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

为提高铁熔体的脱气效率，采用真空吸力脱气法进行了脱碳、脱氢和脱氧化实验研究。这种脱气方法是基于使用多孔耐火材料，在真空条件下将熔体与外部空间分离。脱气反应发生在熔体-多孔材料界面处，气体产物很容易通过渗透多孔材料从界面中析出。必要条件是熔体不应渗透到材料中。由于熔体-多孔材料界面的面积可以任意增加，因此可以任选地增加脱气速率。在铁熔体脱碳方面，采用固体氧化物，尝试在熔体中浸入Al_2O_3-2-30%Fe_2O_3多孔管以获得较高的脱碳率。C与Fe_2O_3 （amd/ O）反应脱碳。随着管中Fe_2O_3含量的增加，脱碳率增加，熔液中氧含量也增加。此外，由于高Fe_2O_3含量的管的热强度不够，在较低的内压下，实验过程中管发生变形，管的透气性降低。在这种情况下，脱碳速率也降低了。因此，Al_2O_3-Fe_2O_3管的脱碳速率并不优于我们之前实验中使用的Al_2O_3-SiO_2管。用氩气吹入铁熔体表面，用或不浸入Al_2O_3多孔管对铁熔体进行脱氢实验。结果表明，脱氢速率受气液相传质控制。采用混合控制模型计算了管-熔界面的传质系数。气相传质系数越大，气相传质系数越大。采用MgO-10-30%C浸没多孔管对铁熔体进行了氧化实验。熔体中的氧与管内的C反应生成CO，或与MgO-C反应产生的Mg蒸气反应生成MgO，氧化反应有效进行。用MgO- c粉末浸泡MgO多孔管进行氧化实验。在这种情况下，熔体中的氧只能与Mg蒸气发生反应，并且Mg蒸气对氧化的贡献是明确的。少

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