Slag entrainment within the mold is a significant cause of surface defects in continuously cast slabs. As a key component for controlling molten steel flow, the structure of the submerged entry nozzle directly influences the flow field characteristics and slag entrainment behavior within the mold. This paper employs a 1:4-scale water-oil physical model combined with numerical simulation to investigate the effects of elliptical and circular submerged entry nozzles on slag entrainment behavior in a wide slab mold under different casting speeds and immersion depths. High-speed cameras were used to visualize meniscus fluctuations and oil droplet entrainment processes. An alternating control variable method was employed to quantitatively delineate a slag-free "safe zone" and a "slag entrainment zone" where oil droplets fall, determining the critical casting speed and critical immersion depth under different operating conditions. The results show that, given the nozzle immersion depth and slag viscosity, the maximum permissible casting speed range without slag entrainment can be obtained, providing a reference for industrial production parameter control. The root mean square (RMS) of surface fluctuations was introduced to characterize the activity of the meniscus flow. It was found that the RMS value decreases with increasing nozzle immersion depth and increases with increasing casting speed, showing a good correlation with the frequency of slag entrainment. Numerical simulation results show that compared with elliptical nozzles, circular nozzles form a more symmetrical flow field structure in the upper recirculation zone, with a left-right vortex center deviation of less than 5%, resulting in higher flow stability near the meniscus and thus reducing the risk of slag entrainment.

To increase the casting speed of φ150 mm round billets, a 3D mathematical model is established to investigate the effects of casting speed, mold parameters, and electromagnetic stirring (M‐EMS) on molten steel flow and heat transfer. The results indicate that higher casting speeds deepen the impingement zone and enlarge the high‐temperature region, leading to thinner shells and higher surface temperatures. When casting speed rises from 2.2 to 2.6 m min −1 , mold level fluctuation amplitude increases from 0.652 to 2.013 mm, and surface flow velocity rises from 0.0247 to 0.0293 m s −1 . Using a submerged entry nozzle (SEN) with a 25 mm diameter shifts the high‐temperature zone upward, accelerates superheat dissipation, and enhances heat transfer to the mold wall. The velocity distribution of molten steel near the solidification front correlates positively with shell growth in the M‐EMS zone. Both shell uniformity and remelting index decrease with increasing current intensity of M‐EMS. Industrial trials on 20# steel show that center porosity and segregation are controlled at grade 0.5 or below. When the superheat exceeds 25 °C, the proportion of billets with center shrinkage cavities below grade 0.5 decreases from 84.62% to 65%, while the occurrence of core defects increases significantly.

The Southwire Continuous Rod (SCR) process is widely used for producing low-oxygen copper rods, yet pore defects remain a significant challenge, affecting the performance and drawability of copper wire. In this study, the influence of casting speed on solidification behavior and porosity formation in low-oxygen copper casting rods was investigated by combining numerical simulation and plant trials. The simulation results indicate that increasing the casting speed elevates the flow velocity and impact depth of molten copper in the casting wheel. Simultaneously, higher casting speeds could raise the temperature of the casting rod and extend the liquid phase region, which suppresses the precipitation of dissolved gases from the melt. However, when the casting speed exceeds 26 t/h, the center temperature of the casting rod at the outlet remains close to the melting point of copper, retaining 10–20% liquid fraction. This predisposes the rod to remelting and the formation of remelt holes, and thus it fails to meet the design requirement for complete solidification of the SCR technology. Further industrial trials confirm that a casting speed of 23 t/h is optimal under current process conditions, yielding the lowest size and number of porosity defects in the casting rod.

In this paper, the influence of the novel design of a ladle shroud (LS) on the liquid steel flow structure inside the working volume of a two-strand slab tundish was assessed, determining the best solutions for LS use to achieve the optimal level of active flow zones and protect the tundish lining. A 0.33 scale water model was used for physical experiments. Numerical simulations were carried out in the Ansys-Fluent 12.1 software for a 1:1 scale tundish. The effect of the influence of LS type, LS immersion depth, LS side ports position, LS misalignment and casting speed was examined. Finally, the use of the "umbrella" ladle shroud allows stable hydrodynamics to be maintained even with shroud misalignment. Moreover, the "umbrella" ladle shroud effectively decreases the average velocity of liquid steel inside the tundish and significantly decreases shear stresses and dynamic pressure at the tundish lining in the tundish pouring area.

Effect of mould operation and wear on product quality in a copper casting and rolling line

Liquid level fluctuation in the mold has a significant impact on slab quality. As a time‐frequency analysis tool, wavelet transform (WT) has been successfully applied to the analysis of such fluctuation. In this study, the WT is used to decompose the liquid level fluctuation of the mold based on the data of the stable state for a complete casting sequence, and to construct the energy distribution sequence of the liquid level fluctuation. The time‐frequency characteristics of abnormal liquid level fluctuations and their causes are also systematically analyzed in combination with process parameters such as tundish weight and casting speed. The results show that the rate of weight change of the tundish is the key factor inducing the abnormal fluctuation of the liquid level, and the fluctuation of the liquid level is significantly aggravated when the rate of weight decrease exceeds 0.14 t s −1 or the rate of increase exceeds 0.1 t s −1 . When the casting speed is lower than 1.68 m min −1 , it can reduce the frequency of abnormal liquid level fluctuations occurring in the mold when the tundish weight drops during the ladle exchange procedure.

A 1:3 scaled water model experimental system was established based on the similarity principle. High-speed cameras and particle image velocimetry were employed to capture bubble images, and ImageJ was used for image processing to extract bubble trajectories, size distribution, and gas volume fraction. The motion behavior of multi-sized bubbles in the continuous casting mold was systematically investigated. The experimental results indicate that the casting speed, flow rate, mold size, and slag layer all have significant effects on the movement and distribution patterns of multi-sized bubble-like flows within the mold. First, small bubbles exhibit a distinct fan-shaped flow pattern, whereas large bubbles remain confined near the submerged entry nozzle, rising almost vertically. Both casting speed and gas flow rate influence the strength of the upper recirculating flow, which in turn affects the spatial distribution and movement behavior of bubbles. Moreover, the width of the mold influences bubble trajectories by altering the jet impingement area. As the mold width increases from 1050 to 1750 mm, the trajectories of small bubbles gradually evolve into a fan-shaped flow. Consequently, fewer bubbles follow the downward flow into the deeper region of the mold, and the gas volume fraction decreases from 6.52% to 4.26%. In addition, due to its inherent viscous resistance and surface tension, the slag significantly suppresses the gas–liquid two-phase flow. As the slag thickness increases from 0 to 2 cm, the rising velocity of bubbles decreases, and the overall gas volume fraction drops from 5.29% to 2.62%.

Herein, a coupled three‐dimensional large eddy simulation model and volume of fluid model is established to systematically investigate the effect of the argon injection through single‐channel and multi‐channel stopper rods, casting speed, and argon flow rate on the molten steel flow, spatial distribution of bubbles, and jet characteristics of a bifurcated submerged entry nozzle (SEN). The comparison with the water model shows that the current model can accurately predict the bubble distribution in the SEN. The multi‐channel argon blowing makes the argon distribution more uniform and generates bubbles with smaller diameters and larger quantities. The average diameter of bubbles is 16.72 mm in the single‐channel blowing, while the average diameter of bubbles is 12.03 mm in the multi‐channel blowing. The dispersion degree of argon bubbles increases with the increase of casting speed. The jet speed and backflow speed increase with the increase of the casting speed, while the jet vertical angle and the proportion of the backflow zone decrease gradually. With the increase of the argon flow rate, the fluctuation of the backflow speed at the outport will also increase. The injection of argon has a significant impact on the jet characteristics at the outport.

In slab continuous casting, achieving uniform cooling in the secondary cooling zone is essential for ensuring both surface integrity and internal quality. To optimize the process for ship plate steel, a solidification heat transfer model was developed, incorporating radiation, water film evaporation, spray impingement, and roll contact. The influence of secondary cooling water flow on slab temperature distribution was systematically investigated from multiple perspectives. The results show that a weak cooling strategy is crucial for maintaining higher surface temperatures and aligning the solidification endpoint with the soft reduction zone. Along the casting direction, a “strong-to-weak” cooling pattern effectively prevents abrupt temperature fluctuations, while reducing the inner-to-outer arc water ratio from 1.0 to 0.74 mitigates transverse thermal gradients. In addition, shutting off selected nozzles in the later stage of secondary cooling at medium and low casting speeds increases the slab corner temperature in the straightening zone by approximately 50 °C, thereby avoiding brittle temperature ranges. Overall, the proposed multi-dimensional uniform cooling strategy reduces temperature fluctuations and significantly improves slab quality, demonstrating strong potential for industrial application.

Application of a multi-field model for controlling segregation in low-alloyed steel by twin-roll casting

Traditional vertical direct chill (VDC) casting faces challenges such as discontinuous production and safety risks. In contrast, horizontal direct chill (HDC) casting has gained attention for its continuous operation, enhanced safety, and cost-effectiveness. However, fundamental studies on HDC of aluminum alloys remain limited, particularly concerning quality defects caused by asymmetric cooling within the mold. This article reviews the origins of cooling inhomogeneity in aluminum alloy HDC and the strategies developed to mitigate it, with emphasis on mold design optimization, process parameter control, and modification treatments. Research shows that optimized casting speeds, low-frequency electromagnetic fields, combined magnetic fields, and power ultrasonic techniques can refine grains, reduce surface segregation layer thickness, and suppress solute segregation. Despite these advances, challenges remain, including microstructural defects from uneven cooling, limited effectiveness of grain refiners, and an incomplete understanding of multi-field synergistic mechanisms. Future research should focus on developing multi-physics numerical models to establish quantitative links between external field parameters and solidification structures, creating rareearth-enhanced composite modification methods for greater compositional flexibility, designing modular external field devices to improve energy field uniformity in large ingots, and applying AI-driven multi-objective optimization for precise process control.

During electron beam cold hearth melting (EBCHM) of Ti-6wt%Al-4wt%V titanium alloy, aluminum volatilization causes compositional segregation in the ingot, significantly degrading material performance. Traditional methods (e.g., the Langmuir equation) struggle to accurately predict aluminum diffusion and compensation behaviors, while computational fluid dynamics (CFD), although capable of resolving multiphysics fields in the molten pool, suffer from high computational costs and insufficient research on segregation control. To address these issues, this study proposes a CFD-machine learning (backpropagation neural network, CFD-ML(BP)) approach to achieve precise prediction and optimization of aluminum segregation. First, CFD simulations are performed to obtain the molten pool’s temperature field, flow field, and aluminum concentration distribution, with model reliability validated experimentally. Subsequently, a BP neural network is trained using large-scale CFD datasets to establish an aluminum concentration prediction model, capturing the nonlinear relationships between process parameters (e.g., casting speed, temperature) and compositional segregation. Finally, optimization algorithms are applied to determine optimal process parameters, which are validated via CFD multiphysics coupling simulations. The results demonstrate that this method predicts the average aluminum concentration in the ingot with an error of ≤3%, significantly reducing computational costs. It also elucidates the kinetic mechanisms of aluminum volatilization and diffusion, revealing that non-monotonic segregation trends arise from the dynamic balance of volatilization, diffusion, convection, and solidification. Moreover, the most uniform aluminum distribution (average 6.8 wt.%, R2 = 0.002) is achieved in a double-overflow mold at a casting speed of 18 mm/min and a temperature of 2168 K.

Flow field control within slab mold under different casting speeds by electromagnetic swirling flow in nozzle

Slag entrainment in the continuous casting mold has always been the focus of surface quality control of the slab for the steel strips. However, the invisible and nonlinear molten steel flow that determines the defect formation make online measurement and evaluation particularly difficult. We developed a fast prediction method visualising the characteristics of the melt flow and estimating the slag entrainment online by combining numerical simulation and machine learning. The data-driven surrogate model was constructed using the proper orthogonal decomposition method and a fully connected neural network based on the numerical simulation data. The model showed a high hit rate of over 91 % with an absolute error of less than 0.05, and exhibited millisecond-scale real-time responsiveness. With the ultra-high computational efficiency, a high-resolution parameter-defect index map was established to clarify the effect of the operating parameters at multiple dimensions, and to locate the low-risk range, the argon flow rate within 3–8 L/min, the casting speed within 1.0–1.7 m/min, and the nozzle immersion depth within 180–220 mm. This approach provides a promising technical route for the design of an efficient online slag entrainment monitoring system.

The continuous casting of Ti-Nb microalloyed steel was simulated with high temperature confocal laser scanning microscopy (HTCLSM). Evolution of the sample surface morphology was observed in-situ, during cooling conditions chosen to represent different locations in a cast slab. Calculations with a thermodynamics model of carbonitride precipitate formation agreed with the transmission electron microscopy (TEM) analysis that fine reliefs observed on the sample surface were actually caused by interior precipitation of (Ti,Nb)(C,N). Precipitation and the resulting reliefs changed with location beneath the slab surface, simulated casting speed, and steel composition. With the same casting speed and steel composition, reliefs in the simulated slab surface sample appeared earlier and were larger than in the slab center. With increased casting speed, reliefs were observed later and decreased in size. With increased titanium or niobium content, reliefs appeared earlier and increased in number. TEM measurement showed that the precipitate diameters were mainly smaller than 4 nm, with a few between 4 and 8 nm. The property of surface reliefs observed via HTCLSM correlated qualitatively with the number and size of internal precipitates measured with TEM, showing this to be an effective tool for indirectly characterizing nanoscale secondary phase precipitation inside the sample.

The formation mechanism of black streak defects in hot-rolled steel sheets was investigated to address the influence of the process parameters on the surface quality during the production of 304 stainless steels. Macro-/microstructural characterization revealed that the defect regions contained necessary mold slag components (Ca, Si, Al, Mg, Na, K) which originated from the initial stage of solidification in the mold region of the continuous casting process, indicating obvious slag entrapment during continuous casting. On this basis, a three-dimensional coupled finite-element model for the molten steel flow–thermal characteristics was established to evaluate the effects of typical casting parameters using the determination of the critical slag entrapment velocity as the criterion. Numerical simulations demonstrated that the maximum surface velocity improved from 0.29 m/s to 0.37 m/s with a casting speed increasing from 1.0 m/min to 1.2 m/min, which intensified the meniscus turbulence. However, the increase in the port angle and the depth of the submerged entry nozzle (SEN) effectively reduced the maximum surface velocity to 0.238 m/s and 0.243 m/s, respectively, with a simultaneous improvement in the slag–steel interface temperature. Through MATLAB (version 2023b)-based reverse optimization combined with critical velocity analysis, the optimal mold slag properties were determined to be 2800 kg/m3 for the density, 4.756 × 10−6 m2/s for the kinematic viscosity, and 0.01 N/m for the interfacial tension. This systematic approach provides theoretical guidance for process optimization and slag design enhancement in industrial production.

Non-normal casting usually refers to the casting process of tundish where one or more outlets are closed due to the shortage of molten steel supply, difficulty in billet production, equipment failure, sudden accidents and other unconventional problems, which are inevitable in industrial sites. The closure of the outlets will change the flow field of the tundish, which will affect the metallurgical effects such as temperature uniformity and inclusion removal rate, etc. However, the influence of closing various outlets is more controversial at present. In this paper, the influence of non-normal casting under the closures of various outlets on the metallurgical behaviour of an eight-strand tundish is investigated exhaustively by numerical simulation, and new evaluation method of the consistency among the strands based on similarity calculation is proposed. The results show that the abnormal closure of one outlet has little effect on the flow field of the tundish, and the evaluation parameters of the flow characteristics have slightly different from those of the normal casting scheme. Under the condition of abnormal closure of two outlets, the similarity between different strands for the scheme of closing symmetrical outlets is better than that for other schemes, the average residence time and peak time are also extended, and the removal rate of inclusions with the diameters of 5–90 μm increased from 85.95% of normal casting to about 89%. When the production rhythm adjustment needs to reduce the casting speed or selectively close two outlets, closing outlet 1 and outlet 8 is the optimal solution. The consistency among the strands is relatively good, as the average similarity between the outlets is increased from 0.679 under the scheme of reducing the casting speed to 0.736 now. And the low temperature zone is less, and the dead zone ratio is small, 7.85% at the critical velocity of 0.008 m/s. The removal rate of inclusions increased to 89.01%, especially up to 93.62% for large-size (≥50 μm) inclusions. The research results of various schemes for closing the outlets can provide scientific guidance for actual non-normal casting operations.

Mould oscillation monitoring was conducted on a slab continuous casting machine with a thickness of 170 mm, a width of 1500 mm, and a casting speed of 1.8 m/min. The measurements employed non-sinusoidal oscillation characterised by an amplitude of 3.95 mm, a frequency of 2.40 Hz, and a deflection ratio of 0.20. The force calculation model is established and optimised, and the polarisation in casting and width directions is found by the frequency analysis. Results show that the polarisation will gradually stabilise through 40 min after casting speed is unchanged. When the amplitude in casting and width directions decreases from 0.23 mm and 0.11 mm to 0.20 mm and 0.08 mm, the stress on the solidifying shell from is reduced from 4.32 MPa to 3.36 MPa, which is within the range of high-temperature strength of hypo-peritectic steel. Large mould polarisation changes the trajectory of the mould, increases tearing risk in positive strip time, and hinders crack healing in negative strip time, thereby facilitating crack initiation and propagation along the longitudinal direction.

In this study the influence of varying twin-roll casting (TRC) conditions on the microstructure, texture and mechanical properties of a Mg-6.8Y-2.5Zn-0.4Zr alloy (WZ73) was investigated. In particular the twin-roll cast speed and rolling gap were varied. Post twin-roll casting, the microstructure exhibits non-uniformity across the strip thickness and consists of a network-like arrangement of the long period stacking ordered (LPSO) phases and the α-Mg matrix. The α-Mg matrix is characterized by dobulites (flake-like structures). Various defects typical for twin-roll cast strips were observed, along with a notable impact of casting conditions on the precipitation, morphology, and phase composition of the LPSO phases. The twin-roll casting speed significantly influences the resultant microstructural features. Higher casting speeds reduce the average equivalent deformation degree, leading to an increase in the phase fraction of LPSO structures but a reduction in thickness. Additionally, higher TRC speeds result in decreased solidification times, promoting inhomogeneity and segregation defects. These changes also impact the distribution of precipitates and strip temperature at the roll gap exit, delaying solidification and influencing centerline segregation thickness. Kink bands and yttrium-rich precipitates were present in all samples, with LPSO phases precipitating along grain boundaries. No dynamic recrystallization was observed. Texture analysis revealed basal and non-basal slip activation, with lower intensities at higher TRC speeds. The yield strength (YTS) and tensile strength (UTS) behaved similar whilst the elongation remained unchanged by the TRC conditions.

Abstract Focusing on DP590 steel, this study employs numerical simulation to investigate the formation mechanism of temperature field inhomogeneity during continuous casting and its impact on multi-pass rough rolling. A 2D continuous casting temperature field model developed in Abaqus, defined with modeling parameters including a slab size of 1600 × 230 mm, a casting speed of 1.1 m min−1, and specific water volume 1.99 l kg−1, reveals the thermal evolution during the cooling process. A 3D heating-rolling model incorporating defined parameters of work roll radius 500 mm, speed 6 rad s−1 further analyzes how temperature inhomogeneity affects rolling force and stress–strain distribution. The results demonstrate that the non-uniform temperature field significantly exacerbates rolling force fluctuations, with the rolling force under 600 s of heating increasing by approximately 15%–20% compared to a uniform 1200 °C temperature field, while simultaneously inducing a stress gradient along the thickness direction (stress difference exceeding 20 MPa between surface and core) and non-uniform strain distribution (strain difference reaching 0.68); however, extending the heating duration to 1200s reduces the core-surface temperature difference to below 300 °C, achieving stress–strain distribution uniformity comparable to isothermal conditions. Optimized heating processes enhance deformation uniformity, resolving the conflict between low-energy production and product quality in low-speed casting scenarios.