The flow control devices (FCD) play an important role to realize the best metallurgical performance of the tundish. An integrated workflow for designing a single-strand tundish equipped with FCD is ...presented in this paper. Mean age theory was applied to predict the spatial mean age distributions in the tundish. Melt change efficiency (MCE) was used as a key measure to characterize the tundish’s mixing performance. Taguchi method was employed to optimize the design factors, i.e. geometrical parameters of the FCD. The fluid flow and mixing of materials were analyzed based on the numerical simulations of a developed computational fluid dynamics (CFD) model. Compared to the residence time distribution (RTD) method, the mean age theory shows advantages in both numerical accuracy and efficiency. In addition, the size and location of undesired mixing zones can be easily identified which is essential for tundish design. The developed workflow that combined the CFD-Taguchi method and mean age theory can be used as an efficient tool for wide industrial applications.
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 SiO
2
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.
Tundish with channel‐type induction heater plays an important role in the continuous casting of high‐quality steel. Electromagnetic pinch is a unique phenomenon in the tundish with channel type ...induction heater. To have a deep insight into the electromagnetic pinch effect, numerical simulation is applied to investigate the magnetohydrodynamic flow in the tundish. Research results show that the magnetic field, flow field, and temperature field predicted by the mathematical model agree well with the experimental data. Induced current density, magnetic flux density, electromagnetic force, and Joule heat in two channels are symmetrically distributed and are greater than that in the receiving and distributing chambers. The eccentric electromagnetic force leads to the single‐/double‐recirculation zones in the channel. There are larger separation areas in the channel enclosed with the iron core than in the other channel, and it is easy for molten steel to separate from the channel wall surface at the top of the channel. Different forces play different roles in the pinch condition, and the order of importance is as follows: electromagnetic force, stress, gravity, supporting force, centrifugal force, and thermal buoyancy.
Herein, numerical simulation is applied to investigate the magnetohydrodynamic flow in the tundish to have a deep insight into the electromagnetic pinch effect. Different forces play different roles in pinch conditions, and the order of importance is as follows: electromagnetic force, stress, gravity, supporting force, centrifugal force, and thermal buoyancy.
The Role of Powder Used in the Continuous Molding of Alloys Toma, Florin Marian; Stoian, Elena Valentina; Angelescu, Nicolae ...
The Scientific Bulletin of "Valahia" University, Materials and Mechanics,
04/2024, Letnik:
20, Številka:
22
Journal Article
Recenzirano
Odprti dostop
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.
•A fluid–structure coupling heat transfer method is used.•The temperature drop of molten steel in the new tundish is reduced.•The heat transfer mechanism of the tundish is altered by the vacuum ...chambers.•The stress of the new tundish wall is relatively increased.
Vacuum insulation can improve tundish insulation performance while increasing molten steel temperature. The tundish's heat transfer characteristics and thermal stress changed significantly following vacuum modification. A complete understanding of this process can improve the insulation and safety performance of vacuum tundishes. The heat transfer process and stress distribution of a tundish were investigated in this study using a fluid–structure coupling heat transfer analysis method. The variations in the temperature and stress fields of the tundish before and after vacuum modification were discussed, and the numerical model’s accuracy was validated using industrial experiments. Compared to the traditional tundish, the temperature distribution of the molten steel was more uniform; the outlet temperature of the vacuum tundish increased by 1.38 K, whereas the temperature of the outer wall decreased by 46 K. However, the higher temperature of the steel shell in the vacuum tundish resulted in an increase in thermal stress, which reached a maximum of 301.74 MPa. When high-strength Q345 steel was used as the steel shell material, the thermal stress decreased to 272.44 MPa. The results showed that a vacuum tundish can achieve low-superheat pouring of molten steel, and the thermal stress of the tundish can be improved by material selection.
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 (CA6) 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–CA6 refractories. It was observed that the mechanical properties of the material were reduced by the addition of CA6; however, a certain percentage of CA6 and MgO formed a small amount of MgO·Al2O3 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 CA6 and it exhibits excellent resistance to steel corrosion, which is important for clean steel production and the durability of working linings.
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.
With the increase of the content of coarse aggregate, the internal pressure gradient in porous permeable bricks decreases, and more pores are activated, forming 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 gas permeability.
The microporous refractory with low thermal conductivity shows a promising application prospect as tundish lining. In this study, the interactions between microporous magnesia aggregates and oxide ...inclusions in steel were explored. The experimental results and thermodynamic calculation show that the interaction process of microporous magnesia aggregates and oxide inclusions at high temperature can be divided into dissolution, reaction and post-reaction. The microporous magnesia aggregates can absorb the inclusions in steel by reaction and liquid phase penetration. The microporous magnesia aggregates have a strong adsorption for Al2O3 and TiO2. Moreover, the microporous magnesia aggregates mainly absorb SiO2 by penetration, but excessive SiO2 will lead to the serious corrosion of microporous magnesia aggregates.
Swirling flow tundish was developed to enhance the coalescence of inclusions, so as to deeply clean the liquid steel. Inclusions would gather to the center of the swirling flow by centripetal force, ...due to the density difference between inclusions and liquid steel. Thus, small inclusions can coalesce into larger ones, and then float to the free surface by their self-buoyance. Physical experiments were carried out in a 1/2.5 scale single strand tundish to study the flow characteristics of tundish with swirling chamber. Numerical modeling was developed to simulate the movements of small inclusions in swirling flow. Discrete phase model was employed together with the O'Rourke algorithm to characterize the coalescence of the inclusions in the swirling flow. The removal of inclusions was investigated, considering the absorption by upper slag and trapping by outside wall of ladle shroud. Compared with a turbulence inhibitor, a swirling chamber shows a similar effect on flow improvement, while performs better in inclusion removal, owing to the inclusion coalescence caused by centripetal force. The results revealed that swirling chamber in diameter of 450 mm is an optimized scheme for deep cleaning of liquid steel, with only 1.66% of the inclusions flowing out of the tundish nozzle.
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