발간논문

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The optimum conditions for extraction of copper from Korean chalcopyrite concentrate using a ferric chloride were studied at atmospheric and higher pressures. The variables investigated were particle size of the concentrate, weight ratio FeCl₃/CuFeS₂, reaction temperature, and reaction time. The optimum conditions determined in tests at atmospheric pressure were; particles of 6μ in mediar diameter, weight ratio FeCl₃/CuFeS₂ of 4, and temperature of 105℃. Under these conditions, 99% of the copper was extracted in 60 minutes. It was also found that 99% of the copper was extracted in 60 minutes from the unground concentrate as received, under conditions of the weight radio FeCl₃/CuFeS₂ of 4 and temperature of 150℃.

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Effects of ultrasonic wave irradiations on the electrodeposition of hard chromium have been determined at frequencies of 28KHz, 50KHz and 100KHz with Sargent baths. Deposited quantities measurements indicate that ultrasonic waves produce a marked decrease in deposited quantities, while the measurements of the hardness and covering powers indicate that ultrasonic waves increase the hardness and covering powers. These effects are correlated with ionic vibration and disruption of concentration gradients by ultrasonic waves and ultrasonic cavitation at the electrode surface.

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This investigation was carried out to study effects of an amount of sulphur addition, holding time and pouring temperature on refinement of the primary silicon crystals in the hypereutectic Al-Si alloy containing about 21% silicon by the method of metallography. The results obtained are as follows: Addition of 0.4% sulphur to a melt at 750℃ resulted in refinement of primay silicon crystals. The best refining effect was obtained by holding the melt at 850℃ for about 20 minutes after sulphur addition. Refining effect did not improve by holding the melt for more 20 minutes.

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In this work the stage of cell development and the cell morphology in the Al-Zn eutectic have been studied by solidifying the alloy unidirectionally. Cells are shown to develop preferertially from grain boundaries, growth induced boundaries and fault lines. In the Al-Zn eutectic alloy, well developed regular cell shape as in solid solution has not been found, but its typical sharp is rhombic. Besides, chrysanthemum-like shape and some other shape, which seems likely deformed from any hexagonal form irregulary, has been found. At high impurity concentration. 0.52% of Cd, cellular dendrite has been produced.

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High purity aluminum samples are anodized in 2% oxalic acid solution(21.5∼32℃, 0.1∼2.5amp/d㎡, 11.2∼65 volts) and in sulfuric acid solution (5∼25%, -3∼40℃, 1∼2.5amp/d㎡, 6.3∼23 volts). The experimental results lead to the following conclusions. The relationships between the anodization current i, voltage V and the barrier layer thickness D are well expressed as follows: D=203993V/[4.573T(log i-7.342)+29965] where i, V, D and T are expressed in amp/㎠, volt, Angstrom and absolute degree. Cell sizes increase linearly with anodization voltages whereas pore sizes are almost independent of anodization voltages below 30 volts and increase with anodization voltages above 30 volts. Cell and pore sizes are very little function of anodization temperature and current density, which indirectly affect cell and pore sizes through their contribution to anodization voltages. The porosity decreases rapidly with increasing anodization voltages below 30 volts whereas it changes very little above 30 volts.

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Effects of SiC addition to the cemented WC-6% Co alloy were investigated. WC and SiC powders were mixed, compacted and vacuum heated. Then they were recrushed to WC-SiC powders before addition to the cemented alloy. X-ray powder diffraction analysis was performed for the various WC-SiC powders. The (001) plane of tungsten carbide seemed to grow anisotropicaily in the WC-SiC powder which was vacuum heated to 1700℃. After mixing of the alloy powders, compacting and presintering, vacuum. sintering for the WC-SiC-6% Co alloys was performed at temperatures between 1450℃ and 1550℃. It is considered that SiC promoted the anisotropic grain growth of tungsten carbide in the directions parallel to (001) plane and consequently angular carbide grains seemed to appear in the microstructure of the cemented WC-SiC-6% Co alloy. Either increasing SiC content or raising sintering temperature promoted the growth of α₂ and Co grains in the WC-SiC-6% Co alloy.

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It has been already known that the addition of several refining elements had the refining effect of primary silicon crystals in high silicon-aluminum alloy. However, the effect of Cu addition has not yet been studied. The purpose of this study is to clarify effects of an amount of Cu added, pouring temperatures, holding time and the double treatment with S on the refinement of primary silicon crystals in an Al-20% Si alloy. Influences on primary silicon crystals by Cu addition observed with metallographic examinations and X-ray diffraction methode. The results obtained are as follows: 1) With the addition of Cu, the finest primary silicon crystals is high silicon-Al alloys were obtained with 0.6% at 750℃ and, 1% at 800℃ and 850℃. 2) The refining effect increased significantly for first five minutes period after the treatment. However, the longer holding did not improve a refining effect. 3) The refining effect of the double treatment with S was better than the single treatment by Cu

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