The low-reactive tundish flux is urgently required for the smelting of rare-earth steels. The effect of Ce2O3 content on the properties (melting point and viscosity) and structure of ...CaO–Al2O3–Ce2O3–MgO–SiO2 slag were analyzed in the present investigation. The research results indicated that the polymerized QAl4 and QAl3 units were modified to QAl2 units in aluminate, and the depolymerization of SiO4-tetrahedrons from QSi1 to QSi0 units with Ce2O3 addition increasing from 5 wt% to 20 wt%. In addition, when the Ce2O3 addition increased from 15 wt% to 20 wt%, the increasing area fraction in AlO6-octahedral units further led to a decrease in the degree of polymerization (DOP) in the melts. When the Ce2O3 addition increased from 5 wt% to 20 wt%, the melting temperature decreased from 1320°C to 1301°C. Additionally, the softening temperature and the fluidity temperature also decreased 20°C and 24°C, respectively. The viscosity decreased as the Ce2O3 addition increased from 5 wt% to 20 wt%, which was attributed to the decreased DOP and the increased superheat. A reasonable content for Ce2O3 should not be excess 10 wt% in the current slag.
The continuous casting tundish is the last metallurgical reactor where molten metal flows before solidifying in the continuous casting mold. A tundish covering powder can be used for improving steel ...cleanliness; in this case it is named 'active tundish slag'. The objective of this work is to evaluate, in laboratory, the effect of three kinds of tundish covering powders on cleanliness for a SAE 1055 modified steel - a Ca-aluminate, a Ca-Mg-aluminate, and an Al-silicate powder, analysing their interaction with rice hull ash. The forementioned materials were molten on liquid steel, representing different kinds of tundish covering powders which are used in the steel industry: a Ca-Mg-aluminate, an Al-silicate, and a Ca-aluminate. Experiments were performed with and without a top layer of rice hull ash, simulating industrial conditions. Distribution, density, and mean diameter of inclusions were measured through automated inclusion analyses. Through computational thermodynamics it was possible to evaluate deviation from saturation (considering Al2 O3 and MgO from refractory) and slag viscosity. It can be stated that the Ca-aluminate tundish covering powder gives better results regarding cleanliness for the SAE 1055 modified steel under laboratory conditions.
With globalization and increased competitiveness in the steel market, industries are required to produce quality steel at a reasonable cost. This necessitates the introduction of either new ...manufacturing techniques, or to improve quality and yield with the existing processes. It is well established that slags entrapped by the vortexing phenomenon during steelmaking processes are responsible for causing quality issues and lowering the yield of steel produced. Measures are taken to end teeming from tundish before initiation of vortexing to prevent slag entrainment. This premature end of teeming is an inevitable yield loss that needs to be minimized. The present work aims to increase the efficiency of the steelmaking process by control techniques for minimizing tundish slag entrainment during tundish teeming. Experimental and mathematical simulations with different tundish configurations have been carried out to analyze the initiation of slag vortexing. The mathematical simulation uses multiphase models with a steel–slag–air system while the physical simulation uses a water–paraffin oil system to replicate the steel–slag system. It has been observed that the presence of higher turbulence and a thicker slag layer over liquid steel increases vortex initiation height (H
cr
). An empirical correlation between these parameters with H
cr
has been developed to optimize the end of teeming and increase process yield.
Graphic abstract
It is essential to understand the relationship between the electromagnetic field and the transport process in a channel type induction heating tundish precisely to improve the quality of the slab. A ...validated mathematical model was established to investigate the magnetic field characteristics, flow, temperature distribution and the movement of inclusions. In comparison with prior researches, we obtained the effective active zone of the magnetic field by analysing the dimensionless parameters Ha, N and Re. It should contain the channels and the nearby walls connected with the channels. Besides, the electromagnetic force is distributed asymmetrically near the channel outlets, and it is significantly larger within the upper zones of the channel outlets. This leads to the downward flow of the main stream in the distributing chamber, and it also changes the trajectories of the inclusions. When the induction heating is applied, about 75% of the inclusions entering the distribution chamber, regardless of the particle size, will be adsorbed by the tundish covering flux, and about 90% of them will float to the free surface within 120 s. The electromagnetic force can sharply promote the removal of small inclusions (diameter less than 60 µm). The induction heater should not be used intermittently during the casting process because 40%–80% of the inclusions may enter the mold directly during the period of power at 0 kW.
Herein, a numerical simulation of the coupled ladle–shroud–tundish system is developed in the emptying stage of the ladle toward the tundish to analyze the effect of the obstruction of the shroud ...clogging on the fluid dynamics pattern, the thermal behavior, and the removal of inclusions. The thermal stratification of steel in a 150 ton ladle is analyzed during the holding period; subsequently, the ladle emptying to a two‐stranded tundish is carried out considering the average temperature at the end of the holding time, and two considerations are made: the first with the shroud utterly free of obstruction and the second with the shroud partially clogged. Finally, alumina particles are added into the tundish once the quasistable state is reached, and their trajectories are simulated using the discrete‐phase model. The steel temperature during the emptying process is compared against temperature measurements reported by the industrial process, showing a decrease of 0.5 K min−1. The results show that the clogging has little influence on the fluid dynamics structure in the ladle; however, it completely modifies the fluid dynamics and temperature distribution in the tundish, decreasing its efficiency for removing inclusions by up to ≈25% for particles of 10 μm.
A numerical simulation of the coupled ladle–shroud–tundish system is developed to analyze the effect of the obstruction of the shroud clogging on fluid dynamics, thermal behavior, and steel cleanliness. The results show that clogging modifies the fluid dynamics pattern and temperature distribution in the tundish, decreasing its efficiency for removing inclusions by up 25% for particles of 10 μm.
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%.
The flow rate of molten steel at the filter inlet is now below 0.048 m s−1. The total removal rate of inclusions is increased from 64% to 80%. The residence time of molten steel is prolonged from 445 to 738 s. The dead zone volume is reduced from 39.9% to a mere 0.5%.
High-performance alloy steel is distinguished by its purity. Inclusion contamination and oxygen addition to the steel due to long contact between the refractories of the tundish and the steel should ...be avoided. In this study, the static crucible method was used in the interaction experiments between MgO–CA6 composite and low carbon alloy steel. The effects of different proportions of MgO–CA6 on the content of alloying elements in steel were analyzed. Morphology, quantity, size, and distribution of inclusions were also examined. The results indicated that more inclusions (e.g., MnO, FeO, and MnS) were generated between the MgO material and alloy elements (e.g., Fe and Mn) in molten steel. The oxygen content in molten steel of CA6, MgO–0.28CA6, and MgO–0.70CA6 materials, as well as the number of inclusions, were sharply reduced. The particle size was smaller, resulting in good molten steel purification ability. The oxygen content of the steel in contact with the MgO–0.28CA6 material was relatively low, characterized by a reduction in the proportion of inclusion area and particle.
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.
Cui et al.1) proposed a methodology for the fluid flow characterization of asymmetric tundishes that does not rely on any idealized flow model. First, the E curves of each tundish strand is obtained ...through the pulse input experiment. Subsequently, the E curves are converted into F curves by integration. Then, the dead volume fraction of the entire tundish (Vd /V) is calculated so as to evaluate the overall tundish performance. Finally, the flow uniformity among tundish strands is assessed through quantities obtained from the strand F curves (i.e. maximum difference between strand F curves for two-strand tundishes or maximum standard deviation among strand F curves for multi-strand tundishes). In the present work, the calculation procedure for the methodology of Cui et al.1) is discussed in detail. It was identified a problem in the obtention of F curve by Cui et al.1) that modified the actual formulas of Vd /V. In addition, this work presents new equations that facilitate the calculation of Vd /V when physical and mathematical models are employed. Moreover, the most convenient definition of the dead volume fraction is studied. It was found that Vd /V can distinguish different flows more effectively if it is based on one dimensionless residence time rather than two. Furthermore, some parameters for assessing the flow uniformity among tundish strands were compared. The area metric described by Oberkampf and Roy11) is the recommended one.
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