The aim of this study was to fabricate thin and light castings to realize an energy saving highly efficient society. High melt flow rate in a mold cavity is indispensable for the production of thin castings. However, until now, the flow ability of melt has been studied mainly by investigating flow length, but the flow rate is thought to be more important and affected by permeability, specific heat of sand mold, and atmosphere. Consequently, the influence of permeability, atmosphere, air, CO₂, and He on the flow rate was investigated using a fine Teflon tube with pure water system in this study.
  The results show that the flow rate is significantly affected by permeability and gas species, and is the fastest in a He atmosphere, followed by air and CO₂. These results show that the flow rate is a function of the specific density of gases and is not the function of kinetic viscosity.

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  The continuous cooling transformation (CCT) behavior of several multi-component white cast irons, each with molybdenum (Mo) and tungsten (W) contents ranging from 0 to 6 mass% respectively, was investigated at austenitizing temperatures 1273K and 1373K. For the CCT diagrams, pearlite and bainite transformation curves were clearly separated regardless of austenitizing temperature and the contents of Mo and W. When the reciprocal action of Mo and W addition was expressed by a parameter of tungsten equivalence (W_eq (%) ＝ W ＋ 2Mo), the nose temperature of pearlite and bainite transformations did not change regardless of austenitizing temperature even if W_eq value was varied within 2.8 to 18.1%. The nose time of pearlite transformation shifted to the high side with an increase in both austenitizing temperature and Weq value. On the other hand, the nose time of bainite transformation changed little even if the W_eq value and the austenitizing temperature were changed. The M_s temperature was lowered by 50K to 60K when the austenizing temperature was increased by 100K, and this variable rose in proportion to the W_eq value irrespective of austenitizing temperature. The M_f temperature appeared when the W_eq value exceeded 15% at the austenitizing temperature of 1273K. The hardness levels of transformed cast iron specimens depended on the matrix microstructures. The maximum specimen hardness was obtained at conditions where the cooling curve passed through either the pearlite or bainite nose to martensite transformation.

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  The influence of boron on the ferrite formation in pearlite matrix spheroidal graphite cast iron has been investigated using the advanced analytical equipments such as an SEM and a TEM. The surface of spheroidal graphite in the bull's eye structure, produced by the addition of quite small amount of boron, was analyzed for discussing the ferritizing mechanism.
  The microstructure in the spheroidal graphite was investigated using the SEM and TEM, and we found the triangular precipitates, consisted of Fe-Si-Cu-B size of 150nm, in the surface layer of the graphite. These precipitates are consisted of the nano-crystal and act as the nucleus sites of flake graphite size of 0.5μm. The formation of the flake graphite due to the ferritizing above their eutectoid temperature, is the key mechanism of the ferrite formation.

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  A small amount of boron in spheroidal graphite cast iron has been reported to decrease the hardness as well as the pearlite matrixes in pearlitic ductile cast iron. The pearlite content in spheroidal graphite cast iron can be increased by the addition of pearlite promoting alloying elements such as tin. This research was conducted to determine the effects of the tin addition on the mechanical properties and microstructure of spheroidal graphite cast iron containing 50ppm boron. All pearlite matrixes can be achieved by the addition of 0.4% tin. 0.05-0.2% tin addition exhibited greater tensile strength and hardness compared to ductile cast iron not containing boron and tin. In this research, we investigated the tin rich cementite layer on the surface of the graphite nodule, assumed to serve as the barrier to carbon diffusion to the graphite, which is thought to promote pearlite formation during eutectoid transformation.

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  In the present work, a real plant of a regenerative thermal oxidizer (RTO) was applied to treat odor constituents from shell mould castings. As a result, it was found that concentrations of ammonia were about 20ppm, which is higher than that of other odor constituents in exhaust gas from shell mould castings. However, o- and p- cresol contained in the exhaust gas were found to highly contribute to offensive odor more than ammonia due to their low olfactory threshold, and the odor index of the exhausted gas was 40.
  As a result of the treatment of the exhausted gas by the RTO, about 99.7% and 99.5% of the o- and p- cresol was decomposed, and the odor index of treated gas decreased from 40 to 21, which is lower than the regulation value in the offensive odor control act. Thus, it can be concluded that the RTO is suitable for decreasing odor constituents from shell mould castings.
  The material balance of the RTO used for the real plant was calculated by using average values of operating data for 24hours. As a result, 92.4% of thermal efficiency was obtained, which results in higher energy savings than that of typical combustion processes.
  In order to prevent tar adhesion which contributes to offensive odor and to the obstruction of regenerative heat exchanger in the RTO, a stainless filter and pre-heating system were introduced to the RTO. As a result, it was found that pressure loss of the RTO was almost the same as 1.8kPa for 400h. Subsequently, the regenerative heat exchanger was heated up to 623K by means of baking treatment, and it was found that tar was more or less completely removed from ceramic honeycombs in the regenerative heat exchanger.

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