Search

This review article reports the critical issue of reoxidation in clean steel production during secondary refining and continuous casting processes. Reoxidation presents substantial challenges to process stability and final product quality. Various sources of reoxidation, including exposure to oxidizing gases, reducible oxides in slag and refractories, and the presence of ferroalloys are explored. Fundamental reactions and their consequences, such as changes in steel composition, inclusion composition/morphology, and the formation of reaction products at the interface between liquid steel and refractory materials, are reviewed. High oxygen partial pressure on the refractory side is identified as a significant factor, particularly in tundish and continuous casting processes. To address reoxidation effectively, the review discusses modeling approaches like computational fluid dynamics and thermodynamic/kinetic modeling. In the industrial context, reoxidation in the tundish is mainly attributed to open‐eye formation in the tundish flux and reducible oxides like SiO2 in an insulating cover powder, for example, rice hust ash. Maintaining precise tundish flux control is crucial for steel cleanliness. In conclusion, this review highlights the multifaceted nature of reoxidation challenges in clean steel production. A comprehensive understanding of reoxidation mechanisms and the implementation of effective strategies are essential for achieving cleaner steel production. [ABSTRACT FROM AUTHOR]

The interaction between refractories and molten steel in tundish has significant influence on quality of steel. The calcined dolomite and fused magnesia were adopted as raw materials to prepare MgO–CaO based refractories for tundish. Then the reaction behavior between refractories with different contents of calcined dolomite and molten steel was investigated. After reaction with different refractories at 1550 °C for 90 min, the total O and P in steels reduced by 33.9 % and 77 % respectively when increasing calcined dolomite from 0 to 60 wt%, the average size and area proportion of inclusions decreased from 4.92 μm and 9.98 ‰ to 2.47 μm and 4.73 ‰ respectively. Inclusions of FeO wrapped by FeO–P 2 O 5 –MnS translated to FeO coated by FeO–MnS. The CaO introduced by calcined dolomite could reduce the increase of oxygen to molten steel owing to better thermodynamic stability compared with MgO. Meanwhile, CaO could absorb [P] to form Ca 3 (PO 4) 2 on the surface of calcined dolomite particles, which was beneficial for dephosphorization of molten steel. [ABSTRACT FROM AUTHOR]

To optimize the flow field of a multistrand tundish and improve the steel quality, a prediction model integrating the techniques of computational fluid dynamics (CFD) and support vector regression (SVR) is proposed. A total of 125 cases with different structure parameters, i.e., the diameter and inclination angle of the orifices, are designed. The flow field of liquid steel in the tundish is calculated by CFD, and a sample dataset is established. Then, the SVR, combining the genetic algorithm with K‐fold, is employed to train and predict the sample dataset. In the results, it is shown that the SVR model demonstrates good learning performance on the training dataset. The average absolute errors of predictions for dead volume fraction and consistency are 0.50% and 0.71%. In addition, the SVR model takes much less computational cost than the CFD method to predict the flow performance of tundish in a given baffle structure. [ABSTRACT FROM AUTHOR]

A 3D mathematical model was proposed to investigate the molten steel–slag–air multiphase flow in a two-strand slab continuous casting (CC) tundish during ladle change. The study focused on the exposure of the molten steel and the subsequent reoxidation occurrence. The exposure of the molten steel was calculated using the coupled realizable k–ε model and volume of fluid (VOF) model. The diffusion of dissolved oxygen was determined by solving the user-defined scalar (UDS) equation. Moreover, the user-defined function (UDF) was used to describe the source term in the UDS equation and determine the oxidation rate and oxidation position. The effect of the refilling speed on the molten steel exposure and dissolved oxygen content was also discussed. Increasing the refilling speed during ladle change reduced the refilling time and the exposure duration of the molten steel. However, the elevated refilling speed enlarged the slag eyes and increased the average dissolved oxygen content within the tundish, thereby exacerbating the reoxidation phenomenon. In addition, the time required for the molten steel with a high dissolved oxygen content to exit the tundish varied with the refilling speed. When the inlet speed was 3.0 m·s−1 during ladle change, the molten steel with a high dissolved oxygen content exited the outlet in a short period, reaching a maximum dissolved oxygen content of 0.000525wt%. Conversely, when the inlet speed was 1.8 m·s−1, the maximum dissolved oxygen content was 0.000382wt%. The refilling speed during the ladle change process must be appropriately decreased to minimize reoxidation effects and enhance the steel product quality. [ABSTRACT FROM AUTHOR]

To study the influence of filter devices on the cleanliness and flow velocity of molten steel in the tundish, the Reynolds averaged Navier–Stokes equations, the species transport, and the discrete phase model are chosen to analyze and optimize the evolution of molten steel flow field and inclusions removal. The results demonstrate that the filter significantly affects molten steel flow and the removal of inclusions. More filter holes mean more inclusions can contact the filter, and the filter can absorb more inclusions. By changing the number and distribution of filter holes in the filter, the uniform flow of molten steel in the filter section is obtained. The total removal rate of inclusions increases from 64% of the original tundish case to 80% of the optimized case. With the increase in the number of filter holes, the Residence Time Distribution (RTD) curve shape of molten steel changes from narrow and high to wide and short, the tracer's appearance time and peak time at the tundish outlet are prolonged, the average residence time grows from 445 to 738 s, and the dead zone volume is reduced from 39.9% to a mere 0.5%. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This study presents the development of a novel material for a spherical impact pad for tundishes during steel production, focusing on improving steel cleanliness and flow optimization. Traditional low-carbon and ultra-low carbon concrete (LCC/ULCC) materials are replaced with a new cement-free mixture, utilizing a sol–gel method binder. This innovative approach leads to the creation of IPC TECAST BPV CST, a refractory concrete with enhanced resistance to corrosion and shape stability under extreme conditions. The material's effectiveness is demonstrated through operational tests, showing remarkable durability and no erosion defects after extensive use in casting liquid metal. The sol–gel binder significantly reduces the carbon footprint and energy consumption during the drying process, compared to traditional concretes. This study concludes that the new material not only withstands the dynamic environment of liquid steel but also ensures consistent dynamic flow conditions throughout the steel casting process, marking a significant advancement in tundish impact pad technology. [ABSTRACT FROM AUTHOR]

A combination of physical modeling, computational fluid dynamics modeling, and economics with plant trial studies was performed for quality improvement of Special Bar Quality (SBQ) and Oil Country Tubular Goods (OCTG) grade tundish steels. The present study consists of operating parameters like inert gas shrouding, non-isothermal conditions, and flow control devices (FCD) used on the billet product and slab quality. This work uses mathematical modeling using the fluid volume and discrete phase method (DPM) and the standard k-ε turbulence model validated with one-third scale physical water model experiments. A strong correlation between the physical model and computational simulation was found with rejection ratio and inclusion counts. Data about customer demands correlated with operating parameters for proper plant insights with an economic study to predict the cost-related issue. With the incorporation of FCD, the weight of the tundish skull was reduced by 6–10 M USD/year with a simulation studies expenditure of around 200 K. FCD also reduced the customer complaint index (CCI).

Copyright of Refractories / Naihuo Cailiao is the property of Naihuo Cailia (Refractories) Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Results of computational experiments on studying multiphase flow and interphase interaction in the volume of an industrial 50-ton tundish of a continuous caster, including when blowing with argon through bottom blowing blocks, are presented. A mathematical model has been developed that makes it possible to predict the dynamics of melt mixing at a given casting speed. The pattern of influence of the layout of the ladle's working space on the area of "stagnant zones" in the ladle volume has been found. [ABSTRACT FROM AUTHOR]

The increase in market demand for small masses of special purpose steel forces its producers to use the technique of continuous casting with a transition zone. The article presents the results of model tests of limiting the range of the transition zone as a result of the use of an impact pad and changes in the volume of liquid steel in the tundish. A water physical model of a Continuous Steel Casting (CSC) device equipped with a two-outlets tundish was used for the research. The criterion for assessing the range of the transition zone was the value of the minimum time of complete mixing tome of the tracer in the modeling liquid, determined on the basis of the Residence Time Distribution (RTD) curves. Visualization techniques of the modeling liquid mixing process were used to identify hydrodynamic phenomena.

This paper presents the results of studies on the occurrence of transient disturbances in the hydrodynamic system of a tundish feeding area and their effect on the casting process. In addition, the effect of changes in the level of superheating of the molten steel fed to the tundish on the evolution of the hydrodynamic system was analyzed. The studies were conducted with the use of a physical model of the tundish and a numerical model, representing the industrial conditions of the process of the continuous casting of steel. When a tundish is fed through a modified ladle shroud that slows down the momentum of the stream, this creates favorable conditions for the emergence of asymmetrical flow within the working tundish volume. The higher the degree of molten steel reheating in the ladle furnace, the stronger the evolution of the hydrodynamic structures in the tundish during the casting process. [ABSTRACT FROM AUTHOR]

The submitted article deals with the use of physical and numerical modelling to study the process of the steel flow in an asymmetric five-strand tundish that continuously casts steel. For the purposes of physical modelling, a 1:4-scale plexiglass model was used as the operating tundish, and for numerical modelling, the geometry of the operating tundish was created on a 1:1 scale. A model liquid (water) was used in the physical modelling of the melt flow process, while liquid steel was used as the standard flowing medium in the numerical modelling. We assessed the relevant operating parameters influencing the characteristics of the flow of the bath in the tundish—the shape of the turbulence inhibitor, the position of the ladle shroud in relation to the turbulence inhibitor and the distance between the ladle shroud orifice and the bottom of the turbulence inhibitor. The preliminary results show that optimal steel flow characteristic results are achieved by using the TI3-C configuration. The results from both modelling methods achieved the same characteristics, therefore verifying the results of each other and demonstrating that when taken together, the results of physical and numerical modelling can be considered sufficiently informative. [ABSTRACT FROM AUTHOR]

The benefits of using mathematical modeling of the flow are obvious, the final objective being the elimination of as many inclusions as possible during the flow of steel through the tundish, and thus, obtaining steel with superior quality. In this work, a simulation of the movement of the liquid alloy in the tundish was carried out, in order to highlight the erosion of its refractory lining. For this, we used SolidWorks, RealFlow, and ABAQUS programs. Using these simulation programs, the filling method of the tundish, the contact area of the alloy jet with the tundish wall, and the "dead" areas are highlighted, as well as the turbulences that can appear during the flow, which have a negative impact on the quality of the steel.

The tundish is the last refractory metallurgical reactor during the continuous casting process, and the fluid flow in the tundish is one of the key factors to control inclusion collision-coalescence and its removal. Thus, numerical method is applied to obtain the flow field, the RTD curve and the inclusion field. Numerical results showed that the predicted RTD curve and the inclusion number density agree well with the experimental data. In the case of different fluid velocity at tundish inlet, the volume fraction of plug zone, dead zone and well-mixed zone keep unchanged, but the dimensionless tundish inclusion volume concentration, the dimensionless tundish inclusion radius and the inclusion removal ratio have the exponential relation to the fluid velocity at tundish inlet. Further, there is maximum inclusion removal rate for the specific tundish. Another interesting phenomenon is about the inclusion behavior and the characteristic time of the RTD curve. The inclusion removal ratio and the dimensionless tundish inclusion radius have the linear relation to the minimum residence time, the peak concentration time and the average residence time.

This study presents the development of a novel material for a spherical impact pad for tundishes during steel production, focusing on improving steel cleanliness and flow optimization. Traditional low-carbon and ultra-low carbon concrete (LCC/ULCC) materials are replaced with a new cement-free mixture, utilizing a sol–gel method binder. This innovative approach leads to the creation of IPC TECAST BPV CST, a refractory concrete with enhanced resistance to corrosion and shape stability under extreme conditions. The material’s effectiveness is demonstrated through operational tests, showing remarkable durability and no erosion defects after extensive use in casting liquid metal. The sol–gel binder significantly reduces the carbon footprint and energy consumption during the drying process, compared to traditional concretes. This study concludes that the new material not only withstands the dynamic environment of liquid steel but also ensures consistent dynamic flow conditions throughout the steel casting process, marking a significant advancement in tundish impact pad technology.

As the low thermal shock and slag-penetration resistance of the magnesia castables cause the premature failure of tundish flow-control devices leading to the pollution of steel, the microporous magnesia with high closed porosity and intergranular CaZrO3 phase was utilized for simultaneously enhancing the high-temperature performance. The thermomechanical stress and slag corrosion tests indicated that since the micro-closed pores effectively relieved the thermal stress and CaZrO3 absorbed massive crack-propagation energy, the cold modulus of rupture and residual strength ratio respectively reached 14.4 MPa and 73.4% after thermal shock cycles, nearly half higher than that of the fused magnesia based castables. Meanwhile, the synergistic effect of micro-closed pores and intergranular CaZrO3 phase significantly reduced the slag-wettability, improved the interfacial energy and dihedral angle, leading to the decline of slag penetration indice (decreased by ∼34.8%). This study suggests a potential approach to generate new magnesia based castables in tundish for making clean steel.

The article presents the results of the CFD simulation of the method of medium flow and mixing, as well as the movement and removal of solid particles in the model of two-strand tundish as a result of installed internal arrangement. Two variants including turbulence inhibitor and impact pad with a ball cutting area were modeled for the tests. CFD simulations are a continuation of previous tests with the use of the physical water model of the continuous steel casting (CSC) device. [ABSTRACT FROM AUTHOR]

Herein, corundum porous permeable bricks with different coarse aggregate contents are prepared using particle packing method. Based on the similarity principle, a local water model of a tundish is designed to investigate the bubbling behavior in porous permeable bricks at various argon flow rates. Through dimensionless analysis, empirical formulas of bubbling region diameter and initial bubble size in porous permeable bricks are proposed. The results show that an increasing aggregate content can increase the apparent porosity and the proportion of large pores, reduce the surface fractal dimension of the porous permeable bricks, and obtain a higher gas permeability. With the increase of argon flow rate and the decrease of gas permeability, the internal pressure gradient in porous permeable bricks increases. The larger the argon flow rate and the gas permeability value, the more beneficial it is to activate more pores and form a larger bubbling region on the upper surface of porous permeable bricks. The Sauter mean diameter of bubbles and the initial velocity of gas plumes are inversely correlated with the content of coarse aggregate; that is, the porous permeable brick with a higher content of coarse aggregate is beneficial to generating much more small bubbles. [ABSTRACT FROM AUTHOR]

Steel refining in a continuous casting tundish using flow modifiers is a common practice in the steel industry given its positive effect on the removal of inclusions from the steel bath. In this work, the effect of replacing the turbulence inhibitor with dams and the effect of the teeming ladle and ladle shroud set misalignment on inclusion removal have been evaluated through physical model simulation. The effect on the residence time distribution and the refractory wear have also been investigated. It has been shown that for larger particles, the inclusion removal efficiency with turbulence inhibitor was not very different as compared with the dams. However, in the case of smaller particles, the inclusion removal efficiency was 7.15% greater than the case of dams in comparison with the inhibitor. The inlet asymmetry led to a drop in the removal efficiency of smaller inclusion particles. For increased inlet asymmetry, greater refractory wear of the weirs should be expected for configurations without turbulence inhibitors. [ABSTRACT FROM AUTHOR]

A slab caster with a wide casting mix carries high‐frequency steel grade changes using a small, 14 ton capacity tundish and needs to decrease the intermixed steel tonnage. Testing different tundish arrangements, through a water one‐third scale model, permits a flow control design to decrease the amount of mixed steel. A computer fluid dynamics approach, based on the Realizable k–ε model, replicates the experimental results. It helps to elucidate the role of the tundish filling rate, finding that increasing it increases the dissipation rate of kinetic energy coming out from the turbulence inhibitor. At high filling rates, the degraded kinetic energy of the downstream flow drives the residues of the "old" steel, prolonging the intermixing phenomena. In its later stages, the intermixing phenomena imply diffusion and transport on small scales, and both are governed by the Schmidt number given by the ratio of the Batchelor and Kolmogorov length scales, according to lBη=Sc−1/2. The Schmidt, Sc, numbers in steel are in the range of 28–440. These large Sc numbers mean that the diffusion process must reach the dissipative scales of turbulence, that is, beyond Kolmogorov´s scale, to achieve a complete mixing at microscale levels. [ABSTRACT FROM AUTHOR]

During the continuous casting process, the residual oxygen in the tundish can be significantly reduced by argon blowing from the tundish cover (ABTC). As a result, the effect of protective casting can be obviously improved, which helps to reduce the reoxidation of molten steel in the tundish. In the present work, numerical models for the ABTC of a six-strand continuous casting machine were established and verified by the measured oxygen mass fraction in the tundish during the ABTC. The results indicate that the best conditions for ABTC are to install the argon pipes on either side of the tundish cover holes, seal the baking holes, and keep the stopper rod holes open. The argon flow rate should be ≥120 m3/h during the period of empty tundish and ≥60 m3/h during the period of normal casting. Based on the calculation results, industrial testsof ABTC were carried out. The results indicated that the increased nitrogen content in steel(Δw[N]) decreased by 21.5% from 8.78×10- 6 to 6.89×10-6 , from the end of RH to tundish, and the amount of inclusions except for MnS in bloom (scanned size: 8 mm × 8 mm) decreased by 21.3% from 13.43 to 10.57, and the average size of inclusions decreased by 19.0% from 9.27 μm to 7.51 μm.

The article presents the results of the CFD simulation of the method of medium flow and mixing, as well as the movement and removal of solid particles in the model of two-strand tundish as a result of installed internal arrangement. Two variants including turbulence inhibitor and impact pad with a ball cutting area were modeled for the tests. CFD simulations are a continuation of previous tests with the use of the physical water model of the continuous steel casting (CSC) device.

One of the primary factors affecting the quality of continuously cast billets is the way the steel flows and mixes in the tundish of Continuous Steel Casting (CSC) machine. This is of particular importance in the case of continuous billets. The article presents the results of model tests of identifying the mechanism of liquid steel flow through a tundish under the influence of the applied arrangement of the working space. Two models of turbulence inhibitors and an impact pad with the surface of a sphere segment were used for the research. The tests were carried out with the use of the physical water model of the CSC device, and the obtained results were verified by numerical methods.

Minimization of intermixing length during continuous casting of steel is a crucial step towards higher productivity and yield of a continuous casting technology. For such a complex mass transfer problem, physical simulation using scaleddown water models might become indispensable tool to quantify the liquid steel parameters in the tundish. In this paper, such an advanced, water-based model of tundish from Železiarne Podbrezova, a. s. is used to model the intermixing process of two consecutive heats with different chemical composition. Obtaining the non-standard F-curves while manipulating the liquid level and the casting speed simultaneously gave us a valuable insight into the process of intermixing and allowed us to make preliminary conclusions on the intermixing optimization problem.

The quality of steel and continuously cast semi-finished products largely depend on the degree and control of the interaction between slag, gas, and refractories, with the steel melt. In this work, through the analysis of some samples from a used refractory lining of a tundish, with the help of optical microscopy, the wear of the refractory layer was highlighted, due to the erosion and infiltration of steel microparticles into the pores of the lining. The examination of the samples was carried out in the interface area, metal-shotcrete, shotcrete-concrete, and the area with refractory concrete.

The article presents the results of comprehensive studies of hydrodynamic processes and features of single-strand tundish ladles, which can be used for continuous or semicontinuous casting of steel at small metallurgical plants. The results of physical and mathematical modelling of the movement of the melt flows in the tundish using various designs of metal receivers are shown in this article. In addition to this, the article shows how the presence of a stagnant zone between the metal receiver and the right narrow wall of the Tundish increases in time of metal flow into the dispenser zone by an average of 35–60%. It has been established that the position and height of the walls of the metal receiver relative to the axis of the incident jet are very significant for providing a rational picture of the movement of convective flows. When the height of the wall of the metal receiver (from the side of the dispenser) is reduced by 40–60 mm, the zones of increased turbulence may appear in the liquid bath of the tundish in the areas between the metal receiver and the dispenser. The results of evaluating the efficiency of floating non-metallic inclusions in the tundish volume and optimizing the hydrodynamic pattern flows in the central part of the tundish to increase the refining effect by installing a special recess. [ABSTRACT FROM AUTHOR]

Minimization of intermixing length during continuous casting of steel is a crucial step towards higher productivity and yield of a continuous casting technology. For such a complex mass transfer problem, physical simulation using scaleddown water models might become indispensable tool to quantify the liquid steel parameters in the tundish. In this paper, such an advanced, water-based model of tundish from Železiarne Podbrezová, a. s. is used to model the intermixing process of two consecutive heats with different chemical composition. Obtaining the non-standard F-curves while manipulating the liquid level and the casting speed simultaneously gave us a valuable insight into the process of intermixing and allowed us to make preliminary conclusions on the intermixing optimization problem. [ABSTRACT FROM AUTHOR]

One of the primary factors affecting the quality of continuously cast billets is the way the steel flows and mixes in the tundish of Continuous Steel Casting (CSC) machine. This is of particular importance in the case of continuous billets. The article presents the results of model tests of identifying the mechanism of liquid steel flow through a tundish under the influence of the applied arrangement of the working space. Two models of turbulence inhibitors and an impact pad with the surface of a sphere segment were used for the research. The tests were carried out with the use of the physical water model of the CSC device, and the obtained results were verified by numerical methods. [ABSTRACT FROM AUTHOR]

The benefits of using mathematical modeling of the flow are obvious, the final objective being the elimination of as many inclusions as possible during the flow of steel through the tundish, and thus, obtaining steel with superior quality. In this work, a simulation of the movement of the liquid alloy in the tundish was carried out, in order to highlight the erosion of its refractory lining. For this, we used SolidWorks, RealFlow, and ABAQUS programs. Using these simulation programs, the filling method of the tundish, the contact area of the alloy jet with the tundish wall, and the "dead" areas are highlighted, as well as the turbulences that can appear during the flow, which have a negative impact on the quality of the steel. [ABSTRACT FROM AUTHOR]

A series of industrial trials of argon injection into ladle shroud (AIILS) with different argon-blowing rates were conducted in this study. Firstly, bubbles in actual liquid steel of the tundish were captured by the method of "cold steel plate dipping" and characterized by microscope examination. A detailed investigation on the three-dimension morphology of bubbles was carried out by using industrial computerized tomography (ICT). Then, the two-phase flow of liquid steel and argon gas in the tundish was numerically simulated to further investigate the motion behaviors of bubbles in liquid steel of the tundish. The simulated results showed that bubbles in the size range of this investigation had a large enough filtration rate to demonstrate a good performance on inclusion removal. Finally, the effect of AIILS on inclusion removal was analyzed by detecting the variations of inclusions as well as total oxygen content in steels taken from the ladle, tundish, and casting billet. The method of AIILS was more effective at improving the removal of inclusions in the range of 5 to 10 μm and obviously increased the removal rate of total oxygen content. [ABSTRACT FROM AUTHOR]

Using bubbles to remove inclusions in steel is rapidly becoming a popular method for refining. Fine bubbles are thought to be more effective on inclusion removal than big bubbles. The fine bubbles can be formed in molten steel using the argon injection into ladle shroud technology. There are two stages during the formation of fine bubbles in ladle shroud: bubble detachment from wall orifice and detached bubbles splitting into smaller ones in turbulent steel. Many reports have been published on the water model of the argon injection into ladle shroud technology, but industrial experimental research is in its early stage. In this study, high argon flow was injected into a ladle shroud and adopted in continuous casting production to produce fine argon bubbles in a tundish. The bubbles were captured by dipping a cold steel sheet into molten steel. The captured bubbles at the surface of a hot-dipped steel sheet, with a size of 1.0–3.0 mm, characterized the argon bubbles at steel/slag interface and slag phase in the upper part of a tundish rather than those inside molten steel in tundish. The bubbles inside molten steel in tundish were characterized by the captured bubbles in the interior of a hot-dipped steel sheet, and their morphology, size, and number were analyzed using scanning electron microscopy and confocal microscopy. The bubbles inside molten steel in tundish have a spherical shape and occasionally adhere to each other. These bubbles rang in size from 100 to 1000 μm, with an average of 500 μm. They are dispersed at the exit of a ladle shroud in its lower position, with a density of 15.2 cm–2. Moreover, it was observed that a bubble could adhere to inclusion, even multiple inclusions for part of bubbles. Bubbles adhered more strongly to Al2O3 inclusions than that to CaO(‒MgO)‒Al2O3‒SiO2 complex inclusions.

With the increasing demand for special steel, the quality of steel has become critical during the continuous casting tundish process. In recent years, tundish heating technology has played a key role in low superheat casting. Toward this, researchers have reported on the metallurgical effects of induction heating tundish (IHT). From 1984 to date, the channel-type IHT has been investigated in the production of continuous casting of special steel. In this article, the principle of this channel-type IHT technology and equipment composition were illustrated. A brief summary and comments were undertaken on the channel-type IHT, including physical modeling and numerical modeling. The application development trend of tundish induction heating equipment is summarized combined with industrial application data, which provide a reference for a better understanding of the induction heating process of tundish. [ABSTRACT FROM AUTHOR]

The continuous casting tundish serves as the final vessel for molten steel in the smelting process. Resistance to steel corrosion and penetration is critical for clean steel smelting and the durability of working linings. In this study, calcium hexaaluminate (CA 6) was selected to gradually replace the commonly used MgO refractory. We analyzed the phase composition, cold modulus of fracture, cold crushing strength, bulk density, porosity, and resistance to molten steel corrosion and penetration of MgO–CA 6 refractories. It was observed that the mechanical properties of the material were reduced by the addition of CA 6 ; however, a certain percentage of CA 6 and MgO formed a small amount of MgO·Al 2 O 3 at high temperatures to retain its high performance. The materials are less likely to react with [Mn], [Si] and other alloying elements in steel after the addition of CA 6 and it exhibits excellent resistance to steel corrosion, which is important for clean steel production and the durability of working linings. [ABSTRACT FROM AUTHOR]

Issues of the development of the steel casting technology and structures for protecting the stream of liquid metal on the way from the ladle to the tundish are considered. The motion of steel is simulated mathematically. Considering features of the motion of liquid metal as a Newtonian fluid, initial and boundary conditions for the simulation are chosen. An analysis of the simulation results shows the need to modify the plastic refractories installed between the shroud and the equipment of the ladle nozzle. The designed structures allow rational supply of inert gas (argon) to the shroud. This reduces the saturation of liquid steel with nitrogen, which, in turn, reduces the adverse effect of nitrogen on the characteristics of concast billets. [ABSTRACT FROM AUTHOR]

The quality of steel and continuously cast semi-finished products largely depend on the degree and control of the interaction between slag, gas, and refractories, with the steel melt. In this work, through the analysis of some samples from a used refractory lining of a tundish, with the help of optical microscopy, the wear of the refractory layer was highlighted, due to the erosion and infiltration of steel microparticles into the pores of the lining. The examination of the samples was carried out in the interface area, metal-shotcrete, shotcrete-concrete, and the area with refractory concrete. [ABSTRACT FROM AUTHOR]

The ecotoxicological view is one of the least studied aspects of sustainability in the cement sector. Although some regulations starting to include it, since new products incorporating waste materials need to be environmentally safe throughout their circular life cycle. Chemically bonded phosphate cements are a more sustainable alternative to conventional cements due to their lower environmental impact and the promotion of the Circular Economy by incorporating industrial waste. This paper analyzes the potential ecotoxicity over marine biological life of two alternative magnesium phosphate cements obtained from secondary sources of MgO. MPC-LG using the by-product low-grade MgO (LG-MgO) from the air pollution control system of the magnesite calcination kiln, and MPC-TUN using the tundish deskulling waste (TUN) obtained at the end-life of refractory material employed in the last metallurgical vessel of the steel casting process. For this purpose, the ecotoxicity criteria proposed by the European Construction Products Regulation are used as a reference. The Compliance leaching test, as well as two different ecotoxicity tests, the marine bacteria Vibrio fischeri luminescence reduction and the sea urchin Paracentrotus lividus embryo-larval development success, were conducted. No significant effects were observed on the bioluminescent bacteria within the leachate concentration range (until 80 %). In the sea urchin embryo-larval development test it was observed that the MPC-TUN sample showed lower toxicity than the MPC-LG sample. In summary, the results obtained from both ecotoxicity tests show consistency with the leaching behavior of Sust-MPCs, and demonstrate that they are environmentally safe in a marine scenario. • The ecotoxicity of MPCs based on alternative sources of MgO has been analysed. • Some elements become inert in the MPC, such as Ba, Cr, Hg, Pb or Zn. • As, Mo, Se and particularly V increase the mobilization respect to raw materials. • MgO sources and MPCs do not present toxicity effect on bioluminescent bacteria. • Sea urchin embryo-larval development is a sensitive bioassay. [ABSTRACT FROM AUTHOR]

This paper presents the results of studies on the occurrence of transient disturbances in the hydrodynamic system of a tundish feeding area and their effect on the casting process. In addition, the effect of changes in the level of superheating of the molten steel fed to the tundish on the evolution of the hydrodynamic system was analyzed. The studies were conducted with the use of a physical model of the tundish and a numerical model, representing the industrial conditions of the process of the continuous casting of steel. When a tundish is fed through a modified ladle shroud that slows down the momentum of the stream, this creates favorable conditions for the emergence of asymmetrical flow within the working tundish volume. The higher the degree of molten steel reheating in the ladle furnace, the stronger the evolution of the hydrodynamic structures in the tundish during the casting process.

The submitted article deals with the use of physical and numerical modelling to study the process of the steel flow in an asymmetric five-strand tundish that continuously casts steel. For the purposes of physical modelling, a 1:4-scale plexiglass model was used as the operating tundish, and for numerical modelling, the geometry of the operating tundish was created on a 1:1 scale. A model liquid (water) was used in the physical modelling of the melt flow process, while liquid steel was used as the standard flowing medium in the numerical modelling. We assessed the relevant operating parameters influencing the characteristics of the flow of the bath in the tundish—the shape of the turbulence inhibitor, the position of the ladle shroud in relation to the turbulence inhibitor and the distance between the ladle shroud orifice and the bottom of the turbulence inhibitor. The preliminary results show that optimal steel flow characteristic results are achieved by using the TI3-C configuration. The results from both modelling methods achieved the same characteristics, therefore verifying the results of each other and demonstrating that when taken together, the results of physical and numerical modelling can be considered sufficiently informative.

Whereas approximately 96.3% of the steel produced worldwide is made by continuous casting, great emphasis is put on the superior efficiency of this process. The water model of the tundish and mathematical modeling is often used for the simulation of the steel flow during continuous casting. The experiments were performed on a model of the tundish with two outlets, at two casting speeds (0.8 m.s–1 and 1.2 m.s–1). Eight setups of the tundish were evaluated, which differed in the design of the dams (with or without drainage holes), in their distance from the center of the tundish, and their height. The contribution of the work is the analysis of phenomena in the tundish water model in conditions of repeatability (ten repetitions). The goal is to find the setup providing the most symmetrical flow, with the minimum difference in the residence times Δτ on the two outlets. Taking into account the results obtained at both casting speeds, the most preferred is setup 2 with the 87 mm high dams placed 587 mm from the center of tundish (Δτ = 0.5). The setup 3 (Δτ = 8.25) appears to be the least appropriate. The higher the casting speed, the higher the number of unsuitable arrangements.

The article presents the results of research aimed at determining the nature of changes in the mixing of liquid steel in asymmetrical tundish due to the increase in casting speed and the possibility of limiting the use of Flow Control Devices (FCD). The tests were carried out on the water model of the Continuous Steel Casting (CSC) device equipped with the tundish model. Four variants of casting speed were analyzed. The analysis of the obtained results was divided into two stages: qualitative analysis of flow and mixing (visualization process) and quantitative analysis of flow and mixing (by analysis of mixing curves - Residence Time Distribution (RTD) type F).

Due to the need to improve the quality of the produced steel, especially its metallurgical purity, attempts are made to use inert gas bubbling curtain in the tundish. The article presents the results of the research of metal-slag interaction carried out with the use of the trough-type two-strand tundish water model, made on a reducing scale – 1 : 2,5. The tundish model is built with two gas bubbling curtain. The aim of the research was to determine the optimal value of the flow rate of the blown gas, ensuring the safe course of the process taking into account the secondary contamination of liquid steel with atmospheric gases and endogenous inclusions originating from the slag.