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The metallurgical characteristics of hot metal desiliconization by MnO₂-Fe₂O₃ flux containing CaO-CaF₂ were investigated and the following results were obtained. 1) It was found that the flux had nearly equal effectiveness for desiliconization to Fe₂O₃-CaO-CaF₂ flux and manganese content in the hot metal increased with increasing MnO₂ content in the flux, while with Fe₂O₃,-CaO-CaF₂ flux considerable manganese loss was observed. 2) Decarburization degree was about 10%, dephosphorization degree was between 8-12% based on the flux compositions studied. Desulphurization increased to 15-30% when MnO₂ was added in the flux. 3) Increasing slag basicity enhanced desiliconization and recovery of manganese. 4) The initial rate of desiliconization was thought to be controlled by transfer of silicon in hot metal.

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The change of the corrosion potential and polarization characteristics of the specimen were measured by applying the technique of alternating voltage variation. The passive film was formed on the surface of Fe in the saturated Ca(OH)2 solution, which had the alkalinity of pH 12.1. The corrosion potential was at first shifted to the negative direction in the range of 0-2,250mV (50Hz), and then back to the positive direction with the rate of 0.5mV/mV AV above 2,250mV. The corrosion potential shift to the negative direction was due to the formation of the n-type passive film on Fe. Above the critical voltage (2,250mV), the breakdown of the passive film shifted the corrosion potential to the positive direction by the net anodic polarization that was resulted from unsymmetrical behavior of the anodic and cathodic polarizations. The effect of alternating voltage on the breakdown of the passive films increased with decreasing frequency and increasing voltage. The passive region in polarization curve disappeared above 2,000mV at the constant frequency of 50Hz, and the frequency above 250Hz had little effect on the polarization at the constant voltage of 2,000mV.

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Corrosion rates of three types of welded 304 stainless steel specimens immersed in 1 N H₂SO₂ solution at room temperature were obtained from potentiodynamic polarization curves, Tafel plots and polarization resistance curves. Corrosion rate measurements by using AC impedance technique were also carried out in order to investigate whether these values agreed fairly well with the values obtained from other electrochemical techniques. Corrosion rates of welded specimens were increased with increasing frequency of GTAW and decreasing current density of GTAW. It was concluded that an A.C. impedance technique could be successfully utilized for determining a local corrosion rate of welded parts.

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A mathematical model of fluid flow and turbulent characteristics in continuous casting tundishes has been developed with the use of 2-D computational scheme together with adequate modelling of turbulent viscosity. Computations for a various flow control in a tundish are presented via full scale molten steel system. Similary, the behavior of non-metallic inclusions is modelled by establishing a particle force balance in a moving fluid system. The results obtained from these studies are expected to be used semi-quantitatively in the conventional metallurgical processes governed by transport phenomena.

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The effect of ferrite on the hydrogen embrittlement of cast duplex (ferrite + austenite) stainless steels was studied. The hydrogen embrittlement was observed when the strain induced martensite was formed in these steels, and the degree of embrittlement was proportional to the amount of the martensite transformed. The ferrite reduced the degree of embrittlement when the specimens containing the same amount of martensite were compared, but a severe embrittlement occurred as the amount of ferrite increased due to the hydrogen embrittlement of ferrite itself. The specimen fractured in the hydrogen atmosphere showed the many surface cracks and the brittle fracture of the cleavage type.

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The anomalous hydrogen solubilities in the deformed palladiums were analyzed by employing modified Kirchheim`s model with considering the partially coherent strain energy which would induced during hydride precipitation around edge dislocations. The dislocation densities, obtained by this model, of the various cold worked and/or α↔β transformed palladium samples were the order of 10＾(11)㎝^(-2) The partially coherent strain energies were about 3 kJ/㏖H and nearly same in the various samples. This value could be compared with the incoherent strain energy, 0.4kJ/㏖H, which was obtained from the hysteresis on, P-C isotherm, and the coherent strain energy calculated, 9.6kJ/㏖H.

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The effect of the (Cr-Fe) addition in WC-Ni alloy on microstructure, hardness and toughness has been investigated. The specimens of WC-15 (Ni-(Cr-Fe)) with various (Cr-Fe) contents have been prepared by infiltration method. The hardness increased and the toughness decreased with (Cr-Fe) content, and the effect appeared to be dependent mainly on the resultant fine grain size as well as the hardening of matrix alloy phase. The microstructures of the alloy containing more than 20% of (Cr-Fe) in binder showed the complex carbides.

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Orientation dependence of stored energy and coherent domain size during cold rolling was studied by Fourier analysis of X-ray diffraction line profiles in single and polycrystalline Fe-1.7% Si alloy In the polycrystalline specimens, the sequence of stored energy after cold rolling was V(110)$gt; V(112)$gt; V(111)$gt;(100) for any column length, and V(ND)$gt;V(TD)$gt;V(RD) for the reference direction of speciments (ND: normal direction, TD: transverse direction and RD: rolling direction). The sequence of coherent domain size was D(100)$gt;D(112)$gt;D(111)$gt;D(110) at ND and TD, and D(112)$gt;D(110)$gt;D(111)$gt;D(100) at RD. Consequently three dimensional shape of the coherent domain was expected to be thin and elongated for the grain oriented ([112], [110], [111])//ND and equiaxed in some degree for the grain oriented [100]//ND. In the single crystal specimens, more energy was stored for the crystals initially oriented stable. Though the final orientations were the same, large differences were found between the stored energy of different initial orientations. The sequence of coherent domain size for the different crystal orientations was in the reverse order of stored energy.

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