Diffusion of Slufur in Liquid Iron. I : Diffusion in Pure Iron

The diffusion coefficient of sulfur in liquid iron has been measured at the temperature range from 1, 560°to 1, 670℃. Since the concentration of sulfur was low in the present investigation, the diffusion coefficient was calculated by assuming as constants independent of the concentration. The result was expressed as follows : D=4.9×10^exp(-4350/T). The diffusion coefficient and the activation energy are nearly the same as those of carbon, cobalt and phosphorus in liquid iron. The activation energy is about one-tenth of the heat of vaporization and this shows that the holes in liquid iron are small. The theoretical values derived from the absolute reaction rate theory and the diffusion coefficient calculated by the Stokes-Einstein equation are compared with the experimental results

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

In order to clarify the influence of MgO on the viscosity of blast furnace slag, viscosities of synthetic CaO-SiO_2-Al_2O_3-MgO slags were measured by the use of rotating inner-cylinder viscosimeter as in the case of the first report. Iso-viscosity lines at 1, 500 and 1, 600℃ are given in the diagrams. When MgO was added to CaO-SiO_2 slag, the viscosity decreased with increasing amounts of MgO up to about 20%, beyond which, however, it increased. The region of low viscosity in CaO-SiO_2-MgO slag was greater than that in CaO-SiO_2-Al_2O_3 slag. When MgO was added to CaO-SiO_2-Al_2O_3 slag, the viscosity decreased, moreover, change in viscosity at constant temperature caused by the change of slag composition became small, but these beneficial effects of MgO were less noticeable than those reported by McCaffery and coworkers. With respect to the fluxing quality, MgO has nearly the same or a little less influence in reducing the viscosity of slags comparing with that of CaO

Diffusion of Sulfur in Liquid Iron. II : Diffusion of Liquid Iron Saturated with Carbon

The diffusion coefficient of sulfur in liquid iron saturated with carbon has been measured in the temperature range from 1, 390°to 1, 560℃ by using radioactive sulfur S^. It was found to be 2.9-3.6×10^ cm^2/sec and its dependency on temperature was expressed as follows : D=2.8×10^ exp (-3, 800/T) The values of the diffusion coeofficient are lower than those of the same concentration in iron-sulfur binary solution. The decrease of the diffusion coefficient by the presence of carbon can be explained partly as due to the fact that the decrease of activity coefficient of sulfur with concentration is larger than that in binary solution

Rate of Desulphurization of Molten Iron by Slag under Reducing Condition. II : Influence of Silicon and Manganese

The influence of silicon and manganese on the rate of transfer of sulphur across a slag-metal interface under reducing condition has been studied in temperature range from 1, 490°to 1, 560℃. The experimental method was the same as in the former experiment. The rate of transfer of sulphur from metal to slag increases with increasing content of silicon and manganese in iron, while that from slag to metal does not change appreciably ; therefore, the rate of desulphurization of molten iron by slag increases with increasing silicon and manganese. The consideration of sulphur activity does not account for the increase of the rate of desulphurization. The mechanism of desulphurization and the influence of silicon and manganese on the slag-metal sulphur reaction are discussed

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

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

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

Gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid-enhanced magnetic resonance imaging findings of borderline lesions at high risk for progression to hypervascular classic hepatocellular carcinoma

金沢大学医薬保健研究域保健学系OBJECTIVES: The objectives of the study were to assess the imaging features of hypovascular borderline lesions containing hypervascular foci on gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI) and to evaluate the ability of Gd-EOB-DTPA-enhanced MRI to diagnose high-risk borderline lesions possibly consistent with early hepatocellular carcinoma (HCC). METHODS: Institutional review board approval was obtained for this retrospective analysis of imaging findings, and informed consent was obtained from 217 consecutive patients undergoing Gd-EOB-DTPA-enhanced MRI and angiography-assisted computed tomography (CT) for examination of hepatocellular nodular lesions in cirrhotic livers. There were 73 nodules showing hypervascular foci in borderline lesions identified by angiography-assisted CT. Signal intensity patterns of the nodules were evaluated on hepatobiliary-phase Gd-EOB-DTPA-enhanced T1-weighted MRI obtained 20 minutes after intravenous injection of contrast media. RESULTS: Among 73 high-risk borderline lesions, 59 were hypointense (81%), and 14 were isointense (19%), compared with background liver parenchyma. There were 27 untreated lesions followed by CT and/or MRI. Almost half of these nodules transformed into hypervascular HCC, regardless of signal intensities seen on hepatobiliary-phase Gd-EOB-DTPA-enhanced MRI. CONCLUSIONS: Although many high-risk borderline HCC lesions are hypointense on hepatobiliary-phase Gd-EOB-DTPA-enhanced MRI, some high-risk borderline lesions are isointense and transform at the same rate into hypervascular HCC. © 2011 Lippincott Williams & Wilkins, Inc