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Carbon‐bonded alumina filters have been established in the steel industry for decades to increase the quality of cast steel components. The carbon bonding of the filter materials is commonly achieved by using pitches or resins. However, the pyrolysis of both substances results in the release of carcinogenic substances such as free phenols or benzo[a]pyrene. An alternative binder system is provided by lactose and tannin, which is considered to be more environmentally friendly, but they tend to result in insufficient mechanical filter properties.To ensure higher environmental sustainability and good mechanical properties, the effect of the stepwise replacement of the pitch‐binder CarboresP by lactose and tannin is investigated in the present study. Additionally, the impact of semiconductive additives (P‐doped n–Si and SiC) and the filter manufacturing method on the filter properties is analyzed. Based on the most promising filter composition, different lactose/tannin (L/T) ratios (5:1, 4:1, 3:1) are applied and the resulting properties evaluated. The results suggested that the pitch binder can be completely replaced by lactose and tannin by using SiC as additive and adjusting the filter manufacturing process. The variation of the L/T ratio shows no significant impact on the filter prope. [ABSTRACT FROM AUTHOR]

For more than 20 years, high‐temperature laser scanning confocal microscopy (HT‐LSCM) has become worldwide a proven technique for observing various metallurgical phenomena in situ. HT‐LSCM turns out to be a reliable and effective method for the observation of quantification austenite grain growth kinetics in steel, being highly relevant in casting and steel processing. In the present article, the measurement technique is briefly introduced followed by some basics on austenite grain growth. Finally, selected examples of recent research activities are discussed, including investigations into pure iron and the systems Fe–P, Fe–C, Fe–Al–N, and Fe–C–Nb–N. The influence of P on the grain growth kinetics is remarkable. At 1350 °C, the final grain size decreases from 255 μm in pure iron to 145 μm by adding 0.044 wt% P. In contrast, C enhances the grain growth in specific alloying ranges (0–0.30 wt%C), particularly at elevated temperatures. For a Al content of 0.025 wt% and only 50 wt ppm N, AlN loses the pinning effect above 1150 °C. In case of Nb(C,N), an elevated Nb content (0.085 wt%) provides stabilization of Nb(C,N) at 1150 °C, but at 1250 °C, no pinning of Nb(C,N) is visible anymore. [ABSTRACT FROM AUTHOR]

It is herein considered a new product composed of solid–liquid dispersion of a conveniently formulated continuous casting powder in synthetic oil‐based esters, where hypothetical limit to consider this liquid slurry as a liquid powder is a mix with at least 50% in weight powder load preserving suitable fluidity for effective and stable pumping. After a relatively long and intense industrial application period, one of most critical points when using liquid powder for steel continuous casting proves to be mold feeding. This is mainly because of weird properties of such material which behaves as a non‐Newtonian fluid. A thorough rheological study on samples of liquid powder for continuous casting is carried out. Based on meticulous characterization of a set of laboratory samples, the dispersion flow curve is determined. Most commonly used rheological models are then tested for fitting with the experimental data. Sisko model is identified as the best fitting one. This model is then implemented to derive the system curve describing its behavior under its industrial application conditions. The mathematical process to apply Sisko model and its numerical solutions is explained. The results found are consistent with the field experience of the industrial application of the material under study. [ABSTRACT FROM AUTHOR]

Low‐basicity fluorine‐containing mold flux, which forms a porous slag film with NaF pores, is expected to solve the contradiction between heat transfer and lubrication in the continuous casting of peritectic steel. Herein, the kinetic mechanism and the influence of NaF gas formation based on the different fluorine raw materials (NaF, CaF2, and Na3AlF6) at 0.9 basicity and 6 wt% fluorine are investigated by the combination of experiments and calculations. The results show that CaF2 is the first to generate NaF gas at 1189 K, followed by Na3AlF6 (1238 K) and NaF (1328 K). NaF raw material produces the most NaF gas with the lowest activation energy in the three raw materials, due to high Na ion kinetic energy, the simple degree of polymerization, and Na‐F1 bonds. Correspondingly, NaF bubbles in the molten slag are the largest based on their aggregation. Na3AlF6 and CaF2 raw materials rank second and third, with F atoms primarily bonded as Al‐Fx and Ca‐Fx and the higher proportion of QSi−O−Al2$Q_{\text{Si} - \text{O} - \text{Al}}^{2}$ and QSi−O−Si4$Q_{\text{Si} - \text{O} - \text{Si}}^{4}$ structure. Notably, at 0.9 basicity and 6 wt% fluorine, Na3AlF6 as raw material generates a suitable amount of gas, making diffuse and fine NaF bubbles in the molten slag. [ABSTRACT FROM AUTHOR]

The clogging of the submerged entry nozzle (SEN), as an important device to connect the tundish and the mold, has been widely concerned. However, until now, the clogging of the SEN cannot be eliminated during the casting. Herein, the clogging behavior of the SEN during the casting of ultralow‐carbon steel is studied using an external DC electric field. The findings demonstrate that the DC electric field inhibits the growth of the clogging on the outlet and the thickness of the clogging layer is small, which ensures the integrity of the profile of the outlet. After DC treatment, the interface of the clogging is clear and the density is increased, which reduces the pollution to molten steel. At the same time, the fluctuation of the mold level is significantly improved, and the defect rate of cold rolling is effectively reduced to 30% of the original level, which is beneficial to the overall performance of the slab. [ABSTRACT FROM AUTHOR]

In the course of the decarbonization of steel production, electric steel production will continue to gain importance. The processing of low‐quality scrap will also play an important role, which may lead to an increase in the content of so‐called tramp elements in steel production and further processing. This article examines the effect of the elements Cu, Sn, and Ni on the formation of surface cracks under the conditions of the continuous casting process. Results of an in situ bending test are compared with the results of the experimental simulation of high‐temperature oxidation and thermodynamic analysis based on the CALculation of PHase Diagrams (CALPHAD) approach. For a temperature of 900 °C, an equivalent Cu content of 0.20 wt% must be considered as the critical upper limit. The presumable reason is the existence of Cu‐ and Sn‐rich liquid phases at the austenite grain boundaries. The results clearly show the effect of the investigated elements but also point to the importance of the gas atmosphere and cooling conditions on the results. This can be a groundbreaking result for extending the process window for casting steels with increased tramp element contents. [ABSTRACT FROM AUTHOR]

Hot rolling processes have been extensively used to produce round bars by reducing the cross‐sectional area of continuously cast steel. The current trend toward increasing productivity often requires a more aggressive reduction per pass. Establishing safe and optimized hot rolling parameters must be determined to avoid damage while deforming the specific steel composition. Understanding the damage mechanism during the metal forming process is vital for product quality. Herein, a combined experimental and simulation approach is developed to track the evolution potential damage during hot bar rolling. Hot tension tests are conducted on as‐cast vanadium microalloyed 15V38 steel at different hot rolling temperatures and strain rate conditions to develop Johnson–Cook‐type material model. A thermomechanical finite element model is developed to simulate potential damage trends in a 12‐pass square‐to‐round and 8‐pass round‐to‐round standard industrial hot rolling process, employing damage criteria. Results are illustrated by creating a damage map at each rolling pass to determine the critical hot rolling conditions for damage initiation. Several parametric studies are also performed to illustrate the application of the suggested methodology for hot rolling process optimization. Results show that the probability of the damage initiation is higher at higher pass reductions and lower temperatures. [ABSTRACT FROM AUTHOR]

Herein, the effects of the bottom shape of the submerged entry nozzle (SEN) on the molten steel flow and size distribution of argon bubbles are analyzed in a steel continuous casting slab strand using multiple‐size‐group approach. The type of nozzle bottom includes the well bottom, flat bottom, and mountain bottom. Most of argon bubbles are larger than 4.5 mm inside the SEN and the mold at the three types of nozzles. The frequency distribution of bubbles inside the SEN increases from 28.29% to 32.65% and 35.74% for 5.0–5.5 mm bubbles and decreases from 53.71–50.49% and 47.38% for 5.5–6.0 mm bubbles with the nozzle bottom varied from the flat to mountain and well shape, respectively. The number density of argon bubbles with 4.0–5.5 mm diameter in the mold decreases and increases for 5.5–6.0 mm bubbles with the nozzle bottom varying from the well to flat and mountain shape, respectively. In addition, the results of the industrial trials show that inclusions adhesion and aggregation at the bottom of the nozzle are eliminated using the flat bottom SEN casting. Meanwhile, the mechanism of SEN clogging under the different types of nozzle bottoms is analyzed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The formation of defects such as cracks in continuous casting deteriorates the quality of cast products and efficiency of steelmaking. To evaluate the risks and identify the root causes of defect formation, phenomenological quality criteria computed with a solidification and microstructure model known as InterDendritic Solidification (IDS) have previously been applied. This approach is computationally efficient and provides a fundamental perspective to defect formation in continuous casting. The aim of this work is to study the capabilities of these criteria as features in predicting transverse cracking with interpretable machine learning models. IDS is coupled with a heat transfer model known as Tempsimu to simulate the continuous casting process. Measured compositions are utilized in the simulations and defects reported at a steelmaking plant are used as labels in classification. Logistic regression, decision tree, and Gaussian Naïve Bayes classifiers are developed to predict transverse cracking in peritectic C–Mn, low‐carbon B–Ti microalloyed, and peritectic Nb‐microalloyed steels. The corresponding balanced accuracies of the best classifiers from cross‐validation are 92%, 94.6%, and 82.8%. Due to the good performance and the interpretability of the developed classifiers, the fundamental causes of transverse cracking and possibilities of avoiding it by changes in the compositions are identified. [ABSTRACT FROM AUTHOR]

The sigma‐phase distribution in a 2507 super duplex stainless steel continuous casting slab is analyzed using microstructural analyses and thermodynamic calculations. The sigma phase contains high Cr and Mo contents, and precipitates along the phase boundary between austenite and ferrite and grows toward the interior of the ferrite phase in the continuously cast slab. The sigma‐phase fraction at the center of the width direction is higher than that in the one fourth width. Furthermore, the sigma‐phase fraction at the center of the thickness direction is higher than those at the upper and lower surfaces, which is due to the lower cooling rate at the center. The Brinell hardness (HB) at the center increases to 313 HB with an increasing sigma‐phase fraction. The sigma‐phase fraction at the one fourth thickness near the lower surface is higher than that at the one fourth thickness near the upper surface at the same cooling rate. Additionally, Mo and Ni are severely segregated in this zone. A higher Mo content influences the precipitation and stabilization of the sigma phase. Furthermore, Scheil–Gulliver calculations indicate that compositional segregation results in an increase in the sigma‐phase precipitation temperature range. [ABSTRACT FROM AUTHOR]

In order to improve the quality of the transition slabs, the large‐size inclusions in 28 m‐long transition slabs are studied by large sample electrolysis and thermodynamic analysis. The results reveal that the length of transition slabs influenced by ladle exchange is 17 m, which is 4 m before the second steel ladle casting and 13 m after the casting. Large‐size inclusions in transition slabs can be divided into five kinds of Al2O3, Al2O3‐CaO, Al2O3‐CaO‐SiO2, Al2O3‐CaO‐MgO, and entrapment slag. The average contents of total inclusions, the inclusions in the range of 30–100 μm, those of 100–200 μm, and those larger than 200 μm in the transition slabs are 4.8, 19, 2.8, and 4.2 times higher than those in the normal slabs, respectively. For the large inclusions greater than 200 μm, the average contents of the Al2O3, Al2O3‐CaO‐SiO2 inclusions, and entrapment slags significantly increase in the transition slabs, being 9.4, 13.1, and 2.4 times higher than those in the normal slabs, respectively. The sources of Al2O3, Al2O3‐CaO‐SiO2 inclusions, and entrapment slags should be the secondary oxidation in tundish, entrapment of tundish flux, and entrapment of mold powders, respectively. [ABSTRACT FROM AUTHOR]

Microalloyed steel with Nb, V, Ti, and other alloying elements is one of the important steel grades in the steel industry. During continuous casting process, high occurrence rate of transverse corner cracks in slabs restricts the quality and efficiency of the production of microalloyed steel grades, and it has not been effectively solved for a long time. Herein, the research progress on the formation mechanism, influential factors, and typical control technologies of transverse corner cracks during slab continuous casting are reviewed. Considering high‐temperature solidification process of microalloyed steel, the control of growth of microstructures and the precipitation behavior of carbonitrides in slab corners are supposed to be the key to avoid transverse corner cracks during slab continuous casting. [ABSTRACT FROM AUTHOR]

The mechanical properties of two metastable austenitic cast steels are examined by performing tensile tests in a temperature range of −70 to 300 °C. The 16‐6‐6 steel has an Ms temperature of −30 °C and an Md temperature of 100 °C. Athermal martensite formation down to −196 °C can be excluded for X3CrNiCuN17‐6‐4 steel. The Md temperature of X3CrNiCuN17‐6‐4 steel is 130 °C. The results obtained by a semiempirical thermodynamic‐mechanical calculation model are linked to experimental results from the tensile tests. The presented model combines chemical energy amounts from thermodynamic databases with mechanical energy amounts obtained by tensile tests with the aid of the conversion rule proposed by Patel and Cohen. Thermodynamic calculations are performed using the Thermo‐Calc software with the database TCFE10. As a result, the stress–temperature–transformation diagram showing the temperature dependence of proof stress, tensile strength, triggering stress for martensite formation, and the associated critical transformation temperatures (Ms,Md) is obtained. With the aid of the semiempirical thermodynamic‐mechanical model, it can be shown that the mechanical properties and critical temperatures of a metastable austenitic steel can be determined at very low experimental effort. [ABSTRACT FROM AUTHOR]

The clogging behavior of submerged entry nozzle (SEN) is the main reason restricting the continuous casting of steel, which seriously affects the application and popularization of rare‐earth (RE) steel. Through literature analysis, herein, the main influencing factors and mechanism of RE steel continuous casting immersion outlet clogging, and sorts out the main ideas and practices of relevant Japanese enterprises in solving SEN clogging in recent years, are summarized, mainly including the following: 1) optimizing SEN materials to reduce nozzle clogging reactions; 2) using Ar‐blowing SEN; 3) applying electromagnetic field to eliminate charge and inhibiting clogging reaction; and 4) and regulating the composition of molten steel to reduce the possibility of clogging, etc. The combination of these advantages and measures is a feasible way to solve the nozzle clogging of RE steel continuous casting nozzle. [ABSTRACT FROM AUTHOR]

To reduce the occurrence of stickers and longitudinal cracks during continuous casting (CC) of peritectic steel, herein, the use of a mold slag with high basicity and adequate lubrication is proposed. Laboratory results indicate that the mold slag with a basicity of 1.75 and 2.3 wt% Li2O content exhibits a lower break and melting temperatures and relatively fast crystallization rate. The proposed mold slag can rapidly induce crystallization to control the heat flux, and the residual flux after crystallization and formation of the solid slag still exhibits excellent lubrication on the initial shell. Thus, coordination control of heat transfer and lubrication during CC of peritectic steel can be achieved. Industrial trials obtain satisfactory results, the application of the designed mold slag reduces the occurrence of stickers, and longitudinal cracks are reduced at the initial stage of one sequence casting. [ABSTRACT FROM AUTHOR]

Nitrogen‐containing steels have become an attractive material in industrial fields due to their excellent mechanical properties. Nevertheless, the current manufacturing methods to produce nitrogen steels are linked to technologies with high working pressures. Alloying elements such as Cr, Mn, and Mo enhance the solubility of nitrogen in the melt, which allows the production at atmospheric pressure. Herein, carbon–nitrogen martensitic steels are produced at low pressure (7 × 105 Pa). The composition is designed through the CALPHAD method using two carbon contents (0.7 and 1.3 wt%). The alloy is produced in an induction furnace under N2 atmosphere to mitigate desorption. Thermomechanical and heat treatments are performed. The alloys are analyzed using optical emission spectroscopy, X‐ray diffraction, optical microscopy, and scanning electron microscopy (SEM) with energy‐dispersive spectroscopy (EDS). The mechanical evaluation is conducted using hardness analysis. The steel presents a nitrogen content of 0.15 wt%, in agreement with the thermodynamic calculations. SEM and EDS results show the presence of Cr and Nb precipitates in a martensitic structure. The highest hardness values are obtained in specimens heat treated by tempering at 400 °C for 2 h and air cooling, achieving 57.4 and 59.7 Hardness Rockwell C for samples with 0.7 and 1.3 wt% C, respectively. [ABSTRACT FROM AUTHOR]

Based on the finite volume method, a continuum model that coupled enthalpy‐porosity approach is developed herein to investigate the fluid flow, phase transition, and macrosegregation in the solidification process for bloom continuous casting. The optimal parameters of the process of feeding strip technology (FST) are obtained, and the effects of different processes of regular continuous casting, mold electromagnetic stirring (M‐EMS), and FST on the superheat degree and macrosegregation are compared. The results show that the process of FST can not only greatly reduce the superheat degree of liquid steel and improve the macrosegregation in the bloom center, but also effectively avoid the deterioration of negative segregation defects at the edge of bloom, compared with the processes of regular continuous casting and M‐EMS. The best process parameters for the process of FST are as follows: the strip feeding position is 0.12 m far away from the bloom centerline, and the steel strip feeding velocity is 0.20 m s−1. [ABSTRACT FROM AUTHOR]

To reduce the defect ratio of cold‐rolled sheets of ultralow‐carbon steel caused by entrapped large inclusions and mold slags in a solidified shell, the applications of slag with higher viscosity and surface tension and slag with a higher break temperature are proposed herein, with the aim of enhancing the antishearing ability and decreasing the heat transfer. Laboratory results indicate that the reduction of Na2O and F− contents can effectively increase the viscosity and the surface tension of liquid slag. The increase in the break temperature can be realized by increasing the basicity of the mold slag, and the Al2O3 content is intended to decrease at the same time, considering the balance between the controlling heat transfer and the lubricating strand surface. Several runs of trials obtained inspiring effects as both approaches are able to reduce the defect ratios of cold‐rolled sheets. [ABSTRACT FROM AUTHOR]

Market requirements on steel products with the highest surface and internal quality demand stimulate a systematic control of the steel solidification behavior during continuous casting (CC). Computational process modeling is increasingly applied to optimize casting practices and calibrate the soft reduction to guarantee the required product quality. Here in this study, an overview of m2CAST as a "development platform" for the CC process is presented. This platform consists of a numerical heat‐transfer model, considers results of laboratory experiments in the calculations, for example, thermal analysis and nozzle measuring stand (NMS), and provides the option to use relevant process data. Two case studies on a continuous slab caster at voestalpine Stahl Linz GmbH are investigated. In doing so, thermal boundary conditions obtained by the NMS are implemented, and the simulation trials are validated with temperature measurements of the dragged thermocouple method installed during the casting process. The temperature distribution over the strand width is measured additionally with two pyrometers placed in the straightening zone. Excellent agreement between the calculated strand surface temperature and the measured temperature is obtained. Furthermore, the relevance of considering the roller‐bearing areas in defining the boundary conditions is presented to accurately predict the shape of the crater end. [ABSTRACT FROM AUTHOR]

Continuous casting of steel argon injection into the submerged entry nozzle (SEN) via the stopper is common practice. Nonetheless, the resulting phase distribution in the SEN is still under discussion. The main available casting parameters at the steel plant to determine the flow situation in the SEN are usually the stopper rod position, the argon feeding pressure, the argon flow rate, and the casting speed. To show the potential influence of the phase distribution on the stopper characteristic and on the argon feeding pressure, experiments using a 1:3 scale water model are presented. For the experiment, the water flow rate is scaled using Froude similarity, while the air flow rate is chosen to keep the ratio between the liquid and gas volume flow rate constant. The casting parameters and the pressure at three distinct levels of the SEN are measured. To relate this measurement data to the corresponding phase distribution, two cameras are used to document the phase distribution in the SEN. The images show four major phase distribution patterns. These patterns can be linked to significant changes in the measured pressure levels and the behavior of the stopper. [ABSTRACT FROM AUTHOR]

Low‐alloy cast steel with ultrahigh strength is produced by a combination of normalizing and reheating, followed by water quenching and high‐temperature tempering. The cast steel quenched at 1000 °C for 30 min and tempered at 550 °C for 120 min exhibits superior tensile ductility. More precisely, the tensile strength is 1683.5 MPa, yield strength is 1635.3 MPa, elongation is 12.0%, and microhardness is 500.3 HV. The microstructure is composed of martensite lath + ferrite + M23C6 carbide. The strengthening mechanisms of the steel are mainly precipitation, grain refinement, and dislocation strengthening. When the quenching temperature is increased from 950 to 1000 °C, the M3C carbides precipitated between the martensite lath are transformed from short rod‐like to spherical shapes, which improves the plasticity of the steel. When the tempering temperature is increased from 550 to 630 °C, the number and size of the carbides also increase. The M23C6 carbides interact with the dislocations. M23C6 carbides play a crucial role in the precipitation strengthening and efficiently improve the strength of the steel. The fracture is changed from a mixed ductile and brittle fracture to a ductile fracture. [ABSTRACT FROM AUTHOR]

To investigate the effect of reoxidation on inclusions characteristic during casting in Al‐killed steel containing rare earth, two industrial heats, including one of steady casting and the other of reoxidation, are performed with sampling from Rheinstahl Heratus, tundish, submerged entry nozzle, and slab. In the present study, air absorption occurs at the submerged entry nozzle and caused the reoxidation of molten steel. As a result, the number of inclusions increases significantly, and nearly spherical Ce2O2S inclusions are transformed to clustered‐like CeAlO3, which increases the average size of inclusions from 3.92 to 9.21 μm, thereby resulting in serious nozzle clogging and slab defects. The results of thermodynamic calculation show that Ce2O2S is transformed to CeAlO3 with total oxygen content increases under different Ce additions, and this transformation of inclusions can be inhibited by controlling the value of [Ce]/[O] above 2.12. Based on the experimental results and the theoretical analysis, the evolution mechanism of inclusions during reoxidation is clarified. This study can provide theoretical guidance to alleviate the harm of reoxidation to Al‐killed RE‐steel from the inclusion‐controlling perspective. [ABSTRACT FROM AUTHOR]

The residence time distribution (RTD) curve is a simple and useful method to analyze the flow behavior in the tundish. In the last decades, analysis result acquirement based on the RTD curve has been applied to design and optimize the flow control devices in a simple bare tundish or a multistrand tundish. There are many factors to affect the acquirement and analysis of the RTD curve, such as the tracer, the measuring technology, and the analysis model. In order to find a solution for the above issues, the latest progress and research status of RTD curve are discussed in the fields of water model, mathematical model, RTD analysis model, and measuring technology. After comparison, the KCl solution is a good tracer, and its tracer concentration and volume can be determined by the dimensionless tracer parameter (Dtp). The extended combined model can be applied to analyze the RTD curve by pulse input of tracer, and the mean residence time is the key parameter to identify the difference in fluid characteristics among the strands. [ABSTRACT FROM AUTHOR]

Herein, a new Euler–Euler–Lagrange hybrid method is used to simulate the liquid–solid–gas three‐phase flow in a continuous casting mold. In the used method, bubble coalescence and breakup, inclusion aggregation, bubble–inclusion interaction, and complex force balance of bubbles near the solidification front are simultaneously considered. The predicted inclusion size distribution is in good agreement with previous industrial test results. With the application of this method, inclusions can be tracked even if they are collected by bubbles. This characteristic is useful in the study of harmful phenomena in that bubbles are captured by the solidification front after collecting numerous inclusions. Herein, the effects of various simulation factors on results are studied. The descending order of importance of the simulation factors is as follows: bubble–inclusion interaction, bubble coalescence and breakup, and inclusion aggregation. Ignoring any of these factors underestimates the inclusion removal rate and increases the prediction deviation of the inclusion size distribution. Although inclusion aggregation has little effect on the overall removal fraction, it is the most important way to remove small inclusions with a maximum size of 14.14 μm under the conditions of this research. [ABSTRACT FROM AUTHOR]

Nonmetallic inclusions are well known to influence product quality and process stability in the production of steel. A process step that is very sensitive to the presence of nonmetallic inclusion (NMI) is continuous casting. Here, the so‐called clogging phenomenon can occur, resulting in a distinct disruption of the casting process and decreased steel quality. The presence of nonmetallic inclusions considerably contributes to the build‐up of deposits in the submerged entry nozzle provoking instabilities in the flow control system. Numerous research studies have been subject to different clogging mechanisms and related influencing parameters. Interfacial properties significantly influence the behavior of inclusions in the steel–refractory system. The present review demonstrates state of the art concerning the role of NMIs in the appearance of clogging. Particular focus is put on the wetting behavior between the different phases and their consequence for the deposition process. Industrial observations and laboratory methods are summarized and discussed; potential countermeasures are evaluated. A steel group that is especially prone to clogging are Ti‐ ultra low carbon (ULC) steels. An overview of the current understanding of their high clogging tendency and possible influences is presented, considering thermodynamic and interfacial aspects. [ABSTRACT FROM AUTHOR]

Heavy reduction (HR) is an effective process that can significantly minimize the internal porosity and other internal defects in continuous casting steel. Herein, samples taken from different wide‐thick slab positions are examined by scanning acoustic microscopy and 3D reconstructed. The morphology and distribution of microporosities <1 mm in size in the wide‐thick slab are revealed. The microporosities are mainly distributed in a stripping zone symmetric about the centerline within a 1/3‐slab thickness, and most have a considerably obvious long‐ and short‐axis tendency, which can be approximated as ellipsoids. The microporosity evolution in the wide‐thick slab during HR at the solidification end is numerically investigated with a 3D thermal–mechanical coupled model. The microporosity evolution in an aggregated distribution region during HR is little influenced by the surrounding microporosities. With increasing slab centerline‐microporosity distance, the microporosity minimization effect of HR becomes poor. When the axial ratio (long axis/short axis) is 1.43, the microporosity closure is the largest, and the porosity closure is the highest when the long axis is perpendicular to the reduction direction. When the total segment reduction is constant, the reduction mode with gradually decreasing reduction results in the highest total porosity closure and minimum reduction force. [ABSTRACT FROM AUTHOR]

A significant research effort is directed toward development of F‐free fluxes to decrease an environmental impact of steel continuous casting. Another challenging problem in the mold flux design is their stability in the casting of high‐aluminum steel. This article summarizes the results of a study of F‐free CaO–SiO2‐based fluxes and CaO–Al2O3‐based fluxes for the continuous casting of high‐Al steels, obtained at the University of New South Wales, Sydney, in close collaboration with the Baosteel Research Centre, China. This article discusses melting properties, viscosity, flux stability, crystallization, and heat transfer of F‐free CaO–SiO2‐based fluxes and CaO–Al2O3‐based fluxes, and the effect of high‐Al steel–flux reaction on the flux properties. Melting properties of fluxes are determined by the hot stage microscopy method. Viscosity is measured using rotating cylindrical viscometer. Solidification of mold fluxes is examined using single and double hot thermocouple techniques (SHTT and DHTT, respectively). Continuous cooling and isothermal SHTT experiments are used to construct continuous cooling transformation (CCT) and time‐temperature transformation (TTT) diagrams. Heat transfer of mold fluxes is examined using an IR emitter technique. The properties of F‐free CaO–SiO2‐based fluxes and CaO–Al2O3‐based fluxes are compared with the properties of industrial mold fluxes. [ABSTRACT FROM AUTHOR]

This investigation discusses the experimental methods to characterize and evaluate the mold flux performance during continuous casting of liquid steel. The mold fluxes are initially characterized by the conventional techniques for particle size, phase identification, phase transformation during the heating process, viscosity, break temperature, and other high‐temperature properties. Subsequently, the initial solidification behavior of the peritectic and interstitial free (IF) steel in the presence of respective molten mold flux has been simulated using an in‐house designed and developed inverse mold simulator. This simulator takes into account the physical, thermal, and fluid properties of mold flux, liquid steel to be cast, and casting parameters (casting speed, mold oscillation frequency, and stroke length), to assess the performance of liquid steel casting in the continuous caster. A suitable mathematical model has also been developed to predict the transient heat flux and hot face surface temperature of mold at the meniscus level. The current study successfully concludes the importance of a mold simulator along with the conventional characterization techniques to completely evaluate the performance of any mold flux. [ABSTRACT FROM AUTHOR]

Several fluorine‐free mold slag compositions have already been established in the literature. In all cases, the formation of a crystalline phase exhibiting behavior similar to that of cuspidine is emphasized to control horizontal heat transfer without influencing the lubrication performance for the casting of peritectic steel grades. In contrast, for casting soft steels, glassy solidification of the slag is required. Herein, different slag compositions involving the selected oxides are developed with the help of FactSage calculations. Mixtures of pure raw materials are melted at 1673 K and quenched to 295 K. It is observed that B2O3 increases the glass‐forming ability of the slags. To obtain the glassy phase, the composition must satisfy the conditions CaO+MgOAl2O3+SiO2<0.9 and (CaO+MgO)<30wt%. For TiO2 content <10 wt%, glassy solidification is detected after quenching to room temperature. However, this phenomenon‐is not observed for slags with TiO2 content >15 wt%. Moreover, the addition of alumina and alkali oxides enhances crystallization. Based on these findings, promising mold slag compositions are designed and characterized in the laboratory using a furnace crystallization test, mineralogical investigations, and the single/double hot thermocouple technique. From the investigated mixtures, three compositions are suggested for use in continuous casting processes. [ABSTRACT FROM AUTHOR]

Herein, multiphase flow patterns in a continuous casting slab strand are studied using a 3D numerical model and nail board measurement. The motion and turbulence of the argon gas and molten steel are simulated using the Euler–Euler approach and the realizable κ–ϵ turbulence model, respectively. Casting parameters for a 1435 mm × 200 mm mold are optimized by both the simulation and the capillary number. The capillary number is calculated by the measured velocity and used to evaluate the capability of the slag entrainment by the turbulent flow. The optimized values of the casting speed and the gas flow under the current specific continuous casting condition are 1.4 m min−1 and 8 NL min−1, respectively. Slag entrainment might occur near the narrow face under a casting speed of 1.6 m min−1 and near the SEN under a gas flow rate of 15 NL min−1. Meanwhile, effects of casting speed and argon flow rate on the transformation of flow patterns inside the mold with different dimensions are analyzed. A software incorporated by a Graphical User Interface is developed to predict the flow pattern inside the mold for a given steel grade and casting parameters. [ABSTRACT FROM AUTHOR]

Casting is a vital process in steel production where solidification process of molten steel occurs in mold coupled with fluid flow, heat transfer, crystal growth, inclusion motion, solute redistribution, segregation, and so on. All these phenomena are closely related to the steel flow behavior. To optimize the flow field in mold at initial moment, the swirling flow casting technology is developed and has received extensive attention in past years. It is believed to be a promising method to further optimize the steel flow and to improve the solidification process. Herein, the swirling flow steel casting is comprehensively reviewed to introduce different realization technologies, new research progress, and the current situation of their application. This aims to promote the development and usage of swirling flow technology in steel casting. [ABSTRACT FROM AUTHOR]

Solidification end reduction is a novel technique that can effectively refine the microstructure and improve the homogeneity in continuously cast steel. Herein, the static recrystallization (SRX) behaviors and microstructure evolution of microalloyed continuous casting slabs during the heavy reduction (HR) process are simulated and analyzed by means of high‐temperature laser scanning confocal microscopy (HT‐LSCM). According to the statistical results of microstructure, the insulation temperature has a more significant effect on the SRX fraction and recrystallization grain size compared with the strain rate, initial austenite grain size, and prestrain, and a modified SRX kinetic model is proposed. Furthermore, a deforming microstructure is observed at different strains and holding times with electron backscatter diffraction (EBSD), and it is found that the reduction of high‐angle boundaries (HAGBs, θ > 15°) of 25°–35° is related to strain‐induced boundary migration (SIBM). The stored deformation energy of HAGBs is higher than that of very low‐angle boundaries (VLAGBs, θ < 5°) by the detailed misinterpretation profile analysis of the block and lath boundaries. Finally, the combination of in situ observation and EBSD analysis shows that the stored deformation energy provides the driving force for the SRX process, which, in turn, consumes dislocations to stabilize the microstructure. [ABSTRACT FROM AUTHOR]

Continuous casting of premium steel grades requires a process with a high degree of precision and the knowledge about the mechanical behavior of the steel at temperatures above 800 °C. Herein, several origins of effects which lead to unwanted impairment of the hot strand shell like segregations, size, amount, kind, and distribution of precipitates as well as porosities from a metallurgical point of view are dealt. The systematic description of potential defect reasons helps to predict harmful operation parameters in context with the chemical composition of steel grades. A compilation of results from experiments at Department of Ferrous Metallurgy of RWTH Aachen University is complemented by a literature review. It is focused on the high temperature ductility and the underlying mechanisms inside the solidifying steel. Finally, potential measures to adjust the continuous casting process to prevent defects are elaborated. [ABSTRACT FROM AUTHOR]

Hot crack formation in continuously cast steel is significantly influenced by the mechanical properties of the solid shell near its solidus temperature. Herein, a new method to study the high‐temperature mechanical behavior of the solidifying steel shell is introduced. In this method, an apparatus is designed utilizing an electric cylinder that is controlled by a servomotor to apply a specified amount of strain to the solidifying steel shell at a controlled strain rate. A special mold configuration is developed to control the dendrite growth in the direction perpendicular to the applied strain and to ensure that the strain is applied in the region of controlled shell growth. Real‐time load, displacement, and temperature data are monitored by a computer‐assisted data acquisition system. The temperature profile of the casting is predicted by MAGMASOFT and compared with experimental data. The Fourier thermal analysis method is applied to calculate a solid fraction and coupled with the temperature profile to determine the solid shell thickness during the test. The maximum strength at different temperatures for a medium‐carbon steel is determined and compared with that from the submerged split‐chill tensile test and hot tensile tests. [ABSTRACT FROM AUTHOR]

Due to the development of continuous casting technology, the incidence of cracks in the continuous casting process has been significantly reduced. However, a few small cracks still appear during the continuous casting of special steel. For instance, cracks often appear at the corner of the billet during the production of hypoperitectic microalloyed steel. Most research on the causes of corner cracks in hypoperitectic microalloyed steel has focused on investigating the hot ductility of steel and not considered the shrinkage characteristics during solidification. Herein, the hot ductility behavior show that cracks are not related to the hot brittleness of steel. The effects of alloy composition on the phase evolution and shrinkage of steel during solidification are focused. Uneven solidification leads to excessive shrinkage of the corners in the billet, and an air gap is generated between the billet and the mold. The return of temperature in the corner of the billet results in the coarseness of the corner grain. Abnormal solidification also results in the severe deformation of the billet, leading to severe wear with the mold, causing Cu to infiltrate into the billet, and further increasing the crack sensitivity of the steel. [ABSTRACT FROM AUTHOR]

Herein, the fluid flow pattern in a continuous casting slab strand with varied degree of clogging of the submerged entry nozzle is measured using nail boards in industrial trials. The influence of clogging on meniscus velocity, top surface position, surface level fluctuation, and slag entrainment of the strand is investigated. The number density and area fraction of nonmetallic inclusions including Na2O and K2O‐bearing entrained slag ones within the subsurface of steel slabs are inspected using an automatic scanning electron microscope (SEM). The flow pattern in the strand periodically transforms from a double roll flow to a complex flow and/or a single roll flow. The fluid field in the continuous casting mold is unstable and asymmetric under the condition of varied degree of clogging with time. The variation of the meniscus velocity and the surface level fluctuation with time is stochastic. The percentage of >3 mm level fluctuation increases from 4.7% to 10.6% with a serious clogging of the submerged entry nozzle. The amount of entrained slag inclusions with serious clogging is approximately 1.6 times than that with slight clogging. In addition, slag entrainment mechanisms of the shear‐layer instability and the vortex formation are discussed. [ABSTRACT FROM AUTHOR]

The prediction of the solidification structure by means of calculations and simulation programs is of great importance for controlling the quality of continuous casting (CC) semis. Plant components, different process control options, and the chemical composition of the as‐cast product require optimized coordination of those factors to be able to set the optimum structure. As the simulation of temperature fields to predict the crater end during final solidification is already state of the art, the precise simulation of the solidification zones in CC semis is the important next step. Therefore, a circular arc caster is simulated with nucleation, grain growth, and sedimentation considered. The asymmetric as‐cast structure is calculated with a good accuracy providing a good base for the implementation of microsegregation in the next development step. [ABSTRACT FROM AUTHOR]

Comparison of re‐heating tensile test (RHT) and re‐melting tensile test (RMT) reveals the effect of interdendritic impurity segregation on hot ductility in low‐carbon steels. Two low‐carbon steels with different amounts [wt%] of impurity elements (Steel A: P = 0.005, S = 0.001; Steel B: P = 0.01, S = 0.004) are tensile‐tested at temperatures 600–1000 °C after re‐heating to 1350 °C and re‐melting at 1570 °C. Steel A shows similar hot ductility behavior in the RHT and RMT, whereas the high‐impurity steel shows a significant decrease in hot ductility at 900 °C in the RMT compared with the RHT. Crack initiation at the interdendritic segregation region is suggested as an origin of the degradation of hot ductility in the high‐impurity steel. The effect of interdendritic impurity segregation on the hot ductility behavior of continuously cast steel is further discussed. [ABSTRACT FROM AUTHOR]

It is a challenge to produce peritectic steels through compact strip production (CSP) technology, due to the large volume shrinkage during the initial solidification of peritectic steels and dramatic thermodynamics variation caused by the significant improvement of casting speed. Herein, two mold fluxes are developed to meet the demands for producing peritectic steels by CSP technology. The results show that the developed mold flux MF‐2 achieves the balance between the heat transfer control and mold lubrication, by increasing the CaO/SiO2 ratio to a particular point at 1.25 and the addition of Li2O content. The oxides of CaO and Li2O act as network breakers that will provide more O2− ions to depolymerize the original silicate structure, which in turn promote the mold flux crystallization capability and an effective heat transfer control. Meanwhile, the system viscosity of MF‐2 is lowered; also a good flow fluidity and break temperature are achieved to guarantee an appropriate mold lubrication behavior. In addition, the further addition of Li2O could lower the melting temperature to ensure a certain thickness of liquid layer as well. Therefore, MF‐2 shows the best overall performance and could be applied to industrial operations. [ABSTRACT FROM AUTHOR]

The tundish as a flow reactor has a special feature, that is, the liquid metal stays in its working capacity for a certain period of time before it enters the mold. This time is effectively used to correct the chemical composition of cast steel. The object of investigation is the wedge‐type tundish, being a component of the continuous casting slab machine. According to the criterion of similarity, the glass model of the tundish is built to a 0.4 linear scale. A tracer is fed into water using the pulse‐step method. During the casting sequences, the time for starting the alloying process, the depth of immersion of the ladle shroud, and the location of feeding the alloy addition change. On the basis of the recorded tracer concentration curves, the mixing time is calculated between the start of feeding the marker to the water and obtaining the required level of chemical homogenization in the water flowing out of the tundish model. Based on the conducted experiments, it is stated that mixing time depends on feeding positions, time of feeding initialization, and hydrodynamic conditions in the tundish during particular stages of the casting sequence. [ABSTRACT FROM AUTHOR]

Contact experiments between low‐reactivity CaO–BaO–Al2O3‐based mold fluxes, F1 and F2, and 1.4–2.2 mass% of Al‐containing steels are conducted to investigate the effect of interfacial reaction on mold flux properties and the ultimate limit of reaction duration capacity of the developed mold flux. F1 contains 30.76% CaO, 17.03% Al2O3, 13.40% BaO, and 10.70% SiO2, whereas F2 consists of 27.90% CaO, 23.60% Al2O3, 12.90% BaO, and 9.57% SiO2 of the mass. The pre‐ and post‐experimental wettability of slag samples on steel substrates and the lubrication behavior of slags are discussed. The main results reveal that SiO2, Na2O, and B2O3 in the mold flux react with [Al] in the molten steel at steel–slag interface. The variations in slag properties indicate that both reaction durations between F1 reacting with twinning‐induced plasticity (TWIP) and F2 reacting with 20Mn23AlV steel can last for 40 min, whereas F2 has wider potential applicability for the continuous casting of Al‐containing steels. Interfacial reaction deteriorates the wettability of slag F2 on 20Mn23AlV steel substrate and reduces slag consumption, as equilibrium contact angle increases from approximately 3° to 37°, but slag consumption prediction is 0.22 kg m−2, which is likely to meet the requirement for lubrication. [ABSTRACT FROM AUTHOR]

Some of the most recent examples of simulations of as‐cast steel ingots are presented in this paper, focusing on discussions concerning available simulation/modeling tools and their capacities and limitations. Although, there has been some success from implementing criterion functions into commercial codes to predict shrinkage porosity and hot tearing, large‐scale ingot sectioning experiments, similar to what is done a century ago, are still needed to investigate other issues, such as macrosegregation, since models are currently unable to predict such issues well. Models with more sophisticated features for macrosegregation prediction that incorporate multiphase transport phenomena are already under development. A limiting factor in application of these models for simulating steel ingots is the demand on large computation resources. Following the recent development trend and the projection of Moore's law (computer hardware), in the foreseeable future, it is predicted that multiphase models will to a great extent reduce the need for the experimental pouring‐sectioning trials. [ABSTRACT FROM AUTHOR]

The current work involves systematic experimental examination of the as-cast microstructure of a Nb-microalloyed Al-free case hardening steel, 18CrNiMo7-6, with 0.078 wt pct Nb. The aim is a thorough quantification and characterization of Nb-microsegregation and eutectic NbC. A combination of optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron probe microanalysis with energy dispersive and wavelength dispersive X-ray spectroscopy (EPMA, EDS, and WDS) are used for this purpose. Eutectic NbC is characterized for its location, shape, size, and amount. Differential scanning calorimetry (DSC) measurements indicate that γ-Fe − NbC eutectic forms in the temperature range of 1399-1390 °C, while Scheil simulation predicts this range to be ≈1418-1402 °C. The average eutectic composition is measured to be 10.91 wt pct Nb using EDS. γ-Fe − NbC eutectic in steel can be classified as an irregular eutectic with faceted (NbC) and non-faceted ( γ-Fe) constituent phases. Scheil solidification simulation predicts that about 30 mole pct of the total NbC in this steel can be present in the form of eutectic. These results, thus, point out the need for modification of the eutectic via alteration of cooling rate or using modifiers. [ABSTRACT FROM AUTHOR]

Application of cast steels instead of hot forged or rolled ones will significantly decrease manufacturing costs and the final product price. However, low levels of mechanical properties in cast steels, especially ductility, can slow down the substitution of forged and rolled steels with the cast. In the present work, the authors study the effect of 0.01-0.12 wt% vanadium additions on the microstructure and mechanical properties of 0.25 wt% C cast steels. The yield stress, ultimate tensile strength, and elongation to failure in the studied cast steels are 730-750 MPa, 955-1002 MPa, and 12.3-21.5%, respectively, which correspond to those in hot forged and rolled steels with similar compositions. So, high property values in the 0.25 wt% C cast steels are shown here for the first time. The simultaneous increase in strength and ductility with an increase in V content follow a decrease in pearlite fraction, interlamellar spacing, and average pearlite area size; an increase in amount of degenerated pearlite; an increase in V-rich particle volume fraction and number density in ferrite and pearlite; the occurrence of interphase precipitation (in 0.12 wt% V steel), and an increase in dislocation density in ferrite and pearlite. [ABSTRACT FROM AUTHOR]

The main factor influencing HCF strength is the size of fracture mechanical defects, whereby improvements can be obtained by reducing their size. In article number 2200578, Lennart Mirko Scholl and co-workers present a correlation between manufacturing-related defect sizes and fatigue strength. Powder metallurgy (PM) steels show significantly higher high-cycle fatigue (HCF) strength than ingot cast steels. [Extracted from the article]

Continuous casting is an established production route for steel slabs. The solidifying slab suffers a combination of internal stresses caused by thermal gradients, phase transformation, and external bending. The complex superimposed stress condition may produce local concentrations of tensile stresses that initiate cracks during cooling and deformation. Samples prepared from low-carbon steel slabs with and without Ni-content are compared and transformation stress phenomena are analyzed. In situ neutron diffraction experiments are carried out to reveal the stress condition within sections of cast steel slabs during cooling while passing the austenite-ferrite transformation temperature. The austenite-ferrite phase transformation is accompanied by an increase of volume of ≈1% between austenite-f.c.c. and ferrite-b.c.c., which causes internal stresses within the thermal stress gradients by cooling from the surface. The superposition of these thermal and transformation stresses is determined during cooling by an additional in situ diffraction experiment at constant macroscopic strain. The crack sensitivity of the Ni-containing slab is attributed to higher internal stresses within the austenite caused by the lower transition temperature than for the Ni-free steel. [ABSTRACT FROM AUTHOR]

Non-metallic inclusions can affect significantly the mechanical properties of metallic materials. Mainly for safety relevant components, it is important to reduce size and number of non-metallic inclusions. Recent research work is focused on the development of new reactive, active, and functionalized filters for the reduction of non-metallic inclusions. A detailed knowledge on the genesis of inclusions is essential to improve the entrapment capability. The paper is focused on the microstructure of inclusions formed in cast steel 42CrMo4 after the application of two filter variants. Both, inclusions on the filter surface as well as inclusions in the as-cast steel are investigated using scanning electron microscopy. Their chemical composition and their crystal structure are identified by combined EBSD and EDS measurements. The three-dimensional morphology of the inclusions is analyzed by deep etching technique as well. Finally, the clusters and agglomerates exhibit a quite complex microstructure. Thus, the majority of inclusion clusters consists of alumina, spinel, mullite, MnS, and TiO x. This agrees well to the scenario of the evolution of inclusions described in the literature. [ABSTRACT FROM AUTHOR]

The containers used for steel slag transportation to the recycling depot undergo high-temperature gradients and often deform plastically. Also, parts of the thereby solidified slag adhere to the pot walls, causing demolding problems and wear. A thorough finite-element analysis of the heat transfer, initiated by filling the pots and essentially driven by radiation, and the thermal stresses is performed. Due to periodic fill-in and discharge, these are assumed to admit a quasi-stationary state referring to the pot temperature before their emptying. The so obtained results aid optimizing the pot shape and the transport process in terms of minimizing maintenance and anti-adhesive cladding. A layer of solidified slag is found to exist throughout the transport process. Although the phase change occurs almost instantaneously at a liquid-solid interface, the 'mushy zone' is considered in the accompanying analytical study of the associated Stefan-type problem. Good correlations of the predicted temperatures to the measured ones and the resultant surface damaging are obtained. [ABSTRACT FROM AUTHOR]

A novel direct quenching-partitioning-tempering (DQ-P-T) process was developed to produce a low-alloy Mn-Si-Cr type high performance cast steel for automobiles without using expensive alloying elements Ni, Mo, or Nb as commonly used in some rolled Q-P-T steels. The cast steel treated by DQ-P-T process exhibits a better combination of strength and ductility as well as higher impact toughness than that treated by the conventional reheat quenching and tempering (RQT) process, and shows the improved microstructure consisting of the dislocation-type lath martensite (or plus a little bainite) and nano-sized flake-like retained austenite between the martensite laths. The DQ-P-T process has shown to be more conducive to enhancing the overall mechanical properties of the cast steel compared with traditional RQT process, and is a promising technique for industrial production. [ABSTRACT FROM AUTHOR]