The effects of sulfur and silicon on inter-graphite spacing λ in gray cast iron has been investigated by unidirectional solidification with Bridgman method. Sulfur content was varied from 0.004 to 0.108mass%, and silicon content was varied from 0.068 to 1.10mass%. The speed of crucible V was varied from 0.00015 to 0.01000cm/s. The temperature gradient at solid-liquid interface was 18∼21K/cm. The experimental equations of λ-V were obtained by using linear regression analysis. It was clarified that the transition from flake to undercooled graphite shifted differently according to sulfur and silicon content.

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  A study was carried out on the effect of phosphorus content on the elevated temperature brittleness (ETB) of ferritic ductile iron. ETB indicated the marked decrease in ductility at around 673K. Testing heats containing low phosphorus content manifested ETB at temperatures between 650K and 700K. There was a consistent correlation between the fractional increase in intergranular fracture appearance and the decrease in elongation. Addition of phosphorus exceeding about 0.032% prevented ETB caused by grain boundary brittleness.

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  This paper proposes the method of ferrite-grain refinement of the spheroidal graphite cast iron (s. g. iron) by heat treatment. The effects of the graphite nodule diameter and the ferrite grain size on the tensile properties of the resulting s. g. iron are also discussed in this study. The results obtained are as follows : (1) It is possible to convert into the s. g. iron with the mean ferrite grains of approximately 8μm in size by rapidly heating the iron with the uniform ferrite-pearlite fine-duplex structure just above the lower limit of the eutectoid transformation temperature range. (2) Ferrite-grain refinement of s. g. iron improves the tensile strength and the proof stress. The relationship between the yield stress and ferrite grain size follows the Hall-Petch relation. The yield-point phenomenon changes from continuous yielding to the yield drop with the decrease of ferrite grain size. (3) The improvement of the tensile strength and the proof stress resulting from the refinement of the graphite nodule depend highly on the strengthening of the matrix structure, as a consequence of grain refinement.

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  Semi-solid press-forming process is applied for AC9B aluminum alloy in order to suppress the floating of primary Si by press-forming at semi-solid state and to improve the mechanical properties by refining eutectic Si. By heating 15% strain-introduced bulk specimen, a microstructure is able to be obtained in which nearly spherical aluminum solid solution and primary Si distribute uniformly. Furthermore, eutectic Si becomes finer than that of as cast specimen due to rapid cooling. Tensile strength of the press-formed specimen from room temperature to 473K are more or less equal to those of as cast specimen because cracks occur in primary Si. The strain-introduced bulk can be injected into cavity with thickness of 1mm at the semi-solid temperature, and the spherical aluminum solid particles, primary Si and eutectic phases distribute uniformly in the formed specimen.

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  For the prediction of air-entrapment in aluminum die castings, we proposed the Critical Point Searching Method (CPM) : a technique for searching for points where the velocity vector is zero. The positions of the critical points can be found by searching all cells in the flow field. The flow field was calculated using a casting flow simulator Stefan 3D, developed by Tohoku University. The tetrahedral-cell based approach was used to calculate steadily and efficiently. Three examples of fluid flow simulation were conducted. Close relations were found between the simulated results and the results of X-ray penetration examinations and CT pictures of castings.

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  The reduction rates of FeO in the CaO-SiO₂-Al₂O₃ slag by coke were measured under various conditions. The reduction rate was found to increase with increasing FeO content in slag and temperature. Based on the observed coke-slag reaction rates and models for the reaction of slag and coke with iron-based alloy, the composition profiles of slag and metal in the well of a cupola were predicted.

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