The general relationship between oxygen in the liquid iron and iron oxide in the slag is well understood as the distribution of oxygen. There are many reports dealing with the equilibrium between ternary slag FeO-CaO-SiO2 and FeO-MnO-SiO2 and oxygen in the liquid iron. And also, thermodynamical consideration on the variation in chemical properties of oxides in the slag has been made by many workers. It is, however considered that their theories involved in themselves some questions and assumptions. Authors measured the effects of the following oxides, namely, CaO, Al2O3, MnO, CrO, on the distribution of oxygen and examined the distribution coefficients of chromium for the quaternary system, FeO-CrO-CaO-SiO2 saturated with silica and liquid Fe-Cr alloy. Authors discussed on the questions whether or not the distribution of chromium in this system could be given as a linear function of iron oxide as shown by KORBER et al., or activity of iron oxide, the same as FeO-CrO-MnO-SiO2 system reported previously by authors. The equilibrium between the molten iron and the slag was studied in the silica crucible at 1600°C. The results obtained are summarized as follows. 1) The effects of various oxides on the silica content in the silica saturated slag correspond to the melting point of its silicate. 2) The solubility of oxygen decreases with an increase in the added oxide in FeO-SiO2 system. It is recognized that there exists some relationship between the diminution rate of oxygen and the strength in terms of the basicity of added oxide. 3) The effects of various oxides on the activity of iron oxide are relatedwith the strength in terms of the basicity of added oxide. The activity of iron oxide was representedby the following empirical formula. aFeO=0.388-(1.30NM2+-1.14N2M2+)/√I where I refers to the ion-oxygen attraction. 4) The equilibrium relation between three forms of oxygen in silicate melts as shown by RICHARDSON was studied for the ternary slags saturated with silica. The concentration of (O2-) was abruptly changed with the variation of cation in silica saturated slag. 5) Distribution of chromium was obtained for the quaternary slag FeO-CaO-CrO-SiO2. The results show that the distribution coefficient of chromium is affected by CaO. And it can not be represented by the concentration of iron oxide as shown by KORBER et al., but by the activity of iron oxide. It showed good agreement with the results reported previously for the system FeO-CrO-MnO-SiO2 by authors. 6) Expedient method of calculating the activity of iron oxide in the quaternary system can be obtained by using the activity of iron oxide in ternary system. The calculated values showed close agreement with the experimental results.
Under various conditions the liquid iron-carbon alloys were oxidized by blowing A-O2 gas onto the surface of the melt and the decarburization process was followed by sampling either the melt or the gas phase. The results obtained are summarized as follows: 1. In high carbon range the rate of decarburization is independent of the C content and increases in approximate proportion to the oxygen concentration in A-O2 gas. The O content remains constant before the C content reaches the critical values which depend on the oxygen concentration in the gas. 2. In low carbon range the rate of carbon removal decreases as the C content decreases. The reaction was accompanied by the emission of iron oxide fume and an increase of the O content. 3. When the alumina tube is situated at a distance of 25mm from the surface, the rate of carbon removal is independent of its area and, therefore, the reaction takes place merely on the small portion of the surface. Owing to the gaseous diffusion into the A-O2 gas stream, about 10 minutes is necessary for the decarburization to reach steady state. 4. When the tube is located at a distance of 125mm, the rate of decarburization is much lower than in the case of 25mm within the range of oxygen concentration 0-40% and in this range the fume is evolved noticeably. 5. In high carbon range the oxygen in the gas burns the evolved CO and the reaction O2+2CO=2CO2 goes on to completion at the flame front. 6. The rate of decarburization increases as temperature lowers, especially in the case where the tube is located at a distance of 125mm. 7. The mechanism of the formation of iron oxide fume is discussed in relation to the rate of vaporization of molten iron and the flux of CO2 which diffuses through the vapor phase. 8. It is confirmed that in both ranges of C content the gaseous diffusion to the surface of the melt controls the decarburization in these experiments.
1) Mass-transfer coefficient, k, from rotated or static solid metal cylinder surface into liquid metal, was measured chemically or gravimetrically. In this report, steel-Al, steel-Zn, Cu-Pb, Zn-Hg and Sn-Hg were employed as the combination of solid metal cylinder-liquid metal bath. Correlation of mass-transfer coeff. to the physical properties of liquid metal, diffusion coeff., characteristic length of the cylinder and experimental conditions (temperature, speed of rotation, etc.) was analysed non-dimensionally. Results obtained are as follows: Jd=(k/U)(Sc)2/3=0.065(Re)-0.25: rotated cylinder (Sh)=0.124 (Gr·m×Sc)1/3: static cylinder 2) These equations were rearranged to estimate the mass-transfer coeff. in the dissolution process of steel cylinder into liquid Fe-C alloy at about 1400°C. k=9.14×10-4 (L)-0.25(U)0.75: rotated cylinder k=1.17×10-2 (Δρ) 0.333: static cylinder Experimental results fairly agreed with the estimated values in the case of rotated cylinder but were about 30% lower than estimated values in the case of static cylinder, as averaged k. 3) It would be concluded that the non-dimensional correlation of mass-transfer, predicted in common fluid at lower temperature, holds fairly well even with high temperature liquid metal such as Fe-C alloy at 1400°C in spite of technical difficulties of experiment at high temperature (especially in free convection) and the lack of the fundamental data on physical properties, diffusion coeff. of liquid metals.