range reached 40.03%, and the proportion of bubbles smaller than 5 mm was as high as 92.10%, an increase of 80.25% compared to conditions without the electromagnetic field. The turbulence intensity of molten steel under electromagnetic fields with different rotation periods and the corresponding bubble refinement effects were compared, with the optimal rotation period range identified as 3-5 s.