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During high-speed continuous casting, the effect of secondary cooling on the quality of the billet is more obvious, and the possibility of quality problems is higher. This study takes the continuous casting machine producing 165 mm × 165 mm billet as the research object. The six different secondary cooling schemes are designed with the 4.5 m/min casting speed. By comparing the shell deformation, surface stress, surface temperature recovery, and metallurgical lengths at different secondary cooling schemes, the secondary cooling scheme applied in the high-speed continuous casting process is selected. The results show that the surface temperature recovery and stress of the billet in Scheme 1 are higher than those of other cooling schemes. The metallurgical length and shell deformation of the billet in Scheme 4 are higher than those of other cooling schemes. In Schemes 2, 3, 5, and 6, the shell deformation of Schemes 3 and 5 is higher than that of Schemes 2 and 6. In Schemes 2 and 6, the maximum surface central stress of the continuous casting billet in the secondary cooling zone is 36.3 MPa and 31 MPa, respectively. Scheme 6 is used as the secondary cooling scheme of high-speed continuous casting in this study. The water quantity in secondary cooling zone 1 ~ 5 segments of Scheme 6 is 28 m3/h, 31 m3/h, 16 m3/h, 10 m3/h, and 6 m3/h, respectively. Finally, the industrial trial is carried out, which proves that Scheme 6 can be applied to high-speed continuous casting. [ABSTRACT FROM AUTHOR]

Transverse corner cracks are among the most common defects in high carbon and high carbon micro-alloyed grade slab casting. Calculation and analysis were done to minimize the negative strip time of mold oscillation, which is responsible for reducing the depth of the oscillation mark formed on the slab surface. The value of negative strip time decreases with an increase in the frequency of mold oscillation. Based on the trial results, it was suggested that the oscillation proportionality be adjusted from 1.2 to either 1.25 or 1.3. This adjustment will reduce the depth of oscillation marks and the tendency to form transverse cracks. The transverse crack on the narrow face of the slab was examined for crack analysis and compositional analysis. Microstructural analysis revealed that the crack has no branching and consists of an iron scale inside it. Furthermore, it is observed that the crack propagates across the allotriomorphic ferrite grains. [ABSTRACT FROM AUTHOR]

Due to the growing interest in lightweight constructions, the continuous casting of nonferrous metals is continuously developing as a result of the cost-effectiveness of this process, which combines several stages of sheet production. Unfortunately, because of the characteristics of the process, the parameters in the roll gap, such as, for example, pressure and temperature, are unknown, significantly affects the understanding of the phenomena occurring in the material during rolling. Therefore, at IMF Freiberg, a sensor consisting of a piezo sensor and two thermocouples measuring the temperature at two different heights was mounted on the surface of the roll, making it possible to control the process parameters live during the TRC trial. The measurements were further supported by a digital twin in the form of a layer model, combining a viscous and solid region for each layer in a single tool. The computations in this tool are performed offline and the computation time is in the order of seconds, thus much less than that of the finite element method. Because the layer model measures the temperature of the magnesium strip, FEM simulations were used to validate measurements from thermocouples. Experimental results have been obtained that allow for a direct correlation between the development of the pressure and temperature and the length of the fully solidified LD part in the roll gap zone, which correlates directly with the effective total equivalent strain. Using the sensor and layer model, it is possible to train a digital twin that can be used for online estimation of the final strip properties obtained in the TRC process. [ABSTRACT FROM AUTHOR]

In order to develop the aluminum sheets suitable for the twin-belt continuous casting and direct rolling, the composition optimization of Al-Mg-Mn alloys evolved from AA5052 (Al-2.5 Mg) alloy was firstly carried out via the synergy between the PANDAT software and the micro–hardness test. Subsequently, the influence of Er and Zr on the microstructure and mechanical properties of the optimized Al-Mg-Mn sheet (Al-1.5 Mg-0.8Mn) was investigated in this work. The results showed that the tensile properties of Al-1.5 Mg-0.8Mn sheets processed by the rolling and the subsequent annealing were improved by the co-addition of the Zr and Er. The optimized tensile properties (UTS: 320.5 MPa; YS: 231.6 MPa; E.L.: 6.75%) were achieved in Al-1.5 Mg-0.8Mn sheets modified by 0.2 wt.% Zr and 0.3 wt.% Er, which is attributed to the finest fibrous grains, the fine, homogeneously distributed residual Al6Mn, Al3Zr and Al3(Zr, Er) second phases and more nano-sized Al3(Zr, Er) precipitations. [ABSTRACT FROM AUTHOR]

In the current study, a three-dimensional mathematical model that integrated the large eddy simulation (LES) turbulent model, volume of fluid (VOF) multiphase model, and the dynamic mesh model, was developed to investigate the influence of the mold oscillation on the steel, slag, and air multiphase flow and the slag entrainment in a slab continuous casting mold. The results indicated that the mold oscillation led to an increase of about 0.35 m/s in the speed of molten steel at the impact point of the upper and lower circulation on the narrow surface. However, it reduced about 0.047 m/s in the maximum speed of the meniscus at 1/4 width of the mold. The Fast Fourier Transform (FFT) analysis revealed that the characteristic frequency of the speed fluctuation in the gravity direction of the meniscus near the narrow surface was 1.27 Hz without the consideration of the mold oscillation. Upon the application of the mold oscillation, a new characteristic frequency of 3 Hz, matching the mold oscillation frequency, emerged with twice the intensity of the original 1.27 Hz frequency. Moreover, the mold oscillation had little effect on the characteristic frequency of the speed fluctuation on the meniscus far away from the narrow surface. A user-defined function (UDF) was employed to quantify the number, size, and spatial distribution of entrained slag droplets. The net slag entrainment rate was reduced from 0.0152 to 0.0113 kg/s after the consideration of the mold oscillation, and the number of entrained slag droplets was also decreased. The effect of mold oscillation on the size distribution of entrained slag droplets and the occurrence location of the slag entrainment on the meniscus were not significant. [ABSTRACT FROM AUTHOR]

As a typical metallurgical defect, macrosegregation seriously affects the internal quality of the continuous casting billet, and it cannot be solved by processes such as high-temperature diffusion and rolling. For continuous casting billet, the solidification shrinkage and thermal shrinkage of the microstructure directly affect the macrosegregation defect. In order to reveal the effects of solidification shrinkage and thermal shrinkage on the melt flow, microstructure distribution, and solute segregation, a multiphase solidification model based on the Eulerian–Eulerian approach was established in this work. The growth behaviors of the columnar dendrite trunk and the columnar dendrite tip were fully considered, as well as the nucleation, growth, free migration of equiaxed grains, and the columnar-to-equiaxed transition (CET). Besides, the corresponding relationship between the secondary dendrite arm spacing (SDAS) and the cooling rate has also been taken into account in the model, which makes the net mass transport source term of the mass conservation equations more accurate. The calculation results show that when no any shrinkage behavior is considered in the model, the melt flow velocity in front of the solidification end will gradually decrease until it is the same as the casting speed, and the segregation index at the billet center will gradually increase until it reaches the maximum value at the solidification end. Both thermal shrinkage and solidification shrinkage can generate a negative pressure zone in the billet center, sucking the poor-solute melt located the upstream of continuous casting strand flows towards the solidification end, and mixing with the enriched-solute melt before the solidification end, thereby inhibiting macrosegregation. However, compared with the solidification shrinkage, the effect of thermal shrinkage on reducing the positive segregation index in the billet center is limited. [ABSTRACT FROM AUTHOR]

Understanding the formation of a slag rim on the mold meniscus is crucial for controlling surface defects in the initial shell. However, there is a scarcity of quantitative studies on this matter. This study has developed a comprehensive three-dimensional (3D) numerical model for analyzing the meniscus multi-phase flow, heat transfer, and solidification, considering mold oscillation. The 3D morphology of the solidifying shell and the slag rim in the meniscus region were accurately reproduced. The solidification depth (DIS), solidification length (LIS) and oscillation mark depth (DOM) of the initial shell were used to quantify the morphological characteristics of the initial shell. The results confirmed that the formation position difference of the slag rim along the circumferential direction of the mold significantly affects the initial solidification and uniform growth of the shell. In the corner of the mold, the deeper overflow makes the oscillation mark extend 2.8 to 3.2 mm in the direction of casting. In addition, in order to quantitatively investigate the influence of the slag rim, a two-dimensional (2D) model is established with phenomena and parameters considered the same as those of the 3D model. According to the slag rim morphology obtained by the 3D model, in the 2D model, it is proposed to construct three slag rims with the same maximum thickness of 6 mm at 10, 20 and 35 mm above the meniscus (HRim). The simulation of initial shell morphology revealed that a lower formation position of the slag rim led to more severe overflow of molten steel from the meniscus, resulting in non-uniform continuous growth of the initial shell. This increases the likelihood of potential blockage in the liquid slag flow towards the slag channel between solidified shell and mold. [ABSTRACT FROM AUTHOR]

Direct measurement of the wetting angles of the mold fluxes is a strenuous work and time-consuming, and a mathematical model relating the wetting angle of mold flux to its chemical composition is rarely found up to now. In this work, multiple linear regression (MLR), backpropagation neural network (BPNN), and GA-BP neural network (GA-BPNN) are used to model and predict the wetting angle of mold flux. Results show that the accuracy of MLR, BPNN, and GA-BPNN model is 76, 62, and 83 pct; the GA-BPNN model has the highest prediction accuracy. In addition, according to the standardized coefficients in the MLR model, the influence degree of different chemical components on the wetting angle of mold fluxes is analyzed. The importance of the influence of various components on the wetting angle is Fe2O3, F−, Li2O, Na2O, R, MnO, Al2O3, B2O3, and MgO from high to low. Among them, Fe2O3, Li2O, Na2O, R, and MnO have a negative effect on the wetting angle of mold flux, while F−, Al2O3, B2O3, and MgO have a positive effect. The established GA-BPNN model could facilitate the design and optimization of mold slag in the steel continuous casting process. [ABSTRACT FROM AUTHOR]

Feeding strip significantly enhances continuous cast slab quality. To clarify its impact on inclusion distribution, a mathematical model coupling flow, solidification and inclusion motion have been developed. The upper recirculation, lower recirculation, and unformed recirculation flow occur during continuous casting. Under the resultant forces of drag, virtual mass, pressure gradient, Saffman, gravity, buoyancy, etc., the inclusion motion can be divided into two stages: Injection and Split flow. Feeding strip mainly affects inclusion motion by altering the drag, virtual mass, pressure gradient, and Saffman forces, which are closely related to the molten steel flow. After feeding strip, the lower recirculation on the strip feeding side is compressed, while it on the no-feeding side is expanded. The unformed recirculation flow on strip feeding side squeezes the flow below lower recirculation on no-feeding side. A higher strip feeding speed promotes downward inclusion motion, increasing the chance of being captured between the slab edge and strip. Unformed recirculation flow guides inclusions on the no-feeding side toward the slab edge, while expanded flow directs them toward the center. Consequently, inclusions on strip feeding side gradually gather between slab edge and quarter, while inclusions on no-feeding side first gather toward center and then toward edge of slab with increased strip feeding speed. [ABSTRACT FROM AUTHOR]

Thin slab casting and rolling (TSCR) is a near-net-shape manufacturing process and a key development technology in China's iron and steel industry. This study uses cross-scale calculations to analyze the complete process of thin slab casting. The focus is on simulating and predicting the final solidification structure by adjusting process parameters. The aim is to enable further investigation into material performance and establish a foundation for researching deformation and phase transformation. To achieve this, a coupled model has been developed to simulate the entire thin slab casting process, using hot stamping steel as the research subject. The model encompasses fluid flow, heat transfer, and solidification. The study identifies the optimal combination for flow field, temperature distribution, and equiaxed grain ratio within the specified parameter range at a casting speed of 4.0 m/min and a superheat of 40 °C. The aim of the study is to establish an integrated computational materials engineering (ICME) research system for near-net-shape automotive steel casting processes. [ABSTRACT FROM AUTHOR]

In the current study, the quantity, size, and spatial distribution of non-metallic inclusions along the thickness direction of an ultralow carbon IF steel were detected employing an automatic SEM-EDS scanning system. And the distribution of the slab subsurface inclusions was mainly analyzed. In addition, the total oxygen content in the steel and the solidification structure of the slab were analyzed. Upon the application of M-EMS, the solidification front was flushed due to the stirring effect generated by the electromagnetic force, promoting the floating removal of inclusions, thereby improving the overall cleanliness of the slab. However, the probability of the collision and agglomeration of inclusions was increased by applying M-EMS, resulting in an increase in the size of inclusions. The influence of M-EMS on inclusions was primarily on the slab subsurface. Following the application of M-EMS, the inclusions in the slab subsurface were experienced a reduction in number density from 9.99 to 6.11 #/mm2, and the area fraction was decreased from 69.51 × 10−6 to 57.31 × 10−6. However, the average size of inclusions was increased from 2.45 to 2.87 μm. With the application of M-EMS, the total oxygen content in the subsurface of the slab was reduced by 1–3 ppm, and the total oxygen content in the center of the slab was reduced by 0–1 ppm. These results indicated that the adoption of M-EMS contributed positively to the reduction of inclusions from the slab subsurface, thereby enhancing the surface quality of the slabs. Furthermore, the analysis revealed that the equiaxed crystal area comprised 12.06 pct of the total area without the consideration of M-EMS, while with the application of M-EMS, this proportion increased to 20.99 pct. [ABSTRACT FROM AUTHOR]

Non-uniform solidification of shell in continuous casting mold is the main cause of the high incidence of surface cracks of ultra-large beam blank (ULBB). To investigate the behaviors of the shell non-uniform heat transfer and its micro-structure growth, a thermomechanical model (TMM) of shell solidification in mold with the consideration of the mold flux and air gap dynamically filling in the shell-mold interface and a cellular automata-finite element (CAFE) model to describe the micro-structure growth of the shell were developed. In the models, the interfacial heat flux between the ULBB surface and mold calculated from the TMM was loaded on the CAFE model, and therefore, the cross-scale simulation of the shell solidification and the micro-structure growth were coupled. The results show that the air gap would not form at the positions of the web, fillet, and the center area of narrow face of the ULBB during the whole solidification in the mold. The thick air gap forms and concentrates in the flange tip, inner and outer corners of the flange as well as theirs surrounding areas. The thick mold flux mainly distributes in the areas of the flange outer corner, and the flange tip and the narrow face that are 0 to 45 mm and 0 to 31 mm away from the two edges of the flange outer corner. The maximum thicknesses of the air gap and mold flux appear at the positions of the inner and outer corners of the flange to the joints of the flange tip at the mold exit, which are about 0.75 mm and 0.99 mm, respectively. The maximum differences of the thickness of air gap and mold flux along the circumference of the mold are about 0.75 mm and 0.67 mm at the mold exit. The highest and lowest temperatures of the shell with a difference of 215 K appear at the flange tip and the flange inner corner. The maximum and minimum thickness of the shell appear at the center of the flange inner corner and the fillet of 617 mm from the center of the web, which are about 27.0 mm and 16.3 mm, with a difference of 10.7 mm. The maximum and minimum average grain sizes of the shell appear at the fillet and the flange inner corner, which are about 507.1 μm and 474.5 μm, with a difference of 32.6 μm. [ABSTRACT FROM AUTHOR]

Fe-Mn-C-Al high manganese steel has a large tendency to hot tearing, making it difficult to continuously cast and even leading to steel leakage accidents. In this paper, the effects of cooling rate and strain rate on the hot tearing behavior of Fe-18Mn-0.6C-2.6Al (18Mn) steel are investigated. The results show that 18Mn steel is prone to forming multiple cracks. When cracks propagate at higher temperatures, the stress rapidly decreases and exhibits brittle fracture characteristics. However, when the crack propagation temperature is lower, the rate of stress reduction significantly decreases, exhibiting ductile fracture characteristics. The temperature range of hot tearing of 18Mn steel is 1364 °C to 1344 °C, corresponding to the solid fraction of 0.88 to 0.99, and the initial crack propagation stress was 10.73 to 20.03 MPa. It indicates that, with the increase of the strain rate or the decrease of the cooling rate, the cracking temperature increases, and the peak stress decreases. In addition, when the propagation temperature is lower than the solidus, the cracks are no longer called hot tearing, but it will still cause damage in production. This study is valuable for the prediction of hot tearing and process design of continuous casting of Fe-Mn-C-Al high manganese steel. [ABSTRACT FROM AUTHOR]

In the continuous casting process, clogging of the submerged entry nozzle (SEN) significantly increases the risk of slag entrainment and the incidence of defects in the slab. A water model at 0.6 scale was created for this study. Acrylic glass particles of different sizes were pasted on the inner walls of the SEN to simulate different clogging rates. Wavelet transform combined with energy was used to analyze the mold level fluctuation. The mold flow field and the distribution of the mold slag were observed. According to the findings, it is necessary to monitor fluctuations on both sides of the narrow face of the mold (NF). An accurate assessment of the bias flow may be made by the wavelet transform combined with energy to analyze the mold level fluctuation at the NF on both sides of the mold. This is a promotion and innovation in traditional fluctuations analysis methods. The frequency at NF is higher on the side with a larger clogging rate when asymmetric clogging occurs in SEN. The upper circulating flow (UCF) velocity on the side with lower clogging is more significant. The mold slag cannot completely cover the molten steel because of the velocity difference. The UCF vortex center on the severe side of the clogging shifts toward the NF as the asymmetric clogging increases, and the velocity of the molten steel there gradually rises. This increases the frequency of slag entrainment and the range of molten steel exposure. [ABSTRACT FROM AUTHOR]

In the current study, a three-dimensional mathematical model was established, integrating with the large eddy simulation (LES) turbulent model, the volume of fluid (VOF) multiphase model, and the magnetohydrodynamics (MHD) model to investigate the influence of the mold electromagnetic stirring (M-EMS) on the multiphase flow field in a slab continuous casting mold. The results indicated that the application of M-EMS altered the flow pattern of molten steel in the mold, thereby intensifying the meniscus fluctuation. Moreover, it increased the probability of the slag entrainment, elevating the net slag entrainment rate by nearly ten times. With the increase in current intensity, the stirring effect of M-EMS not only intensified the meniscus fluctuation but also increased the net slag entrainment rate. A user-defined function (UDF) was employed to quantify the number, size, and spatial distribution of entrained slag droplets. The increase in current intensity led to an increase in the number of large-size entrained slag droplets. The greater stirring intensity at a current intensity of 600 A led to the fragmentation of the larger entrained slag droplets into several smaller droplets, thus the proportion of large-size entrained slag droplets was reduced. The stirring effect of the electromagnetic force led to the formation of numerous vortices along the centerline of the mold thickness. Consequently, this phenomenon led to an increase in the occurrence and probability of slag entrainment along the centerline of the mold thickness. Under the influence of M-EMS, the effect of slag viscosity on the multiphase flow field appeared to be less significant, while an increase in viscosity reduced the slag entrainment rate. The submerged entry nozzle angle directly influenced the flow field in the upper circulation, consequently affecting the slag entrainment rate. The size distribution of entrained slag droplets remained unaffected by the slag viscosity and the nozzle angle. [ABSTRACT FROM AUTHOR]

Breakout is the most destructive accident that interrupts the smooth production process of continuous casting, which needs to take effective and accurate measures to predict. In light of the "Y" form tear trace left at slab surface when sticking breakout happens, computer vision techniques are used in this paper to convert the one-dimensional temperature signal measured in time sequence by thermocouples into two-dimensional temperature rate thermography of mold copper plate, forecasting breakout by capturing the "Y" shape sticking region characteristic in thermography. In an effort to process big quantity of thermography data in a precise and stable way and differentiate between sticking breakout sample and normal condition sample, deep convolutional neural network model is constructed for recognizing between these two, and we develop a mold breakout prediction model based on identifying abnormal visual sticking region through CNN (convolutional neural network). The test result indicates that model is able to detect sticking breakout samples out of different temperature patterns and exclude normal condition samples at the same time. With achieving a 100 pct prediction accuracy for true sticking breakout, fine-grained classification model obtains a lower false positive rate compared to transfer learning model and a better generalization performance, offering a new train of thought into establishing data-driven abnormality detection methods during continuous casting process. [ABSTRACT FROM AUTHOR]

As an important refractory material in the continuous casting process, the clogging of submerged entry nozzle (SEN) can negatively affect the quality of the slab. In this paper, the effect of electric current pulse (ECP) on the interfacial reaction between molten steel and SEN during continuous casting of ultra-low carbon steel was studied. The results show that the application of ECP can effectively inhibit the adhesion and growth of clogging. After employing ECP, the structure of clogging at the interface changes and its density increases. The newly formed clogging is more stable and can effectively resist the impact of high-speed molten steel. In particular, applying ECP improves the qualification rate of liquid level fluctuation on the mold. The number of large-size inclusions and defects in the slab are significantly reduced, which has a positive effect on improving the quality of the slab and prolonging the service life of the SEN. [ABSTRACT FROM AUTHOR]

Three-dimensional mathematical model was established to investigate the solidification behavior during the continuous casting of a round bloom with the diameter of 0.7 m, where a novel swirling flow submerged entry nozzle (SEN) combined with mold electromagnetic stirring (M-EMS) method was used. The results show that an impinging flow phenomenon, which was normally formed in conventional single-port SEN casting, was effectively eliminated by adopting the new method. Molten steel from the swirling flow SEN port uniformly moved to the solidification front, which improved the dissipation rate of molten steel super-heat. When the rotational direction of the swirling flow in SEN was in the same direction as M-EMS, the super-heat of molten steel in mold can be decreased by 5 K, compared to the use of a conventional SEN with M-EMS. As the current intensity decreased from 310 to 100 A, the super-heat of molten steel in the mold center region was reduced by 3 K. This is due to that the shielding effect of M-EMS on rotational flow momentum from the swirling flow SEN became weak as the stirring intensity decreased. In addition, molten steel temperature near the meniscus under the current intensity of 310 and 100 A was 1787 K and 1790 K, respectively. The solidified shell thickness obtained by using 100 A current intensity was about 1 × 10−3 m larger than that of 310 A current intensity. [ABSTRACT FROM AUTHOR]

Strand electromagnetic stirring (SEMS) is widely applied in thin-slab continuous casting to promote the equiaxed crystal ratio (ECR). However, the effects of alternate electromagnetic stirring on the evolution of solidification macrostructure and ECR remain poorly understood. And the formation of the equiaxed crystal region beneath the stand and equiaxed-to-columnar transition (ECT) have been overlooked in most previous models. This study first introduces a novel equiaxed-columnar solidification model to comprehensively analyze the effects of alternate electromagnetic stirring in thin-slab continuous casting. A complete macrostructure feature of the slab, including the equiaxed crystal region beneath the strand, ECT, well-developed columnar dendrites, columnar-to-equiaxed transition, and center equiaxed crystal zone, could be simulated accurately. The multiphase model was validated by the measured ECR and columnar growing direction from a pickling corrosion experiment. Results showed that alternate stirring could improve the ECR effectively. The ECR was increased by 26 pct compared to the one-way stirring when the switching period of alternate stirring was 8–12 seconds. A multi-vortex flow structure was observed in the secondary cooling zone, which could increase the residence time of the molten steel and the nucleation rate. Furthermore, the vortex-shedding behavior of the upper recirculation alleviated the remelting of equiaxed crystals during the sedimentation. The behavior of multiphase flow under alternate SEMS is a novel finding. These preliminary results are encouraging and should be validated in other continuous casting processes. [ABSTRACT FROM AUTHOR]

Hollow granular mold flux is an essential functional material in the continuous casting process, and its melting behavior significantly influences continuous casting. The existing research mainly focuses on the influence of the characteristics of mold flux on the melting behavior and does not involve the operation of mold flux. This study explored the effect of flux layer thickness on the melting behavior of mold fluxes using a melting rate test method based on a copper bath and numerical simulation. The results show that with the increase in the flux layer thickness, the melting rate of mold fluxes shows the trend of the 'M curve,' including two upward and two downward stages. The 'M curve' is related to the temperature and combustion behavior of carbonaceous materials in the flux layer. In the first stage, as the thickness increases, the thermal insulation of the flux layer is significantly improved, which promotes the melting of the mold flux. In the second stage, the increase in flux layer thickness hinders the diffusion of O2 from the air to the flux layer, and the carbon–oxygen reaction rate decreases, which is not conducive to the combustion of carbonaceous materials and the flux melting. In the third stage, the increase in the flux layer thickness hinders the diffusion of CO2 to the outside, increases the CO2 concentration in the flux layer, promotes the Boudouard reaction, and increases the melting rate. In the fourth stage, with the increase in the flux layer thickness, O2 can only diffuse to the low-temperature zone (< 400 °C) of the flux layer and cannot participate in the carbon–oxygen reaction and form CO2, which decreases the rate of Boudouard reaction and the melting rate of mold flux. [ABSTRACT FROM AUTHOR]

The mold electromagnetic stirring technology and mold feeding steel strip technology are both effective method of reducing center segregation and shrinkage cavities in continuous casting bloom. In this work, a bidirectional flow-solid coupling model was established to investigate the swing and depth of steel strip feeding with the influence of both molten steel and electromagnetic forces. The results indicate that increasing the strip's feeding speed from 0.2 to 0.4 m/s without electromagnetic stirring results in an increase in the swinging amplitude from 6.26 to 11.89 mm. With the implementation of mold electromagnetic stirring, the bottom of the steel strip moves on the "Z" shape periodically, and the swing amplitude increasing with the current strength rising. When the feeding speeds are 0.2, 0.3, and 0.4 m/s, and the current is increased from 200 to 300 A, the maximum swing amplitude of the steel strip increases from 7.30, 12.18, and 21.09 to 10.34, 19.47, and 41.14 mm, respectively. [ABSTRACT FROM AUTHOR]

A new two-way coupled magnetohydrodynamic (MHD) model considering the dynamics change of electromagnetic force at steel–slag interface was established to investigate the multiphase flow and slag entrapment in slab continuous casting under mold electromagnetic stirring (EMS). The transient turbulent flow and the steel–slag interface behavior were described by solving the large eddy simulation (LES) model and volume of fluid (VOF) model. The level fluctuation, the location, and net mass of slag entrapment were quantitatively evaluated. By comparing the predicted level height within the in-situ measurement, the results show that the two-way coupled MHD model can better reveal the multiphase flow under EMS. The type of slag entrapment is closely related to the flow pattern, the vortex formation is predominant under the lower EMS current, while it changes to the shear-layer instability under the relatively high EMS current, the proportion of vortex formation slag entrapment decreases to 30.7 pct under the EMS current is 600 A. The tendency of net slag entrapment rate is the same as that of level fluctuation, with the increase of EMS current and casting speed, both the level height and net slag entrapment rate decrease firstly and then increase. Therefore, it is necessary to match the casting speed and EMS current to avoid the slag entrapment in actual production. The net slag entrapment rate is 0.034 kg/s, under the condition of 1.2 m/min casting speed and 600 A EMS current. [ABSTRACT FROM AUTHOR]

Machine learning (ML) algorithms have been proven to be effective methods in steel design and production processes. In this study, the feature analysis and prediction of slag entrapment in continuous casting process were carried out based on XGBoost model. Results show that the area under the curve (AUC) and accuracy of BO-XGBoost are 0.811 and 0.756, respectively, which are higher than PSO-XGBoost and GA-XGBoost. Feature analysis shows that mold flux, oscillation frequency, serial number, inner arc, casting speed (CS) and slab width are the key features which affect the entrapped slag defect, based on Gini coefficient and SHAP values. In addition, partial dependence plots of SHAP value suggest that it is conducive to product the qualified slabs with less entrapped slag defect, when the oscillation frequency is 60–140 cpm, inner arc is 7.5–9.5 m, CS is 0.35–1.2 m/min, serial number is less than 5, slab width is less than 1300 mm and 2# mold flux. [ABSTRACT FROM AUTHOR]

In this study, we developed a numerical model of a slab continuous casting mold coupled with multi-phase and multi-physical fields, known as MPF-Mold, and explored the effect of Fc-Mold on fluid flow, heat transfer, and solidification in the mold. Firstly, the simulation results were carefully verified from five perspectives. Next, the fast Fourier transform (FFT) is introduced to discuss the difference between MPF-Mold and the model considering only the fluid flow in the simulation results of level fluctuation. Typically, mold oscillation can be disregarded when analyzing the degree of level fluctuation through numerical simulation. However, neglecting multi-phase heat transfer and solidification may lead to overestimations of the severity of level fluctuation, especially in the region near the narrow meniscus. When coupling MPF-Mold with Fc-Mold, the upper backflow in the mold becomes stable, increasing symmetry and reducing level fluctuation severity and abnormalities. The shell uniformity index on the wide face meniscus and the lower part of the narrow face in the mold is significantly improved. This suggests that the upper and lower magnetic poles of Fc-Mold are beneficial to the shell uniform growth of the wide face meniscus and lower part of the narrow face, respectively. However, a new 'concave' appears in the shell near the corner of the mold, as a result of the horizontal vortex caused by deviations in the jet flow. Therefore, the magnetic field needs to be optimized to stabilize the flow field. MPF-Mold demonstrates advantages in achieving a reasonable match of steel grade, equipment, and process, and contributing to the digital transformation of continuous casting. [ABSTRACT FROM AUTHOR]

Longitudinal surface cracks are prevalent in the continuous casting of hypo-peritectic beam blanks, primarily related to multiphysics non-uniformity (multi-phase field, flow field, temperature field) within the mold. Therefore, multi-phase and coupled flow-thermal models were constructed to investigate the non-uniform multiphysics characteristics in the beam blank mold with a single nozzle and its effect on the formation of longitudinal cracks. First, the three-phase flow model reveals significant unevenness slag distribution along the web width, positively correlated to surface velocity of the molten steel. Subsequently, considering the impact of the solidification shell, surface velocity decreases nonlinearly with increasing immersion depth, influenced by web vortex position in the X-direction, which is also influenced by mold curvature, and interaction between web and side vortexes. Furthermore, the temperature field distribution inside the mold is non-uniform. Under the effect of the single-web recirculation flow, the temperature near the meniscus at the NN (position near the nozzle) side of the web is lower than that at the FN (position far away from the nozzle) side, resulting in more intensive initial cooling at this position. Meanwhile, a reheating zone exists at the mold exit of the NN side. Statistical analysis revealed that the absolute values of Spearman coefficient between the non-uniformity of shell thickness and the temperature and flow velocity of the molten steel exceed 0.6, which is related to the depth of the web vortex. Finally, from the perspective of the influence of SEN's immersion depth on multiphysics, the high surface velocity of the steel, strong cooling near the meniscus, and non-uniform shell thickness at the mold exit can be relieved with an immersion depth of 75 mm. The plant experiment confirmed that increasing the immersion depth from 65 to 75 mm leads to a relative reduction of 39 and 43 pct in the longitudinal cracks ratio for strands and rolled products, respectively. [ABSTRACT FROM AUTHOR]

TiN and Ti(C,N) are the main precipitates in Ti micro-alloyed steel during the continuous casting, which directly affect the microstructure and property of the slab. However, due to the solute segregation and the different cooling rates at different locations of the slab section, it is challenging to accurately predict the precipitation behavior of carbonitride during the continuous casting process using the existing thermodynamic model. Taking into account the solute segregation laws at the solid-liquid interface during continuous casting solidification and incorporating the influence of precipitates on solute segregation, this study proposes a model for coupled carbonitride precipitation and solute segregation by introducing dynamic solute partition coefficients. Based on this, a kinetic model is established to describe growth of TiN and Ti(C,N) precipitates during continuous cooling of the slab by utilizing the micro-element superposition method. The nano carbonitride will precipitate in the solid phase upon complete solidification of the slab. The macroscopic solute distribution at different positions of the slab, ranging from the center to the surface, was calculated using a segregation model that incorporates a convective coefficient. Through this, a precipitation model for nano-carbonitrides in Ti microalloyed steel is developed by incorporating the classical nucleation theory. The models are validated by comparing the predicted values of Ti carbonitride precipitation quantity and average precipitate size with experimental data at typical locations, including the surface, 1/4 position, and internal regions of the slab. The accuracy of the predictions reaches over 90 pct. This study enhances the comprehension of precipitation and growth mechanisms of carbonitride in Ti microalloyed steel, contributing to a more comprehensive understanding of this material system. [ABSTRACT FROM AUTHOR]

To successfully prepare bulk metallic glass (BMG) slab with high efficiency and low cost, a new horizontal continuous casting (HCC) process was designed to produce 5-mm thick Zr41.2Ti 13.8Cu12.5Ni10.0Be22.5 (Vit1) amorphous alloy slab. A mathematical model was established based on finite volume method (FVM) to study the temperature field during the HCC process, when the casting temperature was 1123 K and the casting speed was 21 mm/s. The simulation results indicated that a 5 mm thick amorphous alloy slab could be successfully prepared by the new HCC process. Simulated and experimental cooling curves exhibit the same variation trend, which verifies the accuracy of the FVM model. The experimental results showed that Vit1 amorphous alloy slab with thickness of 5 mm was successfully prepared by the new HCC process. The critical thickness of the amorphous alloy slab prepared by the HCC process was further simulated. Theoretically, the maximum thickness of BMG slab cast by the HCC process is 9 mm under the continuous casting parameters. [ABSTRACT FROM AUTHOR]

Ductile iron with different Ni contents (0–10%) was successfully fabricated through horizontal continuous casting technology, and the effects of Ni content on ductile iron's microstructure and mechanical properties were investigated. The results showed that the Ni addition affected the diffusion of carbon atoms, altering the phase constituents during solid-state transformation. The ductile iron with Ni amounts less than 2% was composed of spheroidal graphite and ferrite. The addition of the 2% Ni addition led to more than 40% pearlite in the matrix. When the Ni content exceeded 6%, bainite and martensite were detected, which enhanced strength significantly but deteriorated ductility. Annealing treatment facilitated the dissolution of carbides and increased ferrite fraction, contributing to the improvement of ductility. The as-annealed sample with 8% Ni showed an ultimate tensile strength of 1057 MPa and an elongation of 4.6%. [ABSTRACT FROM AUTHOR]

Spinel is known to cause clogging of the submerged entry nozzle in continuous casting. The effect of basicity on the precipitation behavior of MgO·Al2O3 in Al-killed steel with w[Al] = 0.065% at 1550°C was investigated. The inclusions in steel are mainly MgO·Al2O3 spinel after slag-steel reaction, which is consistent with the thermodynamic results. The polygonal spinel transforms to nearly spherical or rod-like with the sizes smaller than 5 μm with the increase of refining-slag basicity. The number of inclusions shows little variation with basicity. In industrial production, it is often observed that spinel inclusions in molten steel are transformed into CaO-Al2O3-MgO inclusions. However, this phenomenon was not observed in this study. Two sets of experiments were conducted; therefore, the reasons behind the lack of transformation from spinel to CaO-Al2O3-MgO inclusions were elucidated. We determined that Mg in MgO·Al2O3 originated from the MgO crucible, and the [Ca] and [Mg] supplied through the steel slag reaction were insufficient to facilitate the modification of Al2O3. [ABSTRACT FROM AUTHOR]

The article compares the efficiency of technologies for feeding liquid metal into the mold of a continuous casting machine (CCM) and its flow within the mold volume under conditions of free and forced mixing. The influence of various designs of the developed mixing devices on the nature of the melt flow in the mold volume is analyzed. The objects of research are the hydrodynamic and thermal flows of liquid metal during the casting of steel into the CCM mold. [ABSTRACT FROM AUTHOR]

The regulation of hydrogen content in the continuous casting process is conducive to the reduction of pore defects in the casting billet. In this paper, the influence of negative pressure (NP) and continuous casting speed (CCS) on hydrogen content in copper rod billet prepared by negative pressure continuous casting (NPCC) technique was analyzed, and the mechanism of the coordinated coupling of NP and melt flow on hydrogen removal was revealed. It is clarified that with the CCS of 20 mm min−1 and an increase in the NP value from − 20 to − 80 kPa, the hydrogen content is reduced from 1.0 to 0.3 ppm. The coordinated action of NP and melt flow induced by CCS can minimize the hydrogen content. When the NP value is − 80 kPa and the CCS is 10 mm min−1, the hydrogen content is as low as 0.2 ppm, and the hydrogen removal rate is 85.7%. The larger the NP, the smaller the critical nucleation radius of the hydrogen bubble, and the larger the growth rate of the hydrogen bubble. The coupling of the NP field and flow field can make the melt which is difficult to nucleate and grow of the hydrogen bubble flow to the position which is easy to nucleate and grow. The effect of the vortex fields in the purification chamber on the removal of hydrogen is not affected by the CCS, but the CCS affects the floating of hydrogen at the solidification front, which leads to a small increase in the hydrogen content with the increase of the CCS. Our study provides a theoretical basis for the preparation of high-quality metal billets. [ABSTRACT FROM AUTHOR]

The formation of edge or surface cracks on continuous cast slabs is a significant problem as these increase the slab processing cost and affect the quality of hot/cold rolled coils. The edge crack formation is greatly influenced by slab composition, caster operation and machine maintenance strategies. The manganese-to-sulfur (Mn/S) ratio of low carbon steels has a significant effect on the formation of edge cracks. The effect of Mn/S ratio on hot ductility and edge crack tendency was investigated for low carbon boron steel over a temperature of 600–1100 °C using a Gleeble thermomechanical simulator. The temperature range of low ductility is a strong function of the Mn/S ratio, and this range decreases with an increase in Mn/S ratio. The underlying mechanism for low ductility is discussed using fractographs and microstructure. Edge cracks on slabs of this grade can be eliminated by maintaining the Mn/S ratio greater than 36 to narrow the low ductility temperature range and ensuring the surface and corner temperature of the slab beyond the temperature range of low ductility especially during unbending. A hard or soft secondary cooling strategy is recommended to maintain the surface and corner temperature of slabs beyond the low ductility temperature range. [ABSTRACT FROM AUTHOR]

Continuous casting processes of metals are the most common in terms of obtaining the input material for metal working processes such as wire drawing. One of the issues regarding the process is maintaining the proper temperature preventing cast rod surface oxidation. Experimental work using a laboratory furnace was conducted to verify the parameters determined using finite element method simulations of continuous casting of CuMg alloys. Furthermore, as the alloys are fully novel and not produced or researched on a large scale, they were subjected to microstructural analysis and basic property tests in order to determine their electrical conductivity, density, hardness, and impact toughness. Additionally, pure copper was cast with the same laboratory furnace and the same parameters to function as a point of reference. The obtained results were also compared to commercial materials used for electrical purposes, such as brasses and bronzes. The obtained results proved that the mechanical properties of tested alloys are 2–2.5 times higher than pure copper. Also, the tested materials exhibit lower densities than commercial brass or bronze alloys and their mechanical properties are similar, while electrical conductivity is significantly higher and, thus, they may be used as a material for electrical applications. [ABSTRACT FROM AUTHOR]

The deleterious effects of brittle and rigid oxides on the quality of high-speed railway wheel steel can be mitigated by wrapping the oxides with sulfides. The investigation reveals the presence of three types of oxide–sulfide complex inclusions in the continuous casting billet. Type 1 possesses a core oxide with high CaO content, and its shell sulfide predominantly comprises CaS. Type 2 presents a core oxide with low CaO content, accompanied by a (Mn,Ca)S shell. The core oxide in Type 3 contains almost no CaO, and the shell sulfide is primarily MnS. The area ratio, defined as the ratio of sulfide area to oxide area, increases successively among the three types of complex inclusions. The formation mechanisms of the three types of complex inclusions vary. In Type 1, the core oxide originates from the refining process. The CaS in the shell sulfide is a product of the reaction between Al and S in the liquid steel and CaO in the oxide. In Type 2, the core oxide is formed during the cooling and solidification process. As the liquid steel solidifies, the segregation of Ca, Mn, and S leads to the formation of (Mn,Ca)S shell around the oxide. The formation temperature of the core oxide in Type 3 is lower than that of Type 1 and Type 2, occurring in the late stages of solidification. A substantial amount of MnS is formed around the oxide near the end of solidification. In the finished wheel, Type 2, characterized by its (Mn,Ca)S shell, exhibits appropriate hardness and resistance to deformation, rendering it the most optimal among three types of complex inclusions. [ABSTRACT FROM AUTHOR]

In the current study, the influence of Li2O and Na2O on the viscosity, crystallization, and structure of the high TiO2-containing mold slag for the continuous casting of high-Ti steel was investigated to improve the property of the CaO–SiO2–TiO2-based slag under the steel-slag reaction through the measurement of the viscosity-temperature relationship, crystallization temperature and phases, and the Raman spectrum. With the increase of Li2O content from 0 to 8 pct, the viscosity at 1300 °C and melting temperature decreased from 0.54 to 0.01 Pa s, and 1151 to 884 °C, respectively. While the viscosity of the slag at 1300 °C increased from 0.20 to 0.62 Pa s, the viscosity of the slag at 1400 °C decreased from 0.16 to 0.09 Pa s, and the melting temperature decreased from 1195 to 1077 °C with the Na2O content from 2 to 10 pct. According to the thermodynamic calculation and XRD measurement, the main crystallization phase of high TiO2 slags was CaTiO3 with the content of Li2O below 4 pct and Na2O of 2 to 10 pct, the crystallization phase gradually changed from CaTiO3 to LiTiO2 with Li2O from 4 to 8 pct, and the morphology of the crystalline nucleus changed from the type of spiky star to barbed sphere. Similarly, with the Li2O content from 2 to 6 pct the initial and complete crystallization temperature decreased and increased, respectively, while those increased with the increase of Na2O content, indicating that the increase of the Li2O below 4 pct and the decrease of the Na2O in the current slag resulted in the weak crystallization ability. With the addition of Li2O content, the complex structural units of Q1, Q2 and Q3 were depolymerized, and the slag viscosity decreased. With the increase of Na2O content, structural units of Q0, Q1 and Q2 structure units had the tendency to increase, and the viscosity of slag at 1400 °C decreased. These results could be used for the selection of typical components of mold slags for continuous casting of high-Ti steel. [ABSTRACT FROM AUTHOR]

A decision support system was developed using supervised machine learning (ML) approach for optimization of calcium (Ca) additions by continuously monitoring the physical state of non-metallic inclusions (NMIs) inside low-alloyed liquid steels. In this work, two instances were considered to design the base algorithm for the proposed supervisory system: (1) Clogging of submerged entry nozzle (SEN) during continuous casting of steels due to accumulation of solid oxide non-metallic inclusions (NMIs) and (2) Ca treatment during secondary steelmaking for modification of oxide NMIs from solid to liquid state to avoid SEN clogging. At first, experimental investigations were carried out on liquid steel samples from three low-alloyed Ca-treated steel grades from the same steel family to evaluate the characteristics of solid oxide NMIs that cause SEN clogging. In the next step, data-driven models were developed using an in-house ML algorithm trained primarily with process data for calculating the value of the newly proposed dummy parameter 'Clog.' These models, after testing, were architected to develop a supervisory system based on experimental investigations and data-driven models. The objective of this proposed supervisory system was to predict the optimum quantity of Ca needed for successful modification of NMIs from solid to liquid state to avoid SEN clogging based on the forecasted 'Clog' value. Finally, industrial data from ~ 3000 heats were tested to verify the results obtained from the developed supervisory system. The results confirmed that this novel supervisory system could predict the optimum class of Ca for all studied steel grades with 95 to 98 pct accuracy. The integration of this online supervisory system in steel production is expected to minimize operators' corrective actions in achieving realistic control of Ca additions. [ABSTRACT FROM AUTHOR]

During continuous casting, accurate real-time prediction of strand solidification ensures the effective implementation of reduction. Due to the influences of the continuous casting production environment, equipment, and other factors, the calculations from a thermal tracking model deviate; these deviations are difficult to find and correct in real time, affecting the effective implementation of the casting process. In this paper, the online calculation processes are explored for the stress–strain and force–reduction relationships during reduction. Based on the calculation results of the finite element model for the cross-sectional strain distribution during reduction, the influences of certain parameters, such as reduction, dimension, steel, and reduction position, on the strain distribution of the bloom cross section during reduction are analyzed. Reduction amount is the main factor affecting the strain distribution; within a certain range, the element strain is linear with the reduction. Based on this finding, a real-time bloom force prediction model is proposed in this paper. The model combines the strain distribution trend of the finite element model of thermal–mechanical coupling and calculates the strain and strain rate of each element of the cross section according to the actual reduction process. By combining the real-time temperature results of the thermal tracking model with the constitutive characteristics of the steel determined in the experiment, the stress–strain and force–reduction relationships during continuous casting are accurately predicted. According to a comparison with the actual force of the on-site reduction process, the error is generally less than 5 pct; however, the error differs for equipment problems. The calculation results show that the ambient temperature (5 °C and 10 °C) also affects the actual compaction force during the reduction process. The force deviation at different ambient temperatures is about 5 to 10 pct. Through a comparison of bloom temperature and force data, the on-site thermal tracking model can be verified in real time, and the conditions of the reduction equipment can be preliminarily diagnosed. [ABSTRACT FROM AUTHOR]

In this study, a novel technique of Vertical Linear Electromagnetic Stirring (V-LEMS) was proposed and applied in the final solidification zone of the 260 mm × 300 mm GCr15 bearing steel continuous casting (CC) bloom. The effects of V-LEMS on melt flow, heat transfer, and solidification have been investigated by establishing a three-dimensional numerical simulation model. The results demonstrate that an effective longitudinal magnetic field is formed in the inner arc of the bloom by applying V-LEMS, which is 1.9 times the height of the V-LEMS device, and the electromagnetic force within this effective longitudinal magnetic field is greater than 1.0 × 10 3 N · m - 3 . The V-LEMS induces longitudinal circulation flow in the liquid core of the bloom, whose height reaches 1.8 times of the V-LEMS device, so as to promote longitudinal mixing of the melt. The longitudinal circulation flow transports the high-temperature melt in the upper region of the liquid core to the lower region of the bloom, which improves the temperature uniformity of the liquid core, and it is beneficial to increase the proportion of equiaxed grains in the center of the bloom. By applying V-LEMS in the final solidification zone of the bloom, the melt temperature near the solidification front in the liquid core is 6.5 K higher than that without V-LEMS, and the width of the liquid core is 4.3 mm wider than that without V-LEMS. These effects are beneficial to improve the fluidity and feeding ability of the melt in the liquid core and reduce defects such as porosity, shrinkage cavity, and cracks in the center of the bloom. [ABSTRACT FROM AUTHOR]

In this paper, a neural network model is introduced, which uses Convolutional Neural Network model optimized by Genetic Algorithm (GA-CNN) to predict the liquid level fluctuation of continuous casting mold in real time. The experimental data were obtained from the practical production process of an iron and steel plant in China. For the two-stream continuous caster in this factory, two sets of mold liquid level fluctuation value data sets were established. These data sets are categorized into the first- and the second-stream mold liquid surface fluctuation data set. Both data sets comprise 138 production parameters along with the mold liquid level fluctuation values. Random Forest feature screening and data preprocessing are carried out on the data set, so that the processed data can be learned and trained by the model, thus obtaining the mold liquid level fluctuation prediction model. To facilitate the analysis, the sensitivity analysis of related continuous casting production parameters and mold level fluctuation data was carried out. Subsequently, the influence of production parameters on the fluctuation value of mold liquid level was investigated by characteristic thermal diagram and Shapley additional explanations diagram, and the influence degree of each parameter on the model performance was determined. The results indicate that the GA-CNN model demonstrates strong predictive capability, with a high correlation coefficient (R2) of 0.98, a low mean absolute error (MAE) of 0.1093, and a mean square error (MSE) of 0.0225. Notably, the position of the stopper was identified as a critical factor significantly affecting mold level fluctuations. The model has high prediction accuracy and can meet the needs of practical application in steel plants. [ABSTRACT FROM AUTHOR]

Multiscale titanium carbides are one of the main causes of corner crack defects of 0.37 pct Ti–Mo steel slab. In this work, the evolution of titanium carbides precipitation under different cooling rates were investigated by high-temperature laser scanning confocal microscopy, transmission electron microscope, and thermal simulation. The research revealed that micron TiC particles are derived from eutectic reactions at the end of solidification which are divided into dendritic TiC and lamellar TiC according to the precipitation order. According to Thermo-Calc simulation, the titanium elements play a leading role on the titanium-carbide/γ interface movement. Nano-(Ti,Mo)C are mainly precipitated from the high-temperature austenite after solidification. The micrometer TiC is gradually broken and refined, and the distribution is transferred from grain boundary to grain interior with the increase of cooling rate. High cooling rate can reduce the production of micron TiC but promote the formation of ferrite film and destroy the hot ductility. [ABSTRACT FROM AUTHOR]

The grain refinement and Si phase modification of A356 alloy are important for the improvement of mechanical properties, so the development of a master alloy for the refinement and modification of A356 alloy is very necessary. In this work, an Al-5Sr-5Ti-0.2C master alloy prepared by the fluoride salt method, and continuous rheo-extrusion (CRE) technology was introduced. The phase and microstructure of Al-5Sr-5Ti-0.2C were analyzed using XRD, SEM, and TEM, and the genetic behavior of Al-5Sr-5Ti-0.2C on the microstructure and tensile properties of A356 alloy was investigated. Different from the conventional casting method, CRE process can break the TiAl3 and Al4Sr phases in Al-5Sr-5Ti-0.2C alloy and promote the uniform distribution of TiC particles. Also, CRE Al-5Sr-5Ti-0.2C acquired the best refinement and modification effect on A356 alloy at the addition of 0.6 wt%, which led to the refined size of 231 ± 14 μm for α-Al grain and 1.75 ± 0.29 μm for eutectic Si in A356 alloy. Simultaneously, the optimal ultimate tensile strength (UTS), yield strength (YS), and elongation (EL) of refined A356 alloy were 191.8 MPa, 93.4 MPa, and 10.1%, respectively, 23.5%, 9.7%, and 110.4% higher than the original A356 alloy. [ABSTRACT FROM AUTHOR]

A Cu-0.4Mg (wt.%) alloy with high strength and high conductivity was fabricated by upward continuous casting and multi-pass drawing at room temperature. The microstructure, properties and strengthening mechanism of the Cu-0.4Mg alloy were studied. Results show that Cu-0.4Mg alloy reveals excellent comprehensive properties of ultimate tensile strength of 717 MPa and electrical conductivity of 70.4% IACS. The increment of strength was mainly contributed by grain refinement and dislocation strengthening. As the preparation method is simple and effective, it is a potential method for industrial production. [ABSTRACT FROM AUTHOR]

Occasional irregular initial solidification phenomena, including stickers, deep oscillation marks, depressions, and surface cracks of strand shells in continuous casting molds, are important limitations for developing the high-efficiency continuous casting of steels. The application of mold thermal monitoring (MTM) systems, which use thermocouples to detect and respond to temperature variations in molds, has become an effective method to address irregular initial solidification phenomena. Such systems are widely applied in numerous steel companies for sticker breakout prediction. However, monitoring the surface defects of strands remains immature. Hence, in-depth research is necessary to utilize the potential advantages and comprehensive monitoring of MTM systems. This paper summarizes what is included in the irregular initial solidification phenomena and systematically reviews the current state of research on these phenomena by the MTM systems. Furthermore, the influences of mold slag behavior on monitoring these phenomena are analyzed. Finally, the remaining problems of the formation mechanisms and investigations of irregular initial solidification phenomena are discussed, and future research directions are proposed. [ABSTRACT FROM AUTHOR]

In the present study, a Ni–Cr–Mo–V alloyed ductile iron with high hardness was developed. The Ni–Cr–Mo–V alloyed ductile iron fabricated by horizontal continuous casting was composed of dendritic austenite, martensite, carbides and graphite nodules and exhibited a hardness as high as 58.3 HRC. The microstructure was transformed into austenite and graphite nodules through austenitization at 1050 °C for 6 h and water quenching with a hardness of 23.0 HRC. Tempering treatment effectively increased the hardness to 56.6 HRC due to the precipitation of carbides and phase transformation from austenite to martensite. [ABSTRACT FROM AUTHOR]

Problems in the field of metallurgical engineering have been identified. A production scheme for steel hollow blanks using a combined casting and deformation unit has been proposed. The stress state of the dies–hollow billets system has been studied. The distribution of temperature and thermoelastic stresses in the dies of the unit when obtaining steel hollow billets is shown. Approximate parameters of an industrial combined casting and deformation unit for producing steel hollow billets are given. [ABSTRACT FROM AUTHOR]

An integrated model was proposed in the current study to predict the composition distribution of inclusions along the thickness of a tire cord steel continuous casting billet. The thermodynamics, kinetics, fluid flow, heat transfer, solidification, and element segregation were combined in the integrated model. More accurate results were obtained using the current model compared with the published work, indicating the great importance of the kinetics and element segregation in the inclusion predication. Thermodynamic calculation showed the equilibrium composition of inclusions at 1073 K was approximately 92 wt pct SiO2–3 wt pct MnO–4 wt pct Al2O3–1 wt pct CaO, which was obviously different from measured results, even though the element segregation was premeditated, indicating the insufficiency of the thermodynamics in predicting the inclusions composition in the billet. A large positive segregation of C, Si, Mn, and S at the center of the billet was revealed, and the average segregation index was simulated to be 1.89, 1.05, 1.08, and 1.26, respectively. The strong element segregation of the steel induced a fluctuation in the composition of inclusions along billet thickness, which was more accurate compared with the model ignoring the element segregation. [ABSTRACT FROM AUTHOR]

The numerical methods based on the unsteady Reynolds-averaged Navier–Stokes (URANS) equations are robust tools to model the turbulent flow for the industrial processes. They allow an acceptable grid resolution along with reasonable calculation time. Herein, the URANS approach is validated against a water model experiment for the special single port submerged entry nozzle (SEN) design used in the thin slab casting (TSC) process. A 1-to-2 under-scaled water model was constructed, including the SEN, mold, and strand Plexiglas segments. Paddle-type sensors were instrumented to measure the submeniscus velocity supported by videorecording of the dye injections to provide both qualitative and quantitative verification of the SEN flow simulations. Two advanced URANS-type models (realizable k–ε and shear stress transport k–ω) were applied to calculate velocity pattern on meshes with various resolutions. An oscillating single jet flow was detected in the experiment, which the URANS simulations initially struggled to reflect. The dimensionless analysis of the mesh properties and corresponding adjustment of the boundary layers inside the SEN allowed to resolve the flow pattern. The performed fast Fourier transform (FFT) verified a good numerical prediction of the flow frequency spectrum. The corresponding simulation strategy is proposed for the industrial CC process using the URANS approach. [ABSTRACT FROM AUTHOR]

Clogging in the submerged entry nozzle is a common concern during the continuous casting of Al-killed steels, deteriorating the steel quality and impeding the continuity of mold operations. Water experiments were carried out to investigate the multiphase flow in the mold under different nozzle clogging modes. Bubble measurement was achieved by projection methodology using a high-speed camera. The LES-VOF-DPM model was developed based on size distributions of bubbles obtained from water modeling, to evaluate the effects of nozzle clogging on bubble capture by solidifying shell and slag-metal interface behaviors. The results show that clogging at the nozzle groove inhibits the bubble break-up by turbulent flow. Bubbles remaining in large sizes float vertically, leading to concentrated impacts on the slag-metal interface. Clogging at two nozzle ports increases the entry velocity under a constant casting speed. Due to the broken effect of the strong turbulent flow, 9.23 pct of the bubbles are smaller than 0.5mm. Small bubbles tend to reach a narrow face following the entry flow and then are trapped by the solidifying shell. The present study provides a comprehensive approach to evaluating the life cycle of SEN. [ABSTRACT FROM AUTHOR]

The growth of columnar grains and the distribution of equiaxed grains in the continuous casting process of round blooms had a significant impact on the solute distribution properties of the product. External physical fields, including gravity, electromagnetic stirring (EMS), and temperature, directly affected the growth of the columnar grains and the nucleation, growth, and movement of the equiaxed grains, and thereby influenced the final distribution characteristics of the solidification structure and of the phase fractions. In this study, a model for the growth of the columnar grains, and the nucleation, growth, and movement of the equiaxed grains was developed. The control variable method was employed, and the effects of different mold electromagnetic stirring (M-EMS) parameters, casting temperatures, and casting speeds on the solidification structure were individually calculated and analyzed. The results indicated that under the influence of gravity, the equiaxed grains migrated from the inner arc side to the outer arc side, which resulted in asymmetry in the microstructure on both sides. By increasing the electromagnetic stirring current, reducing the casting temperature, and lowering the casting speed, the equiaxed grain ratio can be increased. The effect of reducing the casting temperature is most significant, with the equiaxed grain ratio raising from 51.2 to 65.5 pct when the casting temperature is reduced from 1519 °C to 1514 °C. Lowering the superheat, lowering the casting speed, and enhancing M-EMS all lower the overall temperature of the blooms, leading to more pronounced asymmetrical characteristics in the structure. This model can efficiently calculate the heat transfer behavior, evolution, and distribution characteristics of the solidification structure of continuous casting round blooms under different external field effects and casting process parameters, providing a theoretical basis for improving the internal quality of round blooms in production. [ABSTRACT FROM AUTHOR]

During an oscillation cycle of the mold, the fluid flow, heat transfer, and solidification behavior within the meniscus region control the slag infiltration, lubrication, and formation of oscillation marks, which are of great significance to the smooth running of continuous casting and the surface quality of slab. A comprehensive two-dimensional (2D) transient thermal-fluid model has been developed to study the fluid flow, heat transfer, dynamic shape of steel/slag interface, as well as the growth of shell in the meniscus region during an oscillation cycle. In addition, calculations of slag consumption were performed, and the results were consistent with previous research, thereby the reliability of the model is validated. During an oscillation cycle, the upstroke and downstroke cause the meniscus profile to bulge and collapse, which dominates the increase and decrease of heat flux in the Eulerian reference frame reference frame. However, the variation of heat flux in the Lagrangian reference frame is determined by the instantaneous position. The freezing and overflow behaviors of the meniscus are the primary factors contributing to the formation of oscillation marks, and the final profile of oscillation marks is determined by the two freezing events of the meniscus within an oscillation cycle. The positive slag consumption primarily occurs during the negative strip time (NST), while there is also positive slag consumption during certain periods of positive strip time (PST), which is closer to the motion state of the mold. This research contributes to explaining and understanding the formation mechanism of surface defects and issues of continuous casting strands, aiming to facilitate the improvement of related problems. [ABSTRACT FROM AUTHOR]