Nozzle shape plays a key role in determining the flow pattern in the mold of the continuouscasting process under both steady-state and transient conditions. This work applies computational models and experiments with a one-third scale water model to characterize flow in the nozzle and mold to evaluate well-bottom and mountain-bottom nozzle performance. Velocities predicted with the three-dimensional k-e turbulence model agree with both particle-image velocimetry and impeller measurements in the water model. The steady-state jet velocity and angle leaving the ports is similar for the two nozzle-bottom designs. However, the results show that nozzles with a mountain-shaped bottom are more susceptible to problems from asymmetric flow, low-frequency surface-flow variations, and excessive surface velocities. The same benefits of the well-bottom nozzle are predicted for flow in the steel caster.
The initial stages of solidification near the meniscus during continuous casting of steel slabs involve many complex inter-related transient phenomena, which cause periodic oscillation marks (OMs), subsurface hooks, and related surface defects. This article presents a detailed mechanism for the formation of curved hooks and their associated OMs, based on a careful analysis of numerous specially etched samples from ultra-low-carbon steel slabs combined with previous measurements, observations, and theoretical modeling results. It is demonstrated that hooks form by solidification and dendritic growth at the liquid meniscus during the negative strip time. Oscillation marks form when molten steel overflows over the curved hook and solidifies by nucleation of undercooled liquid. The mechanism has been justified by its explanation of several plant observations, including the variability of hook and OM characteristics under different casting conditions, and the relationships with mold powder consumption and negative/positive strip times.
The electrolytic production of magnesium from magnesium chloride containing sodium chloride-rich melts has been studied using mono-polar cell, where originally designed in consideration of current efficiency and energy consumption. The magnesium was formed well at the surface of cathode and floated at the free surface of the molten salt, and chlorine gas was generated at the anode without any inverse reaction between the magnesium which is produced electrolysis process. The magnesium was collected about 200 g/hr by operating an optimized mono-polar cell with 500 A for 24 hours. The metallic magnesium produced from this study had a high purity with 99.92 %.
The titanium reduction from titanium tetrachloride (TiCl4) by molten magnesium pool, called the Kroll process, is regarded as a well-known process for the commercial-scale production of titanium sponge. Purified titanium tetrachloride vapor reduced by magnesium, forms sponge titanium with generating excessive heal. The heal transfer phenomena in a Kroll reactor should be thoroughly understood for productivity and quality enhancement. In this work, a computational modeling method to describe the thermal behavior in the TiCl4 reduction reactor was investigated and validated with the measured temperature distribution in a 500kg titanium sponge-capacity pilot-scale reactor in terms of various reduction ratios. The approach model for heat flow phenomenon in a reduction reactor could be utilized as a tool to predict the influence of operating process parameters on the optimization of Kroll process.
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