발간논문

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An investigation was carried out on the extraction of Fe(III) from 0.5M aqueous sulfate solution by using secondary amine (LA-1) diluted in benzene. The results obtained in these experiments were summarized as follows: 1. The equilibrium constant, K, of the reaction, (R₂NH₂)₂S0₄+H₂SO₄⇔2(R₂NH)HSO₄, was found to be 4,480. 2. The relationships between log (distribution coefficient) vs pH and log (distribution coefficient) vs log (amine concentration) showed the linearity with slope of 1 and 2 respectively. These mean that dimerization of the species of FeOH^(2+) at 0.01M Fe(III) concentration is not able to occur. 3. An empirical relationship; distribution coefficient=1.75 ([amine concentration)-6[Fe(III)] concentration-in organic phase]) was obtained by varing Fe (III) concentration in these experimental conditions. 4. The decrease in extration percentage of Fe(III) due to the addition of foreign anions showed the following sequence of tendency: Cl^-くNO₃^-くCIO₄^- . 5. The efficiency of Fe(III) extraction decreased with increasing temperature as well as the concentration of sulfate solution.

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Three kinds of domestic natural clay bonded sands-Wolsung, Donghae, and Euchang-have been studied the green properties of molding sand on the moisture content. It has been found that the sand with high clay contains 7,0% temper moisture and 7±1% temper moisture ranges and the sand with low clay contains 4.5% temper moisture and 4.5±0.5% the range. S.S.I, moldability index, compactability and shatte index could be used for temper moisture in molding sand. Green compressive strength, permeability, moldability index, S.S.I. compactability and shatte index of natural clay bonded sand are changed by moisture content.

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The cyclic creep behavior of Al-Zn alpha solid solution alloys (20, 30, 35, 40 & 60 at.% Zn) under repeated tension loading at 633°K is investigated. The experimental results are showing that the creep rate under repeated loading is lower than that of static loading at the same temperature. The stress exponent value for both cyclic and static creep is observed to be about 3 except for the 60 at.% Zn composition. These results indicate that the fundamental microcreep mechanism of the static and cyclic creep is probably same for the Al-Zn system. The most important experimental observation in this study is that the UTS at the elevated temperature influences on the cyclic creep strength of Al-Zn solid solution alloys. The larger the UTS, the higher creep strength of the Al-Zn alloys, and the UTS and cyclic creep strength have a correlation of σ_c∝σ_u^½ for the same value of ε˙/D. From this relation, the empirical cyclic creep equation can he obtained as follow, ε˙=KD(σ_c/σ_u^½)ⁿ

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A study has been made on the mechanical behaviors of dual phase of C1020 steel, in which both ferrite and martensite phases are present. The heat treatment with varying the quenching temperature, Q_T, was carried out for the determination of the fraction martensite as a function of Q_T. The tensile properties of dual phase C1020 steel were correlated with its martensite content, and the strength and ductility of C1020 dual phase steel was found to be mostly linear relationship to the fraction martensite. The expressions for relationship of mechanical properties of steel were derived as a function of percent martensite. Ductility for C1020 steel increases substantially until 24.5% in going from the as quenched to a tempered condition. The ultimate tensile strength of the tempered martensite for C1020 steel was determined from 311 Mpa to 1065 Mpa with varying the Q_T. The mode of failure for dual phase C1020 steel was due partly to microvoid coalescence (dimple patterns) and intergranular cleavage (ferrite grains).

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Reduction reaction of synthetic Wustite by graphite through the gaseous intermediates CO and CO₂occuring during the reaction was carried out isothermally within the temperature range 950℃ to 1075℃ in an inert Ar atmosphere with T.G.-D.T.A. analysis technique. The mechanism and the rate of reduction reaction were investigated with modified physico-chemical model derived by Rao and the suitability of Rao`s model to this reaction system was studied, too. The effects of variables such as C/FeO molar ratio, Wustite powder size to the rate of reduction reaction and the compactness of mixed powder were discussed. The overall reduction reaction but the initial stage and the tail part of reaction was considered to be well fitted to the modified physico-chemical model. The activation energy for the Wustite reduction by graphite through the gaseous intermediates is calculated to be 57Kcal/㏖ and this value is reasonably in good agreement with the literature. The rate equation of reduction reaction through the gaseous intermediates was found to be X=2av [1-exp (-kt).〕.

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