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In this work, the placement of an electromagnetic swirl flow generator (EMSFG) around a submerged entry nozzle (SEN) was proposed as a method for generating a rotating electromagnetic field in a continuous casting (CC) process of steel. First, two kinds of a full type EMSFG and a half type EMSFG were designed based on mathematical modeling. Then, distributions of magnetic flux intensity in an EMSFG as well as distributions of Lorentz force in molten steel were simulated. It was found that the EMSFG structure and electromagnetic parameters have an important effect on magnetic flux intensity and Lorentz force distributions. For both a full type and a half type EMSFG, the magnetic flux intensity and Lorentz force increases as the magnetomotive force increases. Especially, for a full type EMSFG, the magnetic flux intensity is distributed evenly in molten steel. Moreover, the Lorentz force increases along a radial direction in the molten steel in the SEN. However, for a half type EMSFG, the magnetic flux intensity and Lorentz force decreases gradually towards the region without an EMSFG. Consequently, a full type EMSFG with a 44 000 AT magnetomotive force and a 50 Hz frequency is more suitable to apply in the operation of an EMSFG under actual production conditions., QC 20150511. Updated from manuscript to article in journal.

In the preceding work, the inclusion behavior in a submerged entry nozzle (SEN) and mold induced by using a swirl flow has been investigated. The results showed that a swirl flow can effectively promote the inclusions removal to the meniscus as well as reduce the inclusions entrapment at the solidified shell wall. Moreover, that the swirl flow was generated by using a full type electromagnetic swirl flow generator (EMSFG). In the present work, a kind of a half type EMSFG was investigated, since it is easier to implement in a production scale. The influence of the stirrer on the fluid flow, heat transfer, and inclusion behavior in the SEN and mold was studied. Furthermore, a comparison between these two types of EMSFG from the aspects of flow field, temperature field, and inclusion behavior was done. In addition, the effect of different magnetomotive forces, inclusion sizes, densities as well as boundary conditions on the inclusion behavior was studied. The results show that the effect of a half type EMSFG (88000 AT) on the molten steel is very close to a full type case (44000 AT). More specifically, the flow pattern, temperature distribution as well as inclusion behavior in the SEN and mold look very similar. Also, it was found that from the viewpoints of the inclusions separation to the mold meniscus and the inclusions trapping at the solidified shell wall, better results could be obtained for a “Trap” boundary condition when using half type EMSFGs., QC 20151026

Carbide precipitation and eutectic phase transformation during solidification of Fe-C-Cr-Ti-Mn-Mo-Ni-Si Ti-added high-chromium cast irons (HCCIs) were studied numerically and experimentally by the help of Partial Equilibrium approximation, DSC thermal analyses and EDX analyses. The main carbides formed during the solidification are distinguished as MC, primary M7C3 and eutectic M7C3 from their distinguished constitution, while other researchers didn't distinguish the primary and eutectic M7C3 carbide. Through comparing the prediction of Partial Equilibrium approximation with DSC thermal analysis measurement, the precipitation sequence of the eutectic structure in HCCIs is clarified to follow the sequence of FCC prior to the eutectic M7C3, although they were usually expected to precipitate simultaneously. The hardness index of the HCCIs is evaluated quantatively by summation of the contributions of the Vickers hardness of MC, primary M7C3 and eutectic M7C3 carbides with predicted precipitation amount and composition / constitution. The effects of C, Ti and Cr contents on the precipitation sequence, the amount and the composition of carbides as well as the hardness of the HCCIs are discussed deeply. Finally, the validity of Partial Equilibrium approximation is shown in prediction of the solidification in multicomponent system with large amount of precipitated carbides., QC 20140414

In Fe-C-V-W-Cr-Mo high speed steels, the nature of carbides during the solidification are discussed as a function of C, V and W content by the help of Partial Equilibrium (PE) approximation and thermodynamic calculations. The results show that the solidification path and carbide precipitation can be reasonably predicted by the Partial Equilibrium approximation for cooling rate lower than 10-13 K min(-1). From the viewpoint of hardness control by carbides, it is found that among the main carbides MC, M6C and M7C3, the increase of C favours the formation of MC, M7C3 but decreases the hardness of M7C3 by increasing the Fe content in it. Meanwhile, the increase of V only increases the amount of MC and V content therein, and the increase of W largely increases the amount of M6C and W content in it. As a result, the addition of V and W improves the hardness of MC and M6C carbides., QC 20130506

In this study, a new method for swirling flow generation in submerged entry nozzle (SEN) in continuous casting of steel process has been proposed. A rotating electromagnetic field is set up around the SEN to induce swirling flow in it by the Lorentz force. And this kind of electromagnetic swirling flow in the SEN is proposed to use in square billet continuous casting of steel process. The effects of coil current intensity and nozzle structure on the flow and temperature fields in the SEN and mold are numerically simulated and verified by an electromagnetic swirling model experiment of low melting point alloy. The overall results of the study show that the magnetic flux density and the swirling flow velocity in the SEN increase with the increase of coil current intensity. The largest swirling flow velocity in the SEN can reach about 3 m/s when coil current intensity 500 A, frequency 50 Hz. The electromagnetic swirling flow in the SEN can reduce the impinging depth of the flow and increase the upward flow. An impinging flow near the mold corner can be observed. The flow field changes mentioned above result in a uniform temperature field in the mold, increase the meniscus temperature, effectively increase the temperature at the mold corner. The divergent nozzle used in this new process also reduces the impinging depth, increases the upward flow and makes the meniscus temperature increase significantly., QC 20130826

Increasing alumina production in China and improvements in production technology have resulted in the depletion of high-quality bauxite resources. A calcification-carbonation method is described for the treatment of middle- to low-grade bauxite and red mud. Experiments using synthetic mixtures of pure NaOH, Al(OH)3, CaO and Na2SiO3 indicated that sodium aluminosilicate hydrate was transformed into hydrogarnet with increasing additions of CaO, but the alumina-silica ratio increased and the sodium-silica ratio decreased. The hydrogarnet was decomposed with CO2 at 120 degrees C at a CO2 partial pressure of 1.2 MPa. The alumina extraction efficiency was up to 63.6% and the alumina-silica ratio of the final product was reduced to 0.54. Treatment of diasporic bauxite, gibbsite and red mud under conditions of a calcification temperature of 240 degrees C for diasporic bauxite or 180 degrees C for gibbsite and red mud, a calcium oxide/silica molar ratio of 3:0.64, a carbonation temperature of 120 degrees C, and CO2 pressure of 1.2MPa reduced the alumina/silica ratios of the final products to 0.44, 0.82 and 0.43, respectively, and the sodium oxide contents to 0.12%, 0.57% and 0.44%. The final red mud product was suitable for direct use in the cement industry., Increasing alumina production in China and improvements in production technology have resulted in the depletion of high-quality bauxite resources. A calcification-carbonation method is described for the treatment of middle- to low-grade bauxite and red mud. Experiments using synthetic mixtures of pure NaOH, Al(OH)3, CaO and Na2SiO3 indicated that sodium aluminosilicate hydrate was transformed into hydrogarnet with increasing additions of CaO, but the alumina-silica ratio increased and the sodium-silica ratio decreased. The hydrogarnet was decomposed with CO2 at 120 degrees C at a CO2 partial pressure of 1.2 MPa. The alumina extraction efficiency was up to 63.6% and the alumina-silica ratio of the final product was reduced to 0.54. Treatment of diasporic bauxite, gibbsite and red mud under conditions of a calcification temperature of 240 degrees C for diasporic bauxite or 180 degrees C for gibbsite and red mud, a calcium oxide/silica molar ratio of 3:0.64, a carbonation temperature of 120 degrees C, and CO2 pressure of 1.2MPa reduced the alumina/silica ratios of the final products to 0.44, 0.82 and 0.43, respectively, and the sodium oxide contents to 0.12%, 0.57% and 0.44%. The final red mud product was suitable for direct use in the cement industry.

A method is proposed for dealing with by-product magnesium chloride resulting from the production of titanium sponge in the Kroll process. If Cl is to be circulated to titanium smelting and Mg to magnesium metal by way of aluminothermic or silicothermic reduction, the pyrolysis of MgCl2 must first be understood and its dynamics investigated. Experiments were carried out on anhydrous MgCl2 to determine the effects of temperature, time, oxygen partial pressure and gas flow rate on the efficiency of molten MgCl2 pyrolysis in a tubular furnace., A method is proposed for dealing with by-product magnesium chloride resulting from the production of titanium sponge in the Kroll process. If Cl is to be circulated to titanium smelting and Mg to magnesium metal by way of aluminothermic or silicothermic reduction, the pyrolysis of MgCl2 must first be understood and its dynamics investigated. Experiments were carried out on anhydrous MgCl2 to determine the effects of temperature, time, oxygen partial pressure and gas flow rate on the efficiency of molten MgCl2 pyrolysis in a tubular furnace.

The kinetics of the reactive diffusion at the liquid Al/solid Cu interface was investigated at T = 973 K, 1023 K, and 1073K in a high magnetic field of 11.5 T. During the annealing process, three stable compounds (delta, xi(2), and eta(2)) layers were formed at the interface of the couples, and a power function relationship between the mean thickness of the diffusion layers and the annealing time kept stable. Without magnetic field, the exponent of the power function for each compound layer was higher than 0.5, but it was close to or even smaller than 0.5 with a magnetic field. Compared with the field-free environment, the migration of the liquid/solid interface due to interdiffusion decreased in the presence of a magnetic field. A considerable decrease in the effective diffusion coefficient under a magnetic field provided a likely explanation for the experimental results., QC 20120412

Recently the studies on the effects of high magnetic fields on solidification processes have been paid much attention both from the fundamental and applied points of view With the aid of the enhanced Lorentz force and magnetization effect caused by the remarkably increased magnetic field intensity several interesting phenomena such as the control of fluid flow and particle migration in a melt crystal orientation and phase alignment have been obtained Moreover the magnetic force induced by the interaction of magnetization and high magnetic field gradient has been evidenced to show significant effects on the microstructure evolution of alloys In this paper the recent development of the control of the solidification process by high magnetic fields is reviewed from the view point of uniform magnetic fields and magnetic field gradients, QC 20110303

A microsegregation model for the solidification of multicomponent alloys is developed It couples the volume-averaged conservation equations for total mass solute mass and energy assuming a uniform temperature The diffusion in the liquid and solid phases the growth kinetics of the solidifying microstructures and the velocity of the solid/liquid and solid/solid phase interfaces are considered in the model Equilibrium between phases is taken into account and computed using dedicated thermodynamic software The thermodynamic properties and their evolutions during solidification are directly retrieved from a database Illustration is provided by the solidification of a Fe-C-Cr alloy The occurrence of the recalescence due to the growth of the microstructure and the progress of solidification are predicted The solidification behavior near to recalescence is evaluated By adjusting the cooling intensity and the solute diffusivities extreme approximations are retrieved The model shows potentials to be coupled with a macrosegregation model for application to the solidification of multicomponent alloys, QC 20110303

The solidification microstructure evolution and the Columnar to Equiaxed Transition (CET) during Al-Si and Al-Cu binary alloy solidification processes are analyzed by the help of Cellular Automaton-Finite Difference (CA-FD) model The effects of the physical properties except the effects of the nucleation parameters and the operation parameters on the cooling curves the dendrite growth the solidification morphologies and the CET of the Al-Si and Al-Cu binary alloys are emphatically discussed Results show that the solidification morphologies are internally influenced by the physical properties related to the dendrite tip growth kinetics Besides the solute diffusivity in liquid D-L and the growth restriction parameter Q=mC(o)(k(S/L)-1) the Gibbs-Thomson coefficient Gamma shows a great effect on dendrite tip growth rate Their effects on the dendrite tip kinetics are ordered as m(k(S/L)-1)>Gamma>D-L The growth rate can be predicted efficiently by the present simplified expression based on GGAN model combining several physical parameters and the local under-cooling which clearly shows the physical meaning of the constant coefficients in the simplified expression based on KGT model The equiaxed ratio related to the solidification morphologies can also be evaluated as a function of those physical properties, QC 20110303

The dendrite tip growth kinetics in the flow field and the decentred quadrilateral growth algorithm for describing the evolution of grain growth are combined in Cellular Automaton model to predict the deflective growth of dendrites inclined toward upstream direction. The influences of flow intensity, cooling rate (or solidification rate), nucleation density at ingot surface on the deflective growth of dendrites are discussed. The increase of flow intensity dominantly forces the dendrites to grow in upstream direction; on the contrary, the increases of nucleation density at ingot surface and cooling rate suppress slightly this deflective growth. The relations predicted among deflection angle, flow intensity and solidification rate for AI-Si alloy and Al-Cu alloy show the same tendency as that in Okano et al.'s empirical expression deduced from experiments on steel. The deflection angle predicted for Al-Cu alloy fits well with previous experimental results., QC 20110304 Conference on Cutting Edge of Studies in Inclusions and Precipitates Behavior Related to Microstructure Control, Kumamoto, JAPAN, SEP, 2008

A Cellular Automaton (CA)-Finite Difference (FD) coupling model was developed to analyze the evolution of solidification microstructure and the columnar-to-equiaxed transition (CET) in AI-Si alloy. Kobayashi's microsegregation equation was adopted to describe the solute diffusion in solid phase, and a "decentred square" growth algorithm with coordinate transformation was performed to describe the grain growth and the entrapment of neighbor cells. Through the examination on the effects of operation parameters and nucleation parameters on solidification morphologies, it was found that the length of columnar grains is controlled by the dendrite tip growth kinetics, and that the width of columnar grains is controlled by the implicit relationship between nucleation density and cooling rate at ingot surface. It was also found that the size of equiaxed grains is controlled by the competition of the nucleation and the grain growth. With the controllability of nucleation density in the bulk of liquid for equiaxed grain size, the nucleant and the nucleation density in actual AI-Si alloy were estimated. Both of the CET criteria based on the solidification path by CA-FD coupling model and the one based on the curves of critical temperature gradient conditions by Hunt's model were strongly dependent on nucleation undercooling and Si concentration. A good agreement was obtained between these two., QC 20110304 Conference on Cutting Edge of Studies in Inclusions and Precipitates Behavior Related to Microstructure Control, Kumamoto, JAPAN, SEP, 2008

The effects of uniform and gradient magnetic fields on gravity segregation in Al-5wt%Cu and Al-10wt%Mg alloys are investigated. The results show that high magnetic fields can be used to control the solute distribution and thus control gravity segregation caused by the difference of physical properties such as density and magnetic susceptibility between the bulk liquid and the solute-enriched liquid. The effects of the field can be attributed to performances of Lorentz and magnetic forces., QC 20110304 Conference on Cutting Edge of Studies in Inclusions and Precipitates Behavior Related to Microstructure Control, Kumamoto, JAPAN, SEP, 2008

The effects of high magnetic fields on the migration and rotation of TiAl3 particles in an Al-7 wt.% Si alloy were studied. Without magnetic fields, the rod-like TiAl3 particles segregate at the lower part of the solidified structure. Under high uniform magnetic fields, these particles rotate to an orientation with their longitudinal axes parallel to the direction of the magnetic flux. The segregation of the particles reduces with the increase of the magnetic flux density. A negative gradient field enhances the effect of the uniform magnetic field. By altering high magnetic fields, Al-Si alloy samples containing homogeneously distributed and preferably aligned TiAl3 particles were prepared., QC 20110412

Solidification experiments of aluminum-nickel binary alloys under uniform high magnetic fields have been conducted. The effects of high magnetic fields on the crystal orientation of Al3Ni were investigated by XRD and the alignment of primary phases Al3Ni were also analyzed. Experimental results showed that the easy magnetization axis of Al3Ni crystal oriented parallel to the imposed magnetic fields and the primary phase Al3Ni aligned perpendicular to the magnetic fields. Magnetic orientation of crystal was determined by magnetic anisotropy energy. Whereas the phase alignment should be contributed to the combined effects of magnetic orientation, crystal growth and the effects of magnetic fields on mass transport during solidification., QC 20110531