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.
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.
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.
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.
In the continuous casting process, the fluid flow of molten steel in the tundish is in a non-isothermal state. Because of the geometric shape and process parameters of a multi-strand tundish, the ...fluid flow behavior of each strand is quite inhomogeneous, and the difference in temperature, composition and inclusion content between each strand is great, which directly affects the quality of the steel products. In this paper, the fluid flow, heat transfer phenomena and inclusion trajectories in a four-strand tundish with and without flow-control devices (FCDs) are investigated using a water model and numerical simulation in isothermal and non-isothermal conditions. The results show that natural convection has a significant influence on the flow pattern and temperature distributions of molten steel in the tundish. Without FCDs, the average residence times of the molten steel in the tundish obtained by the isothermal water model, non-isothermal water model and non-isothermal mathematical model were 251.2 s, 263.3 s and 266.0 s, respectively, and the dead zone volumes were 21.51%, 29.26% and 28.21%, respectively. With FCDs, the average residence times of the molten steel obtained by the isothermal water model, non-isothermal water model and non-isothermal mathematical model were 293.0 s, 304.0 s and 305.2 s, respectively, and the dead zone volumes were 43.98%, 50.23% and 52.78%, respectively. The flow characteristics of the molten steel in the tundish were different between the isothermal and non-isothermal conditions. Compared with isothermal conditions, the numerical simulation results were closer to the water model results in non-isothermal conditions. The trial results showed that the fluid flow in a tundish has a non-isothermal characteristic, and the results in non-isothermal conditions can better reflect the actual fluid flow and heat transfer behaviors of molten steel in a tundish.
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.
Numerical and experimental approaches to one‐third scale water model of a tundish with different flow control device arrangements demonstrate that using a large inhibitor, a baffle, and vortex eliminator yield a smaller intermixed liquid. Also, the turbulent kinetic energy in the inhibitor increases with high filling rates, delaying the expulsion of the “old” steel residues and prolonging the intermixing time.
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•Micro-closed pores relieved the thermal stress and deflected cracks propagation.•The transgranular cracks propagation owing to CaZrO3 consumed great fracture energy.•The synergistic ...effect of pores and CaZrO3 increased the interfacial dihedral angle.•Slag penetration and thermal shock resistances were enhanced by microporous magnesia.
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.
In response to the frequent problem of inconsistent quality of billet castings and their rolled products from each strand by a five-strand tundish, the flow field in tundish is optimized by ...presenting new flow control devices and conducting isothermal physical modelling along with numerical simulation. The results show that the dead volume fraction of the optimized case A6 is reduced from 27.74% to 19%, the stagnation time is prolonged from 12 s to 35 s, and the flow dynamic consistency for each strand is improved as well. In the subsequent industry production tests, the temperature difference of molten steel at the outlet of each strand is reduced to 1–5°C. The maximum difference of the as-cast equiaxed crystal rate among five strands is reduced from 5.67% to 2.7%, and the consistency of carbon segregation index is also improved with a basically identical appearance through the billet cross section. The maximum differences in oxygen and nitrogen contents for the rolled products of all strands are 2.7 ppm and 5.7 ppm respectively, which are lower than 5.0 ppm and 13.8 ppm before tundish optimization. The yield strength of rolled products is stabilized with much less divergence as compared to the products with the original tundish. Thus, it is believed that the reasonable flow field optimization to a multi-strand tundish not only will have a well-known positive impact on its tranditional metallurgical effect, but also may bring out an approaching identical steel quality from the same caster as we expected.
Numerical simulation is an effective tool to analyze the inclusion behavior in the tundish with channel induction heating. And the inclusion mass/population conservation model is applied to predict ...and describe inclusion physical field. Due to the channel induction heating, Archimedes slipping velocity and Archimedes collision are applied to describe the inclusion behavior in the tundish with channel induction heating. The predicted values agree with the experimental data for the inclusion model. Numerical results show that Joule heat and electromagnetic force can prompt the inclusion removal rate. Compared with Joule heat, electromagnetic force is a more important factor to affect the inclusion’s movement and Archimedes collision is also one of the important collision mechanisms for inclusion coalescence. The inclusion removal rate in the channels is up to one third of the inclusion removal rate in the tundish, and the inclusion removal rate in the tundish increases from 21.4% to 35.05% if channel induction heating is applied.
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–P2O5–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 Ca3(PO4)2 on the surface of calcined dolomite particles, which was beneficial for dephosphorization of molten steel.
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