The gas quantity of melts affect the microstructure of castings, therefore the degassing process is one of the most important processes to improve the mechanical properties of castings. To obtain high fatigue properties of Al-5 % Cu-0.4 % Mg-0.2 % Si alloy and Al-5 % Si-l % Cu-0.5 % Mg alloy castings, the degassing processes of melts, i. e. vacuum degassing and Ar gas degassing, were examined. In this study, the effect of melt cleanliness on fatigue property of both alloy castings fabricated with permanent mold were clarified. The vacuum degassing with dynamic melt movement is very effective degassing process for both alloys melt and the gas quantity level of 0.15 cm³/100 g is easily obtained. The fatigue properties of the castings remarkably increase with decreasing gas quantity of melts in both alloys. Al-Cu-Mg-Si alloy has a tendency to make micro porosity with small gas quantity and the fatigue properties of castings increases with eliminating small quantities of casting defects.

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  Generic CAD systems are not functional enough for use for the specific planning of the manufacturing process such as casting. In this study, an intelligent casting design system has been developed by considering the requirements from practical casting. The objectives of the system are to achieve more efficient and reasonable design as well as to succeed the traditional technologies of casting mold design including risering and gating. We considered an activity model which includes task models structured as a tree and related back ground information. Because drawings do not provide why and how the dimension is determined, design background information is stored and linked to each casting object in this system. It is also helpful to verify necessary design conditions. Furthermore, semi-automatic drawing functions for casting objects such as runners, gates, risers, machining allowances and core prints have been developed. As a result, it is found that this system is very useful for practical use.

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  It is known that dendrite arm spacing (DAS) and mechanical strength of aluminum alloy castings are strongly affected by the coagulation cooling rate and shape of the casting. In this investigation, AC4B square column castings with different thicknesses and masses were tested in order to determine the mass effect on DAS and mechanical strength. In addition, since aluminum alloy castings are often treated with T₆ to strengthen the material, both T₆-Treated and untreated castings were tested with regard to DAS and mechanical strength. It was found that these parameters were proportional to the nth power of the casting modulus (V/S)ⁿ, and the exponent was determined.

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  In order to improve soil corrosion resistance of spheroidal graphite cast iron, the effect of alloying elements was investigated. Considering the mechanism of microbially influenced corrosion, the corrosion resistance was examined in acetic acid solution with small amounts of salts over the range of pH 2.5-5.0. Alloying elements have no effect on the corrosion resistance in the pH range of 3.5-5.0. Some alloying elements affect the corrosion rate, when the pH is less than 3.O. Sn greatly improves corrosion resistance. Cu, Mo and Ni also improve the corrosion resistance, if the pH is 2.75 or below. The corrosion resistance of spheroidal graphite cast iron containing Sn or Cu is superior to those of SUS403 and SUS430.

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  Solid morphology and viscosity of semi-solid cast iron were investigated using the dual cylinder method in which the inner cylinder is rotated within the crucible. The appearance of liquid and solid was examined for a broad range of solid fractions. Structures of dendrite and solid network were produced at high cooling rate, and agglomerated structures formed at low rotation speed, resulting in a large change of the apparent viscosity of semi-solid cast iron with the change of the cooling rate and rotation speed. The measured apparent viscosity of semisolid cast iron is predicted reasonably using the model proposed by Hirai, et al.. At the higher solid fraction, the structure was observed to be denser in solid particles in outer region than in the inner one in the crucible. The non-uniform solid distribution was considered to be due to the centrifugal effect produced by cylinder rotation.

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  The effects of dipping in water for a long period on tensile properties of spheroidal graphite cast iron (SG iron) having various matrices was investigated from the viewpoints of corrosion and water embrittlement. The tensile strength and elongation of ADI, pearlitic and quenchtempering SG iron, tested under the wet condition after immersing in water for 480 hours, were lower than those in air and in condition of contact with water, drastic water embrittlement was observed. Especially, ADI showed the most remarkable water embrittlement. When the specimens were dipped in tap water for a long period, the water embrittlement was increased more remarkably than the specimens dipped in ion exchange water. This is because the growth of corrosion pits was promoted by the tap water. In the case specimens were dipped in the tap water for a long period, the tensile strength and elongation were recovered to a certain degree by drying. The tensile properties of specimen dried after immersing were not completely recovered to the level tested in air because of reduction of cross sectional area due to the corrosion pits and surface dissolution. The tensile properties of ferritic SG iron dipped in the tap water for a long period had little effect, only the small reduction of tensile strength and elongation was observed.

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  Alteration of the graphite structure by the Modified Inmold Process which has two reaction chambers in the mold was investigated. A new hybrid iron material with the graphite alteration morphology from one side having spheroidal to the other side having flake continuously was produced by combination with a spheroidizer and an inoculant. This phenomenon was probably attributed to the specific density difference in separately-treated iron melts. Effect of Si content on the morphology was examined. Fluid flow in the mold with this process was simulated by commercially developed software.

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