발간논문

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To apply the autoradiographic methods, using AR-10 high resolution stripping film to metallurgical problems, a preliminary experiment for determining appropriate exposure time and three processing methods for providing a standardized procedure were carried out and they were compared one another. By using a standard C^(14) specimen, the appropriate exposure time for S^(35)-melted-in silicon-iron was determined to be about 24 days for the activity of 550 counts/m/㎠. The undesired interaction between silicon-iron specimen and water or processing solutions could be prevented by exposing the film first in the air, removing it from the specimen, and then making it adhere to the gelatine coated glass slide in water before developing. Film expansion during above processes and consequent difficulties in comparing the autoradiograph with its micrograph could be prevented by floating the film on the surface of water so as to be expanded in advance and making it adhere to the gelatine coated glass slide before exposing. The interaction between the specimen and the emulsion in the presence of moisture during the exposure could be prevented by thin gold coating on the surface of the specimen and exposing in dry atmosphere.

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To investigate the flotation of low grade scheelite ore obtained from Sangdong mine in Korea, the batch flotation tests were carried out with Menhaden fish oil as a collector. Fish oil contains the high unsaturated fatty acid, and costs cheaply. In order to improve the grade and recovery of scheelite, the flotation tests in various conditions such as pulp temp., collector concentration, conditioning time and pulp density have been conducted. Also, the efficacy of sodium carbonate and sodium silicate as modifiers was discussed with regard to the pH regulating, water softening, soap making and gangue depressing. It is found that fish oil is more effective than oleic acid at low temp. (12-15℃) and the required amounts of the collector can be half of that of oleic acid when fish oil is used. It is further suggested from the results of flotation tests using fish oil instead of oleic acid that the grade and recovery of scheelite is both increasing.

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Result of the tests led to the following Conclusions: 1. The Optimum Size was-35 mesh in electromagnetic separation of pyrrhotite ore but the undersize of 230 mesh must be removed by classifier before separation. 2. The Optimum size was-140 mesh in roasting of the ore. 3. The optimum temperature at-140 mesh are in roasting of pyrrhotite ore ranges from 600℃ to 700℃. 4. The optimum retaining time of the ore in roaster at-140 mesh ore was 40 minutes. 5. SO₂and O₂volume percentage in the gas would be from roaster 6% to 7% and 7% respectively. 6. The cinder will be able to use in the iron making by sintering.

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A preliminary study has been made of the reduction by mixtures of CO and H₂ of natural hematite ore. Effects of gas composition, temperature, and gas flow rate on the reduction rate were studied. Preferable reduction performance was achieved with an elevated temperature, a H₂ rich gas mixture, and increased gas flow rate. Based on the preliminary work, a larger scale test in a low shaft vessel with ore burden and coke, into which an oxygen-steam blast was blown, has also been made to approach the physical chemical behavior to the practical operation. From the test, it was evaluated that shaft furnace for iron ore reduction could be shortened in its height than conventional blast furnace, since the temperature gradient in the shaft vessel was so steepened and bosh gas composition was much more powerful than that of blast furnace. A proposed sheet was attempted fox the ironmaking process with oxygen-steam blast, using cleaned top gas as an auxiliary fuel, excluding blast hot stove, causing decreased coke ratio and increased production.

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This paper deals with the time study of crane operation and pouring stand occupation for a new 32 tons arc furnace installation adjacent to an existing electric melting shop comprising four arc furnaces, 50, 32, 16, 14, ton each and two electric high frequency furnaces 10, 7 ton each. This combination enables the tapping and pouring time to be delaid by the waiting time of cranes and pouring stands. This paper also describes the waiting time and weight loss of molten steel because of installation of a new arc furnace compared with the existing melting shop, supposing the following conditions for a special one week period from April 18 to 23, 1966.

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