新脱ガス法(真空吸引脱ガス法)による融体の高純度化に関する研究

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A vacuum suction degassing method (VSD method) has been proposed and applied to remove gas-forming impurities in molten metal. The melt is separated from the outside by means of a porous partition wall permeable to gas and impermeable to the melt, and outside is kept at a reduced pressure. Then, the gas-forming impurities gasify at the partition wall-melt interface and the formed gas is sucked through the wall to the outside. Thus, the removal of the impurities from the molten metal is enhanced.Experiments of decarburization, denitrogenation of molten iron have been performed in the ranges of low concentrations by immersing a porous refractory tube into the melt. The decarburization proceeds by a reaction between the carbon in the melt and the refractory oxide, such as Al_2O_3, SiO_2, etc. The carbon concentration of the melt decreases down to a very low value of a few ppm, while the oxygen concentration is kept below 50ppm. The rate of decarburization with an Al_2O_3-SiO_2 tube is muc … More h higher than that with an Al_2O_3 tube. In crease in gas permeability of the porous tube makes the decarburization rate larger. It is shown that the vacuum suction degassing method can greatly increase the decarburization rate of molten iron. The VSD method has been applied to denitrogenate molten iron. The rate of denitrogenation increases by the simultaneous decarburization. The chemical reaction rate constant for the denitrogenation at the porous tube-molten iron interface is almost equal to that obtained previously by gas blowing onto the melt surface.The deoxidation of molten copper with graphite has been studied by applying the VSD method. The deoxidation rate decreases due to suction of CO gas and hence lack of stirring by the CO bubbles. However, the minimum oxygen concentration decreases to a lower value than that obtained without using the VSD method.The VSD method is also shown to be effective in dehydrogenating molten iron and molten aluminum. It is found that the dehydrogenation of molten iron is controlled by the liquid phase and the gas phase mass transfer and that of molten aluminum by the liquid phase mass transfer.A test of practical application could not have been carried out and is the subject of a future study. Less