STUDY ON IMPROVING DEGASSING EFFICIENCY OF IRON MELT WITH VACUUM SUCTION DEGASSING METHOD

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Experimental studies on decarburization, dehydrogenization and dcoxidation have been performed for improving the efficiency of degassing of iron melt with applying the vacuum suction degassing method. This degassing method is based on using a porous refractory material, which separates the melt from the outer space under a vacuum condition. The degassing reaction takes place at the melt-porous material interface and the gascous products are easily removed from the interface by permeating the porous material. The necessary condition is that the melt should not permeate the material. Since the area of the melt-porous material interface can be arbitrarily increased, it is possible to increase the degassing rate optionally.As for decarburization of iron melt, with using solid oxide, an attempt was made to obtain a high decarburization rate by immersing an Al_2O_3-2-30%Fe_2O_3 porous tube in the melt. The decarburization proceeded by the reaction between C and Fe_2O_3 (amd/or O). The decarb … More urization increased with increasing Fe_2O_3 content of the tube, but the oxygen content of the melt also increased. In addition, since the hot strength of the tube of high Fe_2O_3 content was not sufficient, deformation of the tube took place during the experiment at lower internal pressure of the tube, and the gas permeability of the tube decreased. In this case, the decarburization rate also decreased. Hence, the Al_2O_3-Fe_2O_3 tube was not superior in the decarburization rate to the Al_2O_3-SiO_2 tube used in our previous experiments.Experiments on dehydrogenization of iron melt were made with blowing Ar gas onto the melt surface and with or without immersing an Al_2O_3 prorous tube. It is shown that the dehydrogenization rate is controlled by gas-and liquid-phase mass transfers. The mass transfer coefficients for the tube-melt interface and obtained by applying a mixed control model. The gas-phase mass transfer coefficients is larger for the tube of higher gas permeability.Dcoxidation experiments of iron melt were made with immersing MgO-10-30%C porous tube. Oxygen in the melt reacted with C of the tube to form CO and/or with Mg vapor produced by the MgO-C reaction to form MgO,and the dcoxidation proceeded effectively. Dcoxidation experiments were also made with immersing a MgO prorous tube filled with MgO-C powder. In this case, oxygen in the melt could react only with Mg vapor, and contribution of the Mg vapor to the dcoxidation is made clear. Less