발간논문

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The cold work dependence of the change of oxidation rate was studied. Specimens cut into 2.0 ㎜ thickness disk from zirconium rod (99.9%) were annealed in the vaccum tube furnace at 800℃ for 1 hour, and than uniaxially cold compressed from 0 to 30% with 10% increment. The oxidation rate was decreased with increase in the degree of cold work. The activation energy was calculated to be 36.6 and 45.7 ㎉/mole for low temperature (425-490℃) and high temperature region (490℃-550℃), respectively. The constant of Arrhenius rate equation was dependent variable of the degree of cold work (D%) and best expressed by the following from A_d=A_o (1-0.008D). The cold work dependent rate can be expressed as follows: 425℃-490℃ K_c=1.85×10^(-5)(1-0.008D) exp (-36.000/RT) 490℃-550℃ K_c=6.95×10^(-3)(1-0.008D) exp (-45.700/RT)

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Effects of Pco/Pco₂ on the contents of chromium, manganese, cobalt and nickel in molten binary alloy steels are investigated at 1650℃ under basic slag, and equilibria for oxidation of chromium and manganese in molten steel by CO₂ gas are discussed. When Pco/Pco₂ is more than 1.5, the activity of chromium in liquid steel is proportional to Pco/Pco₂, for chromium contents within the range 9∼12 wt.% and stags saturated with chromium oxides. α_(cr)=5.35×10^(-2)Pco/Pco₂ or Cr wt.%≒5.8×Pco/Pco₂ Close agreement between these experimental results and equilibrium data calculated leads to predictions that chromium oxide is present in the divalent form, CrO, in slag, under CO gas atmosphere, which could not be confirmed on the investigations of Cr-O system. There is a miscibility gap below Pco/Pco₂=1.5 and Cr=9 wt.% that activity of chromium dully decreases, as Pco/Pco₂ decreases, Activity of manganese of liquid steel in equilibrium with CO-CO₂ gas mixture is agreed with the value calculated from the standard free energy changes at Mn=9 wt.%, but above this, the experimental data is less than the value owing to difficulty of saturation of slag with MnO. Nickel and cobalt oxides were reduced by iron during melting. According to oxidation loss of iron by CO₂ gas in Fe-Ni and Fe-Co binary alloy, the contents of nickel and cobalt increase below Pco/Pco₂=1.5. Carbon contents slowly reduce as chromium and manganese contents decrease in equilibrium with CO·CO₂ gas mixture, but drop suddenly as partial pressure of CO₂ gas increases. Equilibrium problems in Fe-Cr-C-O and Fe-Mn-C-O system are more complicated owing to oxidation of iron by CO₂ gas and oxides in slag with increasing partial pressure of CO₂ gas.

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The thermodynamic properties of the liquid aluminum-indium system have been investigated by the following reversible galvanic cell in the temperature range 700 to 950℃. Al(ℓ) ｜ KCl-NaCl, AlCl₃ ｜ Al-In(ℓ) The activities derived show considerable positive deviations from Raoult`s law. The experimental results agree with the activities estimated from the liquidus line or those derived from Lumsden`s model. The activity coefficients at infinite dilution were determined at 700℃ to be 11.4 and 13.2 for aluminum and indium, respectively. Limits of the miscibility gap and the location of critical point which had involved uncertainty were confirmed with the observed lines of electromotive force. Various partial and integral thermodynamic quantities were derived from expeimental data, and it was found that the heats of mixing obtained were in good agreement with those determined directrly with calorimeter by Wittig. Furthermore, the interaction energy and the short-range order parameter in this liquid alloy have been evaluated by the aid of the theory of quaisichemical approach, and the results obtained show reasonable agreements with those derived by the classical thermodynamic method.

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This research aims to find out the temperature range of the chilled ball metal mold, 170℃∼250℃ for sound surface in chilled ball casting, and to observe the depth of chill, surface hardness and Shrinkage cavity situation in ball according to chemical composition variety within this temperature range, the optimum chemical composition range for wear found to be C 3.4∼4.0%, Si 0.6% shrinkage cavity in ball has a tendency to situate at center of ball when the chill depth is deep.

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The effects of copper and zinc ion on the flotability, froth and sediment volume of scheelite particles were studied by using oleic acid as a collector. The following results were obtained: 1. Copper and zinc ion have a depressing action of scheelite on the flotation in the pH range where those ions are precipitated into hydroxide 2. Copper and zinc ion effectively destruct froth of oleic acid and decrease the sediment volume of scheelite particles which is conditioned by oleic acid. Therefore copper and zinc ion increase the efficiency of tabling and thickening of scheelite particles.

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Today a few iron and steel makers produce a foundry pig iron for casting with iron ore that is mainly produced from home land according to demand of foundry pig iron for casting in rapid growth of casting industry field. Some men try to make to reduce of casting cost which uses a little of lathe chip of steel that out-puted from machine shop. This paper is discussed a few of characters which arise on operation of M. B. C. to make a foundry pig iron with 80% lathe chip of steel and 20% light steel scrap.

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Das Plateau der Adsorptionsmenge-Zeit Kurven kanu neben seiner Bedeutung als Vollbedeckungszust-and auch als Vorstufe der Oxydation interpretiert werden. Bei der Untersuchung der Oxydaton, die der Adsorption folgt, konnte festgestellt werden, daß die Oxydation von Kupfer bei l00℃ nach einem logarithmischen Zeitgesetz abla¨uft and daß die Oxydationsrate im Bereich von 1 bis 13 Torr unabha¨ngig vom Druck zu sein scheint.

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