Diffusion of Silicon and Manganese in Liquid Iron. I : Diffusion in Liquid Iron Saturated with Carbon

Diffusion coefficients of silicon and manganese in liquid iron (carbon-saturated) were determined in temperature range between 1, 300°and 1, 600°by the method of so-called semi-infinite medium. Blank values accompanied with the measurement of diffusion in liquid state were examined and the following results were obtained : (i) Diffusion coefficients of silicon in Fe-C (saturated)-Si(1.5%) alloys can be expressed as follows : log D (cm^2sec^) = -3.62 - 0.179 × 10^4/T, activation energy Q = 8.2 kcal/g・atom. (ii) Diffusion coefficients of manganese in Fe-C(saturated)-Mn(2.5%) alloys can be expressed as follows : log D (cm^2sec^) = -3.71 - 0.127 × 10^/ T, activation energy Q = 5.8 kcal/g・atom

Absorption of Nitrogen by Molten Iron Alloys. II : Study on Fe-Ni, Fe-Cr and Fe-Mn Alloys

The absorption phenomena of nitrogen by molten iron alloys (Fe-Cr, Fe-Mn and Fe-Ni binary alloys) were studied, and the experimental results were discussed from the view of the statistical thermodynamics under the same conception formerly reported

Absorption of Diatomic Gas by Binary Alloys. I

Experimental results formerly reported on the absorption of nitrogen gas by molten binary alloys were considered from the viewpoint of statistical thermodynamics. According to the former results, gas atoms α dissolved in the interlattice positions in quasi-crystal of molten alloy lattice are not distributed uniformly and the distribution depends upon the amount of interaction energies φBα and φAα of α-atom with metal atoms A and B ; that is, nitrogen atoms have a tendency to cluster around chromium or manganese atoms when nitrogen is absorbed by molten Fe-Cr or Fe-Mn alloys. Taking the above-mentioned fact into account, the theoretical formula concerning the absorption of diatomic gas by binary alloys was derived. It could explain satisfactorily the results formerly obtained with respect to nitrogen absorption by molten Fe-Cr, Fe-Mn and Fe-Ni alloys. Further, the validity of the present theory was checked by some previous data on the absorption of diatomic gases (nitrogen, hydrogen or oxygen) by binary solid solutions

Absorption of Nitrogen by Molten Iron Alloys. I : Study on Pure Iron

The experiments on the absorption of nitrogen by molten iron were performed between 1, 530°and 1, 750℃, and the results obtained were fairly well interpreted from the view of the statistical thermodynamics, basing on the fundamental conception that the structure of molten iron is quasi-crystalline and absorbed gas atoms are situated at the vacant spaces in iron lattice interstitially

Interaction Parameters of Alloying Elements in Binary Alloys of Molten Iron

The interaction parameters of alloying elements in dilute binary alloys of molten iron were calculated by a statistical-thermodynamical method similar to that used in the previous work on ternary alloys. The interaction parameter ∈ (X)X of a substitutional alloying element X is given by ∈ (X)X=-2/RTW_, and that of an interstitial alloying element X by ∈ (X)X=2-2/RTN°X_X. The interchange energy W in the above equation was estimated from the following modified Mott\u27s equation : W_=V^M(δ_-δ_X)^2-23060 n (X_-X_X)^2, whereδ_ andδ_X are the solubility parameters, X_ and X_x the electronegativities of iron and X respectively, V^M the molar volume of mixture, and n the appropriate number of Fe-X bond in the mixture. The values of interaction parameters thus calculated for the substitutional alloys were compared with the experimental ones and reasonable agreements were found in Fe-Al, Fe-P, Fe-S, Fe-Cr and Fe-Ni systems. For the interstitial alloys, discussions are omitted because the data on -X_X are not yet available

On the Viscosities of Molten Slags. I : Viscosities of CaO-SiO_2-Al_2O_3 Slags

Viscosities of synthetic CaO-SiO_2-Al_2O_3 slags were measured by rotating inner-cylinder viscosimeter, and iso-viscosity lines at 1, 500 and 1, 600℃ are drawn on the diagram. Viscosity of CaO-SiO_2 slags at 1, 600℃ decreased with the increase of CaO content and anomaly was not found at the composition corresponding to CaO・SiO_2. By the addition of a small amount of Al_2O_3 to CaO-SiO_2 slag, viscosity was almost unchanged as in the case of the previous investigator, but at more than 20% Al_2O_3 the increase of viscosity became remarkable. In CaO-Al_2O_3 slags, a minimum of viscosity was found on the isothermal line at low temperatures at about 50% Al_2O_3. Viscosities of CaO-Al_2O_3 side slags which had hitherto never been determined were low and comparable to those of the low viscosity region in CaO-SiO_2 side slags. And some considerations on structures of these molten slags were given from the experimental results

Rate of Desulphurization of Molten Iron by Slag under Reducing Condition

The rate of transfer of sulphur across a metal-slag interface under reducing condition was studied at the temperature range from 1, 440°to 1, 570℃. Radioactive sulphur, S^, was used to improve the accuracy of the experiment. The net rate of transfer of sulphur from metal to slag increases with increasing basicity of the slag and with temperature. This is ascribable to the fact that the rate of transfer of sulphur from metal to slag increases rapidly with increasing basicity of slag and with temperature, while that from slag to metal does not change appreciably with change in slag composition and temperature. In the case of high viscosity slags, the rate of transfer of sulphur was interpreted on an assumption that the transfer is the reaction of the first order, but this assumption was inadequate for explaining the experimental results obtained with low viscosity slags. The rate of transfer of sulphur seems to be affected remarkably by side reaction

Diffusion of Sulfur in Molten CaO-SiO_2-Al_2O_3 Slag

As the first step in the study on the kinetics of desulfurization of iron by slag, the rate of diffusion of sulfur in molten CaO-SiO_2-Al_2O_3 slag was determined by the use of radioactive sulfur S^. Iron sulfide powder made from barium sulfide containing S^ was mixed with powdered CaO-SiO_2-Al_2O_3 slag, and after melting, this radioactive sample was poured into a graphite tube, which was coupled with a graphite crucible containing a non-radioactive sample of nearly the same composition as the radioactive sample. Then, the couple was heated in a high frequency induction furnace in a nitrogen atmosphere for a definite time. After cooling in the furnace, thin slices were successively cut off from the top of the slag column, and the radioactive intensity of the polished surfaces of the remainder was measured by a Geiger-Muller counter. From these measurements, the diffusion coefficient D of sulfur in a molten basic slag was determined as follows : D=1.4e-49, 000/RT. The diffusion coefficient in an acid slag at 1, 440℃ was nearly the same as in the basic slag, but its values at higher temperatures could not be measured, owing to the evolution of gas by the reaction, SiO_2+2C→Si+2CO

Diffusion of Calcium in Liquid Slags

Self-diffusion coefficients of calcium in molten slags (CaO-SiO_2, CaO-Al_2O_3, CaO-SiO_2-Al_2O_3 and CaO-SiO_2-Al_2O_3-MgO systems) were measured by the method of semi-infinite medium in the temperature range from 1350°to 1600℃. The diffusion coefficients were of the order of 10^6～10^7cm^2 sec^ and the activation energies were 40～70kcal/g・mol for all slags investigated. The diffusion coefficient has good correspondence to both the specific electric conductivity and the viscosity coefficient. Some behaviors of Al_2O_3 and MgO in basic slags were also discussed

Elimination of Nitrogen Dissolved in Iron by Addition of Aluminium

When nitrogen gas is reacted on melts of binary Fe-Al alloys under a pressure of one atmosphere, a part of the nitrogen enters the melts, (1) as non-metallic inclusions in the form of AlN compound, while the other part becomes (2) interstitially dissolved nitrogen in its atomic state. We measured the quantity of nitrogen in the two above states separately with respect to samples of Fe-Al alloys of various compositions. In particular, we investigated the relation between the quantity of the interstitially dissolved nitrogen and the aluminium content of the various samples, and arrived at important results suggesting a basic relation in the elimination of nitrogen in iron. melt at variance with the theory accepted hitherto. A statistico-thermodynamical study of the results gave satisfactory answers