Abstract Currently, the setting of cast drying conditions relies more on the experience of engineers, lacking effective methods for quantitative testing and intelligent control. In this paper, the actual drying process of ultra-thin ceramic sheets using infrared perception during the high-speed casting was investigated. The influence of different drying conditions on the microstructure and properties of ceramic sheets was clarified. The infrared perception results show that there are significant differences between the actual temperatures and the set values. Compared to the set temperature, there is a stronger correlation between the actual temperature and sheet properties. The constant temperature drying period is critical for the formation of sheet microstructure and properties. Finally, a general intelligent drying strategy is proposed to meet the diverse needs of the sheet.

In the secondary cooling stage of continuous casting, the cooling rate and uniformity of spray jets are crucial for high-speed casting. As high-pressure spray cooling technology operating at pressures greater than 1.0 MPa becomes more widely used in continuous casting, understanding its flow field characteristics is essential for improving cooling efficiency. This study combines experimental methods with Particle Image Velocimetry to analyse the velocity fields and water flux density distributions of three high-pressure, wide-coverage fan-shaped nozzles under different water pressures and jet heights. The results show that at 2.0 MPa, the maximum velocity directly beneath the nozzle is more than twice that at 0.5 MPa. Additionally, a dimensionless characterisation of the nozzle jet velocity field is proposed, along with the typical effective operating ranges of nozzles, offering theoretical guidance for optimising the flow performance of fan-shaped water nozzles.

With the acceleration of slab continuous casting, achieving a balance between the thermal resistance and lubrication of mould flux has become increasingly challenging. This study proposes a composite regulation strategy involving a 40 mT static magnetic field and 0% to 1% Li 2 O addition. The effects of magnetic fields and Li 2 O on crystallisation behaviour were investigated using isothermal crystallisation and micro-structural analysis. Results show that the magnetic field effect is temperature-dependent: it significantly shortens nucleation time (>70%) at 1300 °C and 1250 °C, has minimal impact at 1200 °C, and promotes nucleation but delays overall crystallisation at 1150 °C due to insufficient nuclei. Li 2 O addition modifies this effect, turning crystallisation promotion into suppression at 1300 °C and weakening the magnetic field's influence between 1250 °C and 1200 °C. At 1150 °C, Li 2 O enhances crystal growth suppression. At temperatures ≥1200 °C, Li 2 O synergises with the magnetic field to accelerate crystallisation and alters the crystal growth mode from unidirectional to multidirectional, inducing secondary nucleation and forming a bimodal structure. These findings provide theoretical guidance for the design of mould flux under high-speed casting conditions.

ABSTRACT Low-carbon alloy steels exhibit a wide mushy zone, making them prone to cracks, segregation, and porosity that degrade slab quality. To achieve high-speed continuous casting, this study developed a Cellular Automaton-Finite Element (CAFE) model to elucidate solidification structure evolution and quantify the influence of process parameters on equiaxed grain ratio, columnar grain width, and average equiaxed grain area. Results show that increasing superheat (10–30 K), casting speed (0.9–1.3 m/min), and mold cooling water flow (8150–12750 L/min) reduced equiaxed grain ratio by 34.49%, 19.70%, and 9.98%, respectively, while enlarging columnar width and average grain area. Raising specific water flow in the secondary cooling zone (0.6–0.8 L/kg) decreased equiaxed grain ratio by 35.09%, widened columnar grains, and caused average grain area to rise initially then decline. Optimal conditions include maintaining 15–20 K superheat, appropriately increasing mold cooling, and ensuring higher secondary cooling to achieve stable high-speed casting and improved quality.

This critical review synthesizes evidence on the multifactorial coupling mechanisms and time-dependent evolution of lateral pressure in concrete formworks, addressing significant limitations in current design standards (GB50666, CIRIA 108, ACI 347). Through a structured analysis of 60+ experimental and theoretical studies, we establish that lateral pressure is governed by nonlinear interactions between concrete rheology, casting dynamics, thermal conditions, and formwork geometry. The key findings reveal that (1) casting rate increments >5 m/h amplify peak pressure by 15–27%, while SCC thixotropy (Athix > 0.5) reduces it by 15–27% at <5 m/h; (2) secondary vibration induces 52–61% pressure surges through liquefaction; and (3) sections with a width >2 m exhibit 40% faster pressure decay due to arching effects. (4) Temporal evolution follows three distinct phases—rapid rise (0–2 h), slow decay (2–10 h), and sharp decline (>10 h)—with the temperature critically modulating transition kinetics. Crucially, the existing codes inadequately model temperature dependencies, SCC/HPC rheology, and high-speed casting (>10 m/h). This work proposes a parameter-specific framework integrating rheological thresholds (Athix, Rstr), casting protocols, and real-time monitoring to enhance standard accuracy, enabling an optimized formwork design and risk mitigation in complex scenarios, such as water conveyance construction and slipforming.

Multi-field coupling analysis of twin-roll casting process for achieving thin aluminum strip high-speed casting and fabricating laminated metal cladding materials

As the third generation of thin slab continuous casting and rolling technology, endless strip production (ESP) has been widely used in the steelmaking industry. The key equipment in this process, the funnel-type mold, is prone to accidents such as slag entrainment, surface cracks and steel leakage under high casting speed conditions. To reduce the incidence of the above accidents, the numerical model of flow, heat transfer and solidification in the funnel-type mold is established by using the k-ε model, enthalpy–porosity method and magnetohydrodynamics (MHD), and the influence mechanism of the mold cavity and submerged entry nozzle (SEN) on the molten steel is studied, providing a new solution for optimizing the ESP process. The results show that compared with the type-I mold, the influence of the geometric disturbance of the top cavity on the flow state of the middle and lower body is localized, while the type-II funnel mold increases the thickness of the solidified shell at the outlet of mold; the marked enhancement in solidified shell thickness and uniformity at the mold exit achieved through the type-II SEN due to the distribution of temperature and velocity are more reasonable, reducing the risk of surface cracks and steel leakage.

The main feature of high-efficiency continuous casting production is the increase in casting speed. This leads to an increased risk of slag entrapment in the liquid surface area of the mould and steel leakage due to the bonding of the casting billet. Both traditional mould flux and non-Newtonian fluid mould flux with only shear-thinning properties cannot effectively solve these problems. This study selected a practical high-casting speed thin slab mould flux from a steel plant as the original mould flux. Add 4.6–12.1% Al2O3 and 3.6–4.9% MnO and other additives to prepare a new type of mould flux with both shear thinning characteristics and high surface tension. The shear-thinning properties, interface properties and microstructure of the mould flux were detected and studied using methods such as the rotating cylinder method. The results showed that with the increase of Al2O3 content, the shear-thinning properties of the mould flux first enhanced and then weakened. The strongest effect was observed when the Al2O3 content was 8.7%. The contact angle, surface tension and interface tension of the mould flux were significantly improved and the degree of molecular polymerisation gradually increased. The shear-thinning properties of mould flux are mainly related to the Si–O–Al structure. The interaction force between Al3+ in the slag and the surface O2− of the mould flux increases, and the surface tension of the mould flux increases. When the Al2O3 content is more than 10.5%, a large amount of AlO2− will be repelled to the surface of the mould flux, and the change in surface tension is no longer significant.

Production practices have shown that the morphology and dimensions of the solidification structure in blooms are pivotal in determining solute distribution, thereby influencing the consistency of hardenability in high-quality gear steels. To address the issue of asymmetric lengths between the inner and outer arc columnar crystal zones caused by dendrite sedimentation in continuously cast blooms, a treatment considering dendrite sedimentation was proposed using the solidification structure simulation model (CAFE model) in the commercial software ProCAST. The effects of superheat, casting speed, specific water amount, and current intensity of mold electromagnetic stirring (M-EMS) on the equiaxed crystal ratio and the symmetry of the solidification structure of 20CrMnTiH gear steel blooms were simulated and analysed. The results showed that increasing superheat from 30°C to 50°C reduced the equiaxed crystal ratio from 25.77% to 15.73% and decreased the length difference between the inner and outer arc columnar crystal zones from 20.6 mm to 11.7 mm. A higher casting speed from 0.85 m·min−1 to 1.15 m·min−1 also reduced the equiaxed crystal ratio from 24.60% to 20.10%, but increased the length difference from 16.5 mm to 18.0 mm. Additionally, as the specific water amount raised from 0.264 L·kg−1 to 0.462 L·kg−1, the equiaxed crystal ratio dropped from 24.88% to 17.23%, while the length difference decreased from 18.6 mm to 15.1 mm. Lowering the M-EMS current intensity from 300 A to 100 A further reduced the equiaxed crystal ratio from 21.63% to 10.05% and decreased the length difference from 18.1 mm to 8.0 mm. These findings suggest that increasing superheat and decreasing M-EMS current intensity are effective strategies for enhancing the symmetry of the solidification structure in 20CrMnTiH gear steel blooms during continuous casting. Based on these results, an optimized process was proposed: with an M-EMS current of 100 A, superheat of 40°C, casting speed of 1.05 m·min−1, and a specific water amount of 0.33 L·kg−1, the resulting columnar crystal length was extended, and the symmetry was significantly improved. Consequently, the hardenability differences of the J9 and J15 of rolled products were minimized to 0.3 and 1.0 HRC, respectively, thereby meeting the numerical simulation control strategy and customer requirements.

The numerical simulation is combined with high‐temperature measurement to study the effects of electromagnetic braking (EMBr) and casting speed on the flow field, the fluctuation of the interface of the steel and slag, the distribution of argon gas bubbles, and the removal ratios of inclusions in the mold with a size of 1050 × 230 mm. The numerical simulation results and the high‐temperature measurement results of the velocities of molten steel at the 1/4 width and center of the thickness near the mold surface are in good agreement. The EMBr can reduce the velocity near the mold surface, the fluctuation of the interface between steel and slag, and the number of argon gas bubbles near narrow walls and decrease the total removal ratio of inclusions from 27.29 to 23.24%. When the casting speed is increased from 1.6 to 2.0 m min−1 with EMBr, the velocity of molten steel near the mold surface is increased. Even under the condition of a high casting speed of 2.0 m s−1, the velocity of molten steel near the surface is still in a reasonable range with EMBr. The total removal ratio of inclusions increases from 20.76 to 23.90%.

Reasonable corner design of the mould is conducive to the uniform heat transfer of the billet, especially for the crack-sensitive steel such as Q235 under high casting speed. Based on the Ansys finite element analysis platform, three kinds of mould corner configurations were designed in this study, and the temperature and stress distribution of the billet and mould corresponding to different mould were compared and analysed. The results show that the cooling uniformity of the C-type mould (petal-type) was better than that of other corner configurations, the maximum temperature at the mould corner was reduced by 43.66 °C, the minimum temperature at the billet corner was increased by 109.73 °C, and the maximum Von-Mises equivalent stress at the corner of the billet was reduced by 28.09 MPa. Therefore, the C-type mould can further improve the quality of the billet and is conducive to the improvement of production efficiency.

Effective control of intense turbulence is a crucial challenge for achieving steady production with ultra-high casting speed in thin slab continuous casting. In thin slab casting process, specially designed multi-port submerged entry nozzle (SEN) with four outlets is utilised to ensure an ample supply of molten steel, necessitating the selection and optimisation of suitable Electromagnetic Braking (EMBr) equipment for steel jet control. This study established a comprehensive three-dimensional model of a funnel-type mould, employing a combined experimental-numerical approach to validate and investigate the flow, heat transfer, solidification and electromagnetic behaviour in the mould. The steel grade studied in the simulation is Q235B, and its physical properties were calculated based on its composition with a temperature range of 1450–1826 K. To analyse the influence of high casting speed on the flow and solidification behaviour in the mould, three casting speeds were selected for the study, which were 6, 7 and 8 m/min. The results indicate that the novel Bowl EMBr significantly suppressed the penetration of steel jet and thus enhanced the thickness and uniformity of the solidified shell. As the casting speed increases from 6 to 8 m/min, the solidified shell thickness at the mould exit decreases from 7.91 to 5.94 mm, with the stagnant growth region approaching the mould exit. This highlights the requirement to correspondingly increase EMBr strength under ultra-high casting speed condition to avoid remelting of the shell and the risk of molten steel leakage. The coupled mathematical model established in this study provides guidance for optimising EMBr structures and casting speed under special multi-port SEN conditions, offering recommendations for the rational control of flow, heat transfer and solidification process in the mould.

Abstract The increasing casting speed of billets is beneficial for improving single-machine production efficiency, reducing refractory material consumption, and achieving energy conservation and consumption reduction. However, as the casting speed increases, the probability of steel leakage also increases. An analysis of the thickness of the billet shell under high casting speed allows us to analyze the reasons for steel leakage and propose targeted solutions. This article analyzes the steel leakage billet shell of grade 40 steel and concludes that the thickness of the billet shell is between 8-20 mm at the upper of the mold, and only 5-10 mm at the lower of the mold. At the beginning of its formation, the shell of the cast billet is not uniform, with a maximum difference of up to 8 mm. As the casting progresses, the shell of the billet actually becomes thinner. At a distance of 100-200 mm from the mold, the maximum air gap between the billet shell and the copper tube reaches about 5.5 mm. The air gap reduces the uniformity of heat transfer, resulting in an uneven billet shell. After the liquid steel is injected into the shell, it will cause remelting of the solidification shell, resulting in thinning of the casting shell and causing steel leakage at the outlet of the mold.

A graphics‐processing‐unit (GPU)‐accelerated 3D heat‐transfer and solidification model is proposed to predict the temperature field and solidification field for continuously cast slab. The fully 3D model is developed based on the finite difference method and implemented on the compute unified device architecture (CUDA)/C++ platform. The model is verified by solving the 1D Stefan problem and validated by surface temperature measurements. The model is proven to be 18.91 times faster for the coarsest mesh of 35 million nodes and 22.92 times faster for the finest mesh of 50 million nodes than a central‐processing‐unit (CPU)‐based parallel version with 28 threads. The corresponding relative calculational times are 0.19 and 0.32, which indicate that the model has great computation efficiency. The model is proven to be robust enough for the dynamic continuous casting (CC) process via a test of dynamic casting speed. Further analysis of the nonuniform heat transfer and solidification shows that the model is able to predict the nonuniform heat transfer efficiently. In the studied cases, a higher casting speed will lead to a remarkable enhancement of the unevenness of heat transfer and solidification in general.

During the continuous casting process, electromagnetic stirring (EMS) can control the flow pattern of the molten steel on the meniscus in the slab mould, while it is difficult to effectively control the entire molten steel. To this end, a novel composite magnetic field structure of EMS and electromagnetic braking (EMBr) is proposed, and the EMS–EMBr synergistic mechanism is analysed. The flow field of molten steel without a magnetic field is analysed. The magnetic field regulation strategy required to control the molten steel is clarified. The coil core structure layout of existing EMS is analysed. The action mechanism of EMS is studied through simulation, revealing the poor control effect of EMS on the molten steel under high casting speeds. Thus, a novel EMS–EMBr structure layout is proposed to enable the braking magnetic field to cover the key areas within the slab mould, ensuring that the main flow is effectively suppressed. On this basis, the effects of EMS–EMBr synergy and different process parameters on the flow pattern of molten steel are studied. The results indicate that the EMS–EMBr composite magnetic field structure proposed can more effectively control the molten steel, providing technical support for the development of electromagnetic metallurgical equipment.

The utilization of the twin-roll casting process to fabricate aluminium (Al) - lithium (Li) alloys is regarded as an efficient and energy-saving strategy to meet the aerospace industry’s demands for reducing processing steps, cost-effectiveness, and corrosion resistance. This study successfully achieved the preparation of Al-Li alloy twin-roll cast slabs across various processing ranges to investigate the corrosion resistance differences in different processing conditions. Remarkable macro segregation phenomena were observed in the fabrication under high twin-roll casting speeds for TRC-3. By combining temperature and flow rate calculations, we comprehensively analysed the results of this segregation mechanism. The segregation is inherited into the final T6 state microstructure, exacerbating the precipitation of the T1 phases and deteriorating the ultimate corrosion resistance performance. We delved into a profound discussion regarding the mechanistic impact of segregation on corrosion behaviour. Ultimately, this study postulates a process parameter range for twin-roll casting of Al-Li alloys, aimed at attaining minimal segregation and maximal corrosion resistance.

In recent years, there has been significant development in the large-scale utilisation of round bloom continuous casting, which has led to an increase in the strand spacing of the tundish. However, this increase often accompanies issues such as poor consistency among each strand. This study focuses on the three-strand asymmetric tundish used in super-large round bloom continuous casting and uses a combination of numerical simulation and physical experiment to investigate the impact of different dam and retaining wall structures on the flow, temperature and removal of inclusions in the super-large round bloom tundish. The reliability of the model is verified through isothermal Water model experiments. The results indicate that by employing an optimised flow control structure with a U-shaped retaining wall featuring small diversion holes and a dam near each of strands No.1 and No.3, several improvements are achieved compared to the prototype tundish. The dead zone ratio of the tundish is reduced by 16.33%, the standard deviation of average residence time decreases by 167.07 s, the volume of the tundish's low temperature zone decreases by 7.79% and the total inclusion removal ratio increases by 14.44%. By appropriately incorporating dams, reducing the area of diversion holes and modifying the retaining wall structure in the tundish, the flow, temperature and inclusion removal consistency of each strand can be effectively improved. This enhances the overall metallurgical efficiency of the tundish. Even when encountering strand blocking operation, the dead zone ratio can be further reduced to 22.44% using the optimised structure proposed in this study. This demonstrates that the optimised structure not only improves the steady-state metallurgical behaviour of the asymmetric three-strand tundish with large strand spacing for super-large round bloom but is also suitable for addressing unsteady-state metallurgical behaviour caused by on-site working conditions, such as production scheduling or high casting speed. By implementing the findings of this study, it is expected that the efficiency and effectiveness of the super-large round bloom continuous casting process will be significantly enhanced.

In this paper, the fluid flow, slag entrainment and solidification process in a slab mold were studied using physical modeling and numerical simulation. The effect of two types of submerged entry nozzles (SENs) was also studied. The results showed that the surface velocity for type A SEN was larger than that using type B SEN. For type A SEN, the maximum surface velocity was 0.63 m/s and 0.56 m/s, and it was 0.20 m/s and 0.18 m/s for type B SEN. The larger shear effect on the top surface made the slag at narrow face impacted to the vicinity of 1/4 wide face, while the slag layer at the top surface was relatively stable for type B SEN. Increasing the immersion depth of SEN decreased the surface velocity and slag entrainment. For type A SEN, the thickness of the solidified shell at the narrow face of the mold outlet was thin (12.3 mm) and there was a risk of breakout. For type B SEN, the liquid steel with high temperature would flow to the meniscus and it was beneficial to the melting of the mold flux. The thickness of the solidified shell at the narrow face of the mold outlet was increased. Furthermore, the surface velocity was also increased and it was not recommended for high casting speed.

Cracks occur on the surface of Al-Mg strips cast using a high-speed twin-roll caster. Surface cracking of the as-cast strip decreases with decreasing roll load. However, the difficulty of roll casting increases as the roll load is decreased because the strip becomes brittle and is easily broken because the strip is not completely solidified. In the present study, an unequal-diameter twin-roll caster, which is capable of high-speed casting, was used with a lip attached to a back-dam plate in an attempt to decrease surface cracking without deceasing the roll load. The thickness of the solidified layer was found to decrease as the length of the solidified region decreased. The thickness of the solidified layer at the center of the width direction of a strip on the lower roll decreased by shortening the solidification length by a lip attached to a back dam-plate. The solidified layer at the edges was thicker than that inside the cast strip. The thickness of semisolid metal inside the cast strip increased more than that at the edges of the roll bite. The roll load at the width of the lip decreased. The effect of the lip length on surface cracks was investigated.

To reduce the solidification structure defects and the macrosegregation of the Φ300 mm continuous casting round bloom, the pulsed magneto‐oscillation (PMO) treatment is added at the secondary cooling zone. A numerical model for calculating the pulsed electromagnetic field, flow field, and temperature field in continuous casting is established, and the coupling simulations of multiphysical fields under different casting parameters and PMO parameters are performed. Their influence on solidification process and the appropriate parameters are discussed. The industrial experiments conducted under the recommended parameters yield good results. Industrial experiments show that when the peak current is increased from 1350 to 1550 KIA and the casting speed is increased from 0.75 to 0.90 m min−1, PMO can increase the equiaxed grain zone and reduce the carbon macrosegregation of the bloom. Moreover, at high casting speed, PMO treatment can significantly promote columnar‐to‐equiaxed transition and increase the width of mixed grain zone.