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This study has been undertaken to observe the effect of the melting parameters in Electro Slag Casting Process. Lead/Tin alloy was chosen because of its low melting point. By changing the slag quantity, slag composition and power, we concluded the following. 1. The melt rate increases with power or wt.% NaCl in slag composition, while decreases with the slag quantity. 2. The melting parameters have the same effect on the metal pool depth as on the melt rate. And the metal pool depth is proportional to the melting rate. 3. The slag resistance increases with the slag quantity, but decreases with the power or wt.% NaCI in slag composition. 4. The current density is exclusively concentrated on the center of the slag pool. 5. Directional solidification is observed in ESC products.

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The morphology and fracture mode of the bainite in a Fe-C-Mn high-strength hypereutectoid steel have been examined by means of optical, scanning electron, and transmission electron microscopy, and also the isothermal decomposition of a Fe-1.35% C-2.06% Mn austenite has been investigated in connection with its hardenability. It is shown that the bainite transformation has taken place both by columnar type growth along grain boundaries forming the grain boundary allotriomorphic form and by nodular type growing into the grain, which are distinctly different from the usual bainite appearances. It is also shown that there may be no transition temperature from upper to lower bainite. It is found by the fractographic study that fracture is predominantly transcrystalline showing cleavage facet. But, there are the small amount of quasi-cleavage and dimple fracture in bainite phases transformed at lower temperature, and also the fracture unit in them is relatively finer. It seems the inferiority of fracture ductility in this steel is attributed to proeutectoid cementites along austenite boundaries or a Widmansta¨tten type of cementites grown into bainite grains, which can be removed by the proper heat treatment alternative, rather than to its peculiar bainite.

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Solid reaction between ilmenite and solid NaOH is studied. The reaction rate is determined by the diffusion process of NaOH into the spherical reaction product layer of ilmenite particles and the activation energy for diffusion is calculated as av. 25.4 ㎉/㏖. Decomposition of ilmenite by NaOH is proceeded obviously by chemical reaction and DTA experiments show that the activation energy of the decomposition reaction is 13.3 ㎉/㏖, which is the half to that of diffusion. Production of NaFeO₂, Na₂TiO₃, by further chemical reaction with excess NaOH is wnfirmed by X-ray diffraction analysis of the reaction product.

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From slip traces produced by microhardness indentation, orientation of grains in a commercial Cu-30 Zn brass has been determined before and after rolling reduction of 30% at room temperature. Different deformation structures were observed on grains, where the Schmid factor analysis shows that they depend on the number of active slip systems at rolling. When the primary slip system is unique, deformation is homogeneous, but when more than one slip system are equally active, deformation is heterogeneous; in particular, large, distinct subgrains can be formed. It was also observed that when a twin axis is parallel to the transverse direction, regions contiguous to the twin boundary rotate together, thus remaining a narrow band of twin couple after rolling. From these observations, it was concluded that slip mechanism, during the first stage of cold-rolling, may include (1) multi-directional rotations on the same grain and (2) a binding force of the twin boundary on contiguous regions.

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In order to study development of residual stresses in tubes due to roll straightening, a transverse compression test has been made. Development of tensile residual stress in the outer layer and compressive stress in the inner layer of tube, and expansion of the tube diameter have been found to be inherent problems in the roll straightening.

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Many studies on the solidification process of cast iron were reported, but the studios on the melting morphology of cast iron are rare. Therefore, in this work the melting has been done by rapid melting method and melting morphology has been examined, according to graphite shape in cast iron. The main results are summarized as follows: 1. In white cast iron of Fe-C-Si system, melt appears first along the interface between temper carbon and austenite matrix, after the minute temper carbon which was decomposed from Fe₃C diffuses to austenite to eutectic composition. 2. In either hypo or hyper-eutectic gray cast iron, it is observed that the melt appears first at the boundary of eutectic cell. In case of the eutectic gray cast iron, the vicinity of all graphites melts at the same time. 3. In rapidly heated and water quenched specimen of hypereutectic gray cast iron, the crystallization of fine graphites near kish graphite leads to the conclusion that kish graphite does not dissolve easily. 4. In case of nodular cast iron, the boundary between austenite shell and austenite matrix melts first and nodular graphite dissolves very slowly.

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