발간논문

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A study on the oxidation mechanism of stibnite was carried out to find out the possibility of its direct smelting. Stibnite sample was brought into the electric tube furnace and the temperature was varied from 700℃ to 1000℃ determine the oxidation rate and the oxidation mechanism of stibnite. The results of this experiment are as follows; 1) The activation energy in the oxidation of stibnite by air is 2.1 ㎉/㏖ and stibnite is oxidized easily. 2) Sb metal is produced during the oxidation of stibnite by air at a temperature higher than 900℃, which suggests the possibility of direct smelting stibnite into metal. 3) Addition of lime accelerates the oxidation rate as the content of lime increases.

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The effects of cooling rates after controlled rolling (C.R.) on the mechanical properties were investigated for the Mo-Ni-Nb-V type HSLA line pipe steels. The accelerated cooling was carried out after C.R. in the temperature range from 800℃ to 600℃ followed by air cooling. Cooling methods employed were air cooling (1.3℃/sec), compressed air cooling (4.1℃/S), oil quenching (9.5℃/S) and water spray cooling (13.6℃/S). It was found from this work that controlled rolled 0.3%Mo-0.3%Ni type steel exhibited 40% yield strength increments by water spray cooling, while impact energy was not changed greatly. For the conventionally rolled boron containing steel, impact energy at -20℃ was increased from about 3 to 17㎏f.m under water spray cooled condition.

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A study was made of the effects of cold working and annealing on the stress corrosion cracking of AlSl 304 stainless steel in boding 42% MgCl₂solution. When the 60% or 76% of yield stress was applied, the resistance to SCC showed maximum at 30% of cold work. However, when the same load was applied to the annealed specimens after cold working, the resistance to SCC decreased abruptly at 675℃ annealing. The fracture mode changed mixed →intergranular →transgranular as the amount of cold work increased.

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The anodic dissolution of chalcopyrite in hydrochloric acid was studied by use of electrochemical methods. From the anodic polarization curves and the rest potentials of chalcopyrite in ferric chloride solution, the slow rate of chalcopyrite leaching was interpreted to be due to the high overvoltage for the reduction of ferric ion on the chalcopyrite surface. A Galvanic cell of the type, chalcopyrite/HCl solution/FeCl₃, solution/graphite was proposed as an effective leaching method to improve the reaction rate of chalcopyrite in ferric chloride leaching.

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A theoretical model was proposed to predict the temperature profile within the solid cylindrical conductor subject to induction heating. The model takes into an account of heat conduction inside the conductor with the volumetric heat source supplied by induced current, incorporated with heat transfer between the cylindrical conductor and surrounding fluid. It is found that the geometrical shape and the frequency can affect the temperature distribution within the conductor.

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