Casting Speed Research Articles

The effect of tape casting parameters on the properties of textured porous silicon nitride ceramics

AbstractA method of enhancing the mechanical properties of porous silicon nitride ceramics by involving texture structure through tape casting was explored. The influence of grain orientation was systematically studied by varying the sintering temperature, casting speed, and gap height. The results indicate that increasing the sintering temperature and casting speed can improve the degree of grain orientation. The mechanical properties of ceramics are significantly affected by the degree of grain orientation, the sample with the highest Lotgering factor demonstrated a flexural strength of 441 ± 12 MPa and a fracture toughness of 5.6 MPa·m1/2 at a porosity of 39%. The relative permittivity of ceramics is predominantly governed by the porosity, with the grain orientation exerting a relatively minor effect.

Study on solidification and heat transfer of billet shell in a new-structure high-speed continuous casting mold

In this work, a three-dimensional finite element model of a newly structured high-speed continuous casting mold was established to study the heat transfer and solidification process of the billet shell. A complete billet shell, from the meniscus to the secondary cooling zone, was obtained through flame cutting. Using both simulations and test verification, detailed analyses were conducted on the temperature field distribution, thickness variation law, and cooling rate law of the billet shell within the mold, revealing its solidification behavior. Additionally, the effects of casting speed, molten steel superheat, and mold taper on the solidification behavior of the billet shell were discussed. Results showed that the simulation data were basically consistent with the test verification results. Within 200 mm from the meniscus, the heat dissipation accounted for three-quarters of the mold's total heat dissipation. The cooling rate at the corners of the billet shell was slightly higher than that at the sides. Between 200 mm and 400 mm from the meniscus, air gaps caused the temperature at the corners of the billet shell to rise. Afterwards, the whole billet shell eventually reached a similar the heat dissipation rates. The thickness of the billet shell increased exponentially within 110 mm from the curved meniscus, and from 110 mm to the exit of the mold, the thickness increased linearly but slowly. The effect of molten steel superheat within a range of 10 °C on billet shell solidification was relatively minor. Increasing the casting speed reduced the billet shell thickness and raised the billet shell surface temperature. However, increasing the taper of the mold had the opposite effect. Both adjustments shifted the gap formation position backward.

Large eddy simulation of various EMBr effects on the fluid flow, heat transfer and solidification process in an ultra-high speed thin slab casting mould with multi-port SEN

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.

Corner structure optimisation design of billet mould tube for Q235 with high casting speed

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.

Multi-grooved channel design in continuous casting mold for enhancing heat transfer efficiency considering pressure drop and flow rate loss

An efficient, speedy, multi-grooved (ESMG) mold was designed and manufactured for optimization to address issues such as low heat transfer rate, slow casting speed, and quality defects in traditional continuous casting molds. The flow resistance mechanism of multi-grooved channels with varying parameters was investigated by considering the ESMG geometric model, the convective heat transfer characteristic variation trends were revealed with different channel designs. Considering constraints of the dimensional chain and supply pressure, variation trends and mechanisms of the pressure drop, flow rate loss, and convective heat transfer coefficient of the ESMG mold were explored using multiple channel variables. Based on the numerical model of the ESMG channel, temperature variation trends in the copper mold were verified by comparison with relevant literature data, supporting the convective-heat-transfer model and variation trends of the ESMG mold. A high-efficiency heat-transfer ESMG assembly that casts U71Mn high-carbon large rectangular billets was fabricated, achieving a closed-loop dimensional chain and replacing traditional molds. Experimental validation on the continuous casting machine (CCM) proved directly that redesigning the ESMG mold cooling channel improved heat transfer efficiency and reduced CO2 emissions. After 504 h on the CCM, the ESMG mold casting speed increased from 1.1 to 1.6 m/min, the heat transfer efficiency was 17.6% higher than that of traditional molds and CO2 emissions were estimated to decrease by 31.2%. The billets produced by the ESMG mold had no quality defects in shape or surface with the original casting conditions, which provided enhanced support for accelerating continuous casting lines.

A multi-field couped model for controlling segregation in twin-roll casting

So-called center and edge segregation are formed during twin-roll casting, which cannot be effectively eliminated in subsequent rolling and heat treatment, thus significantly diminishing the quality of final product. Numerous studies have been conducted on such segregations so far, unfortunately, without fully considering conservation of mass, momentum, energy and solute throughout the process, as well as synergy of thermodynamics and kinetics for interfacial migration. Accordingly, a two-phase Eulerian-Eulerian volume-averaged model is herein established to predict the segregation upon twin-roll casting for Al–Si alloys, which, for the first time, addresses effects due to the interfacial migration and the solute diffusion on the solute transfer process, and so-called correlation between thermodynamics and kinetics (i.e., thermo-kinetic correlation). On this basis, the model accurately predicts the flow field upon twin-roll casting, where, the increased casting speed leads to the descended kissing point, thus gradually causing the decreased vortex area and the increased cooling rate. Whereas, the increased heat transfer coefficient leads to the ascended kissing point, thus gradually causing the increased vortex area and the decreased cooling rate. In the modeling, the increased thermodynamic driving force for interfacial migration is always accompanied by the decreased kinetic energy barrier, and vice versa. Furthermore, the model also accurately predicts the segregation upon twin-roll casting, where, the thermodynamic driving force increases with the casting speed, thus decreasing the central segregation, whereas, the heat transfer coefficient increases, thus enhancing the generalized stability and in turn, effectively suppressing the edge segregation. By employing a strategy involving high driving force in the early stage and high generalized stability in the late stage, it was determined that the anticipated center and edge segregation could be effectively suppressed.

Analysis of carbon shell of billets with high casting speed

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.

Mathematical modeling of the flat ingot casting process or solving automation problems

Aluminum alloys are widely used in the production of aircraft due to their strength, lightness, corrosion resistance, and necessary electrical conductivity. At the same time, aluminum ingots used in further processing of the space industry must be of high quality. Technological problems and defects arise when temperature, speed, and other technological parameters of casting are not observed, or when modes change. At the same time, foundry processes are partially automated; the human factor significantly affects product quality and work safety. Therefore, automation of these complex processes using mathematical models to predict casting parameters is an urgent task. The goal of the work is to create mathematical models available for use in automated process control systems (APCS), as well as for the development of a digital twin. The work presents simplified formulas for modeling the temperature distribution of an aluminum ingot during the casting process, cooling the metal when moving along a metal path, and test calculations of the temperature distribution inside the ingot when the ingot reaches a fixed length. The results of this work can be used to improve the efficiency and accuracy of controlling the process of casting aluminum ingots, to eliminate emergency situations.

Harmful Effects, Origin, and Control of Banded Structures in Electroplated Fasteners of High‐Carbon Steel

In this study, the harmful effects of a banded structure on the bending fracture of electroplated fasteners are investigated. The origins and ways to control these structures are also explored. The fracture surfaces of the fasteners exhibit stepwise cracks and numerous intergranular facets associated with ductile tearing, which is a characteristic of hydrogen embrittlement. The origin of these stepwise cracks can be traced to the internal banded structures. Therefore, the internal banded structures promote fracturing during the bending test. The internal banded structures in the fasteners can be traced back to the internal cracks in the bloom, and inappropriate soft‐reduction processes lead to internal cracks. Notably, the carbon segregation at the internal cracks is severe. This is attributed to the proximity of the internal cracks to the center of the bloom, causing the enriched liquid in the interdendritic region to be sucked into these internal cracks. The optimal reduction position and amount are determined by employing heat‐transfer and soft‐reduction models. Fluctuations in superheat and casting speed significantly influence this optimal position and reduction amount.

LEVERAGING LEAN SIX SIGMA TECHNIQUES FOR ACCELERATED ON-SITE CASTING: FACTORS AND STRATEGIES

In the construction industry, issues such as excessive waste, rising costs, and strained relationships are prevalent. A pressing matter of plunged casting time during mass concreting activities has engulfed numerous construction contracting firms around the world. The increased time of concrete utilization not only risks the commencement of the heat of hydration but also initiates the setting time of concrete. The use of admixtures has often been a boon to curb this situation but human errors are almost impossible to escape from as inappropriate dosage of the admixtures can result in changing the properties of the concrete, affects the quality and pumping ability, which ultimately reducing the speed of casting and elapsed schedules. Other factors on site, though minor, vastly affect the pumping efficiency and causes considerable delays in the casting which not only affects the schedules but also causes time overrun and affects the productivity at site. The focus of this study is to address the issues encountered at the site that directly affect the speed of on-site casting and corrective actions.

Graphics‐Processing‐Unit‐Accelerated 3D Online Heat Transfer and Solidification Model for Continuously Cast Slab

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.

Study on electromagnetic stirring–braking structure layout design and its synergistic mechanism in electromagnetic metallurgy

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.

Investigation of segregation behaviour in 2060 aluminium-lithium alloy during twin-roll casting

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.

Numerical modelling of continuous casting of round billets with turbulence in the melt

The present work aims to solve the continuous casting benchmark problem in axisymmetry with turbulence in the melt by the meshless method. The physical model of the liquid-solid system that involves mass, momentum and energy conservation is formulated in the mixture continuum approximation. The melt is assumed Newtonian and incompressible. A k-epsilon Reynolds averaged Navier-Stokes turbulence model is implemented with Abe-Kondoh-Nagano closures. The mushy region is modelled as a Darcy porous media with the Kozeny-Carman permeability model. The solution of partial differential equations is implemented locally using collocation with radial basis functions and explicit time-stepping. The velocity pressure coupling is performed using the fractional step method. The validation of the model is assessed by comparing its outcomes with the results of the finite volume method. A sensitivity study of the varying casting speed and temperature on the velocity, temperature, and solid fraction fields is shown.

Simulation and Study of Influencing Factors on the Solidification Microstructure of Hazelett Continuous Casting Slabs Using CAFE Model.

The Hazelett continuous casting and rolling process represents a leading-edge production method for cold-rolled aluminum sheet and strip billets in the world. Its solidification microstructure significantly influences the quality of billets produced for cold rolling of aluminum sheets and strips. In this study, employing the CAFE (Cellular Automaton-Finite Element) method, we developed a coupled computational model to simulate the solidification microstructure in the Hazelett continuous casting process. We investigated the impact of nucleation parameters, casting temperature, and continuous casting speed on the microstructural evolution of the continuous casting billet. Through integrated metallographic analyses, we aimed to elucidate the controlling mechanisms underlying the Hazelett continuous casting process and its resultant microstructure. The results demonstrate that the equiaxed rate of grains increases with an increase in nucleation density, and the grain size decreases under constant cooling strength. With other nucleation parameters held constant, the grain size decreases as undercooling increases, and the columnar crystal zone expands. The nucleation density of the Hazelett continuous casting aluminum alloy has been determined to range between 1011 m-3 and 1013 m-3, and the undercooling ranges between 1 °C and 2.5 °C. The solidified grain structure can be controlled between 35 μm and 72 μm. The grain size of the continuous casting billet increases with an increase in pouring temperature and decreases as the casting speed increases. Elevating the pouring temperature positively impacts the fraction of high-angle grain boundaries and promotes the dendritic to equiaxed grain transition. Moreover, there exists potential for further optimization of continuous casting process parameters.

Design and heat transfer numerical analysis of high-speed continuous casting mold water slot system

The water slot structure can reduce the temperature of the mold and increase the heat transfer between the mold and cooling water. It has significant impacts on high-speed continuous casting. Therefore, a three-dimensional model of heat transfer from mold to cooling water was used to analyze the influence of water slot size on the cooling capacity of a single water slot. Then, the fluid flow, heat transfer, and solidification three-dimensional models were used to analyze the temperature distribution and cooling effect of three kinds of water slot molds and non-water slot molds. Finally, the water slot mold was designed to achieve high-speed continuous casting. The results show that to make full use of the cooling water in the water slot, the width and height of a single water slot should be less than 8 mm. Compared with the conventional mold without the water slot structure, the temperature of the mold with the water slot structure significantly decreases. The final design of the mold water slot system is as follows: the water slot width and depth are 8 mm, and the number of water slots on one side of the mold is 9. The water slots have a symmetrical distribution, and the symmetrical plane is the middle plane of the mold. The high-speed continuous casting experiment was carried out, and the casting speed can reach 4–4.5 m/min. The water slot mold in this study can be applied in the high-speed continuous casting process.

The Role of Powder Used in the Continuous Molding of Alloys

Abstract In this paper, a technology for obtaining powdery materials with special characteristics, in the metallurgical field, is presented. The compositions of these powders are from the calcium oxide - alumina - silica system, by adding CaF2, Na2O and C. The choice of oxide compositions will be made according to a series of parameters: the composition of the cast steel, the casting speed, the viscosity or the surface tension of molten steel.

Influence of Submerged Entry Nozzles on Fluid Flow, Slag Entrainment, and Solidification in Slab Continuous Casting

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.

Numerical Simulation of Macro-Segregation Phenomena in Transition Blooms with Various Carbon Contents

This paper presents a numerical simulation of the steel grade transition from the ladle nozzle to the solidification end of the bloom. The simulation is based on models encompassing fluid flow, solidification, heat transfer, an electromagnetic field, and solute transport. To validate the accuracy of the steel grade transition model, transition blooms of high-carbon steel are sampled. Subsequently, the model is applied to investigating the steel grade transition between medium-carbon steel and low-carbon steel. The findings indicate that the regions exhibiting significant differences between their molten steel flow velocity and bloom casting speed in the strand model are primarily concentrated within 1 m below the meniscus. Additionally, the mushy zone in the strand model possesses a substantial volume. Solute elements continuously permeate the liquid phase from the solid phase through the mushy zone. Consequently, the distribution of solute elements in the transition bloom is primarily influenced by the molten steel flow in the tundish and macro-segregation in the casting process. The segregation degree of each solute element varies among grades with different carbon contents. In the austenite phase, the segregation degree of each element follows the order C > Si > Mo > Mn > Cr > Ni, while in the ferrite phase, the segregation degree is ordered as C > Si = Mn. Considering macro-segregation, the transition bloom partition model proves to be more stringent than the original partition method. This results in longer transition blooms when a significant difference exists between the new and old grades. For example, in Scheme 1, the original plan transition bloom length is 8.88 m, whereas the new plan transition bloom length is 10.88 m. Similarly, in Scheme 2, the original plan transition bloom length is 34.64 m, and the new plan transition bloom length is 35.16 m. Conversely, shorter partition intervals occur when there is an overlap in the composition of the new and old grades. In Scheme 3, the original plan partition interval for the new and old grades is 4.08 m, while the new plan partition interval is reduced to 0.94 m.

Porosity forming mechanism and numerical simulation of casting process optimization of nickel-based heat-resistant alloy electrode ingot with large height to diameter ratio

Based on the simulation results of ProCAST software for the filling and solidification process, the formation mechanism of the VIM electrode ingot's pipe and porosities and the influence of the casting process on the formation of electrode shrinkage were studied in detail. The research results indicate that the critical condition for the formation of 200 kg grade C650R heat-resistant alloy is verified to be G/R≤5.0 (K·s)0.5/cm. In addition to the alloy's inherent characteristics, the substantial height to diameter ratio (H/D) of the VIM electrode ingot is the primary factor contributing to the formation of deep pipe and severe porosities. Simply adjusting the casting time or casting speed alone does not significantly improve the solidification quality of the ingot. While the use of a hot top can eliminate pipe, its effectiveness is limited, as the alloy melt at the hot top location has minimal influence on the solidification process in the lower regions of the electrode ingot, thereby failing to effectively reduce the formation of porosities. Properly reducing the casting speed and casting superheat lead to the formation of a V-shaped melt at localized positions during the final stage of solidification. This enhances the ability of the liquid phase for further feeding, ultimately significantly decreasing both the depth of pipe and the porosity rate. The optimal casting process optimization solution for C650R alloy electrode ingot with a size of Φ130 mm × 1240 mm is the casting speed of 60 kg/min and the superheat of 40 °C.