The present research was conducted to verify the effects of sulfur and oxygen on graphite morphologies using a Fe-C-120 massppm S mother alloy. In order to control the sulfur content in melt, three kinds of crucibles, namely, alumina, calcia, and calcia crucible with CaO-CaF₂ powders were used. To control oxygen partial pressure, air, argon, and Ar-3%H₂ atmosphere were employed.
  After melting in the alumina crucible, only flake graphite was formed in the specimen containing 78～98 massppm S. In the case of calcia crucible, aggregated and chunky graphite were observed in the specimen containing 11～20 massppm S. The specimen melted in a calcia crucible with CaO-CaF₂ powders, showed spheroidal graphite with chunky graphite whose sulfur content was 1 to 11 massppm.
  We confirmed that the spheroidal graphite is formed due to the low activity of sulfur and oxygen below critical levels. The critical levels changed with the cooling rate of samples. In addition, the cooling curve of the specimen melted in calcia crucible with CaO-CaF₂ powders did not show constant eutectic temperature, which is generally observed in that of flake graphite cast iron. This result is attributed to the solidification mode of spheroidal graphite, which differs from that of the flake graphite cast iron.

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  Water of 648K and 22.1MPa or more is called super critical water, and it has an excellent organic solvent characteristic. Recently, the application of supercritical water for various fields is being attempted. Especially, supercritical water oxidation is researched as an effective processing method of PCB and radioactive waste. However, metal corrodes in supercritical water environments, especially, reactive containers corrode conspicuously with hydrochloric acid generated in the processing of PCB.
  Therefore, corrosion is a serious problem in terms of the lifespan of the reactive container.
  Moreover, economical problems are also faced because hastelloy used in general is expensive. In this study, the corrosion behavior of 99.9%Fe, 99.9%Ni, 99.9%Cr and SUS316L was investigated in supercritical water at 523 to 873K and 20 to 60MPa for 3.6×10³ to 5.22×10⁵sec. Similar tests of surface treated specimens were carried out. As a result, the corrosion rate increased as the examination temperature increased in an materials. Moreover, transpassive corrosion was observed in Cr at 623K. The corrosion rate increased as pressure increased. Moreover, corrosion of metals in super critical water was influenced by the permittivity of water. Nitrided specimens showed excellent corrosion resistivity in super critical water environments.

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  Semi solid forming testing machine which has the same system as a runner-less injection machine has been made on an experimental basis. Temperature control system has been established to obtain the homogeneous solid-liquid coexisted state in its injection cylinder. Rod specimens were cast into a permanent mold by this machine in the semi solid state. The effect of solid fraction on the microstructure and the casting defect has been investigated and the results obtained as follows:
  A shearing in the part of nozzle of injection cylinder is the most important to reveal thixotropic property of alloy slurry in semi solid forming process by injection machine. So it needs controlling of solid fraction to affect it. In order to decrease casting defect and hold homogeneous structure, solid fraction more over 50% is needed. But when the solid fraction increases to 60%, primary solid particles glow coarser, so the primary solid particle size control technique is required to suppress it. In the case of less than 50% of solid fraction, alloy liquid preferentially fills inside the permanent mold and alloy slurry continue to fill the mold after alloy liquid. Then large casting defect form at the boundary of both flows.

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