발간논문

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Thermodynamic Characteristics for the formation of tungsten carbide in CO atmosphere were studied by measuring the temperatures of formation of tungsten carbide. It was observed that tungstic oxide rapidly converted to the carbide in comparison with the metallic tungsten under same conditions. The equilibrium constant of the following reaction W+2CO=WC+CO₂ was determined as log K=10,950/T-10.11 then, Gibbs free energy change was calculated as follows ΔG=-50,129+46.3T Some reaction kinetics on the formation of tungsten carbide under various partial pressures of CO gas and temperatures were investigated and the particle sizes of the products obtained at various conditions were checked.

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The kinetics regarding to the pressure leaching of pyrite ores at elevated temperature and pressure was investigated. The leaching rates were proportional to the oxygen partial pressure, temperatures and the specific surface area of the sample, and were independent of the concentration of the sulfuric acid. The activation energy of the domestic pyrite ores for pressure leaching was 10.1 kcal. per mol. Pyrite ores were completely decomposed into free sulfur and ferrous or ferric sulfate when leaching was carried out for 4 hours at 115℃ under 20 atom, of oxygen partial pressure in dilute sulfuric acid solutions. Some electrolytic effect was briefly tested by applying anodic current during the pressure leaching at a means of accelerating the rate of leaching. It was proved that the combination method of acid leaching and anodic dissolution was effective for pressure leaching of pyrite ores.

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Rotary piercing consists of the formation of a hollow by peripherally rolling a cylindrical hot billet over a conical piercer point by driven reducing roll cones set askew to the longitudinal center line of the mill assembly. The outside diameter of the resultant hollow is controlled by grooved disk or stationary guide. This investigation was to analyze piercing conditions using guide rollers in place of disk and stationary guides presently equipped with the piercing mill. As a result of this investigation, it is concluded that new guide rollers enable to provide a smooth outside surface and an easy control of the pierced hollow diameter. Also the guide rollers eliminate frictional forces which exist between the billet and presently used disk and stationary guides. Consequently, the guide rollers perform their function of controlling the diameter of hollow product formed by piercing the billet with a minimum of wear and product surface roughening. This investigation was originally conducted with a model rotary piercing mill using analog billet and the analysis of this study was verified with the model mill.

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In the magnetic alloy which consists of three principal elements, namely iron, carbon and aluminum, the effect of chemical composition, pre-heated metallic mold temp, and tempering temperature on residual induction and hardness were studied for the simple ternary alloys. In addition to the above, the effect of Mn and Si as the impurity, and Co and Ni as the additional element on residual induction were studied too. The optimum conditions for casting into pre-heated metallic mold are as follows. (1) chemical composition; C＝2.0∼2.1% Al＝7.5∼7.8% (2) pre-heated mold : 150℃ (3) tempering temp : 350℃ (4) structure : β-martensite＋austenite (little) and this residual induction is similar to the alloy quenched after solid solution treatment. In other words, the chilled effect is same as quenched state in Fe-Al-C type permanent magnet under above chemical composition.

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E.m.f measurement was carried out to study the lead-antimony binary system which forms a basic mechanism of Sb behavior in liquid Pb. As a part of the fundamental study in softening or fire refining, thermodynamic function, i.e., ΔFi, ΔF, Li, ΔH, ΔS were determined also by this study. Activity curve of respective component of lead and antimony shows small negative deviation from ideality at 475℃. However, according to lowering the temperature activity coefficient seemed to be slowly increased in Pb rich side composition, and slightly decreased in Sb rich side composition. Furthermore, it should be studied to determine the activity of this liquid Pb rich alloy more than Npb 0.90.

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A feasibility study on sulfide mineral bearing iron ore from Yangyang iron mine was made to eliminate sulfur contents. The study indicated that by magnetic separation and flotation a portion of sulfide minerals could be removed. Magnetic separation, alone, was not amenable to eliminate effectively the sulfur contents to meet the iron ore concentrate specification. Petrographic examination showed that dendritical intrusion of sulfide minerals into magnetite grains needed fine grinding over 100 mesh for liberation.

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Mining Research Center is making a study to establish and develop a practical ore-dressing procedure with low grade iron ore in Hongchon area and the Report 1, Jaun iron mine, issued on October 20th, 1967. Now, Government is planning to exploit the relatively high grade iron ore as selective mining at Hongchon mine which is estimated about 3,200,000 ton containing around 32% Fe prior to regular mine exploitation in this area. Hereby, a beneficiation study was mainly carried out with the composite sample taken from 4 outcrops at Hongchon mine which consisted mostly with magnetite and some pyrite, 38.7% Fe (39.3% of total Fe), 1.1% S, 0.75% P, 2.9% Mn and etc. Through various studies, magnetite concentrate could be successfully yielded up to 60 % Fe concentrate containing 0.22% S and 0.20% P with about 82 % of recovery by wet magnetic separation to grind minus 28 mesh, pyrite flotation concentrate containing up to 40% S with about 65% of recovery to regrind to minus 65 mesh using 200 g/t of copper sulfate, 60 g/t of Z-6, 48 g/t of pine oil and at pH 7 to 7.5.

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